File: | lib/Transforms/Scalar/SimpleLoopUnswitch.cpp |
Warning: | line 2039, column 24 The left operand of '<' is a garbage value |
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1 | //===- SimpleLoopUnswitch.cpp - Hoist loop-invariant control flow ---------===// | |||
2 | // | |||
3 | // The LLVM Compiler Infrastructure | |||
4 | // | |||
5 | // This file is distributed under the University of Illinois Open Source | |||
6 | // License. See LICENSE.TXT for details. | |||
7 | // | |||
8 | //===----------------------------------------------------------------------===// | |||
9 | ||||
10 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | |||
11 | #include "llvm/ADT/DenseMap.h" | |||
12 | #include "llvm/ADT/STLExtras.h" | |||
13 | #include "llvm/ADT/Sequence.h" | |||
14 | #include "llvm/ADT/SetVector.h" | |||
15 | #include "llvm/ADT/SmallPtrSet.h" | |||
16 | #include "llvm/ADT/SmallVector.h" | |||
17 | #include "llvm/ADT/Statistic.h" | |||
18 | #include "llvm/ADT/Twine.h" | |||
19 | #include "llvm/Analysis/AssumptionCache.h" | |||
20 | #include "llvm/Analysis/CodeMetrics.h" | |||
21 | #include "llvm/Analysis/LoopAnalysisManager.h" | |||
22 | #include "llvm/Analysis/LoopInfo.h" | |||
23 | #include "llvm/Analysis/LoopPass.h" | |||
24 | #include "llvm/IR/BasicBlock.h" | |||
25 | #include "llvm/IR/Constant.h" | |||
26 | #include "llvm/IR/Constants.h" | |||
27 | #include "llvm/IR/Dominators.h" | |||
28 | #include "llvm/IR/Function.h" | |||
29 | #include "llvm/IR/InstrTypes.h" | |||
30 | #include "llvm/IR/Instruction.h" | |||
31 | #include "llvm/IR/Instructions.h" | |||
32 | #include "llvm/IR/IntrinsicInst.h" | |||
33 | #include "llvm/IR/Use.h" | |||
34 | #include "llvm/IR/Value.h" | |||
35 | #include "llvm/Pass.h" | |||
36 | #include "llvm/Support/Casting.h" | |||
37 | #include "llvm/Support/Debug.h" | |||
38 | #include "llvm/Support/ErrorHandling.h" | |||
39 | #include "llvm/Support/GenericDomTree.h" | |||
40 | #include "llvm/Support/raw_ostream.h" | |||
41 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | |||
42 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | |||
43 | #include "llvm/Transforms/Utils/Cloning.h" | |||
44 | #include "llvm/Transforms/Utils/LoopUtils.h" | |||
45 | #include "llvm/Transforms/Utils/ValueMapper.h" | |||
46 | #include <algorithm> | |||
47 | #include <cassert> | |||
48 | #include <iterator> | |||
49 | #include <numeric> | |||
50 | #include <utility> | |||
51 | ||||
52 | #define DEBUG_TYPE"simple-loop-unswitch" "simple-loop-unswitch" | |||
53 | ||||
54 | using namespace llvm; | |||
55 | ||||
56 | STATISTIC(NumBranches, "Number of branches unswitched")static llvm::Statistic NumBranches = {"simple-loop-unswitch", "NumBranches", "Number of branches unswitched", {0}, {false} }; | |||
57 | STATISTIC(NumSwitches, "Number of switches unswitched")static llvm::Statistic NumSwitches = {"simple-loop-unswitch", "NumSwitches", "Number of switches unswitched", {0}, {false} }; | |||
58 | STATISTIC(NumTrivial, "Number of unswitches that are trivial")static llvm::Statistic NumTrivial = {"simple-loop-unswitch", "NumTrivial" , "Number of unswitches that are trivial", {0}, {false}}; | |||
59 | ||||
60 | static cl::opt<bool> EnableNonTrivialUnswitch( | |||
61 | "enable-nontrivial-unswitch", cl::init(false), cl::Hidden, | |||
62 | cl::desc("Forcibly enables non-trivial loop unswitching rather than " | |||
63 | "following the configuration passed into the pass.")); | |||
64 | ||||
65 | static cl::opt<int> | |||
66 | UnswitchThreshold("unswitch-threshold", cl::init(50), cl::Hidden, | |||
67 | cl::desc("The cost threshold for unswitching a loop.")); | |||
68 | ||||
69 | static void replaceLoopUsesWithConstant(Loop &L, Value &LIC, | |||
70 | Constant &Replacement) { | |||
71 | assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?")(static_cast <bool> (!isa<Constant>(LIC) && "Why are we unswitching on a constant?") ? void (0) : __assert_fail ("!isa<Constant>(LIC) && \"Why are we unswitching on a constant?\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 71, __extension__ __PRETTY_FUNCTION__)); | |||
72 | ||||
73 | // Replace uses of LIC in the loop with the given constant. | |||
74 | for (auto UI = LIC.use_begin(), UE = LIC.use_end(); UI != UE;) { | |||
75 | // Grab the use and walk past it so we can clobber it in the use list. | |||
76 | Use *U = &*UI++; | |||
77 | Instruction *UserI = dyn_cast<Instruction>(U->getUser()); | |||
78 | if (!UserI || !L.contains(UserI)) | |||
79 | continue; | |||
80 | ||||
81 | // Replace this use within the loop body. | |||
82 | *U = &Replacement; | |||
83 | } | |||
84 | } | |||
85 | ||||
86 | /// Update the IDom for a basic block whose predecessor set has changed. | |||
87 | /// | |||
88 | /// This routine is designed to work when the domtree update is relatively | |||
89 | /// localized by leveraging a known common dominator, often a loop header. | |||
90 | /// | |||
91 | /// FIXME: Should consider hand-rolling a slightly more efficient non-DFS | |||
92 | /// approach here as we can do that easily by persisting the candidate IDom's | |||
93 | /// dominating set between each predecessor. | |||
94 | /// | |||
95 | /// FIXME: Longer term, many uses of this can be replaced by an incremental | |||
96 | /// domtree update strategy that starts from a known dominating block and | |||
97 | /// rebuilds that subtree. | |||
98 | static bool updateIDomWithKnownCommonDominator(BasicBlock *BB, | |||
99 | BasicBlock *KnownDominatingBB, | |||
100 | DominatorTree &DT) { | |||
101 | assert(pred_begin(BB) != pred_end(BB) &&(static_cast <bool> (pred_begin(BB) != pred_end(BB) && "This routine does not handle unreachable blocks!") ? void ( 0) : __assert_fail ("pred_begin(BB) != pred_end(BB) && \"This routine does not handle unreachable blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 102, __extension__ __PRETTY_FUNCTION__)) | |||
102 | "This routine does not handle unreachable blocks!")(static_cast <bool> (pred_begin(BB) != pred_end(BB) && "This routine does not handle unreachable blocks!") ? void ( 0) : __assert_fail ("pred_begin(BB) != pred_end(BB) && \"This routine does not handle unreachable blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 102, __extension__ __PRETTY_FUNCTION__)); | |||
103 | ||||
104 | BasicBlock *OrigIDom = DT[BB]->getIDom()->getBlock(); | |||
105 | ||||
106 | BasicBlock *IDom = *pred_begin(BB); | |||
107 | assert(DT.dominates(KnownDominatingBB, IDom) &&(static_cast <bool> (DT.dominates(KnownDominatingBB, IDom ) && "Bad known dominating block!") ? void (0) : __assert_fail ("DT.dominates(KnownDominatingBB, IDom) && \"Bad known dominating block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 108, __extension__ __PRETTY_FUNCTION__)) | |||
108 | "Bad known dominating block!")(static_cast <bool> (DT.dominates(KnownDominatingBB, IDom ) && "Bad known dominating block!") ? void (0) : __assert_fail ("DT.dominates(KnownDominatingBB, IDom) && \"Bad known dominating block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 108, __extension__ __PRETTY_FUNCTION__)); | |||
109 | ||||
110 | // Walk all of the other predecessors finding the nearest common dominator | |||
111 | // until all predecessors are covered or we reach the loop header. The loop | |||
112 | // header necessarily dominates all loop exit blocks in loop simplified form | |||
113 | // so we can early-exit the moment we hit that block. | |||
114 | for (auto PI = std::next(pred_begin(BB)), PE = pred_end(BB); | |||
115 | PI != PE && IDom != KnownDominatingBB; ++PI) { | |||
116 | assert(DT.dominates(KnownDominatingBB, *PI) &&(static_cast <bool> (DT.dominates(KnownDominatingBB, *PI ) && "Bad known dominating block!") ? void (0) : __assert_fail ("DT.dominates(KnownDominatingBB, *PI) && \"Bad known dominating block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 117, __extension__ __PRETTY_FUNCTION__)) | |||
117 | "Bad known dominating block!")(static_cast <bool> (DT.dominates(KnownDominatingBB, *PI ) && "Bad known dominating block!") ? void (0) : __assert_fail ("DT.dominates(KnownDominatingBB, *PI) && \"Bad known dominating block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 117, __extension__ __PRETTY_FUNCTION__)); | |||
118 | IDom = DT.findNearestCommonDominator(IDom, *PI); | |||
119 | } | |||
120 | ||||
121 | if (IDom == OrigIDom) | |||
122 | return false; | |||
123 | ||||
124 | DT.changeImmediateDominator(BB, IDom); | |||
125 | return true; | |||
126 | } | |||
127 | ||||
128 | // Note that we don't currently use the IDFCalculator here for two reasons: | |||
129 | // 1) It computes dominator tree levels for the entire function on each run | |||
130 | // of 'compute'. While this isn't terrible, given that we expect to update | |||
131 | // relatively small subtrees of the domtree, it isn't necessarily the right | |||
132 | // tradeoff. | |||
133 | // 2) The interface doesn't fit this usage well. It doesn't operate in | |||
134 | // append-only, and builds several sets that we don't need. | |||
135 | // | |||
136 | // FIXME: Neither of these issues are a big deal and could be addressed with | |||
137 | // some amount of refactoring of IDFCalculator. That would allow us to share | |||
138 | // the core logic here (which is solving the same core problem). | |||
139 | static void appendDomFrontier(DomTreeNode *Node, | |||
140 | SmallSetVector<BasicBlock *, 4> &Worklist, | |||
141 | SmallVectorImpl<DomTreeNode *> &DomNodes, | |||
142 | SmallPtrSetImpl<BasicBlock *> &DomSet) { | |||
143 | assert(DomNodes.empty() && "Must start with no dominator nodes.")(static_cast <bool> (DomNodes.empty() && "Must start with no dominator nodes." ) ? void (0) : __assert_fail ("DomNodes.empty() && \"Must start with no dominator nodes.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 143, __extension__ __PRETTY_FUNCTION__)); | |||
144 | assert(DomSet.empty() && "Must start with an empty dominator set.")(static_cast <bool> (DomSet.empty() && "Must start with an empty dominator set." ) ? void (0) : __assert_fail ("DomSet.empty() && \"Must start with an empty dominator set.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 144, __extension__ __PRETTY_FUNCTION__)); | |||
145 | ||||
146 | // First flatten this subtree into sequence of nodes by doing a pre-order | |||
147 | // walk. | |||
148 | DomNodes.push_back(Node); | |||
149 | // We intentionally re-evaluate the size as each node can add new children. | |||
150 | // Because this is a tree walk, this cannot add any duplicates. | |||
151 | for (int i = 0; i < (int)DomNodes.size(); ++i) | |||
152 | DomNodes.insert(DomNodes.end(), DomNodes[i]->begin(), DomNodes[i]->end()); | |||
153 | ||||
154 | // Now create a set of the basic blocks so we can quickly test for | |||
155 | // dominated successors. We could in theory use the DFS numbers of the | |||
156 | // dominator tree for this, but we want this to remain predictably fast | |||
157 | // even while we mutate the dominator tree in ways that would invalidate | |||
158 | // the DFS numbering. | |||
159 | for (DomTreeNode *InnerN : DomNodes) | |||
160 | DomSet.insert(InnerN->getBlock()); | |||
161 | ||||
162 | // Now re-walk the nodes, appending every successor of every node that isn't | |||
163 | // in the set. Note that we don't append the node itself, even though if it | |||
164 | // is a successor it does not strictly dominate itself and thus it would be | |||
165 | // part of the dominance frontier. The reason we don't append it is that | |||
166 | // the node passed in came *from* the worklist and so it has already been | |||
167 | // processed. | |||
168 | for (DomTreeNode *InnerN : DomNodes) | |||
169 | for (BasicBlock *SuccBB : successors(InnerN->getBlock())) | |||
170 | if (!DomSet.count(SuccBB)) | |||
171 | Worklist.insert(SuccBB); | |||
172 | ||||
173 | DomNodes.clear(); | |||
174 | DomSet.clear(); | |||
175 | } | |||
176 | ||||
177 | /// Update the dominator tree after unswitching a particular former exit block. | |||
178 | /// | |||
179 | /// This handles the full update of the dominator tree after hoisting a block | |||
180 | /// that previously was an exit block (or split off of an exit block) up to be | |||
181 | /// reached from the new immediate dominator of the preheader. | |||
182 | /// | |||
183 | /// The common case is simple -- we just move the unswitched block to have an | |||
184 | /// immediate dominator of the old preheader. But in complex cases, there may | |||
185 | /// be other blocks reachable from the unswitched block that are immediately | |||
186 | /// dominated by some node between the unswitched one and the old preheader. | |||
187 | /// All of these also need to be hoisted in the dominator tree. We also want to | |||
188 | /// minimize queries to the dominator tree because each step of this | |||
189 | /// invalidates any DFS numbers that would make queries fast. | |||
190 | static void updateDTAfterUnswitch(BasicBlock *UnswitchedBB, BasicBlock *OldPH, | |||
191 | DominatorTree &DT) { | |||
192 | DomTreeNode *OldPHNode = DT[OldPH]; | |||
193 | DomTreeNode *UnswitchedNode = DT[UnswitchedBB]; | |||
194 | // If the dominator tree has already been updated for this unswitched node, | |||
195 | // we're done. This makes it easier to use this routine if there are multiple | |||
196 | // paths to the same unswitched destination. | |||
197 | if (UnswitchedNode->getIDom() == OldPHNode) | |||
198 | return; | |||
199 | ||||
200 | // First collect the domtree nodes that we are hoisting over. These are the | |||
201 | // set of nodes which may have children that need to be hoisted as well. | |||
202 | SmallPtrSet<DomTreeNode *, 4> DomChain; | |||
203 | for (auto *IDom = UnswitchedNode->getIDom(); IDom != OldPHNode; | |||
204 | IDom = IDom->getIDom()) | |||
205 | DomChain.insert(IDom); | |||
206 | ||||
207 | // The unswitched block ends up immediately dominated by the old preheader -- | |||
208 | // regardless of whether it is the loop exit block or split off of the loop | |||
209 | // exit block. | |||
210 | DT.changeImmediateDominator(UnswitchedNode, OldPHNode); | |||
211 | ||||
212 | // For everything that moves up the dominator tree, we need to examine the | |||
213 | // dominator frontier to see if it additionally should move up the dominator | |||
214 | // tree. This lambda appends the dominator frontier for a node on the | |||
215 | // worklist. | |||
216 | SmallSetVector<BasicBlock *, 4> Worklist; | |||
217 | ||||
218 | // Scratch data structures reused by domfrontier finding. | |||
219 | SmallVector<DomTreeNode *, 4> DomNodes; | |||
220 | SmallPtrSet<BasicBlock *, 4> DomSet; | |||
221 | ||||
222 | // Append the initial dom frontier nodes. | |||
223 | appendDomFrontier(UnswitchedNode, Worklist, DomNodes, DomSet); | |||
224 | ||||
225 | // Walk the worklist. We grow the list in the loop and so must recompute size. | |||
226 | for (int i = 0; i < (int)Worklist.size(); ++i) { | |||
227 | auto *BB = Worklist[i]; | |||
228 | ||||
229 | DomTreeNode *Node = DT[BB]; | |||
230 | assert(!DomChain.count(Node) &&(static_cast <bool> (!DomChain.count(Node) && "Cannot be dominated by a block you can reach!" ) ? void (0) : __assert_fail ("!DomChain.count(Node) && \"Cannot be dominated by a block you can reach!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 231, __extension__ __PRETTY_FUNCTION__)) | |||
231 | "Cannot be dominated by a block you can reach!")(static_cast <bool> (!DomChain.count(Node) && "Cannot be dominated by a block you can reach!" ) ? void (0) : __assert_fail ("!DomChain.count(Node) && \"Cannot be dominated by a block you can reach!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 231, __extension__ __PRETTY_FUNCTION__)); | |||
232 | ||||
233 | // If this block had an immediate dominator somewhere in the chain | |||
234 | // we hoisted over, then its position in the domtree needs to move as it is | |||
235 | // reachable from a node hoisted over this chain. | |||
236 | if (!DomChain.count(Node->getIDom())) | |||
237 | continue; | |||
238 | ||||
239 | DT.changeImmediateDominator(Node, OldPHNode); | |||
240 | ||||
241 | // Now add this node's dominator frontier to the worklist as well. | |||
242 | appendDomFrontier(Node, Worklist, DomNodes, DomSet); | |||
243 | } | |||
244 | } | |||
245 | ||||
246 | /// Check that all the LCSSA PHI nodes in the loop exit block have trivial | |||
247 | /// incoming values along this edge. | |||
248 | static bool areLoopExitPHIsLoopInvariant(Loop &L, BasicBlock &ExitingBB, | |||
249 | BasicBlock &ExitBB) { | |||
250 | for (Instruction &I : ExitBB) { | |||
251 | auto *PN = dyn_cast<PHINode>(&I); | |||
252 | if (!PN) | |||
253 | // No more PHIs to check. | |||
254 | return true; | |||
255 | ||||
256 | // If the incoming value for this edge isn't loop invariant the unswitch | |||
257 | // won't be trivial. | |||
