Bug Summary

File:lib/Transforms/Scalar/Reassociate.cpp
Warning:line 169, column 8
Dereference of null pointer (loaded from variable '__begin1')

Annotated Source Code

Press '?' to see keyboard shortcuts

clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name Reassociate.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-eagerly-assume -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-7/lib/clang/7.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-7~svn329677/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn329677/build-llvm/include -I /build/llvm-toolchain-snapshot-7~svn329677/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/backward -internal-isystem /usr/include/clang/7.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-7/lib/clang/7.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-7~svn329677/build-llvm/lib/Transforms/Scalar -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-checker optin.performance.Padding -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-04-11-031539-24776-1 -x c++ /build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp
1//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
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// This pass reassociates commutative expressions in an order that is designed
11// to promote better constant propagation, GCSE, LICM, PRE, etc.
12//
13// For example: 4 + (x + 5) -> x + (4 + 5)
14//
15// In the implementation of this algorithm, constants are assigned rank = 0,
16// function arguments are rank = 1, and other values are assigned ranks
17// corresponding to the reverse post order traversal of current function
18// (starting at 2), which effectively gives values in deep loops higher rank
19// than values not in loops.
20//
21//===----------------------------------------------------------------------===//
22
23#include "llvm/Transforms/Scalar/Reassociate.h"
24#include "llvm/ADT/APFloat.h"
25#include "llvm/ADT/APInt.h"
26#include "llvm/ADT/DenseMap.h"
27#include "llvm/ADT/PostOrderIterator.h"
28#include "llvm/ADT/SetVector.h"
29#include "llvm/ADT/SmallPtrSet.h"
30#include "llvm/ADT/SmallSet.h"
31#include "llvm/ADT/SmallVector.h"
32#include "llvm/ADT/Statistic.h"
33#include "llvm/Analysis/GlobalsModRef.h"
34#include "llvm/Analysis/Utils/Local.h"
35#include "llvm/Analysis/ValueTracking.h"
36#include "llvm/IR/Argument.h"
37#include "llvm/IR/BasicBlock.h"
38#include "llvm/IR/CFG.h"
39#include "llvm/IR/Constant.h"
40#include "llvm/IR/Constants.h"
41#include "llvm/IR/Function.h"
42#include "llvm/IR/IRBuilder.h"
43#include "llvm/IR/InstrTypes.h"
44#include "llvm/IR/Instruction.h"
45#include "llvm/IR/Instructions.h"
46#include "llvm/IR/Operator.h"
47#include "llvm/IR/PassManager.h"
48#include "llvm/IR/PatternMatch.h"
49#include "llvm/IR/Type.h"
50#include "llvm/IR/User.h"
51#include "llvm/IR/Value.h"
52#include "llvm/IR/ValueHandle.h"
53#include "llvm/Pass.h"
54#include "llvm/Support/Casting.h"
55#include "llvm/Support/Debug.h"
56#include "llvm/Support/ErrorHandling.h"
57#include "llvm/Support/raw_ostream.h"
58#include "llvm/Transforms/Scalar.h"
59#include <algorithm>
60#include <cassert>
61#include <utility>
62
63using namespace llvm;
64using namespace reassociate;
65
66#define DEBUG_TYPE"reassociate" "reassociate"
67
68STATISTIC(NumChanged, "Number of insts reassociated")static llvm::Statistic NumChanged = {"reassociate", "NumChanged"
, "Number of insts reassociated", {0}, {false}}
;
69STATISTIC(NumAnnihil, "Number of expr tree annihilated")static llvm::Statistic NumAnnihil = {"reassociate", "NumAnnihil"
, "Number of expr tree annihilated", {0}, {false}}
;
70STATISTIC(NumFactor , "Number of multiplies factored")static llvm::Statistic NumFactor = {"reassociate", "NumFactor"
, "Number of multiplies factored", {0}, {false}}
;
71
72#ifndef NDEBUG
73/// Print out the expression identified in the Ops list.
74static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
75 Module *M = I->getModule();
76 dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
77 << *Ops[0].Op->getType() << '\t';
78 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
79 dbgs() << "[ ";
80 Ops[i].Op->printAsOperand(dbgs(), false, M);
81 dbgs() << ", #" << Ops[i].Rank << "] ";
82 }
83}
84#endif
85
86/// Utility class representing a non-constant Xor-operand. We classify
87/// non-constant Xor-Operands into two categories:
88/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
89/// C2)
90/// C2.1) The operand is in the form of "X | C", where C is a non-zero
91/// constant.
92/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
93/// operand as "E | 0"
94class llvm::reassociate::XorOpnd {
95public:
96 XorOpnd(Value *V);
97
98 bool isInvalid() const { return SymbolicPart == nullptr; }
99 bool isOrExpr() const { return isOr; }
100 Value *getValue() const { return OrigVal; }
101 Value *getSymbolicPart() const { return SymbolicPart; }
102 unsigned getSymbolicRank() const { return SymbolicRank; }
103 const APInt &getConstPart() const { return ConstPart; }
104
105 void Invalidate() { SymbolicPart = OrigVal = nullptr; }
106 void setSymbolicRank(unsigned R) { SymbolicRank = R; }
107
108private:
109 Value *OrigVal;
110 Value *SymbolicPart;
111 APInt ConstPart;
112 unsigned SymbolicRank;
113 bool isOr;
114};
115
116XorOpnd::XorOpnd(Value *V) {
117 assert(!isa<ConstantInt>(V) && "No ConstantInt")(static_cast <bool> (!isa<ConstantInt>(V) &&
"No ConstantInt") ? void (0) : __assert_fail ("!isa<ConstantInt>(V) && \"No ConstantInt\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 117, __extension__ __PRETTY_FUNCTION__))
;
118 OrigVal = V;
119 Instruction *I = dyn_cast<Instruction>(V);
120 SymbolicRank = 0;
121
122 if (I && (I->getOpcode() == Instruction::Or ||
123 I->getOpcode() == Instruction::And)) {
124 Value *V0 = I->getOperand(0);
125 Value *V1 = I->getOperand(1);
126 const APInt *C;
127 if (match(V0, PatternMatch::m_APInt(C)))
128 std::swap(V0, V1);
129
130 if (match(V1, PatternMatch::m_APInt(C))) {
131 ConstPart = *C;
132 SymbolicPart = V0;
133 isOr = (I->getOpcode() == Instruction::Or);
134 return;
135 }
136 }
137
138 // view the operand as "V | 0"
139 SymbolicPart = V;
140 ConstPart = APInt::getNullValue(V->getType()->getScalarSizeInBits());
141 isOr = true;
142}
143
144/// Return true if V is an instruction of the specified opcode and if it
145/// only has one use.
146static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
147 auto *I = dyn_cast<Instruction>(V);
148 if (I && I->hasOneUse() && I->getOpcode() == Opcode)
149 if (!isa<FPMathOperator>(I) || I->isFast())
150 return cast<BinaryOperator>(I);
151 return nullptr;
152}
153
154static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
155 unsigned Opcode2) {
156 auto *I = dyn_cast<Instruction>(V);
157 if (I && I->hasOneUse() &&
158 (I->getOpcode() == Opcode1 || I->getOpcode() == Opcode2))
159 if (!isa<FPMathOperator>(I) || I->isFast())
160 return cast<BinaryOperator>(I);
161 return nullptr;
162}
163
164void ReassociatePass::BuildRankMap(Function &F,
165 ReversePostOrderTraversal<Function*> &RPOT) {
166 unsigned Rank = 2;
167
168 // Assign distinct ranks to function arguments.
169 for (auto &Arg : F.args()) {
5
Assuming '__begin1' is not equal to '__end1'
6
Null pointer value stored to '__begin1'
7
Assuming '__begin1' is not equal to '__end1'
8
Dereference of null pointer (loaded from variable '__begin1')
170 ValueRankMap[&Arg] = ++Rank;
171 DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rankdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Calculated Rank[" <<
Arg.getName() << "] = " << Rank << "\n"; }
} while (false)
172 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Calculated Rank[" <<
Arg.getName() << "] = " << Rank << "\n"; }
} while (false)
;
173 }
174
175 // Traverse basic blocks in ReversePostOrder
176 for (BasicBlock *BB : RPOT) {
177 unsigned BBRank = RankMap[BB] = ++Rank << 16;
178
179 // Walk the basic block, adding precomputed ranks for any instructions that
180 // we cannot move. This ensures that the ranks for these instructions are
181 // all different in the block.
182 for (Instruction &I : *BB)
183 if (mayBeMemoryDependent(I))
184 ValueRankMap[&I] = ++BBRank;
185 }
186}
187
188unsigned ReassociatePass::getRank(Value *V) {
189 Instruction *I = dyn_cast<Instruction>(V);
190 if (!I) {
191 if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
192 return 0; // Otherwise it's a global or constant, rank 0.
193 }
194
195 if (unsigned Rank = ValueRankMap[I])
196 return Rank; // Rank already known?
197
198 // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
199 // we can reassociate expressions for code motion! Since we do not recurse
200 // for PHI nodes, we cannot have infinite recursion here, because there
201 // cannot be loops in the value graph that do not go through PHI nodes.
202 unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
203 for (unsigned i = 0, e = I->getNumOperands();
204 i != e && Rank != MaxRank; ++i)
205 Rank = std::max(Rank, getRank(I->getOperand(i)));
206
207 // If this is a not or neg instruction, do not count it for rank. This
208 // assures us that X and ~X will have the same rank.
209 if (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I) &&
210 !BinaryOperator::isFNeg(I))
211 ++Rank;
212
213 DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Calculated Rank[" <<
V->getName() << "] = " << Rank << "\n";
} } while (false)
;
214
215 return ValueRankMap[I] = Rank;
216}
217
218// Canonicalize constants to RHS. Otherwise, sort the operands by rank.
219void ReassociatePass::canonicalizeOperands(Instruction *I) {
220 assert(isa<BinaryOperator>(I) && "Expected binary operator.")(static_cast <bool> (isa<BinaryOperator>(I) &&
"Expected binary operator.") ? void (0) : __assert_fail ("isa<BinaryOperator>(I) && \"Expected binary operator.\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 220, __extension__ __PRETTY_FUNCTION__))
;
221 assert(I->isCommutative() && "Expected commutative operator.")(static_cast <bool> (I->isCommutative() && "Expected commutative operator."
) ? void (0) : __assert_fail ("I->isCommutative() && \"Expected commutative operator.\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 221, __extension__ __PRETTY_FUNCTION__))
;
222
223 Value *LHS = I->getOperand(0);
224 Value *RHS = I->getOperand(1);
225 if (LHS == RHS || isa<Constant>(RHS))
226 return;
227 if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS))
228 cast<BinaryOperator>(I)->swapOperands();
229}
230
231static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
232 Instruction *InsertBefore, Value *FlagsOp) {
233 if (S1->getType()->isIntOrIntVectorTy())
234 return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
235 else {
236 BinaryOperator *Res =
237 BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
238 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
239 return Res;
240 }
241}
242
243static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
244 Instruction *InsertBefore, Value *FlagsOp) {
245 if (S1->getType()->isIntOrIntVectorTy())
246 return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
247 else {
248 BinaryOperator *Res =
249 BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
250 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
251 return Res;
252 }
253}
254
255static BinaryOperator *CreateNeg(Value *S1, const Twine &Name,
256 Instruction *InsertBefore, Value *FlagsOp) {
257 if (S1->getType()->isIntOrIntVectorTy())
258 return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
259 else {
260 BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
261 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
262 return Res;
263 }
264}
265
266/// Replace 0-X with X*-1.
267static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
268 Type *Ty = Neg->getType();
269 Constant *NegOne = Ty->isIntOrIntVectorTy() ?
270 ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
271
272 BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
273 Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
274 Res->takeName(Neg);
275 Neg->replaceAllUsesWith(Res);
276 Res->setDebugLoc(Neg->getDebugLoc());
277 return Res;
278}
279
280/// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael
281/// function. This means that x^(2^k) === 1 mod 2^Bitwidth for
282/// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
283/// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
284/// even x in Bitwidth-bit arithmetic.
285static unsigned CarmichaelShift(unsigned Bitwidth) {
286 if (Bitwidth < 3)
287 return Bitwidth - 1;
288 return Bitwidth - 2;
289}
290
291/// Add the extra weight 'RHS' to the existing weight 'LHS',
292/// reducing the combined weight using any special properties of the operation.
293/// The existing weight LHS represents the computation X op X op ... op X where
294/// X occurs LHS times. The combined weight represents X op X op ... op X with
295/// X occurring LHS + RHS times. If op is "Xor" for example then the combined
296/// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
297/// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
298static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
299 // If we were working with infinite precision arithmetic then the combined
300 // weight would be LHS + RHS. But we are using finite precision arithmetic,
301 // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
302 // for nilpotent operations and addition, but not for idempotent operations
303 // and multiplication), so it is important to correctly reduce the combined
304 // weight back into range if wrapping would be wrong.
305
306 // If RHS is zero then the weight didn't change.
307 if (RHS.isMinValue())
308 return;
309 // If LHS is zero then the combined weight is RHS.
310 if (LHS.isMinValue()) {
311 LHS = RHS;
312 return;
313 }
314 // From this point on we know that neither LHS nor RHS is zero.
315
316 if (Instruction::isIdempotent(Opcode)) {
317 // Idempotent means X op X === X, so any non-zero weight is equivalent to a
318 // weight of 1. Keeping weights at zero or one also means that wrapping is
319 // not a problem.
320 assert(LHS == 1 && RHS == 1 && "Weights not reduced!")(static_cast <bool> (LHS == 1 && RHS == 1 &&
"Weights not reduced!") ? void (0) : __assert_fail ("LHS == 1 && RHS == 1 && \"Weights not reduced!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 320, __extension__ __PRETTY_FUNCTION__))
;
321 return; // Return a weight of 1.
322 }
323 if (Instruction::isNilpotent(Opcode)) {
324 // Nilpotent means X op X === 0, so reduce weights modulo 2.
325 assert(LHS == 1 && RHS == 1 && "Weights not reduced!")(static_cast <bool> (LHS == 1 && RHS == 1 &&
"Weights not reduced!") ? void (0) : __assert_fail ("LHS == 1 && RHS == 1 && \"Weights not reduced!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 325, __extension__ __PRETTY_FUNCTION__))
;
326 LHS = 0; // 1 + 1 === 0 modulo 2.
327 return;
328 }
329 if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
330 // TODO: Reduce the weight by exploiting nsw/nuw?
331 LHS += RHS;
332 return;
333 }
334
335 assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&(static_cast <bool> ((Opcode == Instruction::Mul || Opcode
== Instruction::FMul) && "Unknown associative operation!"
) ? void (0) : __assert_fail ("(Opcode == Instruction::Mul || Opcode == Instruction::FMul) && \"Unknown associative operation!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 336, __extension__ __PRETTY_FUNCTION__))
336 "Unknown associative operation!")(static_cast <bool> ((Opcode == Instruction::Mul || Opcode
== Instruction::FMul) && "Unknown associative operation!"
) ? void (0) : __assert_fail ("(Opcode == Instruction::Mul || Opcode == Instruction::FMul) && \"Unknown associative operation!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 336, __extension__ __PRETTY_FUNCTION__))
;
337 unsigned Bitwidth = LHS.getBitWidth();
338 // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
339 // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
340 // bit number x, since either x is odd in which case x^CM = 1, or x is even in
341 // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
342 // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
343 // which by a happy accident means that they can always be represented using
344 // Bitwidth bits.
345 // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
346 // the Carmichael number).
347 if (Bitwidth > 3) {
348 /// CM - The value of Carmichael's lambda function.
349 APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
350 // Any weight W >= Threshold can be replaced with W - CM.
351 APInt Threshold = CM + Bitwidth;
352 assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!")(static_cast <bool> (LHS.ult(Threshold) && RHS.
ult(Threshold) && "Weights not reduced!") ? void (0) :
__assert_fail ("LHS.ult(Threshold) && RHS.ult(Threshold) && \"Weights not reduced!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 352, __extension__ __PRETTY_FUNCTION__))
;
353 // For Bitwidth 4 or more the following sum does not overflow.
354 LHS += RHS;
355 while (LHS.uge(Threshold))
356 LHS -= CM;
357 } else {
358 // To avoid problems with overflow do everything the same as above but using
359 // a larger type.
360 unsigned CM = 1U << CarmichaelShift(Bitwidth);
361 unsigned Threshold = CM + Bitwidth;
362 assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&(static_cast <bool> (LHS.getZExtValue() < Threshold &&
RHS.getZExtValue() < Threshold && "Weights not reduced!"
) ? void (0) : __assert_fail ("LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold && \"Weights not reduced!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 363, __extension__ __PRETTY_FUNCTION__))
363 "Weights not reduced!")(static_cast <bool> (LHS.getZExtValue() < Threshold &&
RHS.getZExtValue() < Threshold && "Weights not reduced!"
) ? void (0) : __assert_fail ("LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold && \"Weights not reduced!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 363, __extension__ __PRETTY_FUNCTION__))
;
364 unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
365 while (Total >= Threshold)
366 Total -= CM;
367 LHS = Total;
368 }
369}
370
371using RepeatedValue = std::pair<Value*, APInt>;
372
373/// Given an associative binary expression, return the leaf
374/// nodes in Ops along with their weights (how many times the leaf occurs). The
375/// original expression is the same as
376/// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
377/// op
378/// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
379/// op
380/// ...
381/// op
382/// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
383///
384/// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
385///
386/// This routine may modify the function, in which case it returns 'true'. The
387/// changes it makes may well be destructive, changing the value computed by 'I'
388/// to something completely different. Thus if the routine returns 'true' then
389/// you MUST either replace I with a new expression computed from the Ops array,
390/// or use RewriteExprTree to put the values back in.
391///
392/// A leaf node is either not a binary operation of the same kind as the root
393/// node 'I' (i.e. is not a binary operator at all, or is, but with a different
394/// opcode), or is the same kind of binary operator but has a use which either
395/// does not belong to the expression, or does belong to the expression but is
396/// a leaf node. Every leaf node has at least one use that is a non-leaf node
397/// of the expression, while for non-leaf nodes (except for the root 'I') every
398/// use is a non-leaf node of the expression.
399///
400/// For example:
401/// expression graph node names
402///
403/// + | I
404/// / \ |
405/// + + | A, B
406/// / \ / \ |
407/// * + * | C, D, E
408/// / \ / \ / \ |
409/// + * | F, G
410///
411/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
412/// that order) (C, 1), (E, 1), (F, 2), (G, 2).
413///
414/// The expression is maximal: if some instruction is a binary operator of the
415/// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
416/// then the instruction also belongs to the expression, is not a leaf node of
417/// it, and its operands also belong to the expression (but may be leaf nodes).
418///
419/// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
420/// order to ensure that every non-root node in the expression has *exactly one*
421/// use by a non-leaf node of the expression. This destruction means that the
422/// caller MUST either replace 'I' with a new expression or use something like
423/// RewriteExprTree to put the values back in if the routine indicates that it
424/// made a change by returning 'true'.
425///
426/// In the above example either the right operand of A or the left operand of B
427/// will be replaced by undef. If it is B's operand then this gives:
428///
429/// + | I
430/// / \ |
431/// + + | A, B - operand of B replaced with undef
432/// / \ \ |
433/// * + * | C, D, E
434/// / \ / \ / \ |
435/// + * | F, G
436///
437/// Note that such undef operands can only be reached by passing through 'I'.
438/// For example, if you visit operands recursively starting from a leaf node
439/// then you will never see such an undef operand unless you get back to 'I',
440/// which requires passing through a phi node.
441///
442/// Note that this routine may also mutate binary operators of the wrong type
443/// that have all uses inside the expression (i.e. only used by non-leaf nodes
444/// of the expression) if it can turn them into binary operators of the right
445/// type and thus make the expression bigger.
446static bool LinearizeExprTree(BinaryOperator *I,
447 SmallVectorImpl<RepeatedValue> &Ops) {
448 DEBUG(dbgs() << "LINEARIZE: " << *I << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "LINEARIZE: " << *I <<
'\n'; } } while (false)
;
449 unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
450 unsigned Opcode = I->getOpcode();
451 assert(I->isAssociative() && I->isCommutative() &&(static_cast <bool> (I->isAssociative() && I
->isCommutative() && "Expected an associative and commutative operation!"
) ? void (0) : __assert_fail ("I->isAssociative() && I->isCommutative() && \"Expected an associative and commutative operation!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 452, __extension__ __PRETTY_FUNCTION__))
452 "Expected an associative and commutative operation!")(static_cast <bool> (I->isAssociative() && I
->isCommutative() && "Expected an associative and commutative operation!"
) ? void (0) : __assert_fail ("I->isAssociative() && I->isCommutative() && \"Expected an associative and commutative operation!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 452, __extension__ __PRETTY_FUNCTION__))
;
453
454 // Visit all operands of the expression, keeping track of their weight (the
455 // number of paths from the expression root to the operand, or if you like
456 // the number of times that operand occurs in the linearized expression).
457 // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
458 // while A has weight two.
459
460 // Worklist of non-leaf nodes (their operands are in the expression too) along
461 // with their weights, representing a certain number of paths to the operator.
462 // If an operator occurs in the worklist multiple times then we found multiple
463 // ways to get to it.