258 | if (!L.isLoopInvariant(PN->getIncomingValueForBlock(&ExitingBB))) | |||
259 | return false; | |||
260 | } | |||
261 | llvm_unreachable("Basic blocks should never be empty!")::llvm::llvm_unreachable_internal("Basic blocks should never be empty!" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 261); | |||
262 | } | |||
263 | ||||
264 | /// Rewrite the PHI nodes in an unswitched loop exit basic block. | |||
265 | /// | |||
266 | /// Requires that the loop exit and unswitched basic block are the same, and | |||
267 | /// that the exiting block was a unique predecessor of that block. Rewrites the | |||
268 | /// PHI nodes in that block such that what were LCSSA PHI nodes become trivial | |||
269 | /// PHI nodes from the old preheader that now contains the unswitched | |||
270 | /// terminator. | |||
271 | static void rewritePHINodesForUnswitchedExitBlock(BasicBlock &UnswitchedBB, | |||
272 | BasicBlock &OldExitingBB, | |||
273 | BasicBlock &OldPH) { | |||
274 | for (PHINode &PN : UnswitchedBB.phis()) { | |||
275 | // When the loop exit is directly unswitched we just need to update the | |||
276 | // incoming basic block. We loop to handle weird cases with repeated | |||
277 | // incoming blocks, but expect to typically only have one operand here. | |||
278 | for (auto i : seq<int>(0, PN.getNumOperands())) { | |||
279 | assert(PN.getIncomingBlock(i) == &OldExitingBB &&(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB && "Found incoming block different from unique predecessor!" ) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 280, __extension__ __PRETTY_FUNCTION__)) | |||
280 | "Found incoming block different from unique predecessor!")(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB && "Found incoming block different from unique predecessor!" ) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 280, __extension__ __PRETTY_FUNCTION__)); | |||
281 | PN.setIncomingBlock(i, &OldPH); | |||
282 | } | |||
283 | } | |||
284 | } | |||
285 | ||||
286 | /// Rewrite the PHI nodes in the loop exit basic block and the split off | |||
287 | /// unswitched block. | |||
288 | /// | |||
289 | /// Because the exit block remains an exit from the loop, this rewrites the | |||
290 | /// LCSSA PHI nodes in it to remove the unswitched edge and introduces PHI | |||
291 | /// nodes into the unswitched basic block to select between the value in the | |||
292 | /// old preheader and the loop exit. | |||
293 | static void rewritePHINodesForExitAndUnswitchedBlocks(BasicBlock &ExitBB, | |||
294 | BasicBlock &UnswitchedBB, | |||
295 | BasicBlock &OldExitingBB, | |||
296 | BasicBlock &OldPH) { | |||
297 | assert(&ExitBB != &UnswitchedBB &&(static_cast <bool> (&ExitBB != &UnswitchedBB && "Must have different loop exit and unswitched blocks!") ? void (0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 298, __extension__ __PRETTY_FUNCTION__)) | |||
298 | "Must have different loop exit and unswitched blocks!")(static_cast <bool> (&ExitBB != &UnswitchedBB && "Must have different loop exit and unswitched blocks!") ? void (0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 298, __extension__ __PRETTY_FUNCTION__)); | |||
299 | Instruction *InsertPt = &*UnswitchedBB.begin(); | |||
300 | for (PHINode &PN : ExitBB.phis()) { | |||
301 | auto *NewPN = PHINode::Create(PN.getType(), /*NumReservedValues*/ 2, | |||
302 | PN.getName() + ".split", InsertPt); | |||
303 | ||||
304 | // Walk backwards over the old PHI node's inputs to minimize the cost of | |||
305 | // removing each one. We have to do this weird loop manually so that we | |||
306 | // create the same number of new incoming edges in the new PHI as we expect | |||
307 | // each case-based edge to be included in the unswitched switch in some | |||
308 | // cases. | |||
309 | // FIXME: This is really, really gross. It would be much cleaner if LLVM | |||
310 | // allowed us to create a single entry for a predecessor block without | |||
311 | // having separate entries for each "edge" even though these edges are | |||
312 | // required to produce identical results. | |||
313 | for (int i = PN.getNumIncomingValues() - 1; i >= 0; --i) { | |||
314 | if (PN.getIncomingBlock(i) != &OldExitingBB) | |||
315 | continue; | |||
316 | ||||
317 | Value *Incoming = PN.removeIncomingValue(i); | |||
318 | NewPN->addIncoming(Incoming, &OldPH); | |||
319 | } | |||
320 | ||||
321 | // Now replace the old PHI with the new one and wire the old one in as an | |||
322 | // input to the new one. | |||
323 | PN.replaceAllUsesWith(NewPN); | |||
324 | NewPN->addIncoming(&PN, &ExitBB); | |||
325 | } | |||
326 | } | |||
327 | ||||
328 | /// Unswitch a trivial branch if the condition is loop invariant. | |||
329 | /// | |||
330 | /// This routine should only be called when loop code leading to the branch has | |||
331 | /// been validated as trivial (no side effects). This routine checks if the | |||
332 | /// condition is invariant and one of the successors is a loop exit. This | |||
333 | /// allows us to unswitch without duplicating the loop, making it trivial. | |||
334 | /// | |||
335 | /// If this routine fails to unswitch the branch it returns false. | |||
336 | /// | |||
337 | /// If the branch can be unswitched, this routine splits the preheader and | |||
338 | /// hoists the branch above that split. Preserves loop simplified form | |||
339 | /// (splitting the exit block as necessary). It simplifies the branch within | |||
340 | /// the loop to an unconditional branch but doesn't remove it entirely. Further | |||
341 | /// cleanup can be done with some simplify-cfg like pass. | |||
342 | static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT, | |||
343 | LoopInfo &LI) { | |||
344 | assert(BI.isConditional() && "Can only unswitch a conditional branch!")(static_cast <bool> (BI.isConditional() && "Can only unswitch a conditional branch!" ) ? void (0) : __assert_fail ("BI.isConditional() && \"Can only unswitch a conditional branch!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 344, __extension__ __PRETTY_FUNCTION__)); | |||
345 | DEBUG(dbgs() << " Trying to unswitch branch: " << BI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch branch: " << BI << "\n"; } } while (false); | |||
346 | ||||
347 | Value *LoopCond = BI.getCondition(); | |||
348 | ||||
349 | // Need a trivial loop condition to unswitch. | |||
350 | if (!L.isLoopInvariant(LoopCond)) | |||
351 | return false; | |||
352 | ||||
353 | // FIXME: We should compute this once at the start and update it! | |||
354 | SmallVector<BasicBlock *, 16> ExitBlocks; | |||
355 | L.getExitBlocks(ExitBlocks); | |||
356 | SmallPtrSet<BasicBlock *, 16> ExitBlockSet(ExitBlocks.begin(), | |||
357 | ExitBlocks.end()); | |||
358 | ||||
359 | // Check to see if a successor of the branch is guaranteed to | |||
360 | // exit through a unique exit block without having any | |||
361 | // side-effects. If so, determine the value of Cond that causes | |||
362 | // it to do this. | |||
363 | ConstantInt *CondVal = ConstantInt::getTrue(BI.getContext()); | |||
364 | ConstantInt *Replacement = ConstantInt::getFalse(BI.getContext()); | |||
365 | int LoopExitSuccIdx = 0; | |||
366 | auto *LoopExitBB = BI.getSuccessor(0); | |||
367 | if (!ExitBlockSet.count(LoopExitBB)) { | |||
368 | std::swap(CondVal, Replacement); | |||
369 | LoopExitSuccIdx = 1; | |||
370 | LoopExitBB = BI.getSuccessor(1); | |||
371 | if (!ExitBlockSet.count(LoopExitBB)) | |||
372 | return false; | |||
373 | } | |||
374 | auto *ContinueBB = BI.getSuccessor(1 - LoopExitSuccIdx); | |||
375 | assert(L.contains(ContinueBB) &&(static_cast <bool> (L.contains(ContinueBB) && "Cannot have both successors exit and still be in the loop!" ) ? void (0) : __assert_fail ("L.contains(ContinueBB) && \"Cannot have both successors exit and still be in the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 376, __extension__ __PRETTY_FUNCTION__)) | |||
376 | "Cannot have both successors exit and still be in the loop!")(static_cast <bool> (L.contains(ContinueBB) && "Cannot have both successors exit and still be in the loop!" ) ? void (0) : __assert_fail ("L.contains(ContinueBB) && \"Cannot have both successors exit and still be in the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 376, __extension__ __PRETTY_FUNCTION__)); | |||
377 | ||||
378 | auto *ParentBB = BI.getParent(); | |||
379 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, *LoopExitBB)) | |||
380 | return false; | |||
381 | ||||
382 | DEBUG(dbgs() << " unswitching trivial branch when: " << CondValdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " unswitching trivial branch when: " << CondVal << " == " << LoopCond << "\n" ; } } while (false) | |||
383 | << " == " << LoopCond << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " unswitching trivial branch when: " << CondVal << " == " << LoopCond << "\n" ; } } while (false); | |||
384 | ||||
385 | // Split the preheader, so that we know that there is a safe place to insert | |||
386 | // the conditional branch. We will change the preheader to have a conditional | |||
387 | // branch on LoopCond. | |||
388 | BasicBlock *OldPH = L.getLoopPreheader(); | |||
389 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI); | |||
390 | ||||
391 | // Now that we have a place to insert the conditional branch, create a place | |||
392 | // to branch to: this is the exit block out of the loop that we are | |||
393 | // unswitching. We need to split this if there are other loop predecessors. | |||
394 | // Because the loop is in simplified form, *any* other predecessor is enough. | |||
395 | BasicBlock *UnswitchedBB; | |||
396 | if (BasicBlock *PredBB = LoopExitBB->getUniquePredecessor()) { | |||
397 | (void)PredBB; | |||
398 | assert(PredBB == BI.getParent() &&(static_cast <bool> (PredBB == BI.getParent() && "A branch's parent isn't a predecessor!") ? void (0) : __assert_fail ("PredBB == BI.getParent() && \"A branch's parent isn't a predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 399, __extension__ __PRETTY_FUNCTION__)) | |||
399 | "A branch's parent isn't a predecessor!")(static_cast <bool> (PredBB == BI.getParent() && "A branch's parent isn't a predecessor!") ? void (0) : __assert_fail ("PredBB == BI.getParent() && \"A branch's parent isn't a predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 399, __extension__ __PRETTY_FUNCTION__)); | |||
400 | UnswitchedBB = LoopExitBB; | |||
401 | } else { | |||
402 | UnswitchedBB = SplitBlock(LoopExitBB, &LoopExitBB->front(), &DT, &LI); | |||
403 | } | |||
404 | ||||
405 | // Now splice the branch to gate reaching the new preheader and re-point its | |||
406 | // successors. | |||
407 | OldPH->getInstList().splice(std::prev(OldPH->end()), | |||
408 | BI.getParent()->getInstList(), BI); | |||
409 | OldPH->getTerminator()->eraseFromParent(); | |||
410 | BI.setSuccessor(LoopExitSuccIdx, UnswitchedBB); | |||
411 | BI.setSuccessor(1 - LoopExitSuccIdx, NewPH); | |||
412 | ||||
413 | // Create a new unconditional branch that will continue the loop as a new | |||
414 | // terminator. | |||
415 | BranchInst::Create(ContinueBB, ParentBB); | |||
416 | ||||
417 | // Rewrite the relevant PHI nodes. | |||
418 | if (UnswitchedBB == LoopExitBB) | |||
419 | rewritePHINodesForUnswitchedExitBlock(*UnswitchedBB, *ParentBB, *OldPH); | |||
420 | else | |||
421 | rewritePHINodesForExitAndUnswitchedBlocks(*LoopExitBB, *UnswitchedBB, | |||
422 | *ParentBB, *OldPH); | |||
423 | ||||
424 | // Now we need to update the dominator tree. | |||
425 | updateDTAfterUnswitch(UnswitchedBB, OldPH, DT); | |||
426 | // But if we split something off of the loop exit block then we also removed | |||
427 | // one of the predecessors for the loop exit block and may need to update its | |||
428 | // idom. | |||
429 | if (UnswitchedBB != LoopExitBB) | |||
430 | updateIDomWithKnownCommonDominator(LoopExitBB, L.getHeader(), DT); | |||
431 | ||||
432 | // Since this is an i1 condition we can also trivially replace uses of it | |||
433 | // within the loop with a constant. | |||
434 | replaceLoopUsesWithConstant(L, *LoopCond, *Replacement); | |||
435 | ||||
436 | ++NumTrivial; | |||
437 | ++NumBranches; | |||
438 | return true; | |||
439 | } | |||
440 | ||||
441 | /// Unswitch a trivial switch if the condition is loop invariant. | |||
442 | /// | |||
443 | /// This routine should only be called when loop code leading to the switch has | |||
444 | /// been validated as trivial (no side effects). This routine checks if the | |||
445 | /// condition is invariant and that at least one of the successors is a loop | |||
446 | /// exit. This allows us to unswitch without duplicating the loop, making it | |||
447 | /// trivial. | |||
448 | /// | |||
449 | /// If this routine fails to unswitch the switch it returns false. | |||
450 | /// | |||
451 | /// If the switch can be unswitched, this routine splits the preheader and | |||
452 | /// copies the switch above that split. If the default case is one of the | |||
453 | /// exiting cases, it copies the non-exiting cases and points them at the new | |||
454 | /// preheader. If the default case is not exiting, it copies the exiting cases | |||
455 | /// and points the default at the preheader. It preserves loop simplified form | |||
456 | /// (splitting the exit blocks as necessary). It simplifies the switch within | |||
457 | /// the loop by removing now-dead cases. If the default case is one of those | |||
458 | /// unswitched, it replaces its destination with a new basic block containing | |||
459 | /// only unreachable. Such basic blocks, while technically loop exits, are not | |||
460 | /// considered for unswitching so this is a stable transform and the same | |||
461 | /// switch will not be revisited. If after unswitching there is only a single | |||
462 | /// in-loop successor, the switch is further simplified to an unconditional | |||
463 | /// branch. Still more cleanup can be done with some simplify-cfg like pass. | |||
464 | static bool unswitchTrivialSwitch(Loop &L, SwitchInst &SI, DominatorTree &DT, | |||
465 | LoopInfo &LI) { | |||
466 | DEBUG(dbgs() << " Trying to unswitch switch: " << SI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch switch: " << SI << "\n"; } } while (false); | |||
467 | Value *LoopCond = SI.getCondition(); | |||
468 | ||||
469 | // If this isn't switching on an invariant condition, we can't unswitch it. | |||
470 | if (!L.isLoopInvariant(LoopCond)) | |||
471 | return false; | |||
472 | ||||
473 | auto *ParentBB = SI.getParent(); | |||
474 | ||||
475 | // FIXME: We should compute this once at the start and update it! | |||
476 | SmallVector<BasicBlock *, 16> ExitBlocks; | |||
477 | L.getExitBlocks(ExitBlocks); | |||
478 | SmallPtrSet<BasicBlock *, 16> ExitBlockSet(ExitBlocks.begin(), | |||
479 | ExitBlocks.end()); | |||
480 | ||||
481 | SmallVector<int, 4> ExitCaseIndices; | |||
482 | for (auto Case : SI.cases()) { | |||
483 | auto *SuccBB = Case.getCaseSuccessor(); | |||
484 | if (ExitBlockSet.count(SuccBB) && | |||
485 | areLoopExitPHIsLoopInvariant(L, *ParentBB, *SuccBB)) | |||
486 | ExitCaseIndices.push_back(Case.getCaseIndex()); | |||
487 | } | |||
488 | BasicBlock *DefaultExitBB = nullptr; | |||
489 | if (ExitBlockSet.count(SI.getDefaultDest()) && | |||
490 | areLoopExitPHIsLoopInvariant(L, *ParentBB, *SI.getDefaultDest()) && | |||
491 | !isa<UnreachableInst>(SI.getDefaultDest()->getTerminator())) | |||
492 | DefaultExitBB = SI.getDefaultDest(); | |||
493 | else if (ExitCaseIndices.empty()) | |||
494 | return false; | |||
495 | ||||
496 | DEBUG(dbgs() << " unswitching trivial cases...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " unswitching trivial cases...\n" ; } } while (false); | |||
497 | ||||
498 | SmallVector<std::pair<ConstantInt *, BasicBlock *>, 4> ExitCases; | |||
499 | ExitCases.reserve(ExitCaseIndices.size()); | |||
500 | // We walk the case indices backwards so that we remove the last case first | |||
501 | // and don't disrupt the earlier indices. | |||
502 | for (unsigned Index : reverse(ExitCaseIndices)) { | |||
503 | auto CaseI = SI.case_begin() + Index; | |||
504 | // Save the value of this case. | |||
505 | ExitCases.push_back({CaseI->getCaseValue(), CaseI->getCaseSuccessor()}); | |||
506 | // Delete the unswitched cases. | |||
507 | SI.removeCase(CaseI); | |||
508 | } | |||
509 | ||||
510 | // Check if after this all of the remaining cases point at the same | |||
511 | // successor. | |||
512 | BasicBlock *CommonSuccBB = nullptr; | |||
513 | if (SI.getNumCases() > 0 && | |||
514 | std::all_of(std::next(SI.case_begin()), SI.case_end(), | |||
515 | [&SI](const SwitchInst::CaseHandle &Case) { | |||
516 | return Case.getCaseSuccessor() == | |||
517 | SI.case_begin()->getCaseSuccessor(); | |||
518 | })) | |||
519 | CommonSuccBB = SI.case_begin()->getCaseSuccessor(); | |||
520 | ||||
521 | if (DefaultExitBB) { | |||
522 | // We can't remove the default edge so replace it with an edge to either | |||
523 | // the single common remaining successor (if we have one) or an unreachable | |||
524 | // block. | |||
525 | if (CommonSuccBB) { | |||
526 | SI.setDefaultDest(CommonSuccBB); | |||
527 | } else { | |||
528 | BasicBlock *UnreachableBB = BasicBlock::Create( | |||
529 | ParentBB->getContext(), | |||
530 | Twine(ParentBB->getName()) + ".unreachable_default", | |||
531 | ParentBB->getParent()); | |||
532 | new UnreachableInst(ParentBB->getContext(), UnreachableBB); | |||
533 | SI.setDefaultDest(UnreachableBB); | |||
534 | DT.addNewBlock(UnreachableBB, ParentBB); | |||
535 | } | |||
536 | } else { | |||
537 | // If we're not unswitching the default, we need it to match any cases to | |||
538 | // have a common successor or if we have no cases it is the common | |||
539 | // successor. | |||
540 | if (SI.getNumCases() == 0) | |||
541 | CommonSuccBB = SI.getDefaultDest(); | |||
542 | else if (SI.getDefaultDest() != CommonSuccBB) | |||
543 | CommonSuccBB = nullptr; | |||
544 | } | |||
545 | ||||
546 | // Split the preheader, so that we know that there is a safe place to insert | |||
547 | // the switch. | |||
548 | BasicBlock *OldPH = L.getLoopPreheader(); | |||
549 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI); | |||
550 | OldPH->getTerminator()->eraseFromParent(); | |||
551 | ||||
552 | // Now add the unswitched switch. | |||
553 | auto *NewSI = SwitchInst::Create(LoopCond, NewPH, ExitCases.size(), OldPH); | |||
554 | ||||
555 | // Rewrite the IR for the unswitched basic blocks. This requires two steps. | |||
556 | // First, we split any exit blocks with remaining in-loop predecessors. Then | |||
557 | // we update the PHIs in one of two ways depending on if there was a split. | |||
558 | // We walk in reverse so that we split in the same order as the cases | |||
559 | // appeared. This is purely for convenience of reading the resulting IR, but | |||
560 | // it doesn't cost anything really. | |||
561 | SmallPtrSet<BasicBlock *, 2> UnswitchedExitBBs; | |||
562 | SmallDenseMap<BasicBlock *, BasicBlock *, 2> SplitExitBBMap; | |||
563 | // Handle the default exit if necessary. | |||
564 | // FIXME: It'd be great if we could merge this with the loop below but LLVM's | |||
565 | // ranges aren't quite powerful enough yet. | |||
566 | if (DefaultExitBB) { | |||
567 | if (pred_empty(DefaultExitBB)) { | |||
568 | UnswitchedExitBBs.insert(DefaultExitBB); | |||
569 | rewritePHINodesForUnswitchedExitBlock(*DefaultExitBB, *ParentBB, *OldPH); | |||
570 | } else { | |||
571 | auto *SplitBB = | |||
572 | SplitBlock(DefaultExitBB, &DefaultExitBB->front(), &DT, &LI); | |||
573 | rewritePHINodesForExitAndUnswitchedBlocks(*DefaultExitBB, *SplitBB, | |||
574 | *ParentBB, *OldPH); | |||
575 | updateIDomWithKnownCommonDominator(DefaultExitBB, L.getHeader(), DT); | |||
576 | DefaultExitBB = SplitExitBBMap[DefaultExitBB] = SplitBB; | |||
577 | } | |||
578 | } | |||
579 | // Note that we must use a reference in the for loop so that we update the | |||
580 | // container. | |||
581 | for (auto &CasePair : reverse(ExitCases)) { | |||
582 | // Grab a reference to the exit block in the pair so that we can update it. | |||
583 | BasicBlock *ExitBB = CasePair.second; | |||
584 | ||||
585 | // If this case is the last edge into the exit block, we can simply reuse it | |||
586 | // as it will no longer be a loop exit. No mapping necessary. | |||
587 | if (pred_empty(ExitBB)) { | |||
588 | // Only rewrite once. | |||
589 | if (UnswitchedExitBBs.insert(ExitBB).second) | |||
590 | rewritePHINodesForUnswitchedExitBlock(*ExitBB, *ParentBB, *OldPH); | |||
591 | continue; | |||
592 | } | |||
593 | ||||
594 | // Otherwise we need to split the exit block so that we retain an exit | |||
595 | // block from the loop and a target for the unswitched condition. | |||
596 | BasicBlock *&SplitExitBB = SplitExitBBMap[ExitBB]; | |||
597 | if (!SplitExitBB) { | |||
598 | // If this is the first time we see this, do the split and remember it. | |||
599 | SplitExitBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI); | |||
600 | rewritePHINodesForExitAndUnswitchedBlocks(*ExitBB, *SplitExitBB, | |||
601 | *ParentBB, *OldPH); | |||
602 | updateIDomWithKnownCommonDominator(ExitBB, L.getHeader(), DT); | |||
603 | } | |||
604 | // Update the case pair to point to the split block. | |||
605 | CasePair.second = SplitExitBB; | |||
606 | } | |||
607 | ||||
608 | // Now add the unswitched cases. We do this in reverse order as we built them | |||
609 | // in reverse order. | |||
610 | for (auto CasePair : reverse(ExitCases)) { | |||
611 | ConstantInt *CaseVal = CasePair.first; | |||
612 | BasicBlock *UnswitchedBB = CasePair.second; | |||
613 | ||||
614 | NewSI->addCase(CaseVal, UnswitchedBB); | |||
615 | updateDTAfterUnswitch(UnswitchedBB, OldPH, DT); | |||
616 | } | |||
617 | ||||
618 | // If the default was unswitched, re-point it and add explicit cases for | |||
619 | // entering the loop. | |||
620 | if (DefaultExitBB) { | |||
621 | NewSI->setDefaultDest(DefaultExitBB); | |||
622 | updateDTAfterUnswitch(DefaultExitBB, OldPH, DT); | |||
623 | ||||
624 | // We removed all the exit cases, so we just copy the cases to the | |||
625 | // unswitched switch. | |||
626 | for (auto Case : SI.cases()) | |||
627 | NewSI->addCase(Case.getCaseValue(), NewPH); | |||
628 | } | |||
629 | ||||
630 | // If we ended up with a common successor for every path through the switch | |||
631 | // after unswitching, rewrite it to an unconditional branch to make it easy | |||
632 | // to recognize. Otherwise we potentially have to recognize the default case | |||
633 | // pointing at unreachable and other complexity. | |||
634 | if (CommonSuccBB) { | |||
635 | BasicBlock *BB = SI.getParent(); | |||
636 | SI.eraseFromParent(); | |||
637 | BranchInst::Create(CommonSuccBB, BB); | |||
638 | } | |||
639 | ||||
640 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 640, __extension__ __PRETTY_FUNCTION__)); | |||
641 | ++NumTrivial; | |||
642 | ++NumSwitches; | |||
643 | return true; | |||
644 | } | |||
645 | ||||
646 | /// This routine scans the loop to find a branch or switch which occurs before | |||
647 | /// any side effects occur. These can potentially be unswitched without | |||
648 | /// duplicating the loop. If a branch or switch is successfully unswitched the | |||
649 | /// scanning continues to see if subsequent branches or switches have become | |||
650 | /// trivial. Once all trivial candidates have been unswitched, this routine | |||
651 | /// returns. | |||
652 | /// | |||
653 | /// The return value indicates whether anything was unswitched (and therefore | |||
654 | /// changed). | |||
655 | static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT, | |||
656 | LoopInfo &LI) { | |||
657 | bool Changed = false; | |||
658 | ||||
659 | // If loop header has only one reachable successor we should keep looking for | |||
660 | // trivial condition candidates in the successor as well. An alternative is | |||
661 | // to constant fold conditions and merge successors into loop header (then we | |||
662 | // only need to check header's terminator). The reason for not doing this in | |||
663 | // LoopUnswitch pass is that it could potentially break LoopPassManager's | |||
664 | // invariants. Folding dead branches could either eliminate the current loop | |||
665 | // or make other loops unreachable. LCSSA form might also not be preserved | |||
666 | // after deleting branches. The following code keeps traversing loop header's | |||
667 | // successors until it finds the trivial condition candidate (condition that | |||
668 | // is not a constant). Since unswitching generates branches with constant | |||
669 | // conditions, this scenario could be very common in practice. | |||
670 | BasicBlock *CurrentBB = L.getHeader(); | |||
671 | SmallPtrSet<BasicBlock *, 8> Visited; | |||
672 | Visited.insert(CurrentBB); | |||
673 | do { | |||
674 | // Check if there are any side-effecting instructions (e.g. stores, calls, | |||
675 | // volatile loads) in the part of the loop that the code *would* execute | |||
676 | // without unswitching. | |||
677 | if (llvm::any_of(*CurrentBB, | |||
678 | [](Instruction &I) { return I.mayHaveSideEffects(); })) | |||
679 | return Changed; | |||
680 | ||||
681 | TerminatorInst *CurrentTerm = CurrentBB->getTerminator(); | |||
682 | ||||
683 | if (auto *SI = dyn_cast<SwitchInst>(CurrentTerm)) { | |||
684 | // Don't bother trying to unswitch past a switch with a constant | |||
685 | // condition. This should be removed prior to running this pass by | |||
686 | // simplify-cfg. | |||
687 | if (isa<Constant>(SI->getCondition())) | |||
688 | return Changed; | |||
689 | ||||
690 | if (!unswitchTrivialSwitch(L, *SI, DT, LI)) | |||
691 | // Coludn't unswitch this one so we're done. | |||
692 | return Changed; | |||
693 | ||||
694 | // Mark that we managed to unswitch something. | |||
695 | Changed = true; | |||
696 | ||||
697 | // If unswitching turned the terminator into an unconditional branch then | |||
698 | // we can continue. The unswitching logic specifically works to fold any | |||
699 | // cases it can into an unconditional branch to make it easier to | |||
700 | // recognize here. | |||
701 | auto *BI = dyn_cast<BranchInst>(CurrentBB->getTerminator()); | |||
702 | if (!BI || BI->isConditional()) | |||
703 | return Changed; | |||
704 | ||||
705 | CurrentBB = BI->getSuccessor(0); | |||
706 | continue; | |||
707 | } | |||
708 | ||||
709 | auto *BI = dyn_cast<BranchInst>(CurrentTerm); | |||
710 | if (!BI) | |||
711 | // We do not understand other terminator instructions. | |||
712 | return Changed; | |||
713 | ||||
714 | // Don't bother trying to unswitch past an unconditional branch or a branch | |||
715 | // with a constant value. These should be removed by simplify-cfg prior to | |||
716 | // running this pass. | |||
717 | if (!BI->isConditional() || isa<Constant>(BI->getCondition())) | |||
718 | return Changed; | |||
719 | ||||
720 | // Found a trivial condition candidate: non-foldable conditional branch. If | |||
721 | // we fail to unswitch this, we can't do anything else that is trivial. | |||
722 | if (!unswitchTrivialBranch(L, *BI, DT, LI)) | |||
723 | return Changed; | |||
724 | ||||
725 | // Mark that we managed to unswitch something. | |||
726 | Changed = true; | |||
727 | ||||
728 | // We unswitched the branch. This should always leave us with an | |||
729 | // unconditional branch that we can follow now. | |||
730 | BI = cast<BranchInst>(CurrentBB->getTerminator()); | |||
731 | assert(!BI->isConditional() &&(static_cast <bool> (!BI->isConditional() && "Cannot form a conditional branch by unswitching1") ? void ( 0) : __assert_fail ("!BI->isConditional() && \"Cannot form a conditional branch by unswitching1\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 732, __extension__ __PRETTY_FUNCTION__)) | |||
732 | "Cannot form a conditional branch by unswitching1")(static_cast <bool> (!BI->isConditional() && "Cannot form a conditional branch by unswitching1") ? void ( 0) : __assert_fail ("!BI->isConditional() && \"Cannot form a conditional branch by unswitching1\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 732, __extension__ __PRETTY_FUNCTION__)); | |||
733 | CurrentBB = BI->getSuccessor(0); | |||
734 | ||||
735 | // When continuing, if we exit the loop or reach a previous visited block, | |||
736 | // then we can not reach any trivial condition candidates (unfoldable | |||
737 | // branch instructions or switch instructions) and no unswitch can happen. | |||
738 | } while (L.contains(CurrentBB) && Visited.insert(CurrentBB).second); | |||
739 | ||||
740 | return Changed; | |||
741 | } | |||
742 | ||||
743 | /// Build the cloned blocks for an unswitched copy of the given loop. | |||
744 | /// | |||
745 | /// The cloned blocks are inserted before the loop preheader (`LoopPH`) and | |||
746 | /// after the split block (`SplitBB`) that will be used to select between the | |||
747 | /// cloned and original loop. | |||
748 | /// | |||
749 | /// This routine handles cloning all of the necessary loop blocks and exit | |||
750 | /// blocks including rewriting their instructions and the relevant PHI nodes. | |||
751 | /// It skips loop and exit blocks that are not necessary based on the provided | |||
752 | /// set. It also correctly creates the unconditional branch in the cloned | |||
753 | /// unswitched parent block to only point at the unswitched successor. | |||
754 | /// | |||
755 | /// This does not handle most of the necessary updates to `LoopInfo`. Only exit | |||
756 | /// block splitting is correctly reflected in `LoopInfo`, essentially all of | |||
757 | /// the cloned blocks (and their loops) are left without full `LoopInfo` | |||
758 | /// updates. This also doesn't fully update `DominatorTree`. It adds the cloned | |||
759 | /// blocks to them but doesn't create the cloned `DominatorTree` structure and | |||
760 | /// instead the caller must recompute an accurate DT. It *does* correctly | |||
761 | /// update the `AssumptionCache` provided in `AC`. | |||
762 | static BasicBlock *buildClonedLoopBlocks( | |||
763 | Loop &L, BasicBlock *LoopPH, BasicBlock *SplitBB, | |||
764 | ArrayRef<BasicBlock *> ExitBlocks, BasicBlock *ParentBB, | |||
765 | BasicBlock *UnswitchedSuccBB, BasicBlock *ContinueSuccBB, | |||
766 | const SmallPtrSetImpl<BasicBlock *> &SkippedLoopAndExitBlocks, | |||
767 | ValueToValueMapTy &VMap, AssumptionCache &AC, DominatorTree &DT, | |||
768 | LoopInfo &LI) { | |||
769 | SmallVector<BasicBlock *, 4> NewBlocks; | |||
770 | NewBlocks.reserve(L.getNumBlocks() + ExitBlocks.size()); | |||
771 | ||||
772 | // We will need to clone a bunch of blocks, wrap up the clone operation in | |||
773 | // a helper. | |||
774 | auto CloneBlock = [&](BasicBlock *OldBB) { | |||
775 | // Clone the basic block and insert it before the new preheader. | |||
776 | BasicBlock *NewBB = CloneBasicBlock(OldBB, VMap, ".us", OldBB->getParent()); | |||
777 | NewBB->moveBefore(LoopPH); | |||
778 | ||||
779 | // Record this block and the mapping. | |||
780 | NewBlocks.push_back(NewBB); | |||
781 | VMap[OldBB] = NewBB; | |||
782 | ||||
783 | // Add the block to the domtree. We'll move it to the correct position | |||
784 | // below. | |||
785 | DT.addNewBlock(NewBB, SplitBB); | |||
786 | ||||
787 | return NewBB; | |||
788 | }; | |||
789 | ||||
790 | // First, clone the preheader. | |||
791 | auto *ClonedPH = CloneBlock(LoopPH); | |||
792 | ||||
793 | // Then clone all the loop blocks, skipping the ones that aren't necessary. | |||
794 | for (auto *LoopBB : L.blocks()) | |||
795 | if (!SkippedLoopAndExitBlocks.count(LoopBB)) | |||
796 | CloneBlock(LoopBB); | |||
797 | ||||
798 | // Split all the loop exit edges so that when we clone the exit blocks, if | |||
799 | // any of the exit blocks are *also* a preheader for some other loop, we | |||
800 | // don't create multiple predecessors entering the loop header. | |||
801 | for (auto *ExitBB : ExitBlocks) { | |||
802 | if (SkippedLoopAndExitBlocks.count(ExitBB)) | |||
803 | continue; | |||
804 | ||||
805 | // When we are going to clone an exit, we don't need to clone all the | |||
806 | // instructions in the exit block and we want to ensure we have an easy | |||
807 | // place to merge the CFG, so split the exit first. This is always safe to | |||
808 | // do because there cannot be any non-loop predecessors of a loop exit in | |||
809 | // loop simplified form. | |||
810 | auto *MergeBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI); | |||
811 | ||||
812 | // Rearrange the names to make it easier to write test cases by having the | |||
813 | // exit block carry the suffix rather than the merge block carrying the | |||
814 | // suffix. | |||
815 | MergeBB->takeName(ExitBB); | |||
816 | ExitBB->setName(Twine(MergeBB->getName()) + ".split"); | |||
817 | ||||
818 | // Now clone the original exit block. | |||
819 | auto *ClonedExitBB = CloneBlock(ExitBB); | |||
820 | assert(ClonedExitBB->getTerminator()->getNumSuccessors() == 1 &&(static_cast <bool> (ClonedExitBB->getTerminator()-> getNumSuccessors() == 1 && "Exit block should have been split to have one successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 821, __extension__ __PRETTY_FUNCTION__)) | |||
821 | "Exit block should have been split to have one successor!")(static_cast <bool> (ClonedExitBB->getTerminator()-> getNumSuccessors() == 1 && "Exit block should have been split to have one successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 821, __extension__ __PRETTY_FUNCTION__)); | |||
822 | assert(ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB &&(static_cast <bool> (ClonedExitBB->getTerminator()-> getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 823, __extension__ __PRETTY_FUNCTION__)) | |||