464 SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
465 Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
466 bool Changed = false;
467
468 // Leaves of the expression are values that either aren't the right kind of
469 // operation (eg: a constant, or a multiply in an add tree), or are, but have
470 // some uses that are not inside the expression. For example, in I = X + X,
471 // X = A + B, the value X has two uses (by I) that are in the expression. If
472 // X has any other uses, for example in a return instruction, then we consider
473 // X to be a leaf, and won't analyze it further. When we first visit a value,
474 // if it has more than one use then at first we conservatively consider it to
475 // be a leaf. Later, as the expression is explored, we may discover some more
476 // uses of the value from inside the expression. If all uses turn out to be
477 // from within the expression (and the value is a binary operator of the right
478 // kind) then the value is no longer considered to be a leaf, and its operands
479 // are explored.
480
481 // Leaves - Keeps track of the set of putative leaves as well as the number of
482 // paths to each leaf seen so far.
483 using LeafMap = DenseMap<Value *, APInt>;
484 LeafMap Leaves; // Leaf -> Total weight so far.
485 SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order.
486
487#ifndef NDEBUG
488 SmallPtrSet<Value *, 8> Visited; // For sanity checking the iteration scheme.
489#endif
490 while (!Worklist.empty()) {
491 std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
492 I = P.first; // We examine the operands of this binary operator.
493
494 for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
495 Value *Op = I->getOperand(OpIdx);
496 APInt Weight = P.second; // Number of paths to this operand.
497 DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "OPERAND: " << *Op <<
" (" << Weight << ")\n"; } } while (false)
;
498 assert(!Op->use_empty() && "No uses, so how did we get to it?!")(static_cast <bool> (!Op->use_empty() && "No uses, so how did we get to it?!"
) ? void (0) : __assert_fail ("!Op->use_empty() && \"No uses, so how did we get to it?!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 498, __extension__ __PRETTY_FUNCTION__))
;
499
500 // If this is a binary operation of the right kind with only one use then
501 // add its operands to the expression.
502 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
503 assert(Visited.insert(Op).second && "Not first visit!")(static_cast <bool> (Visited.insert(Op).second &&
"Not first visit!") ? void (0) : __assert_fail ("Visited.insert(Op).second && \"Not first visit!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 503, __extension__ __PRETTY_FUNCTION__))
;
504 DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "DIRECT ADD: " << *Op
<< " (" << Weight << ")\n"; } } while (false
)
;
505 Worklist.push_back(std::make_pair(BO, Weight));
506 continue;
507 }
508
509 // Appears to be a leaf. Is the operand already in the set of leaves?
510 LeafMap::iterator It = Leaves.find(Op);
511 if (It == Leaves.end()) {
512 // Not in the leaf map. Must be the first time we saw this operand.
513 assert(Visited.insert(Op).second && "Not first visit!")(static_cast <bool> (Visited.insert(Op).second &&
"Not first visit!") ? void (0) : __assert_fail ("Visited.insert(Op).second && \"Not first visit!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 513, __extension__ __PRETTY_FUNCTION__))
;
514 if (!Op->hasOneUse()) {
515 // This value has uses not accounted for by the expression, so it is
516 // not safe to modify. Mark it as being a leaf.
517 DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "ADD USES LEAF: " <<
*Op << " (" << Weight << ")\n"; } } while (
false)
;
518 LeafOrder.push_back(Op);
519 Leaves[Op] = Weight;
520 continue;
521 }
522 // No uses outside the expression, try morphing it.
523 } else {
524 // Already in the leaf map.
525 assert(It != Leaves.end() && Visited.count(Op) &&(static_cast <bool> (It != Leaves.end() && Visited
.count(Op) && "In leaf map but not visited!") ? void (
0) : __assert_fail ("It != Leaves.end() && Visited.count(Op) && \"In leaf map but not visited!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 526, __extension__ __PRETTY_FUNCTION__))
526 "In leaf map but not visited!")(static_cast <bool> (It != Leaves.end() && Visited
.count(Op) && "In leaf map but not visited!") ? void (
0) : __assert_fail ("It != Leaves.end() && Visited.count(Op) && \"In leaf map but not visited!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 526, __extension__ __PRETTY_FUNCTION__))
;
527
528 // Update the number of paths to the leaf.
529 IncorporateWeight(It->second, Weight, Opcode);
530
531#if 0 // TODO: Re-enable once PR13021 is fixed.
532 // The leaf already has one use from inside the expression. As we want
533 // exactly one such use, drop this new use of the leaf.
534 assert(!Op->hasOneUse() && "Only one use, but we got here twice!")(static_cast <bool> (!Op->hasOneUse() && "Only one use, but we got here twice!"
) ? void (0) : __assert_fail ("!Op->hasOneUse() && \"Only one use, but we got here twice!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 534, __extension__ __PRETTY_FUNCTION__))
;
535 I->setOperand(OpIdx, UndefValue::get(I->getType()));
536 Changed = true;
537
538 // If the leaf is a binary operation of the right kind and we now see
539 // that its multiple original uses were in fact all by nodes belonging
540 // to the expression, then no longer consider it to be a leaf and add
541 // its operands to the expression.
542 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
543 DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "UNLEAF: " << *Op <<
" (" << It->second << ")\n"; } } while (false
)
;
544 Worklist.push_back(std::make_pair(BO, It->second));
545 Leaves.erase(It);
546 continue;
547 }
548#endif
549
550 // If we still have uses that are not accounted for by the expression
551 // then it is not safe to modify the value.
552 if (!Op->hasOneUse())
553 continue;
554
555 // No uses outside the expression, try morphing it.
556 Weight = It->second;
557 Leaves.erase(It); // Since the value may be morphed below.
558 }
559
560 // At this point we have a value which, first of all, is not a binary
561 // expression of the right kind, and secondly, is only used inside the
562 // expression. This means that it can safely be modified. See if we
563 // can usefully morph it into an expression of the right kind.
564 assert((!isa<Instruction>(Op) ||(static_cast <bool> ((!isa<Instruction>(Op) || cast
<Instruction>(Op)->getOpcode() != Opcode || (isa<
FPMathOperator>(Op) && !cast<Instruction>(Op
)->isFast())) && "Should have been handled above!"
) ? void (0) : __assert_fail ("(!isa<Instruction>(Op) || cast<Instruction>(Op)->getOpcode() != Opcode || (isa<FPMathOperator>(Op) && !cast<Instruction>(Op)->isFast())) && \"Should have been handled above!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 568, __extension__ __PRETTY_FUNCTION__))
565 cast<Instruction>(Op)->getOpcode() != Opcode(static_cast <bool> ((!isa<Instruction>(Op) || cast
<Instruction>(Op)->getOpcode() != Opcode || (isa<
FPMathOperator>(Op) && !cast<Instruction>(Op
)->isFast())) && "Should have been handled above!"
) ? void (0) : __assert_fail ("(!isa<Instruction>(Op) || cast<Instruction>(Op)->getOpcode() != Opcode || (isa<FPMathOperator>(Op) && !cast<Instruction>(Op)->isFast())) && \"Should have been handled above!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 568, __extension__ __PRETTY_FUNCTION__))
566 || (isa<FPMathOperator>(Op) &&(static_cast <bool> ((!isa<Instruction>(Op) || cast
<Instruction>(Op)->getOpcode() != Opcode || (isa<
FPMathOperator>(Op) && !cast<Instruction>(Op
)->isFast())) && "Should have been handled above!"
) ? void (0) : __assert_fail ("(!isa<Instruction>(Op) || cast<Instruction>(Op)->getOpcode() != Opcode || (isa<FPMathOperator>(Op) && !cast<Instruction>(Op)->isFast())) && \"Should have been handled above!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 568, __extension__ __PRETTY_FUNCTION__))
567 !cast<Instruction>(Op)->isFast())) &&(static_cast <bool> ((!isa<Instruction>(Op) || cast
<Instruction>(Op)->getOpcode() != Opcode || (isa<
FPMathOperator>(Op) && !cast<Instruction>(Op
)->isFast())) && "Should have been handled above!"
) ? void (0) : __assert_fail ("(!isa<Instruction>(Op) || cast<Instruction>(Op)->getOpcode() != Opcode || (isa<FPMathOperator>(Op) && !cast<Instruction>(Op)->isFast())) && \"Should have been handled above!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 568, __extension__ __PRETTY_FUNCTION__))
568 "Should have been handled above!")(static_cast <bool> ((!isa<Instruction>(Op) || cast
<Instruction>(Op)->getOpcode() != Opcode || (isa<
FPMathOperator>(Op) && !cast<Instruction>(Op
)->isFast())) && "Should have been handled above!"
) ? void (0) : __assert_fail ("(!isa<Instruction>(Op) || cast<Instruction>(Op)->getOpcode() != Opcode || (isa<FPMathOperator>(Op) && !cast<Instruction>(Op)->isFast())) && \"Should have been handled above!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 568, __extension__ __PRETTY_FUNCTION__))
;
569 assert(Op->hasOneUse() && "Has uses outside the expression tree!")(static_cast <bool> (Op->hasOneUse() && "Has uses outside the expression tree!"
) ? void (0) : __assert_fail ("Op->hasOneUse() && \"Has uses outside the expression tree!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 569, __extension__ __PRETTY_FUNCTION__))
;
570
571 // If this is a multiply expression, turn any internal negations into
572 // multiplies by -1 so they can be reassociated.
573 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
574 if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
575 (Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
576 DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "MORPH LEAF: " << *Op
<< " (" << Weight << ") TO "; } } while (false
)
;
577 BO = LowerNegateToMultiply(BO);
578 DEBUG(dbgs() << *BO << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << *BO << '\n'; } } while
(false)
;
579 Worklist.push_back(std::make_pair(BO, Weight));
580 Changed = true;
581 continue;
582 }
583
584 // Failed to morph into an expression of the right type. This really is
585 // a leaf.
586 DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "ADD LEAF: " << *Op <<
" (" << Weight << ")\n"; } } while (false)
;
587 assert(!isReassociableOp(Op, Opcode) && "Value was morphed?")(static_cast <bool> (!isReassociableOp(Op, Opcode) &&
"Value was morphed?") ? void (0) : __assert_fail ("!isReassociableOp(Op, Opcode) && \"Value was morphed?\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 587, __extension__ __PRETTY_FUNCTION__))
;
588 LeafOrder.push_back(Op);
589 Leaves[Op] = Weight;
590 }
591 }
592
593 // The leaves, repeated according to their weights, represent the linearized
594 // form of the expression.
595 for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
596 Value *V = LeafOrder[i];
597 LeafMap::iterator It = Leaves.find(V);
598 if (It == Leaves.end())
599 // Node initially thought to be a leaf wasn't.