823 | "Cloned exit block has the wrong successor!")(static_cast <bool> (ClonedExitBB->getTerminator()-> getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 823, __extension__ __PRETTY_FUNCTION__)); | |||
824 | ||||
825 | // Move the merge block's idom to be the split point as one exit is | |||
826 | // dominated by one header, and the other by another, so we know the split | |||
827 | // point dominates both. While the dominator tree isn't fully accurate, we | |||
828 | // want sub-trees within the original loop to be correctly reflect | |||
829 | // dominance within that original loop (at least) and that requires moving | |||
830 | // the merge block out of that subtree. | |||
831 | // FIXME: This is very brittle as we essentially have a partial contract on | |||
832 | // the dominator tree. We really need to instead update it and keep it | |||
833 | // valid or stop relying on it. | |||
834 | DT.changeImmediateDominator(MergeBB, SplitBB); | |||
835 | ||||
836 | // Remap any cloned instructions and create a merge phi node for them. | |||
837 | for (auto ZippedInsts : llvm::zip_first( | |||
838 | llvm::make_range(ExitBB->begin(), std::prev(ExitBB->end())), | |||
839 | llvm::make_range(ClonedExitBB->begin(), | |||
840 | std::prev(ClonedExitBB->end())))) { | |||
841 | Instruction &I = std::get<0>(ZippedInsts); | |||
842 | Instruction &ClonedI = std::get<1>(ZippedInsts); | |||
843 | ||||
844 | // The only instructions in the exit block should be PHI nodes and | |||
845 | // potentially a landing pad. | |||
846 | assert((static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 848, __extension__ __PRETTY_FUNCTION__)) | |||
847 | (isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) &&(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 848, __extension__ __PRETTY_FUNCTION__)) | |||
848 | "Bad instruction in exit block!")(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 848, __extension__ __PRETTY_FUNCTION__)); | |||
849 | // We should have a value map between the instruction and its clone. | |||
850 | assert(VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!")(static_cast <bool> (VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!") ? void (0) : __assert_fail ("VMap.lookup(&I) == &ClonedI && \"Mismatch in the value map!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 850, __extension__ __PRETTY_FUNCTION__)); | |||
851 | ||||
852 | auto *MergePN = | |||
853 | PHINode::Create(I.getType(), /*NumReservedValues*/ 2, ".us-phi", | |||
854 | &*MergeBB->getFirstInsertionPt()); | |||
855 | I.replaceAllUsesWith(MergePN); | |||
856 | MergePN->addIncoming(&I, ExitBB); | |||
857 | MergePN->addIncoming(&ClonedI, ClonedExitBB); | |||
858 | } | |||
859 | } | |||
860 | ||||
861 | // Rewrite the instructions in the cloned blocks to refer to the instructions | |||
862 | // in the cloned blocks. We have to do this as a second pass so that we have | |||
863 | // everything available. Also, we have inserted new instructions which may | |||
864 | // include assume intrinsics, so we update the assumption cache while | |||
865 | // processing this. | |||
866 | for (auto *ClonedBB : NewBlocks) | |||
867 | for (Instruction &I : *ClonedBB) { | |||
868 | RemapInstruction(&I, VMap, | |||
869 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | |||
870 | if (auto *II = dyn_cast<IntrinsicInst>(&I)) | |||
871 | if (II->getIntrinsicID() == Intrinsic::assume) | |||
872 | AC.registerAssumption(II); | |||
873 | } | |||
874 | ||||
875 | // Remove the cloned parent as a predecessor of the cloned continue successor | |||
876 | // if we did in fact clone it. | |||
877 | auto *ClonedParentBB = cast<BasicBlock>(VMap.lookup(ParentBB)); | |||
878 | if (auto *ClonedContinueSuccBB = | |||
879 | cast_or_null<BasicBlock>(VMap.lookup(ContinueSuccBB))) | |||
880 | ClonedContinueSuccBB->removePredecessor(ClonedParentBB, | |||
881 | /*DontDeleteUselessPHIs*/ true); | |||
882 | // Replace the cloned branch with an unconditional branch to the cloneed | |||
883 | // unswitched successor. | |||
884 | auto *ClonedSuccBB = cast<BasicBlock>(VMap.lookup(UnswitchedSuccBB)); | |||
885 | ClonedParentBB->getTerminator()->eraseFromParent(); | |||
886 | BranchInst::Create(ClonedSuccBB, ClonedParentBB); | |||
887 | ||||
888 | // Update any PHI nodes in the cloned successors of the skipped blocks to not | |||
889 | // have spurious incoming values. | |||
890 | for (auto *LoopBB : L.blocks()) | |||
891 | if (SkippedLoopAndExitBlocks.count(LoopBB)) | |||
892 | for (auto *SuccBB : successors(LoopBB)) | |||
893 | if (auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB))) | |||
894 | for (PHINode &PN : ClonedSuccBB->phis()) | |||
895 | PN.removeIncomingValue(LoopBB, /*DeletePHIIfEmpty*/ false); | |||
896 | ||||
897 | return ClonedPH; | |||
898 | } | |||
899 | ||||
900 | /// Recursively clone the specified loop and all of its children. | |||
901 | /// | |||
902 | /// The target parent loop for the clone should be provided, or can be null if | |||
903 | /// the clone is a top-level loop. While cloning, all the blocks are mapped | |||
904 | /// with the provided value map. The entire original loop must be present in | |||
905 | /// the value map. The cloned loop is returned. | |||
906 | static Loop *cloneLoopNest(Loop &OrigRootL, Loop *RootParentL, | |||
907 | const ValueToValueMapTy &VMap, LoopInfo &LI) { | |||
908 | auto AddClonedBlocksToLoop = [&](Loop &OrigL, Loop &ClonedL) { | |||
909 | assert(ClonedL.getBlocks().empty() && "Must start with an empty loop!")(static_cast <bool> (ClonedL.getBlocks().empty() && "Must start with an empty loop!") ? void (0) : __assert_fail ("ClonedL.getBlocks().empty() && \"Must start with an empty loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 909, __extension__ __PRETTY_FUNCTION__)); | |||
910 | ClonedL.reserveBlocks(OrigL.getNumBlocks()); | |||
911 | for (auto *BB : OrigL.blocks()) { | |||
912 | auto *ClonedBB = cast<BasicBlock>(VMap.lookup(BB)); | |||
913 | ClonedL.addBlockEntry(ClonedBB); | |||
914 | if (LI.getLoopFor(BB) == &OrigL) { | |||
915 | assert(!LI.getLoopFor(ClonedBB) &&(static_cast <bool> (!LI.getLoopFor(ClonedBB) && "Should not have an existing loop for this block!") ? void ( 0) : __assert_fail ("!LI.getLoopFor(ClonedBB) && \"Should not have an existing loop for this block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 916, __extension__ __PRETTY_FUNCTION__)) | |||
916 | "Should not have an existing loop for this block!")(static_cast <bool> (!LI.getLoopFor(ClonedBB) && "Should not have an existing loop for this block!") ? void ( 0) : __assert_fail ("!LI.getLoopFor(ClonedBB) && \"Should not have an existing loop for this block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 916, __extension__ __PRETTY_FUNCTION__)); | |||
917 | LI.changeLoopFor(ClonedBB, &ClonedL); | |||
918 | } | |||
919 | } | |||
920 | }; | |||
921 | ||||
922 | // We specially handle the first loop because it may get cloned into | |||
923 | // a different parent and because we most commonly are cloning leaf loops. | |||
924 | Loop *ClonedRootL = LI.AllocateLoop(); | |||
925 | if (RootParentL) | |||
926 | RootParentL->addChildLoop(ClonedRootL); | |||
927 | else | |||
928 | LI.addTopLevelLoop(ClonedRootL); | |||
929 | AddClonedBlocksToLoop(OrigRootL, *ClonedRootL); | |||
930 | ||||
931 | if (OrigRootL.empty()) | |||
932 | return ClonedRootL; | |||
933 | ||||
934 | // If we have a nest, we can quickly clone the entire loop nest using an | |||
935 | // iterative approach because it is a tree. We keep the cloned parent in the | |||
936 | // data structure to avoid repeatedly querying through a map to find it. | |||
937 | SmallVector<std::pair<Loop *, Loop *>, 16> LoopsToClone; | |||
938 | // Build up the loops to clone in reverse order as we'll clone them from the | |||
939 | // back. | |||
940 | for (Loop *ChildL : llvm::reverse(OrigRootL)) | |||
941 | LoopsToClone.push_back({ClonedRootL, ChildL}); | |||
942 | do { | |||
943 | Loop *ClonedParentL, *L; | |||
944 | std::tie(ClonedParentL, L) = LoopsToClone.pop_back_val(); | |||
945 | Loop *ClonedL = LI.AllocateLoop(); | |||
946 | ClonedParentL->addChildLoop(ClonedL); | |||
947 | AddClonedBlocksToLoop(*L, *ClonedL); | |||
948 | for (Loop *ChildL : llvm::reverse(*L)) | |||
949 | LoopsToClone.push_back({ClonedL, ChildL}); | |||
950 | } while (!LoopsToClone.empty()); | |||
951 | ||||
952 | return ClonedRootL; | |||
953 | } | |||
954 | ||||
955 | /// Build the cloned loops of an original loop from unswitching. | |||
956 | /// | |||
957 | /// Because unswitching simplifies the CFG of the loop, this isn't a trivial | |||
958 | /// operation. We need to re-verify that there even is a loop (as the backedge | |||
959 | /// may not have been cloned), and even if there are remaining backedges the | |||
960 | /// backedge set may be different. However, we know that each child loop is | |||
961 | /// undisturbed, we only need to find where to place each child loop within | |||
962 | /// either any parent loop or within a cloned version of the original loop. | |||
963 | /// | |||
964 | /// Because child loops may end up cloned outside of any cloned version of the | |||
965 | /// original loop, multiple cloned sibling loops may be created. All of them | |||
966 | /// are returned so that the newly introduced loop nest roots can be | |||
967 | /// identified. | |||
968 | static Loop *buildClonedLoops(Loop &OrigL, ArrayRef<BasicBlock *> ExitBlocks, | |||
969 | const ValueToValueMapTy &VMap, LoopInfo &LI, | |||
970 | SmallVectorImpl<Loop *> &NonChildClonedLoops) { | |||
971 | Loop *ClonedL = nullptr; | |||
972 | ||||
973 | auto *OrigPH = OrigL.getLoopPreheader(); | |||
974 | auto *OrigHeader = OrigL.getHeader(); | |||
975 | ||||
976 | auto *ClonedPH = cast<BasicBlock>(VMap.lookup(OrigPH)); | |||
977 | auto *ClonedHeader = cast<BasicBlock>(VMap.lookup(OrigHeader)); | |||
978 | ||||
979 | // We need to know the loops of the cloned exit blocks to even compute the | |||
980 | // accurate parent loop. If we only clone exits to some parent of the | |||
981 | // original parent, we want to clone into that outer loop. We also keep track | |||
982 | // of the loops that our cloned exit blocks participate in. | |||
983 | Loop *ParentL = nullptr; | |||
984 | SmallVector<BasicBlock *, 4> ClonedExitsInLoops; | |||
985 | SmallDenseMap<BasicBlock *, Loop *, 16> ExitLoopMap; | |||
986 | ClonedExitsInLoops.reserve(ExitBlocks.size()); | |||
987 | for (auto *ExitBB : ExitBlocks) | |||
988 | if (auto *ClonedExitBB = cast_or_null<BasicBlock>(VMap.lookup(ExitBB))) | |||
989 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | |||
990 | ExitLoopMap[ClonedExitBB] = ExitL; | |||
991 | ClonedExitsInLoops.push_back(ClonedExitBB); | |||
992 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | |||
993 | ParentL = ExitL; | |||
994 | } | |||
995 | assert((!ParentL || ParentL == OrigL.getParentLoop() ||(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 998, __extension__ __PRETTY_FUNCTION__)) | |||
996 | ParentL->contains(OrigL.getParentLoop())) &&(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 998, __extension__ __PRETTY_FUNCTION__)) | |||
997 | "The computed parent loop should always contain (or be) the parent of "(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 998, __extension__ __PRETTY_FUNCTION__)) | |||
998 | "the original loop.")(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 998, __extension__ __PRETTY_FUNCTION__)); | |||
999 | ||||
1000 | // We build the set of blocks dominated by the cloned header from the set of | |||
1001 | // cloned blocks out of the original loop. While not all of these will | |||
1002 | // necessarily be in the cloned loop, it is enough to establish that they | |||
1003 | // aren't in unreachable cycles, etc. | |||
1004 | SmallSetVector<BasicBlock *, 16> ClonedLoopBlocks; | |||
1005 | for (auto *BB : OrigL.blocks()) | |||
1006 | if (auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB))) | |||
1007 | ClonedLoopBlocks.insert(ClonedBB); | |||
1008 | ||||
1009 | // Rebuild the set of blocks that will end up in the cloned loop. We may have | |||
1010 | // skipped cloning some region of this loop which can in turn skip some of | |||
1011 | // the backedges so we have to rebuild the blocks in the loop based on the | |||
1012 | // backedges that remain after cloning. | |||
1013 | SmallVector<BasicBlock *, 16> Worklist; | |||
1014 | SmallPtrSet<BasicBlock *, 16> BlocksInClonedLoop; | |||
1015 | for (auto *Pred : predecessors(ClonedHeader)) { | |||
1016 | // The only possible non-loop header predecessor is the preheader because | |||
1017 | // we know we cloned the loop in simplified form. | |||
1018 | if (Pred == ClonedPH) | |||
1019 | continue; | |||
1020 | ||||
1021 | // Because the loop was in simplified form, the only non-loop predecessor | |||
1022 | // should be the preheader. | |||
1023 | assert(ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop "(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1025, __extension__ __PRETTY_FUNCTION__)) | |||
1024 | "header other than the preheader "(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1025, __extension__ __PRETTY_FUNCTION__)) | |||
1025 | "that is not part of the loop!")(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1025, __extension__ __PRETTY_FUNCTION__)); | |||
1026 | ||||
1027 | // Insert this block into the loop set and on the first visit (and if it | |||
1028 | // isn't the header we're currently walking) put it into the worklist to | |||
1029 | // recurse through. | |||
1030 | if (BlocksInClonedLoop.insert(Pred).second && Pred != ClonedHeader) | |||
1031 | Worklist.push_back(Pred); | |||
1032 | } | |||
1033 | ||||
1034 | // If we had any backedges then there *is* a cloned loop. Put the header into | |||
1035 | // the loop set and then walk the worklist backwards to find all the blocks | |||
1036 | // that remain within the loop after cloning. | |||
1037 | if (!BlocksInClonedLoop.empty()) { | |||
1038 | BlocksInClonedLoop.insert(ClonedHeader); | |||
1039 | ||||
1040 | while (!Worklist.empty()) { | |||
1041 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1042 | assert(BlocksInClonedLoop.count(BB) &&(static_cast <bool> (BlocksInClonedLoop.count(BB) && "Didn't put block into the loop set!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1043, __extension__ __PRETTY_FUNCTION__)) | |||
1043 | "Didn't put block into the loop set!")(static_cast <bool> (BlocksInClonedLoop.count(BB) && "Didn't put block into the loop set!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1043, __extension__ __PRETTY_FUNCTION__)); | |||
1044 | ||||
1045 | // Insert any predecessors that are in the possible set into the cloned | |||
1046 | // set, and if the insert is successful, add them to the worklist. Note | |||
1047 | // that we filter on the blocks that are definitely reachable via the | |||
1048 | // backedge to the loop header so we may prune out dead code within the | |||
1049 | // cloned loop. | |||
1050 | for (auto *Pred : predecessors(BB)) | |||
1051 | if (ClonedLoopBlocks.count(Pred) && | |||
1052 | BlocksInClonedLoop.insert(Pred).second) | |||
1053 | Worklist.push_back(Pred); | |||
1054 | } | |||
1055 | ||||
1056 | ClonedL = LI.AllocateLoop(); | |||
1057 | if (ParentL) { | |||
1058 | ParentL->addBasicBlockToLoop(ClonedPH, LI); | |||
1059 | ParentL->addChildLoop(ClonedL); | |||
1060 | } else { | |||
1061 | LI.addTopLevelLoop(ClonedL); | |||
1062 | } | |||
1063 | ||||
1064 | ClonedL->reserveBlocks(BlocksInClonedLoop.size()); | |||
1065 | // We don't want to just add the cloned loop blocks based on how we | |||
1066 | // discovered them. The original order of blocks was carefully built in | |||
1067 | // a way that doesn't rely on predecessor ordering. Rather than re-invent | |||
1068 | // that logic, we just re-walk the original blocks (and those of the child | |||
1069 | // loops) and filter them as we add them into the cloned loop. | |||
1070 | for (auto *BB : OrigL.blocks()) { | |||
1071 | auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB)); | |||
1072 | if (!ClonedBB || !BlocksInClonedLoop.count(ClonedBB)) | |||
1073 | continue; | |||
1074 | ||||
1075 | // Directly add the blocks that are only in this loop. | |||
1076 | if (LI.getLoopFor(BB) == &OrigL) { | |||
1077 | ClonedL->addBasicBlockToLoop(ClonedBB, LI); | |||
1078 | continue; | |||
1079 | } | |||
1080 | ||||
1081 | // We want to manually add it to this loop and parents. | |||
1082 | // Registering it with LoopInfo will happen when we clone the top | |||
1083 | // loop for this block. | |||
1084 | for (Loop *PL = ClonedL; PL; PL = PL->getParentLoop()) | |||
1085 | PL->addBlockEntry(ClonedBB); | |||
1086 | } | |||
1087 | ||||
1088 | // Now add each child loop whose header remains within the cloned loop. All | |||
1089 | // of the blocks within the loop must satisfy the same constraints as the | |||
1090 | // header so once we pass the header checks we can just clone the entire | |||
1091 | // child loop nest. | |||
1092 | for (Loop *ChildL : OrigL) { | |||
1093 | auto *ClonedChildHeader = | |||
1094 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | |||
1095 | if (!ClonedChildHeader || !BlocksInClonedLoop.count(ClonedChildHeader)) | |||
1096 | continue; | |||
1097 | ||||
1098 | #ifndef NDEBUG | |||
1099 | // We should never have a cloned child loop header but fail to have | |||
1100 | // all of the blocks for that child loop. | |||
1101 | for (auto *ChildLoopBB : ChildL->blocks()) | |||
1102 | assert(BlocksInClonedLoop.count((static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1105, __extension__ __PRETTY_FUNCTION__)) | |||
1103 | cast<BasicBlock>(VMap.lookup(ChildLoopBB))) &&(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1105, __extension__ __PRETTY_FUNCTION__)) | |||
1104 | "Child cloned loop has a header within the cloned outer "(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1105, __extension__ __PRETTY_FUNCTION__)) | |||
1105 | "loop but not all of its blocks!")(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1105, __extension__ __PRETTY_FUNCTION__)); | |||
1106 | #endif | |||
1107 | ||||
1108 | cloneLoopNest(*ChildL, ClonedL, VMap, LI); | |||
1109 | } | |||
1110 | } | |||
1111 | ||||
1112 | // Now that we've handled all the components of the original loop that were | |||
1113 | // cloned into a new loop, we still need to handle anything from the original | |||
1114 | // loop that wasn't in a cloned loop. | |||
1115 | ||||
1116 | // Figure out what blocks are left to place within any loop nest containing | |||
1117 | // the unswitched loop. If we never formed a loop, the cloned PH is one of | |||
1118 | // them. | |||
1119 | SmallPtrSet<BasicBlock *, 16> UnloopedBlockSet; | |||
1120 | if (BlocksInClonedLoop.empty()) | |||
1121 | UnloopedBlockSet.insert(ClonedPH); | |||
1122 | for (auto *ClonedBB : ClonedLoopBlocks) | |||
1123 | if (!BlocksInClonedLoop.count(ClonedBB)) | |||
1124 | UnloopedBlockSet.insert(ClonedBB); | |||
1125 | ||||
1126 | // Copy the cloned exits and sort them in ascending loop depth, we'll work | |||
1127 | // backwards across these to process them inside out. The order shouldn't | |||
1128 | // matter as we're just trying to build up the map from inside-out; we use | |||
1129 | // the map in a more stably ordered way below. | |||
1130 | auto OrderedClonedExitsInLoops = ClonedExitsInLoops; | |||
1131 | std::sort(OrderedClonedExitsInLoops.begin(), OrderedClonedExitsInLoops.end(), | |||
1132 | [&](BasicBlock *LHS, BasicBlock *RHS) { | |||
1133 | return ExitLoopMap.lookup(LHS)->getLoopDepth() < | |||
1134 | ExitLoopMap.lookup(RHS)->getLoopDepth(); | |||
1135 | }); | |||
1136 | ||||
1137 | // Populate the existing ExitLoopMap with everything reachable from each | |||
1138 | // exit, starting from the inner most exit. | |||
1139 | while (!UnloopedBlockSet.empty() && !OrderedClonedExitsInLoops.empty()) { | |||
1140 | assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!" ) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1140, __extension__ __PRETTY_FUNCTION__)); | |||
1141 | ||||
1142 | BasicBlock *ExitBB = OrderedClonedExitsInLoops.pop_back_val(); | |||
1143 | Loop *ExitL = ExitLoopMap.lookup(ExitBB); | |||
1144 | ||||
1145 | // Walk the CFG back until we hit the cloned PH adding everything reachable | |||
1146 | // and in the unlooped set to this exit block's loop. | |||
1147 | Worklist.push_back(ExitBB); | |||
1148 | do { | |||
1149 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1150 | // We can stop recursing at the cloned preheader (if we get there). | |||
1151 | if (BB == ClonedPH) | |||
1152 | continue; | |||
1153 | ||||
1154 | for (BasicBlock *PredBB : predecessors(BB)) { | |||
1155 | // If this pred has already been moved to our set or is part of some | |||
1156 | // (inner) loop, no update needed. | |||
1157 | if (!UnloopedBlockSet.erase(PredBB)) { | |||
1158 | assert((static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1160, __extension__ __PRETTY_FUNCTION__)) | |||
1159 | (BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) &&(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1160, __extension__ __PRETTY_FUNCTION__)) | |||
1160 | "Predecessor not mapped to a loop!")(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1160, __extension__ __PRETTY_FUNCTION__)); | |||
1161 | continue; | |||
1162 | } | |||
1163 | ||||
1164 | // We just insert into the loop set here. We'll add these blocks to the | |||
1165 | // exit loop after we build up the set in an order that doesn't rely on | |||
1166 | // predecessor order (which in turn relies on use list order). | |||
1167 | bool Inserted = ExitLoopMap.insert({PredBB, ExitL}).second; | |||
1168 | (void)Inserted; | |||
1169 | assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!" ) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1169, __extension__ __PRETTY_FUNCTION__)); | |||
1170 | ||||
1171 | // And recurse through to its predecessors. | |||
1172 | Worklist.push_back(PredBB); | |||
1173 | } | |||
1174 | } while (!Worklist.empty()); | |||
1175 | } | |||
1176 | ||||
1177 | // Now that the ExitLoopMap gives as mapping for all the non-looping cloned | |||
1178 | // blocks to their outer loops, walk the cloned blocks and the cloned exits | |||
1179 | // in their original order adding them to the correct loop. | |||
1180 | ||||
1181 | // We need a stable insertion order. We use the order of the original loop | |||
1182 | // order and map into the correct parent loop. | |||
1183 | for (auto *BB : llvm::concat<BasicBlock *const>( | |||
1184 | makeArrayRef(ClonedPH), ClonedLoopBlocks, ClonedExitsInLoops)) | |||
1185 | if (Loop *OuterL = ExitLoopMap.lookup(BB)) | |||
1186 | OuterL->addBasicBlockToLoop(BB, LI); | |||
1187 | ||||
1188 | #ifndef NDEBUG | |||
1189 | for (auto &BBAndL : ExitLoopMap) { | |||
1190 | auto *BB = BBAndL.first; | |||
1191 | auto *OuterL = BBAndL.second; | |||
1192 | assert(LI.getLoopFor(BB) == OuterL &&(static_cast <bool> (LI.getLoopFor(BB) == OuterL && "Failed to put all blocks into outer loops!") ? void (0) : __assert_fail ("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1193, __extension__ __PRETTY_FUNCTION__)) | |||
1193 | "Failed to put all blocks into outer loops!")(static_cast <bool> (LI.getLoopFor(BB) == OuterL && "Failed to put all blocks into outer loops!") ? void (0) : __assert_fail ("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1193, __extension__ __PRETTY_FUNCTION__)); | |||
1194 | } | |||
1195 | #endif | |||
1196 | ||||
1197 | // Now that all the blocks are placed into the correct containing loop in the | |||
1198 | // absence of child loops, find all the potentially cloned child loops and | |||
1199 | // clone them into whatever outer loop we placed their header into. | |||
1200 | for (Loop *ChildL : OrigL) { | |||
1201 | auto *ClonedChildHeader = | |||
1202 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | |||
1203 | if (!ClonedChildHeader || BlocksInClonedLoop.count(ClonedChildHeader)) | |||
1204 | continue; | |||
1205 | ||||
1206 | #ifndef NDEBUG | |||
1207 | for (auto *ChildLoopBB : ChildL->blocks()) | |||
1208 | assert(VMap.count(ChildLoopBB) &&(static_cast <bool> (VMap.count(ChildLoopBB) && "Cloned a child loop header but not all of that loops blocks!" ) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1209, __extension__ __PRETTY_FUNCTION__)) | |||
1209 | "Cloned a child loop header but not all of that loops blocks!")(static_cast <bool> (VMap.count(ChildLoopBB) && "Cloned a child loop header but not all of that loops blocks!" ) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1209, __extension__ __PRETTY_FUNCTION__)); | |||
1210 | #endif | |||
1211 | ||||
1212 | NonChildClonedLoops.push_back(cloneLoopNest( | |||
1213 | *ChildL, ExitLoopMap.lookup(ClonedChildHeader), VMap, LI)); | |||
1214 | } | |||
1215 | ||||
1216 | // Return the main cloned loop if any. | |||
1217 | return ClonedL; | |||
1218 | } | |||
1219 | ||||
1220 | static void deleteDeadBlocksFromLoop(Loop &L, BasicBlock *DeadSubtreeRoot, | |||
1221 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | |||
1222 | DominatorTree &DT, LoopInfo &LI) { | |||
1223 | // Walk the dominator tree to build up the set of blocks we will delete here. | |||
1224 | // The order is designed to allow us to always delete bottom-up and avoid any | |||
1225 | // dangling uses. | |||
1226 | SmallSetVector<BasicBlock *, 16> DeadBlocks; | |||
1227 | DeadBlocks.insert(DeadSubtreeRoot); | |||
1228 | for (int i = 0; i < (int)DeadBlocks.size(); ++i) | |||
1229 | for (DomTreeNode *ChildN : *DT[DeadBlocks[i]]) { | |||
1230 | // FIXME: This assert should pass and that means we don't change nearly | |||
1231 | // as much below! Consider rewriting all of this to avoid deleting | |||
1232 | // blocks. They are always cloned before being deleted, and so instead | |||
1233 | // could just be moved. | |||
1234 | // FIXME: This in turn means that we might actually be more able to | |||
1235 | // update the domtree. | |||
1236 | assert((L.contains(ChildN->getBlock()) ||(static_cast <bool> ((L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks .end()) && "Should never reach beyond the loop and exits when deleting!" ) ? void (0) : __assert_fail ("(L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks.end()) && \"Should never reach beyond the loop and exits when deleting!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1238, __extension__ __PRETTY_FUNCTION__)) | |||
1237 | llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks.end()) &&(static_cast <bool> ((L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks .end()) && "Should never reach beyond the loop and exits when deleting!" ) ? void (0) : __assert_fail ("(L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks.end()) && \"Should never reach beyond the loop and exits when deleting!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1238, __extension__ __PRETTY_FUNCTION__)) | |||
1238 | "Should never reach beyond the loop and exits when deleting!")(static_cast <bool> ((L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks .end()) && "Should never reach beyond the loop and exits when deleting!" ) ? void (0) : __assert_fail ("(L.contains(ChildN->getBlock()) || llvm::find(ExitBlocks, ChildN->getBlock()) != ExitBlocks.end()) && \"Should never reach beyond the loop and exits when deleting!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1238, __extension__ __PRETTY_FUNCTION__)); | |||
1239 | DeadBlocks.insert(ChildN->getBlock()); | |||
1240 | } | |||
1241 | ||||
1242 | // Filter out the dead blocks from the exit blocks list so that it can be | |||
1243 | // used in the caller. | |||
1244 | llvm::erase_if(ExitBlocks, | |||
1245 | [&](BasicBlock *BB) { return DeadBlocks.count(BB); }); | |||
1246 | ||||
1247 | // Remove these blocks from their successors. | |||
1248 | for (auto *BB : DeadBlocks) | |||
1249 | for (BasicBlock *SuccBB : successors(BB)) | |||
1250 | SuccBB->removePredecessor(BB, /*DontDeleteUselessPHIs*/ true); | |||
1251 | ||||
1252 | // Walk from this loop up through its parents removing all of the dead blocks. | |||
1253 | for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop()) { | |||
1254 | for (auto *BB : DeadBlocks) | |||
1255 | ParentL->getBlocksSet().erase(BB); | |||
1256 | llvm::erase_if(ParentL->getBlocksVector(), | |||
1257 | [&](BasicBlock *BB) { return DeadBlocks.count(BB); }); | |||
1258 | } | |||
1259 | ||||
1260 | // Now delete the dead child loops. This raw delete will clear them | |||
1261 | // recursively. | |||
1262 | llvm::erase_if(L.getSubLoopsVector(), [&](Loop *ChildL) { | |||
1263 | if (!DeadBlocks.count(ChildL->getHeader())) | |||
1264 | return false; | |||
1265 | ||||
1266 | assert(llvm::all_of(ChildL->blocks(),(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)) | |||
1267 | [&](BasicBlock *ChildBB) {(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)) | |||
1268 | return DeadBlocks.count(ChildBB);(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)) | |||
1269 | }) &&(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)) | |||
1270 | "If the child loop header is dead all blocks in the child loop must "(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)) | |||
1271 | "be dead as well!")(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlocks.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1271, __extension__ __PRETTY_FUNCTION__)); | |||
1272 | LI.destroy(ChildL); | |||
1273 | return true; | |||
1274 | }); | |||
1275 | ||||
1276 | // Remove the mappings for the dead blocks. | |||
1277 | for (auto *BB : DeadBlocks) | |||
1278 | LI.changeLoopFor(BB, nullptr); | |||
1279 | ||||
1280 | // Drop all the references from these blocks to others to handle cyclic | |||
1281 | // references as we start deleting the blocks themselves. | |||
1282 | for (auto *BB : DeadBlocks) | |||
1283 | BB->dropAllReferences(); | |||
1284 | ||||
1285 | for (auto *BB : llvm::reverse(DeadBlocks)) { | |||
1286 | DT.eraseNode(BB); | |||
1287 | BB->eraseFromParent(); | |||
1288 | } | |||
1289 | } | |||
1290 | ||||
1291 | /// Recompute the set of blocks in a loop after unswitching. | |||
1292 | /// | |||
1293 | /// This walks from the original headers predecessors to rebuild the loop. We | |||
1294 | /// take advantage of the fact that new blocks can't have been added, and so we | |||
1295 | /// filter by the original loop's blocks. This also handles potentially | |||
1296 | /// unreachable code that we don't want to explore but might be found examining | |||
1297 | /// the predecessors of the header. | |||
1298 | /// | |||
1299 | /// If the original loop is no longer a loop, this will return an empty set. If | |||
1300 | /// it remains a loop, all the blocks within it will be added to the set | |||
1301 | /// (including those blocks in inner loops). | |||
1302 | static SmallPtrSet<const BasicBlock *, 16> recomputeLoopBlockSet(Loop &L, | |||
1303 | LoopInfo &LI) { | |||
1304 | SmallPtrSet<const BasicBlock *, 16> LoopBlockSet; | |||
1305 | ||||
1306 | auto *PH = L.getLoopPreheader(); | |||
1307 | auto *Header = L.getHeader(); | |||
1308 | ||||
1309 | // A worklist to use while walking backwards from the header. | |||
1310 | SmallVector<BasicBlock *, 16> Worklist; | |||
1311 | ||||
1312 | // First walk the predecessors of the header to find the backedges. This will | |||
1313 | // form the basis of our walk. | |||
1314 | for (auto *Pred : predecessors(Header)) { | |||
1315 | // Skip the preheader. | |||
1316 | if (Pred == PH) | |||
1317 | continue; | |||
1318 | ||||
1319 | // Because the loop was in simplified form, the only non-loop predecessor | |||
1320 | // is the preheader. | |||
1321 | assert(L.contains(Pred) && "Found a predecessor of the loop header other "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1323, __extension__ __PRETTY_FUNCTION__)) | |||
1322 | "than the preheader that is not part of the "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1323, __extension__ __PRETTY_FUNCTION__)) | |||
1323 | "loop!")(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1323, __extension__ __PRETTY_FUNCTION__)); | |||
1324 | ||||
1325 | // Insert this block into the loop set and on the first visit and, if it | |||
1326 | // isn't the header we're currently walking, put it into the worklist to | |||
1327 | // recurse through. | |||
1328 | if (LoopBlockSet.insert(Pred).second && Pred != Header) | |||
1329 | Worklist.push_back(Pred); | |||
1330 | } | |||
1331 | ||||
1332 | // If no backedges were found, we're done. | |||
1333 | if (LoopBlockSet.empty()) | |||
1334 | return LoopBlockSet; | |||
1335 | ||||
1336 | // Add the loop header to the set. | |||
1337 | LoopBlockSet.insert(Header); | |||
1338 | ||||
1339 | // We found backedges, recurse through them to identify the loop blocks. | |||
1340 | while (!Worklist.empty()) { | |||
1341 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1342 | assert(LoopBlockSet.count(BB) && "Didn't put block into the loop set!")(static_cast <bool> (LoopBlockSet.count(BB) && "Didn't put block into the loop set!" ) ? void (0) : __assert_fail ("LoopBlockSet.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1342, __extension__ __PRETTY_FUNCTION__)); | |||
1343 | ||||
1344 | // Because we know the inner loop structure remains valid we can use the | |||
1345 | // loop structure to jump immediately across the entire nested loop. | |||
1346 | // Further, because it is in loop simplified form, we can directly jump | |||
1347 | // to its preheader afterward. | |||
1348 | if (Loop *InnerL = LI.getLoopFor(BB)) | |||