600 continue;
601 assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!")(static_cast <bool> (!isReassociableOp(V, Opcode) &&
"Shouldn't be a leaf!") ? void (0) : __assert_fail ("!isReassociableOp(V, Opcode) && \"Shouldn't be a leaf!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 601, __extension__ __PRETTY_FUNCTION__))
;
602 APInt Weight = It->second;
603 if (Weight.isMinValue())
604 // Leaf already output or weight reduction eliminated it.
605 continue;
606 // Ensure the leaf is only output once.
607 It->second = 0;
608 Ops.push_back(std::make_pair(V, Weight));
609 }
610
611 // For nilpotent operations or addition there may be no operands, for example
612 // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
613 // in both cases the weight reduces to 0 causing the value to be skipped.
614 if (Ops.empty()) {
615 Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
616 assert(Identity && "Associative operation without identity!")(static_cast <bool> (Identity && "Associative operation without identity!"
) ? void (0) : __assert_fail ("Identity && \"Associative operation without identity!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 616, __extension__ __PRETTY_FUNCTION__))
;
617 Ops.emplace_back(Identity, APInt(Bitwidth, 1));
618 }
619
620 return Changed;
621}
622
623/// Now that the operands for this expression tree are
624/// linearized and optimized, emit them in-order.
625void ReassociatePass::RewriteExprTree(BinaryOperator *I,
626 SmallVectorImpl<ValueEntry> &Ops) {
627 assert(Ops.size() > 1 && "Single values should be used directly!")(static_cast <bool> (Ops.size() > 1 && "Single values should be used directly!"
) ? void (0) : __assert_fail ("Ops.size() > 1 && \"Single values should be used directly!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 627, __extension__ __PRETTY_FUNCTION__))
;
628
629 // Since our optimizations should never increase the number of operations, the
630 // new expression can usually be written reusing the existing binary operators
631 // from the original expression tree, without creating any new instructions,
632 // though the rewritten expression may have a completely different topology.
633 // We take care to not change anything if the new expression will be the same
634 // as the original. If more than trivial changes (like commuting operands)
635 // were made then we are obliged to clear out any optional subclass data like
636 // nsw flags.
637
638 /// NodesToRewrite - Nodes from the original expression available for writing
639 /// the new expression into.
640 SmallVector<BinaryOperator*, 8> NodesToRewrite;
641 unsigned Opcode = I->getOpcode();
642 BinaryOperator *Op = I;
643
644 /// NotRewritable - The operands being written will be the leaves of the new
645 /// expression and must not be used as inner nodes (via NodesToRewrite) by
646 /// mistake. Inner nodes are always reassociable, and usually leaves are not
647 /// (if they were they would have been incorporated into the expression and so
648 /// would not be leaves), so most of the time there is no danger of this. But
649 /// in rare cases a leaf may become reassociable if an optimization kills uses
650 /// of it, or it may momentarily become reassociable during rewriting (below)
651 /// due it being removed as an operand of one of its uses. Ensure that misuse
652 /// of leaf nodes as inner nodes cannot occur by remembering all of the future
653 /// leaves and refusing to reuse any of them as inner nodes.
654 SmallPtrSet<Value*, 8> NotRewritable;
655 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
656 NotRewritable.insert(Ops[i].Op);
657
658 // ExpressionChanged - Non-null if the rewritten expression differs from the
659 // original in some non-trivial way, requiring the clearing of optional flags.
660 // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
661 BinaryOperator *ExpressionChanged = nullptr;
662 for (unsigned i = 0; ; ++i) {
663 // The last operation (which comes earliest in the IR) is special as both
664 // operands will come from Ops, rather than just one with the other being
665 // a subexpression.
666 if (i+2 == Ops.size()) {
667 Value *NewLHS = Ops[i].Op;
668 Value *NewRHS = Ops[i+1].Op;
669 Value *OldLHS = Op->getOperand(0);
670 Value *OldRHS = Op->getOperand(1);
671
672 if (NewLHS == OldLHS && NewRHS == OldRHS)
673 // Nothing changed, leave it alone.
674 break;
675
676 if (NewLHS == OldRHS && NewRHS == OldLHS) {
677 // The order of the operands was reversed. Swap them.
678 DEBUG(dbgs() << "RA: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RA: " << *Op <<
'\n'; } } while (false)
;
679 Op->swapOperands();
680 DEBUG(dbgs() << "TO: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "TO: " << *Op <<
'\n'; } } while (false)
;
681 MadeChange = true;
682 ++NumChanged;
683 break;
684 }
685
686 // The new operation differs non-trivially from the original. Overwrite
687 // the old operands with the new ones.
688 DEBUG(dbgs() << "RA: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RA: " << *Op <<
'\n'; } } while (false)
;
689 if (NewLHS != OldLHS) {
690 BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
691 if (BO && !NotRewritable.count(BO))
692 NodesToRewrite.push_back(BO);
693 Op->setOperand(0, NewLHS);
694 }
695 if (NewRHS != OldRHS) {
696 BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
697 if (BO && !NotRewritable.count(BO))
698 NodesToRewrite.push_back(BO);
699 Op->setOperand(1, NewRHS);
700 }
701 DEBUG(dbgs() << "TO: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "TO: " << *Op <<
'\n'; } } while (false)
;
702
703 ExpressionChanged = Op;
704 MadeChange = true;
705 ++NumChanged;
706
707 break;
708 }
709
710 // Not the last operation. The left-hand side will be a sub-expression
711 // while the right-hand side will be the current element of Ops.
712 Value *NewRHS = Ops[i].Op;
713 if (NewRHS != Op->getOperand(1)) {
714 DEBUG(dbgs() << "RA: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RA: " << *Op <<
'\n'; } } while (false)
;
715 if (NewRHS == Op->getOperand(0)) {
716 // The new right-hand side was already present as the left operand. If
717 // we are lucky then swapping the operands will sort out both of them.
718 Op->swapOperands();
719 } else {
720 // Overwrite with the new right-hand side.
721 BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
722 if (BO && !NotRewritable.count(BO))
723 NodesToRewrite.push_back(BO);
724 Op->setOperand(1, NewRHS);
725 ExpressionChanged = Op;
726 }
727 DEBUG(dbgs() << "TO: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "TO: " << *Op <<
'\n'; } } while (false)
;
728 MadeChange = true;
729 ++NumChanged;
730 }
731
732 // Now deal with the left-hand side. If this is already an operation node
733 // from the original expression then just rewrite the rest of the expression
734 // into it.
735 BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
736 if (BO && !NotRewritable.count(BO)) {
737 Op = BO;
738 continue;
739 }
740
741 // Otherwise, grab a spare node from the original expression and use that as
742 // the left-hand side. If there are no nodes left then the optimizers made
743 // an expression with more nodes than the original! This usually means that
744 // they did something stupid but it might mean that the problem was just too
745 // hard (finding the mimimal number of multiplications needed to realize a
746 // multiplication expression is NP-complete). Whatever the reason, smart or
747 // stupid, create a new node if there are none left.
748 BinaryOperator *NewOp;
749 if (NodesToRewrite.empty()) {
750 Constant *Undef = UndefValue::get(I->getType());
751 NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
752 Undef, Undef, "", I);
753 if (NewOp->getType()->isFPOrFPVectorTy())
754 NewOp->setFastMathFlags(I->getFastMathFlags());
755 } else {
756 NewOp = NodesToRewrite.pop_back_val();
757 }
758
759 DEBUG(dbgs() << "RA: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RA: " << *Op <<
'\n'; } } while (false)
;
760 Op->setOperand(0, NewOp);
761 DEBUG(dbgs() << "TO: " << *Op << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "TO: " << *Op <<
'\n'; } } while (false)
;
762 ExpressionChanged = Op;
763 MadeChange = true;
764 ++NumChanged;
765 Op = NewOp;
766 }
767
768 // If the expression changed non-trivially then clear out all subclass data
769 // starting from the operator specified in ExpressionChanged, and compactify
770 // the operators to just before the expression root to guarantee that the
771 // expression tree is dominated by all of Ops.
772 if (ExpressionChanged)
773 do {
774 // Preserve FastMathFlags.
775 if (isa<FPMathOperator>(I)) {
776 FastMathFlags Flags = I->getFastMathFlags();
777 ExpressionChanged->clearSubclassOptionalData();
778 ExpressionChanged->setFastMathFlags(Flags);
779 } else
780 ExpressionChanged->clearSubclassOptionalData();
781
782 if (ExpressionChanged == I)
783 break;
784 ExpressionChanged->moveBefore(I);
785 ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
786 } while (true);
787
788 // Throw away any left over nodes from the original expression.
789 for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
790 RedoInsts.insert(NodesToRewrite[i]);
791}
792
793/// Insert instructions before the instruction pointed to by BI,
794/// that computes the negative version of the value specified. The negative
795/// version of the value is returned, and BI is left pointing at the instruction
796/// that should be processed next by the reassociation pass.
797/// Also add intermediate instructions to the redo list that are modified while
798/// pushing the negates through adds. These will be revisited to see if
799/// additional opportunities have been exposed.
800static Value *NegateValue(Value *V, Instruction *BI,
801 SetVector<AssertingVH<Instruction>> &ToRedo) {
802 if (auto *C = dyn_cast<Constant>(V))
803 return C->getType()->isFPOrFPVectorTy() ? ConstantExpr::getFNeg(C) :
804 ConstantExpr::getNeg(C);
805
806 // We are trying to expose opportunity for reassociation. One of the things
807 // that we want to do to achieve this is to push a negation as deep into an
808 // expression chain as possible, to expose the add instructions. In practice,
809 // this means that we turn this:
810 // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
811 // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
812 // the constants. We assume that instcombine will clean up the mess later if
813 // we introduce tons of unnecessary negation instructions.
814 //
815 if (BinaryOperator *I =
816 isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
817 // Push the negates through the add.
818 I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
819 I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
820 if (I->getOpcode() == Instruction::Add) {
821 I->setHasNoUnsignedWrap(false);
822 I->setHasNoSignedWrap(false);
823 }
824
825 // We must move the add instruction here, because the neg instructions do
826 // not dominate the old add instruction in general. By moving it, we are
827 // assured that the neg instructions we just inserted dominate the
828 // instruction we are about to insert after them.
829 //
830 I->moveBefore(BI);
831 I->setName(I->getName()+".neg");
832
833 // Add the intermediate negates to the redo list as processing them later
834 // could expose more reassociating opportunities.
835 ToRedo.insert(I);
836 return I;
837 }
838
839 // Okay, we need to materialize a negated version of V with an instruction.
840 // Scan the use lists of V to see if we have one already.
841 for (User *U : V->users()) {
842 if (!BinaryOperator::isNeg(U) && !BinaryOperator::isFNeg(U))
843 continue;
844
845 // We found one! Now we have to make sure that the definition dominates
846 // this use. We do this by moving it to the entry block (if it is a
847 // non-instruction value) or right after the definition. These negates will
848 // be zapped by reassociate later, so we don't need much finesse here.