1349 | if (InnerL != &L) { | |||
1350 | assert(L.contains(InnerL) &&(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!" ) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1351, __extension__ __PRETTY_FUNCTION__)) | |||
1351 | "Should not reach a loop *outside* this loop!")(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!" ) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1351, __extension__ __PRETTY_FUNCTION__)); | |||
1352 | // The preheader is the only possible predecessor of the loop so | |||
1353 | // insert it into the set and check whether it was already handled. | |||
1354 | auto *InnerPH = InnerL->getLoopPreheader(); | |||
1355 | assert(L.contains(InnerPH) && "Cannot contain an inner loop block "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1357, __extension__ __PRETTY_FUNCTION__)) | |||
1356 | "but not contain the inner loop "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1357, __extension__ __PRETTY_FUNCTION__)) | |||
1357 | "preheader!")(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1357, __extension__ __PRETTY_FUNCTION__)); | |||
1358 | if (!LoopBlockSet.insert(InnerPH).second) | |||
1359 | // The only way to reach the preheader is through the loop body | |||
1360 | // itself so if it has been visited the loop is already handled. | |||
1361 | continue; | |||
1362 | ||||
1363 | // Insert all of the blocks (other than those already present) into | |||
1364 | // the loop set. The only block we expect to already be in the set is | |||
1365 | // the one we used to find this loop as we immediately handle the | |||
1366 | // others the first time we encounter the loop. | |||
1367 | for (auto *InnerBB : InnerL->blocks()) { | |||
1368 | if (InnerBB == BB) { | |||
1369 | assert(LoopBlockSet.count(InnerBB) &&(static_cast <bool> (LoopBlockSet.count(InnerBB) && "Block should already be in the set!") ? void (0) : __assert_fail ("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1370, __extension__ __PRETTY_FUNCTION__)) | |||
1370 | "Block should already be in the set!")(static_cast <bool> (LoopBlockSet.count(InnerBB) && "Block should already be in the set!") ? void (0) : __assert_fail ("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1370, __extension__ __PRETTY_FUNCTION__)); | |||
1371 | continue; | |||
1372 | } | |||
1373 | ||||
1374 | bool Inserted = LoopBlockSet.insert(InnerBB).second; | |||
1375 | (void)Inserted; | |||
1376 | assert(Inserted && "Should only insert an inner loop once!")(static_cast <bool> (Inserted && "Should only insert an inner loop once!" ) ? void (0) : __assert_fail ("Inserted && \"Should only insert an inner loop once!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1376, __extension__ __PRETTY_FUNCTION__)); | |||
1377 | } | |||
1378 | ||||
1379 | // Add the preheader to the worklist so we will continue past the | |||
1380 | // loop body. | |||
1381 | Worklist.push_back(InnerPH); | |||
1382 | continue; | |||
1383 | } | |||
1384 | ||||
1385 | // Insert any predecessors that were in the original loop into the new | |||
1386 | // set, and if the insert is successful, add them to the worklist. | |||
1387 | for (auto *Pred : predecessors(BB)) | |||
1388 | if (L.contains(Pred) && LoopBlockSet.insert(Pred).second) | |||
1389 | Worklist.push_back(Pred); | |||
1390 | } | |||
1391 | ||||
1392 | // We've found all the blocks participating in the loop, return our completed | |||
1393 | // set. | |||
1394 | return LoopBlockSet; | |||
1395 | } | |||
1396 | ||||
1397 | /// Rebuild a loop after unswitching removes some subset of blocks and edges. | |||
1398 | /// | |||
1399 | /// The removal may have removed some child loops entirely but cannot have | |||
1400 | /// disturbed any remaining child loops. However, they may need to be hoisted | |||
1401 | /// to the parent loop (or to be top-level loops). The original loop may be | |||
1402 | /// completely removed. | |||
1403 | /// | |||
1404 | /// The sibling loops resulting from this update are returned. If the original | |||
1405 | /// loop remains a valid loop, it will be the first entry in this list with all | |||
1406 | /// of the newly sibling loops following it. | |||
1407 | /// | |||
1408 | /// Returns true if the loop remains a loop after unswitching, and false if it | |||
1409 | /// is no longer a loop after unswitching (and should not continue to be | |||
1410 | /// referenced). | |||
1411 | static bool rebuildLoopAfterUnswitch(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | |||
1412 | LoopInfo &LI, | |||
1413 | SmallVectorImpl<Loop *> &HoistedLoops) { | |||
1414 | auto *PH = L.getLoopPreheader(); | |||
1415 | ||||
1416 | // Compute the actual parent loop from the exit blocks. Because we may have | |||
1417 | // pruned some exits the loop may be different from the original parent. | |||
1418 | Loop *ParentL = nullptr; | |||
1419 | SmallVector<Loop *, 4> ExitLoops; | |||
1420 | SmallVector<BasicBlock *, 4> ExitsInLoops; | |||
1421 | ExitsInLoops.reserve(ExitBlocks.size()); | |||
1422 | for (auto *ExitBB : ExitBlocks) | |||
1423 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | |||
1424 | ExitLoops.push_back(ExitL); | |||
1425 | ExitsInLoops.push_back(ExitBB); | |||
1426 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | |||
1427 | ParentL = ExitL; | |||
1428 | } | |||
1429 | ||||
1430 | // Recompute the blocks participating in this loop. This may be empty if it | |||
1431 | // is no longer a loop. | |||
1432 | auto LoopBlockSet = recomputeLoopBlockSet(L, LI); | |||
1433 | ||||
1434 | // If we still have a loop, we need to re-set the loop's parent as the exit | |||
1435 | // block set changing may have moved it within the loop nest. Note that this | |||
1436 | // can only happen when this loop has a parent as it can only hoist the loop | |||
1437 | // *up* the nest. | |||
1438 | if (!LoopBlockSet.empty() && L.getParentLoop() != ParentL) { | |||
1439 | // Remove this loop's (original) blocks from all of the intervening loops. | |||
1440 | for (Loop *IL = L.getParentLoop(); IL != ParentL; | |||
1441 | IL = IL->getParentLoop()) { | |||
1442 | IL->getBlocksSet().erase(PH); | |||
1443 | for (auto *BB : L.blocks()) | |||
1444 | IL->getBlocksSet().erase(BB); | |||
1445 | llvm::erase_if(IL->getBlocksVector(), [&](BasicBlock *BB) { | |||
1446 | return BB == PH || L.contains(BB); | |||
1447 | }); | |||
1448 | } | |||
1449 | ||||
1450 | LI.changeLoopFor(PH, ParentL); | |||
1451 | L.getParentLoop()->removeChildLoop(&L); | |||
1452 | if (ParentL) | |||
1453 | ParentL->addChildLoop(&L); | |||
1454 | else | |||
1455 | LI.addTopLevelLoop(&L); | |||
1456 | } | |||
1457 | ||||
1458 | // Now we update all the blocks which are no longer within the loop. | |||
1459 | auto &Blocks = L.getBlocksVector(); | |||
1460 | auto BlocksSplitI = | |||
1461 | LoopBlockSet.empty() | |||
1462 | ? Blocks.begin() | |||
1463 | : std::stable_partition( | |||
1464 | Blocks.begin(), Blocks.end(), | |||
1465 | [&](BasicBlock *BB) { return LoopBlockSet.count(BB); }); | |||
1466 | ||||
1467 | // Before we erase the list of unlooped blocks, build a set of them. | |||
1468 | SmallPtrSet<BasicBlock *, 16> UnloopedBlocks(BlocksSplitI, Blocks.end()); | |||
1469 | if (LoopBlockSet.empty()) | |||
1470 | UnloopedBlocks.insert(PH); | |||
1471 | ||||
1472 | // Now erase these blocks from the loop. | |||
1473 | for (auto *BB : make_range(BlocksSplitI, Blocks.end())) | |||
1474 | L.getBlocksSet().erase(BB); | |||
1475 | Blocks.erase(BlocksSplitI, Blocks.end()); | |||
1476 | ||||
1477 | // Sort the exits in ascending loop depth, we'll work backwards across these | |||
1478 | // to process them inside out. | |||
1479 | std::stable_sort(ExitsInLoops.begin(), ExitsInLoops.end(), | |||
1480 | [&](BasicBlock *LHS, BasicBlock *RHS) { | |||
1481 | return LI.getLoopDepth(LHS) < LI.getLoopDepth(RHS); | |||
1482 | }); | |||
1483 | ||||
1484 | // We'll build up a set for each exit loop. | |||
1485 | SmallPtrSet<BasicBlock *, 16> NewExitLoopBlocks; | |||
1486 | Loop *PrevExitL = L.getParentLoop(); // The deepest possible exit loop. | |||
1487 | ||||
1488 | auto RemoveUnloopedBlocksFromLoop = | |||
1489 | [](Loop &L, SmallPtrSetImpl<BasicBlock *> &UnloopedBlocks) { | |||
1490 | for (auto *BB : UnloopedBlocks) | |||
1491 | L.getBlocksSet().erase(BB); | |||
1492 | llvm::erase_if(L.getBlocksVector(), [&](BasicBlock *BB) { | |||
1493 | return UnloopedBlocks.count(BB); | |||
1494 | }); | |||
1495 | }; | |||
1496 | ||||
1497 | SmallVector<BasicBlock *, 16> Worklist; | |||
1498 | while (!UnloopedBlocks.empty() && !ExitsInLoops.empty()) { | |||
1499 | assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!" ) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1499, __extension__ __PRETTY_FUNCTION__)); | |||
1500 | assert(NewExitLoopBlocks.empty() && "Didn't clear loop set!")(static_cast <bool> (NewExitLoopBlocks.empty() && "Didn't clear loop set!") ? void (0) : __assert_fail ("NewExitLoopBlocks.empty() && \"Didn't clear loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1500, __extension__ __PRETTY_FUNCTION__)); | |||
1501 | ||||
1502 | // Grab the next exit block, in decreasing loop depth order. | |||
1503 | BasicBlock *ExitBB = ExitsInLoops.pop_back_val(); | |||
1504 | Loop &ExitL = *LI.getLoopFor(ExitBB); | |||
1505 | assert(ExitL.contains(&L) && "Exit loop must contain the inner loop!")(static_cast <bool> (ExitL.contains(&L) && "Exit loop must contain the inner loop!" ) ? void (0) : __assert_fail ("ExitL.contains(&L) && \"Exit loop must contain the inner loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1505, __extension__ __PRETTY_FUNCTION__)); | |||
1506 | ||||
1507 | // Erase all of the unlooped blocks from the loops between the previous | |||
1508 | // exit loop and this exit loop. This works because the ExitInLoops list is | |||
1509 | // sorted in increasing order of loop depth and thus we visit loops in | |||
1510 | // decreasing order of loop depth. | |||
1511 | for (; PrevExitL != &ExitL; PrevExitL = PrevExitL->getParentLoop()) | |||
1512 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | |||
1513 | ||||
1514 | // Walk the CFG back until we hit the cloned PH adding everything reachable | |||
1515 | // and in the unlooped set to this exit block's loop. | |||
1516 | Worklist.push_back(ExitBB); | |||
1517 | do { | |||
1518 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1519 | // We can stop recursing at the cloned preheader (if we get there). | |||
1520 | if (BB == PH) | |||
1521 | continue; | |||
1522 | ||||
1523 | for (BasicBlock *PredBB : predecessors(BB)) { | |||
1524 | // If this pred has already been moved to our set or is part of some | |||
1525 | // (inner) loop, no update needed. | |||
1526 | if (!UnloopedBlocks.erase(PredBB)) { | |||
1527 | assert((NewExitLoopBlocks.count(PredBB) ||(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1529, __extension__ __PRETTY_FUNCTION__)) | |||
1528 | ExitL.contains(LI.getLoopFor(PredBB))) &&(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1529, __extension__ __PRETTY_FUNCTION__)) | |||
1529 | "Predecessor not in a nested loop (or already visited)!")(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1529, __extension__ __PRETTY_FUNCTION__)); | |||
1530 | continue; | |||
1531 | } | |||
1532 | ||||
1533 | // We just insert into the loop set here. We'll add these blocks to the | |||
1534 | // exit loop after we build up the set in a deterministic order rather | |||
1535 | // than the predecessor-influenced visit order. | |||
1536 | bool Inserted = NewExitLoopBlocks.insert(PredBB).second; | |||
1537 | (void)Inserted; | |||
1538 | assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!" ) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1538, __extension__ __PRETTY_FUNCTION__)); | |||
1539 | ||||
1540 | // And recurse through to its predecessors. | |||
1541 | Worklist.push_back(PredBB); | |||
1542 | } | |||
1543 | } while (!Worklist.empty()); | |||
1544 | ||||
1545 | // If blocks in this exit loop were directly part of the original loop (as | |||
1546 | // opposed to a child loop) update the map to point to this exit loop. This | |||
1547 | // just updates a map and so the fact that the order is unstable is fine. | |||
1548 | for (auto *BB : NewExitLoopBlocks) | |||
1549 | if (Loop *BBL = LI.getLoopFor(BB)) | |||
1550 | if (BBL == &L || !L.contains(BBL)) | |||
1551 | LI.changeLoopFor(BB, &ExitL); | |||
1552 | ||||
1553 | // We will remove the remaining unlooped blocks from this loop in the next | |||
1554 | // iteration or below. | |||
1555 | NewExitLoopBlocks.clear(); | |||
1556 | } | |||
1557 | ||||
1558 | // Any remaining unlooped blocks are no longer part of any loop unless they | |||
1559 | // are part of some child loop. | |||
1560 | for (; PrevExitL; PrevExitL = PrevExitL->getParentLoop()) | |||
1561 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | |||
1562 | for (auto *BB : UnloopedBlocks) | |||
1563 | if (Loop *BBL = LI.getLoopFor(BB)) | |||
1564 | if (BBL == &L || !L.contains(BBL)) | |||
1565 | LI.changeLoopFor(BB, nullptr); | |||
1566 | ||||
1567 | // Sink all the child loops whose headers are no longer in the loop set to | |||
1568 | // the parent (or to be top level loops). We reach into the loop and directly | |||
1569 | // update its subloop vector to make this batch update efficient. | |||
1570 | auto &SubLoops = L.getSubLoopsVector(); | |||
1571 | auto SubLoopsSplitI = | |||
1572 | LoopBlockSet.empty() | |||
1573 | ? SubLoops.begin() | |||
1574 | : std::stable_partition( | |||
1575 | SubLoops.begin(), SubLoops.end(), [&](Loop *SubL) { | |||
1576 | return LoopBlockSet.count(SubL->getHeader()); | |||
1577 | }); | |||
1578 | for (auto *HoistedL : make_range(SubLoopsSplitI, SubLoops.end())) { | |||
1579 | HoistedLoops.push_back(HoistedL); | |||
1580 | HoistedL->setParentLoop(nullptr); | |||
1581 | ||||
1582 | // To compute the new parent of this hoisted loop we look at where we | |||
1583 | // placed the preheader above. We can't lookup the header itself because we | |||
1584 | // retained the mapping from the header to the hoisted loop. But the | |||
1585 | // preheader and header should have the exact same new parent computed | |||
1586 | // based on the set of exit blocks from the original loop as the preheader | |||
1587 | // is a predecessor of the header and so reached in the reverse walk. And | |||
1588 | // because the loops were all in simplified form the preheader of the | |||
1589 | // hoisted loop can't be part of some *other* loop. | |||
1590 | if (auto *NewParentL = LI.getLoopFor(HoistedL->getLoopPreheader())) | |||
1591 | NewParentL->addChildLoop(HoistedL); | |||
1592 | else | |||
1593 | LI.addTopLevelLoop(HoistedL); | |||
1594 | } | |||
1595 | SubLoops.erase(SubLoopsSplitI, SubLoops.end()); | |||
1596 | ||||
1597 | // Actually delete the loop if nothing remained within it. | |||
1598 | if (Blocks.empty()) { | |||
1599 | assert(SubLoops.empty() &&(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!" ) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1600, __extension__ __PRETTY_FUNCTION__)) | |||
1600 | "Failed to remove all subloops from the original loop!")(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!" ) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1600, __extension__ __PRETTY_FUNCTION__)); | |||
1601 | if (Loop *ParentL = L.getParentLoop()) | |||
1602 | ParentL->removeChildLoop(llvm::find(*ParentL, &L)); | |||
1603 | else | |||
1604 | LI.removeLoop(llvm::find(LI, &L)); | |||
1605 | LI.destroy(&L); | |||
1606 | return false; | |||
1607 | } | |||
1608 | ||||
1609 | return true; | |||
1610 | } | |||
1611 | ||||
1612 | /// Helper to visit a dominator subtree, invoking a callable on each node. | |||
1613 | /// | |||
1614 | /// Returning false at any point will stop walking past that node of the tree. | |||
1615 | template <typename CallableT> | |||
1616 | void visitDomSubTree(DominatorTree &DT, BasicBlock *BB, CallableT Callable) { | |||
1617 | SmallVector<DomTreeNode *, 4> DomWorklist; | |||
1618 | DomWorklist.push_back(DT[BB]); | |||
1619 | #ifndef NDEBUG | |||
1620 | SmallPtrSet<DomTreeNode *, 4> Visited; | |||
1621 | Visited.insert(DT[BB]); | |||
1622 | #endif | |||
1623 | do { | |||
1624 | DomTreeNode *N = DomWorklist.pop_back_val(); | |||
1625 | ||||
1626 | // Visit this node. | |||
1627 | if (!Callable(N->getBlock())) | |||
1628 | continue; | |||
1629 | ||||
1630 | // Accumulate the child nodes. | |||
1631 | for (DomTreeNode *ChildN : *N) { | |||
1632 | assert(Visited.insert(ChildN).second &&(static_cast <bool> (Visited.insert(ChildN).second && "Cannot visit a node twice when walking a tree!") ? void (0) : __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1633, __extension__ __PRETTY_FUNCTION__)) | |||