849 BinaryOperator *TheNeg = cast<BinaryOperator>(U);
850
851 // Verify that the negate is in this function, V might be a constant expr.
852 if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
853 continue;
854
855 BasicBlock::iterator InsertPt;
856 if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
857 if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
858 InsertPt = II->getNormalDest()->begin();
859 } else {
860 InsertPt = ++InstInput->getIterator();
861 }
862 while (isa<PHINode>(InsertPt)) ++InsertPt;
863 } else {
864 InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
865 }
866 TheNeg->moveBefore(&*InsertPt);
867 if (TheNeg->getOpcode() == Instruction::Sub) {
868 TheNeg->setHasNoUnsignedWrap(false);
869 TheNeg->setHasNoSignedWrap(false);
870 } else {
871 TheNeg->andIRFlags(BI);
872 }
873 ToRedo.insert(TheNeg);
874 return TheNeg;
875 }
876
877 // Insert a 'neg' instruction that subtracts the value from zero to get the
878 // negation.
879 BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
880 ToRedo.insert(NewNeg);
881 return NewNeg;
882}
883
884/// Return true if we should break up this subtract of X-Y into (X + -Y).
885static bool ShouldBreakUpSubtract(Instruction *Sub) {
886 // If this is a negation, we can't split it up!
887 if (BinaryOperator::isNeg(Sub) || BinaryOperator::isFNeg(Sub))
888 return false;
889
890 // Don't breakup X - undef.
891 if (isa<UndefValue>(Sub->getOperand(1)))
892 return false;
893
894 // Don't bother to break this up unless either the LHS is an associable add or
895 // subtract or if this is only used by one.
896 Value *V0 = Sub->getOperand(0);
897 if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
898 isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
899 return true;
900 Value *V1 = Sub->getOperand(1);
901 if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
902 isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
903 return true;
904 Value *VB = Sub->user_back();
905 if (Sub->hasOneUse() &&
906 (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
907 isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
908 return true;
909
910 return false;
911}
912
913/// If we have (X-Y), and if either X is an add, or if this is only used by an
914/// add, transform this into (X+(0-Y)) to promote better reassociation.
915static BinaryOperator *
916BreakUpSubtract(Instruction *Sub, SetVector<AssertingVH<Instruction>> &ToRedo) {
917 // Convert a subtract into an add and a neg instruction. This allows sub
918 // instructions to be commuted with other add instructions.
919 //
920 // Calculate the negative value of Operand 1 of the sub instruction,
921 // and set it as the RHS of the add instruction we just made.
922 Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
923 BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
924 Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
925 Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
926 New->takeName(Sub);
927
928 // Everyone now refers to the add instruction.
929 Sub->replaceAllUsesWith(New);
930 New->setDebugLoc(Sub->getDebugLoc());
931
932 DEBUG(dbgs() << "Negated: " << *New << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Negated: " << *New <<
'\n'; } } while (false)
;
933 return New;
934}
935
936/// If this is a shift of a reassociable multiply or is used by one, change
937/// this into a multiply by a constant to assist with further reassociation.
938static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
939 Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
940 MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
941
942 BinaryOperator *Mul =
943 BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
944 Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
945 Mul->takeName(Shl);
946
947 // Everyone now refers to the mul instruction.
948 Shl->replaceAllUsesWith(Mul);
949 Mul->setDebugLoc(Shl->getDebugLoc());
950
951 // We can safely preserve the nuw flag in all cases. It's also safe to turn a
952 // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
953 // handling.
954 bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
955 bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
956 if (NSW && NUW)
957 Mul->setHasNoSignedWrap(true);
958 Mul->setHasNoUnsignedWrap(NUW);
959 return Mul;
960}
961
962/// Scan backwards and forwards among values with the same rank as element i
963/// to see if X exists. If X does not exist, return i. This is useful when
964/// scanning for 'x' when we see '-x' because they both get the same rank.
965static unsigned FindInOperandList(const SmallVectorImpl<ValueEntry> &Ops,
966 unsigned i, Value *X) {
967 unsigned XRank = Ops[i].Rank;
968 unsigned e = Ops.size();
969 for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
970 if (Ops[j].Op == X)
971 return j;
972 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
973 if (Instruction *I2 = dyn_cast<Instruction>(X))
974 if (I1->isIdenticalTo(I2))
975 return j;
976 }
977 // Scan backwards.
978 for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
979 if (Ops[j].Op == X)
980 return j;
981 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
982 if (Instruction *I2 = dyn_cast<Instruction>(X))
983 if (I1->isIdenticalTo(I2))
984 return j;
985 }
986 return i;
987}
988
989/// Emit a tree of add instructions, summing Ops together
990/// and returning the result. Insert the tree before I.
991static Value *EmitAddTreeOfValues(Instruction *I,
992 SmallVectorImpl<WeakTrackingVH> &Ops) {
993 if (Ops.size() == 1) return Ops.back();
994
995 Value *V1 = Ops.back();
996 Ops.pop_back();
997 Value *V2 = EmitAddTreeOfValues(I, Ops);
998 return CreateAdd(V2, V1, "reass.add", I, I);
999}
1000
1001/// If V is an expression tree that is a multiplication sequence,
1002/// and if this sequence contains a multiply by Factor,
1003/// remove Factor from the tree and return the new tree.
1004Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) {
1005 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1006 if (!BO)
1007 return nullptr;
1008
1009 SmallVector<RepeatedValue, 8> Tree;
1010 MadeChange |= LinearizeExprTree(BO, Tree);
1011 SmallVector<ValueEntry, 8> Factors;
1012 Factors.reserve(Tree.size());
1013 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1014 RepeatedValue E = Tree[i];
1015 Factors.append(E.second.getZExtValue(),
1016 ValueEntry(getRank(E.first), E.first));
1017 }
1018
1019 bool FoundFactor = false;
1020 bool NeedsNegate = false;
1021 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1022 if (Factors[i].Op == Factor) {
1023 FoundFactor = true;
1024 Factors.erase(Factors.begin()+i);
1025 break;
1026 }
1027
1028 // If this is a negative version of this factor, remove it.
1029 if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
1030 if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1031 if (FC1->getValue() == -FC2->getValue()) {
1032 FoundFactor = NeedsNegate = true;
1033 Factors.erase(Factors.begin()+i);
1034 break;
1035 }
1036 } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
1037 if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
1038 const APFloat &F1 = FC1->getValueAPF();
1039 APFloat F2(FC2->getValueAPF());
1040 F2.changeSign();
1041 if (F1.compare(F2) == APFloat::cmpEqual) {
1042 FoundFactor = NeedsNegate = true;
1043 Factors.erase(Factors.begin() + i);
1044 break;
1045 }
1046 }
1047 }
1048 }
1049
1050 if (!FoundFactor) {
1051 // Make sure to restore the operands to the expression tree.
1052 RewriteExprTree(BO, Factors);
1053 return nullptr;
1054 }
1055
1056 BasicBlock::iterator InsertPt = ++BO->getIterator();
1057
1058 // If this was just a single multiply, remove the multiply and return the only
1059 // remaining operand.
1060 if (Factors.size() == 1) {
1061 RedoInsts.insert(BO);
1062 V = Factors[0].Op;
1063 } else {
1064 RewriteExprTree(BO, Factors);
1065 V = BO;
1066 }
1067
1068 if (NeedsNegate)
1069 V = CreateNeg(V, "neg", &*InsertPt, BO);
1070
1071 return V;
1072}
1073
1074/// If V is a single-use multiply, recursively add its operands as factors,
1075/// otherwise add V to the list of factors.
1076///
1077/// Ops is the top-level list of add operands we're trying to factor.
1078static void FindSingleUseMultiplyFactors(Value *V,
1079 SmallVectorImpl<Value*> &Factors) {
1080 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1081 if (!BO) {
1082 Factors.push_back(V);
1083 return;
1084 }
1085
1086 // Otherwise, add the LHS and RHS to the list of factors.
1087 FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
1088 FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
1089}
1090
1091/// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
1092/// This optimizes based on identities. If it can be reduced to a single Value,
1093/// it is returned, otherwise the Ops list is mutated as necessary.
1094static Value *OptimizeAndOrXor(unsigned Opcode,
1095 SmallVectorImpl<ValueEntry> &Ops) {
1096 // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1097 // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1098 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1099 // First, check for X and ~X in the operand list.
1100 assert(i < Ops.size())(static_cast <bool> (i < Ops.size()) ? void (0) : __assert_fail
("i < Ops.size()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1100, __extension__ __PRETTY_FUNCTION__))
;
1101 if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1102 Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1103 unsigned FoundX = FindInOperandList(Ops, i, X);
1104 if (FoundX != i) {
1105 if (Opcode == Instruction::And) // ...&X&~X = 0
1106 return Constant::getNullValue(X->getType());
1107
1108 if (Opcode == Instruction::Or) // ...|X|~X = -1
1109 return Constant::getAllOnesValue(X->getType());
1110 }
1111 }
1112
1113 // Next, check for duplicate pairs of values, which we assume are next to
1114 // each other, due to our sorting criteria.
1115 assert(i < Ops.size())(static_cast <bool> (i < Ops.size()) ? void (0) : __assert_fail
("i < Ops.size()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1115, __extension__ __PRETTY_FUNCTION__))
;
1116 if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1117 if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1118 // Drop duplicate values for And and Or.
1119 Ops.erase(Ops.begin()+i);
1120 --i; --e;
1121 ++NumAnnihil;
1122 continue;
1123 }
1124
1125 // Drop pairs of values for Xor.
1126 assert(Opcode == Instruction::Xor)(static_cast <bool> (Opcode == Instruction::Xor) ? void
(0) : __assert_fail ("Opcode == Instruction::Xor", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1126, __extension__ __PRETTY_FUNCTION__))
;
1127 if (e == 2)
1128 return Constant::getNullValue(Ops[0].Op->getType());
1129
1130 // Y ^ X^X -> Y
1131 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1132 i -= 1; e -= 2;
1133 ++NumAnnihil;
1134 }
1135 }
1136 return nullptr;
1137}
1138
1139/// Helper function of CombineXorOpnd(). It creates a bitwise-and
1140/// instruction with the given two operands, and return the resulting
1141/// instruction. There are two special cases: 1) if the constant operand is 0,
1142/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1143/// be returned.
1144static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1145 const APInt &ConstOpnd) {
1146 if (ConstOpnd.isNullValue())
1147 return nullptr;
1148
1149 if (ConstOpnd.isAllOnesValue())
1150 return Opnd;
1151
1152 Instruction *I = BinaryOperator::CreateAnd(
1153 Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
1154 InsertBefore);
1155 I->setDebugLoc(InsertBefore->getDebugLoc());
1156 return I;
1157}
1158
1159// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1160// into "R ^ C", where C would be 0, and R is a symbolic value.