1633 | "Cannot visit a node twice when walking a tree!")(static_cast <bool> (Visited.insert(ChildN).second && "Cannot visit a node twice when walking a tree!") ? void (0) : __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1633, __extension__ __PRETTY_FUNCTION__)); | |||
1634 | DomWorklist.push_back(ChildN); | |||
1635 | } | |||
1636 | } while (!DomWorklist.empty()); | |||
1637 | } | |||
1638 | ||||
1639 | /// Take an invariant branch that has been determined to be safe and worthwhile | |||
1640 | /// to unswitch despite being non-trivial to do so and perform the unswitch. | |||
1641 | /// | |||
1642 | /// This directly updates the CFG to hoist the predicate out of the loop, and | |||
1643 | /// clone the necessary parts of the loop to maintain behavior. | |||
1644 | /// | |||
1645 | /// It also updates both dominator tree and loopinfo based on the unswitching. | |||
1646 | /// | |||
1647 | /// Once unswitching has been performed it runs the provided callback to report | |||
1648 | /// the new loops and no-longer valid loops to the caller. | |||
1649 | static bool unswitchInvariantBranch( | |||
1650 | Loop &L, BranchInst &BI, DominatorTree &DT, LoopInfo &LI, | |||
1651 | AssumptionCache &AC, | |||
1652 | function_ref<void(bool, ArrayRef<Loop *>)> NonTrivialUnswitchCB) { | |||
1653 | assert(BI.isConditional() && "Can only unswitch a conditional branch!")(static_cast <bool> (BI.isConditional() && "Can only unswitch a conditional branch!" ) ? void (0) : __assert_fail ("BI.isConditional() && \"Can only unswitch a conditional branch!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1653, __extension__ __PRETTY_FUNCTION__)); | |||
1654 | assert(L.isLoopInvariant(BI.getCondition()) &&(static_cast <bool> (L.isLoopInvariant(BI.getCondition( )) && "Can only unswitch an invariant branch condition!" ) ? void (0) : __assert_fail ("L.isLoopInvariant(BI.getCondition()) && \"Can only unswitch an invariant branch condition!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1655, __extension__ __PRETTY_FUNCTION__)) | |||
1655 | "Can only unswitch an invariant branch condition!")(static_cast <bool> (L.isLoopInvariant(BI.getCondition( )) && "Can only unswitch an invariant branch condition!" ) ? void (0) : __assert_fail ("L.isLoopInvariant(BI.getCondition()) && \"Can only unswitch an invariant branch condition!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1655, __extension__ __PRETTY_FUNCTION__)); | |||
1656 | ||||
1657 | // Constant and BBs tracking the cloned and continuing successor. | |||
1658 | const int ClonedSucc = 0; | |||
1659 | auto *ParentBB = BI.getParent(); | |||
1660 | auto *UnswitchedSuccBB = BI.getSuccessor(ClonedSucc); | |||
1661 | auto *ContinueSuccBB = BI.getSuccessor(1 - ClonedSucc); | |||
1662 | ||||
1663 | assert(UnswitchedSuccBB != ContinueSuccBB &&(static_cast <bool> (UnswitchedSuccBB != ContinueSuccBB && "Should not unswitch a branch that always goes to the same place!" ) ? void (0) : __assert_fail ("UnswitchedSuccBB != ContinueSuccBB && \"Should not unswitch a branch that always goes to the same place!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1664, __extension__ __PRETTY_FUNCTION__)) | |||
1664 | "Should not unswitch a branch that always goes to the same place!")(static_cast <bool> (UnswitchedSuccBB != ContinueSuccBB && "Should not unswitch a branch that always goes to the same place!" ) ? void (0) : __assert_fail ("UnswitchedSuccBB != ContinueSuccBB && \"Should not unswitch a branch that always goes to the same place!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1664, __extension__ __PRETTY_FUNCTION__)); | |||
1665 | ||||
1666 | // The branch should be in this exact loop. Any inner loop's invariant branch | |||
1667 | // should be handled by unswitching that inner loop. The caller of this | |||
1668 | // routine should filter out any candidates that remain (but were skipped for | |||
1669 | // whatever reason). | |||
1670 | assert(LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!")(static_cast <bool> (LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!") ? void (0) : __assert_fail ("LI.getLoopFor(ParentBB) == &L && \"Branch in an inner loop!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1670, __extension__ __PRETTY_FUNCTION__)); | |||
1671 | ||||
1672 | SmallVector<BasicBlock *, 4> ExitBlocks; | |||
1673 | L.getUniqueExitBlocks(ExitBlocks); | |||
1674 | ||||
1675 | // We cannot unswitch if exit blocks contain a cleanuppad instruction as we | |||
1676 | // don't know how to split those exit blocks. | |||
1677 | // FIXME: We should teach SplitBlock to handle this and remove this | |||
1678 | // restriction. | |||
1679 | for (auto *ExitBB : ExitBlocks) | |||
1680 | if (isa<CleanupPadInst>(ExitBB->getFirstNonPHI())) | |||
1681 | return false; | |||
1682 | ||||
1683 | SmallPtrSet<BasicBlock *, 4> ExitBlockSet(ExitBlocks.begin(), | |||
1684 | ExitBlocks.end()); | |||
1685 | ||||
1686 | // Compute the parent loop now before we start hacking on things. | |||
1687 | Loop *ParentL = L.getParentLoop(); | |||
1688 | ||||
1689 | // Compute the outer-most loop containing one of our exit blocks. This is the | |||
1690 | // furthest up our loopnest which can be mutated, which we will use below to | |||
1691 | // update things. | |||
1692 | Loop *OuterExitL = &L; | |||
1693 | for (auto *ExitBB : ExitBlocks) { | |||
1694 | Loop *NewOuterExitL = LI.getLoopFor(ExitBB); | |||
1695 | if (!NewOuterExitL) { | |||
1696 | // We exited the entire nest with this block, so we're done. | |||
1697 | OuterExitL = nullptr; | |||
1698 | break; | |||
1699 | } | |||
1700 | if (NewOuterExitL != OuterExitL && NewOuterExitL->contains(OuterExitL)) | |||
1701 | OuterExitL = NewOuterExitL; | |||
1702 | } | |||
1703 | ||||
1704 | // If the edge we *aren't* cloning in the unswitch (the continuing edge) | |||
1705 | // dominates its target, we can skip cloning the dominated region of the loop | |||
1706 | // and its exits. We compute this as a set of nodes to be skipped. | |||
1707 | SmallPtrSet<BasicBlock *, 4> SkippedLoopAndExitBlocks; | |||
1708 | if (ContinueSuccBB->getUniquePredecessor() || | |||
1709 | llvm::all_of(predecessors(ContinueSuccBB), [&](BasicBlock *PredBB) { | |||
1710 | return PredBB == ParentBB || DT.dominates(ContinueSuccBB, PredBB); | |||
1711 | })) { | |||
1712 | visitDomSubTree(DT, ContinueSuccBB, [&](BasicBlock *BB) { | |||
1713 | SkippedLoopAndExitBlocks.insert(BB); | |||
1714 | return true; | |||
1715 | }); | |||
1716 | } | |||
1717 | // Similarly, if the edge we *are* cloning in the unswitch (the unswitched | |||
1718 | // edge) dominates its target, we will end up with dead nodes in the original | |||
1719 | // loop and its exits that will need to be deleted. Here, we just retain that | |||
1720 | // the property holds and will compute the deleted set later. | |||
1721 | bool DeleteUnswitchedSucc = | |||
1722 | UnswitchedSuccBB->getUniquePredecessor() || | |||
1723 | llvm::all_of(predecessors(UnswitchedSuccBB), [&](BasicBlock *PredBB) { | |||
1724 | return PredBB == ParentBB || DT.dominates(UnswitchedSuccBB, PredBB); | |||
1725 | }); | |||
1726 | ||||
1727 | // Split the preheader, so that we know that there is a safe place to insert | |||
1728 | // the conditional branch. We will change the preheader to have a conditional | |||
1729 | // branch on LoopCond. The original preheader will become the split point | |||
1730 | // between the unswitched versions, and we will have a new preheader for the | |||
1731 | // original loop. | |||
1732 | BasicBlock *SplitBB = L.getLoopPreheader(); | |||
1733 | BasicBlock *LoopPH = SplitEdge(SplitBB, L.getHeader(), &DT, &LI); | |||
1734 | ||||
1735 | // Keep a mapping for the cloned values. | |||
1736 | ValueToValueMapTy VMap; | |||
1737 | ||||
1738 | // Build the cloned blocks from the loop. | |||
1739 | auto *ClonedPH = buildClonedLoopBlocks( | |||
1740 | L, LoopPH, SplitBB, ExitBlocks, ParentBB, UnswitchedSuccBB, | |||
1741 | ContinueSuccBB, SkippedLoopAndExitBlocks, VMap, AC, DT, LI); | |||
1742 | ||||
1743 | // Build the cloned loop structure itself. This may be substantially | |||
1744 | // different from the original structure due to the simplified CFG. This also | |||
1745 | // handles inserting all the cloned blocks into the correct loops. | |||
1746 | SmallVector<Loop *, 4> NonChildClonedLoops; | |||
1747 | Loop *ClonedL = | |||
1748 | buildClonedLoops(L, ExitBlocks, VMap, LI, NonChildClonedLoops); | |||
1749 | ||||
1750 | // Remove the parent as a predecessor of the unswitched successor. | |||
1751 | UnswitchedSuccBB->removePredecessor(ParentBB, /*DontDeleteUselessPHIs*/ true); | |||
1752 | ||||
1753 | // Now splice the branch from the original loop and use it to select between | |||
1754 | // the two loops. | |||
1755 | SplitBB->getTerminator()->eraseFromParent(); | |||
1756 | SplitBB->getInstList().splice(SplitBB->end(), ParentBB->getInstList(), BI); | |||
1757 | BI.setSuccessor(ClonedSucc, ClonedPH); | |||
1758 | BI.setSuccessor(1 - ClonedSucc, LoopPH); | |||
1759 | ||||
1760 | // Create a new unconditional branch to the continuing block (as opposed to | |||
1761 | // the one cloned). | |||
1762 | BranchInst::Create(ContinueSuccBB, ParentBB); | |||
1763 | ||||
1764 | // Delete anything that was made dead in the original loop due to | |||
1765 | // unswitching. | |||
1766 | if (DeleteUnswitchedSucc) | |||
1767 | deleteDeadBlocksFromLoop(L, UnswitchedSuccBB, ExitBlocks, DT, LI); | |||
1768 | ||||
1769 | SmallVector<Loop *, 4> HoistedLoops; | |||
1770 | bool IsStillLoop = rebuildLoopAfterUnswitch(L, ExitBlocks, LI, HoistedLoops); | |||
1771 | ||||
1772 | // This will have completely invalidated the dominator tree. We can't easily | |||
1773 | // bound how much is invalid because in some cases we will refine the | |||
1774 | // predecessor set of exit blocks of the loop which can move large unrelated | |||
1775 | // regions of code into a new subtree. | |||
1776 | // | |||
1777 | // FIXME: Eventually, we should use an incremental update utility that | |||
1778 | // leverages the existing information in the dominator tree (and potentially | |||
1779 | // the nature of the change) to more efficiently update things. | |||
1780 | DT.recalculate(*SplitBB->getParent()); | |||
1781 | ||||
1782 | // We can change which blocks are exit blocks of all the cloned sibling | |||
1783 | // loops, the current loop, and any parent loops which shared exit blocks | |||
1784 | // with the current loop. As a consequence, we need to re-form LCSSA for | |||
1785 | // them. But we shouldn't need to re-form LCSSA for any child loops. | |||
1786 | // FIXME: This could be made more efficient by tracking which exit blocks are | |||
1787 | // new, and focusing on them, but that isn't likely to be necessary. | |||
1788 | // | |||
1789 | // In order to reasonably rebuild LCSSA we need to walk inside-out across the | |||
1790 | // loop nest and update every loop that could have had its exits changed. We | |||
1791 | // also need to cover any intervening loops. We add all of these loops to | |||
1792 | // a list and sort them by loop depth to achieve this without updating | |||
1793 | // unnecessary loops. | |||
1794 | auto UpdateLCSSA = [&](Loop &UpdateL) { | |||
1795 | #ifndef NDEBUG | |||
1796 | for (Loop *ChildL : UpdateL) | |||
1797 | assert(ChildL->isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (ChildL->isRecursivelyLCSSAForm( DT, LI) && "Perturbed a child loop's LCSSA form!") ? void (0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1798, __extension__ __PRETTY_FUNCTION__)) | |||
1798 | "Perturbed a child loop's LCSSA form!")(static_cast <bool> (ChildL->isRecursivelyLCSSAForm( DT, LI) && "Perturbed a child loop's LCSSA form!") ? void (0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1798, __extension__ __PRETTY_FUNCTION__)); | |||
1799 | #endif | |||
1800 | formLCSSA(UpdateL, DT, &LI, nullptr); | |||
1801 | }; | |||
1802 | ||||
1803 | // For non-child cloned loops and hoisted loops, we just need to update LCSSA | |||
1804 | // and we can do it in any order as they don't nest relative to each other. | |||
1805 | for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) | |||
1806 | UpdateLCSSA(*UpdatedL); | |||
1807 | ||||
1808 | // If the original loop had exit blocks, walk up through the outer most loop | |||
1809 | // of those exit blocks to update LCSSA and form updated dedicated exits. | |||
1810 | if (OuterExitL != &L) { | |||
1811 | SmallVector<Loop *, 4> OuterLoops; | |||
1812 | // We start with the cloned loop and the current loop if they are loops and | |||
1813 | // move toward OuterExitL. Also, if either the cloned loop or the current | |||
1814 | // loop have become top level loops we need to walk all the way out. | |||
1815 | if (ClonedL) { | |||
1816 | OuterLoops.push_back(ClonedL); | |||
1817 | if (!ClonedL->getParentLoop()) | |||
1818 | OuterExitL = nullptr; | |||
1819 | } | |||
1820 | if (IsStillLoop) { | |||
1821 | OuterLoops.push_back(&L); | |||
1822 | if (!L.getParentLoop()) | |||
1823 | OuterExitL = nullptr; | |||
1824 | } | |||
1825 | // Grab all of the enclosing loops now. | |||
1826 | for (Loop *OuterL = ParentL; OuterL != OuterExitL; | |||
1827 | OuterL = OuterL->getParentLoop()) | |||
1828 | OuterLoops.push_back(OuterL); | |||
1829 | ||||
1830 | // Finally, update our list of outer loops. This is nicely ordered to work | |||
1831 | // inside-out. | |||
1832 | for (Loop *OuterL : OuterLoops) { | |||
1833 | // First build LCSSA for this loop so that we can preserve it when | |||
1834 | // forming dedicated exits. We don't want to perturb some other loop's | |||
1835 | // LCSSA while doing that CFG edit. | |||
1836 | UpdateLCSSA(*OuterL); | |||
1837 | ||||
1838 | // For loops reached by this loop's original exit blocks we may | |||
1839 | // introduced new, non-dedicated exits. At least try to re-form dedicated | |||
1840 | // exits for these loops. This may fail if they couldn't have dedicated | |||
1841 | // exits to start with. | |||
1842 | formDedicatedExitBlocks(OuterL, &DT, &LI, /*PreserveLCSSA*/ true); | |||
1843 | } | |||
1844 | } | |||
1845 | ||||
1846 | #ifndef NDEBUG | |||
1847 | // Verify the entire loop structure to catch any incorrect updates before we | |||
1848 | // progress in the pass pipeline. | |||
1849 | LI.verify(DT); | |||
1850 | #endif | |||
1851 | ||||
1852 | // Now that we've unswitched something, make callbacks to report the changes. | |||
1853 | // For that we need to merge together the updated loops and the cloned loops | |||
1854 | // and check whether the original loop survived. | |||
1855 | SmallVector<Loop *, 4> SibLoops; | |||
1856 | for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) | |||
1857 | if (UpdatedL->getParentLoop() == ParentL) | |||
1858 | SibLoops.push_back(UpdatedL); | |||
1859 | NonTrivialUnswitchCB(IsStillLoop, SibLoops); | |||
1860 | ||||
1861 | ++NumBranches; | |||
1862 | return true; | |||
1863 | } | |||
1864 | ||||
1865 | /// Recursively compute the cost of a dominator subtree based on the per-block | |||
1866 | /// cost map provided. | |||
1867 | /// | |||
1868 | /// The recursive computation is memozied into the provided DT-indexed cost map | |||
1869 | /// to allow querying it for most nodes in the domtree without it becoming | |||
1870 | /// quadratic. | |||
1871 | static int | |||
1872 | computeDomSubtreeCost(DomTreeNode &N, | |||
1873 | const SmallDenseMap<BasicBlock *, int, 4> &BBCostMap, | |||
1874 | SmallDenseMap<DomTreeNode *, int, 4> &DTCostMap) { | |||
1875 | // Don't accumulate cost (or recurse through) blocks not in our block cost | |||
1876 | // map and thus not part of the duplication cost being considered. | |||
1877 | auto BBCostIt = BBCostMap.find(N.getBlock()); | |||
1878 | if (BBCostIt == BBCostMap.end()) | |||
1879 | return 0; | |||
1880 | ||||
1881 | // Lookup this node to see if we already computed its cost. | |||
1882 | auto DTCostIt = DTCostMap.find(&N); | |||
1883 | if (DTCostIt != DTCostMap.end()) | |||
1884 | return DTCostIt->second; | |||
1885 | ||||
1886 | // If not, we have to compute it. We can't use insert above and update | |||
1887 | // because computing the cost may insert more things into the map. | |||
1888 | int Cost = std::accumulate( | |||
1889 | N.begin(), N.end(), BBCostIt->second, [&](int Sum, DomTreeNode *ChildN) { | |||
1890 | return Sum + computeDomSubtreeCost(*ChildN, BBCostMap, DTCostMap); | |||
1891 | }); | |||
1892 | bool Inserted = DTCostMap.insert({&N, Cost}).second; | |||
1893 | (void)Inserted; | |||
1894 | assert(Inserted && "Should not insert a node while visiting children!")(static_cast <bool> (Inserted && "Should not insert a node while visiting children!" ) ? void (0) : __assert_fail ("Inserted && \"Should not insert a node while visiting children!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1894, __extension__ __PRETTY_FUNCTION__)); | |||
1895 | return Cost; | |||