1161//
1162// If it was successful, true is returned, and the "R" and "C" is returned
1163// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1164// and both "Res" and "ConstOpnd" remain unchanged.
1165bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1166 APInt &ConstOpnd, Value *&Res) {
1167 // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1168 // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1169 // = (x & ~c1) ^ (c1 ^ c2)
1170 // It is useful only when c1 == c2.
1171 if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isNullValue())
1172 return false;
1173
1174 if (!Opnd1->getValue()->hasOneUse())
1175 return false;
1176
1177 const APInt &C1 = Opnd1->getConstPart();
1178 if (C1 != ConstOpnd)
1179 return false;
1180
1181 Value *X = Opnd1->getSymbolicPart();
1182 Res = createAndInstr(I, X, ~C1);
1183 // ConstOpnd was C2, now C1 ^ C2.
1184 ConstOpnd ^= C1;
1185
1186 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1187 RedoInsts.insert(T);
1188 return true;
1189}
1190
1191// Helper function of OptimizeXor(). It tries to simplify
1192// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1193// symbolic value.
1194//
1195// If it was successful, true is returned, and the "R" and "C" is returned
1196// via "Res" and "ConstOpnd", respectively (If the entire expression is
1197// evaluated to a constant, the Res is set to NULL); otherwise, false is
1198// returned, and both "Res" and "ConstOpnd" remain unchanged.
1199bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1200 XorOpnd *Opnd2, APInt &ConstOpnd,
1201 Value *&Res) {
1202 Value *X = Opnd1->getSymbolicPart();
1203 if (X != Opnd2->getSymbolicPart())
1204 return false;
1205
1206 // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1207 int DeadInstNum = 1;
1208 if (Opnd1->getValue()->hasOneUse())
1209 DeadInstNum++;
1210 if (Opnd2->getValue()->hasOneUse())
1211 DeadInstNum++;
1212
1213 // Xor-Rule 2:
1214 // (x | c1) ^ (x & c2)
1215 // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1216 // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1217 // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1218 //
1219 if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1220 if (Opnd2->isOrExpr())
1221 std::swap(Opnd1, Opnd2);
1222
1223 const APInt &C1 = Opnd1->getConstPart();
1224 const APInt &C2 = Opnd2->getConstPart();
1225 APInt C3((~C1) ^ C2);
1226
1227 // Do not increase code size!
1228 if (!C3.isNullValue() && !C3.isAllOnesValue()) {
1229 int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
1230 if (NewInstNum > DeadInstNum)
1231 return false;
1232 }
1233
1234 Res = createAndInstr(I, X, C3);
1235 ConstOpnd ^= C1;
1236 } else if (Opnd1->isOrExpr()) {
1237 // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1238 //
1239 const APInt &C1 = Opnd1->getConstPart();
1240 const APInt &C2 = Opnd2->getConstPart();
1241 APInt C3 = C1 ^ C2;
1242
1243 // Do not increase code size
1244 if (!C3.isNullValue() && !C3.isAllOnesValue()) {
1245 int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
1246 if (NewInstNum > DeadInstNum)
1247 return false;
1248 }
1249
1250 Res = createAndInstr(I, X, C3);
1251 ConstOpnd ^= C3;
1252 } else {
1253 // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1254 //
1255 const APInt &C1 = Opnd1->getConstPart();
1256 const APInt &C2 = Opnd2->getConstPart();
1257 APInt C3 = C1 ^ C2;
1258 Res = createAndInstr(I, X, C3);
1259 }
1260
1261 // Put the original operands in the Redo list; hope they will be deleted
1262 // as dead code.
1263 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1264 RedoInsts.insert(T);
1265 if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1266 RedoInsts.insert(T);
1267
1268 return true;
1269}
1270
1271/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1272/// to a single Value, it is returned, otherwise the Ops list is mutated as
1273/// necessary.
1274Value *ReassociatePass::OptimizeXor(Instruction *I,
1275 SmallVectorImpl<ValueEntry> &Ops) {
1276 if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1277 return V;
1278
1279 if (Ops.size() == 1)
1280 return nullptr;
1281
1282 SmallVector<XorOpnd, 8> Opnds;
1283 SmallVector<XorOpnd*, 8> OpndPtrs;
1284 Type *Ty = Ops[0].Op->getType();
1285 APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
1286
1287 // Step 1: Convert ValueEntry to XorOpnd
1288 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1289 Value *V = Ops[i].Op;
1290 const APInt *C;
1291 // TODO: Support non-splat vectors.
1292 if (match(V, PatternMatch::m_APInt(C))) {
1293 ConstOpnd ^= *C;
1294 } else {
1295 XorOpnd O(V);
1296 O.setSymbolicRank(getRank(O.getSymbolicPart()));
1297 Opnds.push_back(O);
1298 }
1299 }
1300
1301 // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
1302 // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
1303 // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
1304 // with the previous loop --- the iterator of the "Opnds" may be invalidated
1305 // when new elements are added to the vector.
1306 for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
1307 OpndPtrs.push_back(&Opnds[i]);
1308
1309 // Step 2: Sort the Xor-Operands in a way such that the operands containing
1310 // the same symbolic value cluster together. For instance, the input operand
1311 // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1312 // ("x | 123", "x & 789", "y & 456").
1313 //
1314 // The purpose is twofold:
1315 // 1) Cluster together the operands sharing the same symbolic-value.
1316 // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
1317 // could potentially shorten crital path, and expose more loop-invariants.
1318 // Note that values' rank are basically defined in RPO order (FIXME).
1319 // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
1320 // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
1321 // "z" in the order of X-Y-Z is better than any other orders.
1322 std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(),
1323 [](XorOpnd *LHS, XorOpnd *RHS) {
1324 return LHS->getSymbolicRank() < RHS->getSymbolicRank();
1325 });
1326
1327 // Step 3: Combine adjacent operands
1328 XorOpnd *PrevOpnd = nullptr;
1329 bool Changed = false;
1330 for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1331 XorOpnd *CurrOpnd = OpndPtrs[i];
1332 // The combined value
1333 Value *CV;
1334
1335 // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1336 if (!ConstOpnd.isNullValue() &&
1337 CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1338 Changed = true;
1339 if (CV)
1340 *CurrOpnd = XorOpnd(CV);
1341 else {
1342 CurrOpnd->Invalidate();
1343 continue;
1344 }
1345 }
1346
1347 if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1348 PrevOpnd = CurrOpnd;
1349 continue;
1350 }
1351
1352 // step 3.2: When previous and current operands share the same symbolic
1353 // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1354 if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1355 // Remove previous operand
1356 PrevOpnd->Invalidate();
1357 if (CV) {
1358 *CurrOpnd = XorOpnd(CV);
1359 PrevOpnd = CurrOpnd;
1360 } else {
1361 CurrOpnd->Invalidate();
1362 PrevOpnd = nullptr;
1363 }
1364 Changed = true;
1365 }
1366 }
1367
1368 // Step 4: Reassemble the Ops
1369 if (Changed) {
1370 Ops.clear();
1371 for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1372 XorOpnd &O = Opnds[i];
1373 if (O.isInvalid())
1374 continue;
1375 ValueEntry VE(getRank(O.getValue()), O.getValue());
1376 Ops.push_back(VE);
1377 }
1378 if (!ConstOpnd.isNullValue()) {
1379 Value *C = ConstantInt::get(Ty, ConstOpnd);
1380 ValueEntry VE(getRank(C), C);
1381 Ops.push_back(VE);
1382 }
1383 unsigned Sz = Ops.size();
1384 if (Sz == 1)
1385 return Ops.back().Op;
1386 if (Sz == 0) {
1387 assert(ConstOpnd.isNullValue())(static_cast <bool> (ConstOpnd.isNullValue()) ? void (0
) : __assert_fail ("ConstOpnd.isNullValue()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1387, __extension__ __PRETTY_FUNCTION__))
;
1388 return ConstantInt::get(Ty, ConstOpnd);
1389 }
1390 }
1391
1392 return nullptr;
1393}
1394
1395/// Optimize a series of operands to an 'add' instruction. This
1396/// optimizes based on identities. If it can be reduced to a single Value, it
1397/// is returned, otherwise the Ops list is mutated as necessary.
1398Value *ReassociatePass::OptimizeAdd(Instruction *I,
1399 SmallVectorImpl<ValueEntry> &Ops) {
1400 // Scan the operand lists looking for X and -X pairs. If we find any, we
1401 // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
1402 // scan for any
1403 // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1404
1405 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1406 Value *TheOp = Ops[i].Op;
1407 // Check to see if we've seen this operand before. If so, we factor all
1408 // instances of the operand together. Due to our sorting criteria, we know
1409 // that these need to be next to each other in the vector.
1410 if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1411 // Rescan the list, remove all instances of this operand from the expr.
1412 unsigned NumFound = 0;
1413 do {
1414 Ops.erase(Ops.begin()+i);
1415 ++NumFound;
1416 } while (i != Ops.size() && Ops[i].Op == TheOp);
1417
1418 DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "\nFACTORING [" << NumFound
<< "]: " << *TheOp << '\n'; } } while (false
)
;
1419 ++NumFactor;
1420
1421 // Insert a new multiply.
1422 Type *Ty = TheOp->getType();
1423 Constant *C = Ty->isIntOrIntVectorTy() ?
1424 ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound);
1425 Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
1426
1427 // Now that we have inserted a multiply, optimize it. This allows us to
1428 // handle cases that require multiple factoring steps, such as this:
1429 // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1430 RedoInsts.insert(Mul);
1431
1432 // If every add operand was a duplicate, return the multiply.
1433 if (Ops.empty())
1434 return Mul;
1435
1436 // Otherwise, we had some input that didn't have the dupe, such as
1437 // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1438 // things being added by this operation.
1439 Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1440
1441 --i;
1442 e = Ops.size();
1443 continue;
1444 }
1445
1446 // Check for X and -X or X and ~X in the operand list.
1447 if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
1448 !BinaryOperator::isNot(TheOp))
1449 continue;
1450
1451 Value *X = nullptr;
1452 if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
1453 X = BinaryOperator::getNegArgument(TheOp);
1454 else if (BinaryOperator::isNot(TheOp))
1455 X = BinaryOperator::getNotArgument(TheOp);
1456
1457 unsigned FoundX = FindInOperandList(Ops, i, X);
1458 if (FoundX == i)
1459 continue;
1460
1461 // Remove X and -X from the operand list.
1462 if (Ops.size() == 2 &&
1463 (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
1464 return Constant::getNullValue(X->getType());
1465
1466 // Remove X and ~X from the operand list.
1467 if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
1468 return Constant::getAllOnesValue(X->getType());
1469
1470 Ops.erase(Ops.begin()+i);
1471 if (i < FoundX)
1472 --FoundX;
1473 else
1474 --i; // Need to back up an extra one.
1475 Ops.erase(Ops.begin()+FoundX);
1476 ++NumAnnihil;
1477 --i; // Revisit element.
1478 e -= 2; // Removed two elements.
1479
1480 // if X and ~X we append -1 to the operand list.
1481 if (BinaryOperator::isNot(TheOp)) {
1482 Value *V = Constant::getAllOnesValue(X->getType());
1483 Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
1484 e += 1;
1485 }
1486 }
1487
1488 // Scan the operand list, checking to see if there are any common factors
1489 // between operands. Consider something like A*A+A*B*C+D. We would like to
1490 // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1491 // To efficiently find this, we count the number of times a factor occurs
1492 // for any ADD operands that are MULs.
1493 DenseMap<Value*, unsigned> FactorOccurrences;
1494
1495 // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1496 // where they are actually the same multiply.
1497 unsigned MaxOcc = 0;
1498 Value *MaxOccVal = nullptr;
1499 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1500 BinaryOperator *BOp =
1501 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1502 if (!BOp)
1503 continue;
1504
1505 // Compute all of the factors of this added value.
1506 SmallVector<Value*, 8> Factors;
1507 FindSingleUseMultiplyFactors(BOp, Factors);
1508 assert(Factors.size() > 1 && "Bad linearize!")(static_cast <bool> (Factors.size() > 1 && "Bad linearize!"
) ? void (0) : __assert_fail ("Factors.size() > 1 && \"Bad linearize!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1508, __extension__ __PRETTY_FUNCTION__))
;
1509
1510 // Add one to FactorOccurrences for each unique factor in this op.
1511 SmallPtrSet<Value*, 8> Duplicates;
1512 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1513 Value *Factor = Factors[i];
1514 if (!Duplicates.insert(Factor).second)
1515 continue;
1516
1517 unsigned Occ = ++FactorOccurrences[Factor];
1518 if (Occ > MaxOcc) {
1519 MaxOcc = Occ;
1520 MaxOccVal = Factor;
1521 }
1522
1523 // If Factor is a negative constant, add the negated value as a factor
1524 // because we can percolate the negate out. Watch for minint, which
1525 // cannot be positivified.
1526 if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
1527 if (CI->isNegative() && !CI->isMinValue(true)) {
1528 Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1529 if (!Duplicates.insert(Factor).second)
1530 continue;
1531 unsigned Occ = ++FactorOccurrences[Factor];
1532 if (Occ > MaxOcc) {
1533 MaxOcc = Occ;
1534 MaxOccVal = Factor;
1535 }
1536 }
1537 } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
1538 if (CF->isNegative()) {
1539 APFloat F(CF->getValueAPF());
1540 F.changeSign();
1541 Factor = ConstantFP::get(CF->getContext(), F);
1542 if (!Duplicates.insert(Factor).second)
1543 continue;
1544 unsigned Occ = ++FactorOccurrences[Factor];
1545 if (Occ > MaxOcc) {
1546 MaxOcc = Occ;
1547 MaxOccVal = Factor;
1548 }
1549 }
1550 }
1551 }
1552 }
1553
1554 // If any factor occurred more than one time, we can pull it out.
1555 if (MaxOcc > 1) {
1556 DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "\nFACTORING [" << MaxOcc
<< "]: " << *MaxOccVal << '\n'; } } while (
false)
;
1557 ++NumFactor;
1558
1559 // Create a new instruction that uses the MaxOccVal twice. If we don't do
1560 // this, we could otherwise run into situations where removing a factor
1561 // from an expression will drop a use of maxocc, and this can cause
1562 // RemoveFactorFromExpression on successive values to behave differently.
1563 Instruction *DummyInst =
1564 I->getType()->isIntOrIntVectorTy()
1565 ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
1566 : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
1567
1568 SmallVector<WeakTrackingVH, 4> NewMulOps;
1569 for (unsigned i = 0; i != Ops.size(); ++i) {
1570 // Only try to remove factors from expressions we're allowed to.
1571 BinaryOperator *BOp =
1572 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1573 if (!BOp)
1574 continue;
1575
1576 if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1577 // The factorized operand may occur several times. Convert them all in
1578 // one fell swoop.
1579 for (unsigned j = Ops.size(); j != i;) {
1580 --j;
1581 if (Ops[j].Op == Ops[i].Op) {
1582 NewMulOps.push_back(V);
1583 Ops.erase(Ops.begin()+j);
1584 }
1585 }
1586 --i;
1587 }
1588 }
1589
1590 // No need for extra uses anymore.
1591 DummyInst->deleteValue();
1592
1593 unsigned NumAddedValues = NewMulOps.size();
1594 Value *V = EmitAddTreeOfValues(I, NewMulOps);
1595
1596 // Now that we have inserted the add tree, optimize it. This allows us to
1597 // handle cases that require multiple factoring steps, such as this:
1598 // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1599 assert(NumAddedValues > 1 && "Each occurrence should contribute a value")(static_cast <bool> (NumAddedValues > 1 && "Each occurrence should contribute a value"
) ? void (0) : __assert_fail ("NumAddedValues > 1 && \"Each occurrence should contribute a value\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1599, __extension__ __PRETTY_FUNCTION__))
;
1600 (void)NumAddedValues;
1601 if (Instruction *VI = dyn_cast<Instruction>(V))
1602 RedoInsts.insert(VI);
1603
1604 // Create the multiply.
1605 Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I, I);
1606
1607 // Rerun associate on the multiply in case the inner expression turned into
1608 // a multiply. We want to make sure that we keep things in canonical form.
1609 RedoInsts.insert(V2);
1610
1611 // If every add operand included the factor (e.g. "A*B + A*C"), then the
1612 // entire result expression is just the multiply "A*(B+C)".
1613 if (Ops.empty())
1614 return V2;
1615
1616 // Otherwise, we had some input that didn't have the factor, such as
1617 // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1618 // things being added by this operation.
1619 Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1620 }
1621
1622 return nullptr;
1623}
1624
1625/// \brief Build up a vector of value/power pairs factoring a product.
1626///
1627/// Given a series of multiplication operands, build a vector of factors and
1628/// the powers each is raised to when forming the final product. Sort them in
1629/// the order of descending power.
1630///
1631/// (x*x) -> [(x, 2)]
1632/// ((x*x)*x) -> [(x, 3)]
1633/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1634///
1635/// \returns Whether any factors have a power greater than one.
1636static bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
1637 SmallVectorImpl<Factor> &Factors) {
1638 // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1639 // Compute the sum of powers of simplifiable factors.
1640 unsigned FactorPowerSum = 0;
1641 for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1642 Value *Op = Ops[Idx-1].Op;
1643
1644 // Count the number of occurrences of this value.
1645 unsigned Count = 1;
1646 for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1647 ++Count;
1648 // Track for simplification all factors which occur 2 or more times.
1649 if (Count > 1)
1650 FactorPowerSum += Count;
1651 }
1652
1653 // We can only simplify factors if the sum of the powers of our simplifiable
1654 // factors is 4 or higher. When that is the case, we will *always* have
1655 // a simplification. This is an important invariant to prevent cyclicly
1656 // trying to simplify already minimal formations.
1657 if (FactorPowerSum < 4)
1658 return false;
1659
1660 // Now gather the simplifiable factors, removing them from Ops.
1661 FactorPowerSum = 0;
1662 for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1663 Value *Op = Ops[Idx-1].Op;
1664
1665 // Count the number of occurrences of this value.
1666 unsigned Count = 1;
1667 for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1668 ++Count;
1669 if (Count == 1)
1670 continue;
1671 // Move an even number of occurrences to Factors.
1672 Count &= ~1U;
1673 Idx -= Count;
1674 FactorPowerSum += Count;
1675 Factors.push_back(Factor(Op, Count));
1676 Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1677 }
1678
1679 // None of the adjustments above should have reduced the sum of factor powers
1680 // below our mininum of '4'.
1681 assert(FactorPowerSum >= 4)(static_cast <bool> (FactorPowerSum >= 4) ? void (0)
: __assert_fail ("FactorPowerSum >= 4", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1681, __extension__ __PRETTY_FUNCTION__))
;
1682
1683 std::stable_sort(Factors.begin(), Factors.end(),
1684 [](const Factor &LHS, const Factor &RHS) {
1685 return LHS.Power > RHS.Power;
1686 });
1687 return true;
1688}
1689
1690/// \brief Build a tree of multiplies, computing the product of Ops.
1691static Value *buildMultiplyTree(IRBuilder<> &Builder,
1692 SmallVectorImpl<Value*> &Ops) {
1693 if (Ops.size() == 1)
1694 return Ops.back();
1695
1696 Value *LHS = Ops.pop_back_val();
1697 do {
1698 if (LHS->getType()->isIntOrIntVectorTy())
1699 LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1700 else
1701 LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
1702 } while (!Ops.empty());
1703
1704 return LHS;
1705}
1706
1707/// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1708///
1709/// Given a vector of values raised to various powers, where no two values are
1710/// equal and the powers are sorted in decreasing order, compute the minimal
1711/// DAG of multiplies to compute the final product, and return that product
1712/// value.
1713Value *
1714ReassociatePass::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1715 SmallVectorImpl<Factor> &Factors) {
1716 assert(Factors[0].Power)(static_cast <bool> (Factors[0].Power) ? void (0) : __assert_fail
("Factors[0].Power", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1716, __extension__ __PRETTY_FUNCTION__))
;
1717 SmallVector<Value *, 4> OuterProduct;
1718 for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1719 Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1720 if (Factors[Idx].Power != Factors[LastIdx].Power) {
1721 LastIdx = Idx;
1722 continue;
1723 }
1724
1725 // We want to multiply across all the factors with the same power so that
1726 // we can raise them to that power as a single entity. Build a mini tree
1727 // for that.
1728 SmallVector<Value *, 4> InnerProduct;
1729 InnerProduct.push_back(Factors[LastIdx].Base);
1730 do {
1731 InnerProduct.push_back(Factors[Idx].Base);
1732 ++Idx;
1733 } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1734
1735 // Reset the base value of the first factor to the new expression tree.
1736 // We'll remove all the factors with the same power in a second pass.
1737 Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1738 if (Instruction *MI = dyn_cast<Instruction>(M))
1739 RedoInsts.insert(MI);
1740
1741 LastIdx = Idx;
1742 }
1743 // Unique factors with equal powers -- we've folded them into the first one's
1744 // base.
1745 Factors.erase(std::unique(Factors.begin(), Factors.end(),
1746 [](const Factor &LHS, const Factor &RHS) {
1747 return LHS.Power == RHS.Power;
1748 }),
1749 Factors.end());
1750
1751 // Iteratively collect the base of each factor with an add power into the
1752 // outer product, and halve each power in preparation for squaring the
1753 // expression.