1896 | } | |||
1897 | ||||
1898 | /// Unswitch control flow predicated on loop invariant conditions. | |||
1899 | /// | |||
1900 | /// This first hoists all branches or switches which are trivial (IE, do not | |||
1901 | /// require duplicating any part of the loop) out of the loop body. It then | |||
1902 | /// looks at other loop invariant control flows and tries to unswitch those as | |||
1903 | /// well by cloning the loop if the result is small enough. | |||
1904 | static bool | |||
1905 | unswitchLoop(Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | |||
1906 | TargetTransformInfo &TTI, bool NonTrivial, | |||
1907 | function_ref<void(bool, ArrayRef<Loop *>)> NonTrivialUnswitchCB) { | |||
1908 | assert(L.isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) && "Loops must be in LCSSA form before unswitching.") ? void (0 ) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1909, __extension__ __PRETTY_FUNCTION__)) | |||
1909 | "Loops must be in LCSSA form before unswitching.")(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) && "Loops must be in LCSSA form before unswitching.") ? void (0 ) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1909, __extension__ __PRETTY_FUNCTION__)); | |||
1910 | bool Changed = false; | |||
1911 | ||||
1912 | // Must be in loop simplified form: we need a preheader and dedicated exits. | |||
1913 | if (!L.isLoopSimplifyForm()) | |||
1914 | return false; | |||
1915 | ||||
1916 | // Try trivial unswitch first before loop over other basic blocks in the loop. | |||
1917 | Changed |= unswitchAllTrivialConditions(L, DT, LI); | |||
1918 | ||||
1919 | // If we're not doing non-trivial unswitching, we're done. We both accept | |||
1920 | // a parameter but also check a local flag that can be used for testing | |||
1921 | // a debugging. | |||
1922 | if (!NonTrivial && !EnableNonTrivialUnswitch) | |||
1923 | return Changed; | |||
1924 | ||||
1925 | // Collect all remaining invariant branch conditions within this loop (as | |||
1926 | // opposed to an inner loop which would be handled when visiting that inner | |||
1927 | // loop). | |||
1928 | SmallVector<TerminatorInst *, 4> UnswitchCandidates; | |||
1929 | for (auto *BB : L.blocks()) | |||
1930 | if (LI.getLoopFor(BB) == &L) | |||
1931 | if (auto *BI = dyn_cast<BranchInst>(BB->getTerminator())) | |||
1932 | if (BI->isConditional() && L.isLoopInvariant(BI->getCondition()) && | |||
1933 | BI->getSuccessor(0) != BI->getSuccessor(1)) | |||
1934 | UnswitchCandidates.push_back(BI); | |||
1935 | ||||
1936 | // If we didn't find any candidates, we're done. | |||
1937 | if (UnswitchCandidates.empty()) | |||
1938 | return Changed; | |||
1939 | ||||
1940 | DEBUG(dbgs() << "Considering " << UnswitchCandidates.size()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Considering " << UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n" ; } } while (false) | |||
1941 | << " non-trivial loop invariant conditions for unswitching.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Considering " << UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n" ; } } while (false); | |||
1942 | ||||
1943 | // Given that unswitching these terminators will require duplicating parts of | |||
1944 | // the loop, so we need to be able to model that cost. Compute the ephemeral | |||
1945 | // values and set up a data structure to hold per-BB costs. We cache each | |||
1946 | // block's cost so that we don't recompute this when considering different | |||
1947 | // subsets of the loop for duplication during unswitching. | |||
1948 | SmallPtrSet<const Value *, 4> EphValues; | |||
1949 | CodeMetrics::collectEphemeralValues(&L, &AC, EphValues); | |||
1950 | SmallDenseMap<BasicBlock *, int, 4> BBCostMap; | |||
1951 | ||||
1952 | // Compute the cost of each block, as well as the total loop cost. Also, bail | |||
1953 | // out if we see instructions which are incompatible with loop unswitching | |||
1954 | // (convergent, noduplicate, or cross-basic-block tokens). | |||
1955 | // FIXME: We might be able to safely handle some of these in non-duplicated | |||
1956 | // regions. | |||
1957 | int LoopCost = 0; | |||
1958 | for (auto *BB : L.blocks()) { | |||
1959 | int Cost = 0; | |||
1960 | for (auto &I : *BB) { | |||
1961 | if (EphValues.count(&I)) | |||
1962 | continue; | |||
1963 | ||||
1964 | if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB)) | |||
1965 | return Changed; | |||
1966 | if (auto CS = CallSite(&I)) | |||
1967 | if (CS.isConvergent() || CS.cannotDuplicate()) | |||
1968 | return Changed; | |||
1969 | ||||
1970 | Cost += TTI.getUserCost(&I); | |||
1971 | } | |||
1972 | assert(Cost >= 0 && "Must not have negative costs!")(static_cast <bool> (Cost >= 0 && "Must not have negative costs!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Must not have negative costs!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1972, __extension__ __PRETTY_FUNCTION__)); | |||
1973 | LoopCost += Cost; | |||
1974 | assert(LoopCost >= 0 && "Must not have negative loop costs!")(static_cast <bool> (LoopCost >= 0 && "Must not have negative loop costs!" ) ? void (0) : __assert_fail ("LoopCost >= 0 && \"Must not have negative loop costs!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1974, __extension__ __PRETTY_FUNCTION__)); | |||
1975 | BBCostMap[BB] = Cost; | |||
1976 | } | |||
1977 | DEBUG(dbgs() << " Total loop cost: " << LoopCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Total loop cost: " << LoopCost << "\n"; } } while (false); | |||
1978 | ||||
1979 | // Now we find the best candidate by searching for the one with the following | |||
1980 | // properties in order: | |||
1981 | // | |||
1982 | // 1) An unswitching cost below the threshold | |||
1983 | // 2) The smallest number of duplicated unswitch candidates (to avoid | |||
1984 | // creating redundant subsequent unswitching) | |||
1985 | // 3) The smallest cost after unswitching. | |||
1986 | // | |||
1987 | // We prioritize reducing fanout of unswitch candidates provided the cost | |||
1988 | // remains below the threshold because this has a multiplicative effect. | |||
1989 | // | |||
1990 | // This requires memoizing each dominator subtree to avoid redundant work. | |||
1991 | // | |||
1992 | // FIXME: Need to actually do the number of candidates part above. | |||
1993 | SmallDenseMap<DomTreeNode *, int, 4> DTCostMap; | |||
1994 | // Given a terminator which might be unswitched, computes the non-duplicated | |||
1995 | // cost for that terminator. | |||
1996 | auto ComputeUnswitchedCost = [&](TerminatorInst *TI) { | |||
1997 | BasicBlock &BB = *TI->getParent(); | |||
1998 | SmallPtrSet<BasicBlock *, 4> Visited; | |||
1999 | ||||
2000 | int Cost = LoopCost; | |||
2001 | for (BasicBlock *SuccBB : successors(&BB)) { | |||
2002 | // Don't count successors more than once. | |||
2003 | if (!Visited.insert(SuccBB).second) | |||
2004 | continue; | |||
2005 | ||||
2006 | // This successor's domtree will not need to be duplicated after | |||
2007 | // unswitching if the edge to the successor dominates it (and thus the | |||
2008 | // entire tree). This essentially means there is no other path into this | |||
2009 | // subtree and so it will end up live in only one clone of the loop. | |||
2010 | if (SuccBB->getUniquePredecessor() || | |||
2011 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | |||
2012 | return PredBB == &BB || DT.dominates(SuccBB, PredBB); | |||
2013 | })) { | |||
2014 | Cost -= computeDomSubtreeCost(*DT[SuccBB], BBCostMap, DTCostMap); | |||
2015 | assert(Cost >= 0 &&(static_cast <bool> (Cost >= 0 && "Non-duplicated cost should never exceed total loop cost!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Non-duplicated cost should never exceed total loop cost!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2016, __extension__ __PRETTY_FUNCTION__)) | |||
2016 | "Non-duplicated cost should never exceed total loop cost!")(static_cast <bool> (Cost >= 0 && "Non-duplicated cost should never exceed total loop cost!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Non-duplicated cost should never exceed total loop cost!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2016, __extension__ __PRETTY_FUNCTION__)); | |||
2017 | } | |||
2018 | } | |||
2019 | ||||
2020 | // Now scale the cost by the number of unique successors minus one. We | |||
2021 | // subtract one because there is already at least one copy of the entire | |||
2022 | // loop. This is computing the new cost of unswitching a condition. | |||
2023 | assert(Visited.size() > 1 &&(static_cast <bool> (Visited.size() > 1 && "Cannot unswitch a condition without multiple distinct successors!" ) ? void (0) : __assert_fail ("Visited.size() > 1 && \"Cannot unswitch a condition without multiple distinct successors!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2024, __extension__ __PRETTY_FUNCTION__)) | |||
2024 | "Cannot unswitch a condition without multiple distinct successors!")(static_cast <bool> (Visited.size() > 1 && "Cannot unswitch a condition without multiple distinct successors!" ) ? void (0) : __assert_fail ("Visited.size() > 1 && \"Cannot unswitch a condition without multiple distinct successors!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2024, __extension__ __PRETTY_FUNCTION__)); | |||
2025 | return Cost * (Visited.size() - 1); | |||
2026 | }; | |||
2027 | TerminatorInst *BestUnswitchTI = nullptr; | |||
2028 | int BestUnswitchCost; | |||
2029 | for (TerminatorInst *CandidateTI : UnswitchCandidates) { | |||
2030 | int CandidateCost = ComputeUnswitchedCost(CandidateTI); | |||
2031 | DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Computed cost of " << CandidateCost << " for unswitch candidate: " << *CandidateTI << "\n"; } } while (false) | |||
2032 | << " for unswitch candidate: " << *CandidateTI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Computed cost of " << CandidateCost << " for unswitch candidate: " << *CandidateTI << "\n"; } } while (false); | |||
2033 | if (!BestUnswitchTI || CandidateCost < BestUnswitchCost) { | |||
2034 | BestUnswitchTI = CandidateTI; | |||
2035 | BestUnswitchCost = CandidateCost; | |||
2036 | } | |||
2037 | } | |||
2038 | ||||
2039 | if (BestUnswitchCost < UnswitchThreshold) { | |||
| ||||
2040 | DEBUG(dbgs() << " Trying to unswitch non-trivial (cost = "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") branch: " << *BestUnswitchTI << "\n"; } } while (false) | |||
2041 | << BestUnswitchCost << ") branch: " << *BestUnswitchTIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") branch: " << *BestUnswitchTI << "\n"; } } while (false) | |||
2042 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") branch: " << *BestUnswitchTI << "\n"; } } while (false); | |||
2043 | Changed |= unswitchInvariantBranch(L, cast<BranchInst>(*BestUnswitchTI), DT, | |||
2044 | LI, AC, NonTrivialUnswitchCB); | |||
2045 | } else { | |||
2046 | DEBUG(dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCostdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCost << "\n"; } } while (false) | |||
2047 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCost << "\n"; } } while (false); | |||
2048 | } | |||
2049 | ||||
2050 | return Changed; | |||
2051 | } | |||
2052 | ||||
2053 | PreservedAnalyses SimpleLoopUnswitchPass::run(Loop &L, LoopAnalysisManager &AM, | |||
2054 | LoopStandardAnalysisResults &AR, | |||
2055 | LPMUpdater &U) { | |||
2056 | Function &F = *L.getHeader()->getParent(); | |||
2057 | (void)F; | |||
2058 | ||||
2059 | DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << L << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << L << "\n"; } } while (false); | |||
2060 | ||||
2061 | // Save the current loop name in a variable so that we can report it even | |||
2062 | // after it has been deleted. | |||
2063 | std::string LoopName = L.getName(); | |||
2064 | ||||
2065 | auto NonTrivialUnswitchCB = [&L, &U, &LoopName](bool CurrentLoopValid, | |||
2066 | ArrayRef<Loop *> NewLoops) { | |||
2067 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | |||
2068 | U.addSiblingLoops(NewLoops); | |||
2069 | ||||
2070 | // If the current loop remains valid, we should revisit it to catch any | |||
2071 | // other unswitch opportunities. Otherwise, we need to mark it as deleted. | |||
2072 | if (CurrentLoopValid) | |||
2073 | U.revisitCurrentLoop(); | |||
2074 | else | |||
2075 | U.markLoopAsDeleted(L, LoopName); | |||
2076 | }; | |||
2077 | ||||
2078 | if (!unswitchLoop(L, AR.DT, AR.LI, AR.AC, AR.TTI, NonTrivial, | |||
2079 | NonTrivialUnswitchCB)) | |||
2080 | return PreservedAnalyses::all(); | |||
2081 | ||||
2082 | // Historically this pass has had issues with the dominator tree so verify it | |||
2083 | // in asserts builds. | |||
2084 | assert(AR.DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (AR.DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("AR.DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2084, __extension__ __PRETTY_FUNCTION__)); | |||
2085 | return getLoopPassPreservedAnalyses(); | |||
2086 | } | |||
2087 | ||||
2088 | namespace { | |||
2089 | ||||
2090 | class SimpleLoopUnswitchLegacyPass : public LoopPass { | |||
2091 | bool NonTrivial; | |||
2092 | ||||
2093 | public: | |||
2094 | static char ID; // Pass ID, replacement for typeid | |||
2095 | ||||
2096 | explicit SimpleLoopUnswitchLegacyPass(bool NonTrivial = false) | |||
2097 | : LoopPass(ID), NonTrivial(NonTrivial) { | |||
2098 | initializeSimpleLoopUnswitchLegacyPassPass( | |||
2099 | *PassRegistry::getPassRegistry()); | |||
2100 | } | |||
2101 | ||||
2102 | bool runOnLoop(Loop *L, LPPassManager &LPM) override; | |||
2103 | ||||
2104 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||
2105 | AU.addRequired<AssumptionCacheTracker>(); | |||
2106 | AU.addRequired<TargetTransformInfoWrapperPass>(); | |||
2107 | getLoopAnalysisUsage(AU); | |||
2108 | } | |||
2109 | }; | |||
2110 | ||||
2111 | } // end anonymous namespace | |||
2112 | ||||
2113 | bool SimpleLoopUnswitchLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) { | |||
2114 | if (skipLoop(L)) | |||
| ||||
2115 | return false; | |||
2116 | ||||
2117 | Function &F = *L->getHeader()->getParent(); | |||
2118 | ||||
2119 | DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << *L << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << *L << "\n" ; } } while (false); | |||
2120 | ||||
2121 | auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); | |||
2122 | auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); | |||
2123 | auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); | |||
2124 | auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); | |||
2125 | ||||
2126 | auto NonTrivialUnswitchCB = [&L, &LPM](bool CurrentLoopValid, | |||
2127 | ArrayRef<Loop *> NewLoops) { | |||
2128 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | |||
2129 | for (auto *NewL : NewLoops) | |||
2130 | LPM.addLoop(*NewL); | |||
2131 | ||||
2132 | // If the current loop remains valid, re-add it to the queue. This is | |||
2133 | // a little wasteful as we'll finish processing the current loop as well, | |||
2134 | // but it is the best we can do in the old PM. | |||
2135 | if (CurrentLoopValid) | |||
2136 | LPM.addLoop(*L); | |||
2137 | else | |||
2138 | LPM.markLoopAsDeleted(*L); | |||
2139 | }; | |||
2140 | ||||
2141 | bool Changed = | |||
2142 | unswitchLoop(*L, DT, LI, AC, TTI, NonTrivial, NonTrivialUnswitchCB); | |||
2143 | ||||
2144 | // If anything was unswitched, also clear any cached information about this | |||
2145 | // loop. | |||
2146 | LPM.deleteSimpleAnalysisLoop(L); | |||
2147 | ||||
2148 | // Historically this pass has had issues with the dominator tree so verify it | |||
2149 | // in asserts builds. | |||
2150 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2150, __extension__ __PRETTY_FUNCTION__)); | |||
2151 | ||||
2152 | return Changed; | |||
2153 | } | |||
2154 | ||||
2155 | char SimpleLoopUnswitchLegacyPass::ID = 0; | |||
2156 | INITIALIZE_PASS_BEGIN(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | |||
2157 | "Simple unswitch loops", false, false)static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | |||
2158 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | |||
2159 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | |||
2160 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | |||
2161 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | |||
2162 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | |||
2163 | INITIALIZE_PASS_END(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | |||
2164 | "Simple unswitch loops", false, false)PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | |||
2165 | ||||
2166 | Pass *llvm::createSimpleLoopUnswitchLegacyPass(bool NonTrivial) { | |||
2167 | return new SimpleLoopUnswitchLegacyPass(NonTrivial); | |||
2168 | } |