1754 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1755 if (Factors[Idx].Power & 1)
1756 OuterProduct.push_back(Factors[Idx].Base);
1757 Factors[Idx].Power >>= 1;
1758 }
1759 if (Factors[0].Power) {
1760 Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1761 OuterProduct.push_back(SquareRoot);
1762 OuterProduct.push_back(SquareRoot);
1763 }
1764 if (OuterProduct.size() == 1)
1765 return OuterProduct.front();
1766
1767 Value *V = buildMultiplyTree(Builder, OuterProduct);
1768 return V;
1769}
1770
1771Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
1772 SmallVectorImpl<ValueEntry> &Ops) {
1773 // We can only optimize the multiplies when there is a chain of more than
1774 // three, such that a balanced tree might require fewer total multiplies.
1775 if (Ops.size() < 4)
1776 return nullptr;
1777
1778 // Try to turn linear trees of multiplies without other uses of the
1779 // intermediate stages into minimal multiply DAGs with perfect sub-expression
1780 // re-use.
1781 SmallVector<Factor, 4> Factors;
1782 if (!collectMultiplyFactors(Ops, Factors))
1783 return nullptr; // All distinct factors, so nothing left for us to do.
1784
1785 IRBuilder<> Builder(I);
1786 // The reassociate transformation for FP operations is performed only
1787 // if unsafe algebra is permitted by FastMathFlags. Propagate those flags
1788 // to the newly generated operations.
1789 if (auto FPI = dyn_cast<FPMathOperator>(I))
1790 Builder.setFastMathFlags(FPI->getFastMathFlags());
1791
1792 Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1793 if (Ops.empty())
1794 return V;
1795
1796 ValueEntry NewEntry = ValueEntry(getRank(V), V);
1797 Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1798 return nullptr;
1799}
1800
1801Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
1802 SmallVectorImpl<ValueEntry> &Ops) {
1803 // Now that we have the linearized expression tree, try to optimize it.
1804 // Start by folding any constants that we found.
1805 Constant *Cst = nullptr;
1806 unsigned Opcode = I->getOpcode();
1807 while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1808 Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1809 Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1810 }
1811 // If there was nothing but constants then we are done.
1812 if (Ops.empty())
1813 return Cst;
1814
1815 // Put the combined constant back at the end of the operand list, except if
1816 // there is no point. For example, an add of 0 gets dropped here, while a
1817 // multiplication by zero turns the whole expression into zero.
1818 if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1819 if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1820 return Cst;
1821 Ops.push_back(ValueEntry(0, Cst));
1822 }
1823
1824 if (Ops.size() == 1) return Ops[0].Op;
1825
1826 // Handle destructive annihilation due to identities between elements in the
1827 // argument list here.
1828 unsigned NumOps = Ops.size();
1829 switch (Opcode) {
1830 default: break;
1831 case Instruction::And:
1832 case Instruction::Or:
1833 if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1834 return Result;
1835 break;
1836
1837 case Instruction::Xor:
1838 if (Value *Result = OptimizeXor(I, Ops))
1839 return Result;
1840 break;
1841
1842 case Instruction::Add:
1843 case Instruction::FAdd:
1844 if (Value *Result = OptimizeAdd(I, Ops))
1845 return Result;
1846 break;
1847
1848 case Instruction::Mul:
1849 case Instruction::FMul:
1850 if (Value *Result = OptimizeMul(I, Ops))
1851 return Result;
1852 break;
1853 }
1854
1855 if (Ops.size() != NumOps)
1856 return OptimizeExpression(I, Ops);
1857 return nullptr;
1858}
1859
1860// Remove dead instructions and if any operands are trivially dead add them to
1861// Insts so they will be removed as well.
1862void ReassociatePass::RecursivelyEraseDeadInsts(
1863 Instruction *I, SetVector<AssertingVH<Instruction>> &Insts) {
1864 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!")(static_cast <bool> (isInstructionTriviallyDead(I) &&
"Trivially dead instructions only!") ? void (0) : __assert_fail
("isInstructionTriviallyDead(I) && \"Trivially dead instructions only!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1864, __extension__ __PRETTY_FUNCTION__))
;
1865 SmallVector<Value *, 4> Ops(I->op_begin(), I->op_end());
1866 ValueRankMap.erase(I);
1867 Insts.remove(I);
1868 RedoInsts.remove(I);
1869 I->eraseFromParent();
1870 for (auto Op : Ops)
1871 if (Instruction *OpInst = dyn_cast<Instruction>(Op))
1872 if (OpInst->use_empty())
1873 Insts.insert(OpInst);
1874}
1875
1876/// Zap the given instruction, adding interesting operands to the work list.
1877void ReassociatePass::EraseInst(Instruction *I) {
1878 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!")(static_cast <bool> (isInstructionTriviallyDead(I) &&
"Trivially dead instructions only!") ? void (0) : __assert_fail
("isInstructionTriviallyDead(I) && \"Trivially dead instructions only!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1878, __extension__ __PRETTY_FUNCTION__))
;
1879 DEBUG(dbgs() << "Erasing dead inst: "; I->dump())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Erasing dead inst: "; I->
dump(); } } while (false)
;
1880
1881 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1882 // Erase the dead instruction.
1883 ValueRankMap.erase(I);
1884 RedoInsts.remove(I);
1885 I->eraseFromParent();
1886 // Optimize its operands.
1887 SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1888 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1889 if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1890 // If this is a node in an expression tree, climb to the expression root
1891 // and add that since that's where optimization actually happens.
1892 unsigned Opcode = Op->getOpcode();
1893 while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
1894 Visited.insert(Op).second)
1895 Op = Op->user_back();
1896 RedoInsts.insert(Op);
1897 }
1898
1899 MadeChange = true;
1900}
1901
1902// Canonicalize expressions of the following form:
1903// x + (-Constant * y) -> x - (Constant * y)
1904// x - (-Constant * y) -> x + (Constant * y)
1905Instruction *ReassociatePass::canonicalizeNegConstExpr(Instruction *I) {
1906 if (!I->hasOneUse() || I->getType()->isVectorTy())
1907 return nullptr;
1908
1909 // Must be a fmul or fdiv instruction.
1910 unsigned Opcode = I->getOpcode();
1911 if (Opcode != Instruction::FMul && Opcode != Instruction::FDiv)
1912 return nullptr;
1913
1914 auto *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
1915 auto *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
1916
1917 // Both operands are constant, let it get constant folded away.
1918 if (C0 && C1)
1919 return nullptr;
1920
1921 ConstantFP *CF = C0 ? C0 : C1;
1922
1923 // Must have one constant operand.
1924 if (!CF)
1925 return nullptr;
1926
1927 // Must be a negative ConstantFP.
1928 if (!CF->isNegative())
1929 return nullptr;
1930
1931 // User must be a binary operator with one or more uses.
1932 Instruction *User = I->user_back();
1933 if (!isa<BinaryOperator>(User) || User->use_empty())
1934 return nullptr;
1935
1936 unsigned UserOpcode = User->getOpcode();
1937 if (UserOpcode != Instruction::FAdd && UserOpcode != Instruction::FSub)
1938 return nullptr;
1939
1940 // Subtraction is not commutative. Explicitly, the following transform is
1941 // not valid: (-Constant * y) - x -> x + (Constant * y)
1942 if (!User->isCommutative() && User->getOperand(1) != I)
1943 return nullptr;
1944
1945 // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
1946 // resulting subtract will be broken up later. This can get us into an
1947 // infinite loop during reassociation.
1948 if (UserOpcode == Instruction::FAdd && ShouldBreakUpSubtract(User))
1949 return nullptr;
1950
1951 // Change the sign of the constant.
1952 APFloat Val = CF->getValueAPF();
1953 Val.changeSign();
1954 I->setOperand(C0 ? 0 : 1, ConstantFP::get(CF->getContext(), Val));
1955
1956 // Canonicalize I to RHS to simplify the next bit of logic. E.g.,
1957 // ((-Const*y) + x) -> (x + (-Const*y)).
1958 if (User->getOperand(0) == I && User->isCommutative())
1959 cast<BinaryOperator>(User)->swapOperands();
1960
1961 Value *Op0 = User->getOperand(0);
1962 Value *Op1 = User->getOperand(1);
1963 BinaryOperator *NI;
1964 switch (UserOpcode) {
1965 default:
1966 llvm_unreachable("Unexpected Opcode!")::llvm::llvm_unreachable_internal("Unexpected Opcode!", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 1966)
;
1967 case Instruction::FAdd:
1968 NI = BinaryOperator::CreateFSub(Op0, Op1);
1969 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1970 break;
1971 case Instruction::FSub:
1972 NI = BinaryOperator::CreateFAdd(Op0, Op1);
1973 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1974 break;
1975 }
1976
1977 NI->insertBefore(User);
1978 NI->setName(User->getName());
1979 User->replaceAllUsesWith(NI);
1980 NI->setDebugLoc(I->getDebugLoc());
1981 RedoInsts.insert(I);
1982 MadeChange = true;
1983 return NI;
1984}
1985
1986/// Inspect and optimize the given instruction. Note that erasing
1987/// instructions is not allowed.
1988void ReassociatePass::OptimizeInst(Instruction *I) {
1989 // Only consider operations that we understand.
1990 if (!isa<BinaryOperator>(I))
1991 return;
1992
1993 if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
1994 // If an operand of this shift is a reassociable multiply, or if the shift
1995 // is used by a reassociable multiply or add, turn into a multiply.
1996 if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
1997 (I->hasOneUse() &&
1998 (isReassociableOp(I->user_back(), Instruction::Mul) ||
1999 isReassociableOp(I->user_back(), Instruction::Add)))) {
2000 Instruction *NI = ConvertShiftToMul(I);
2001 RedoInsts.insert(I);
2002 MadeChange = true;
2003 I = NI;
2004 }
2005
2006 // Canonicalize negative constants out of expressions.
2007 if (Instruction *Res = canonicalizeNegConstExpr(I))
2008 I = Res;
2009
2010 // Commute binary operators, to canonicalize the order of their operands.
2011 // This can potentially expose more CSE opportunities, and makes writing other
2012 // transformations simpler.
2013 if (I->isCommutative())
2014 canonicalizeOperands(I);
2015
2016 // Don't optimize floating-point instructions unless they are 'fast'.
2017 if (I->getType()->isFPOrFPVectorTy() && !I->isFast())
2018 return;
2019
2020 // Do not reassociate boolean (i1) expressions. We want to preserve the
2021 // original order of evaluation for short-circuited comparisons that
2022 // SimplifyCFG has folded to AND/OR expressions. If the expression
2023 // is not further optimized, it is likely to be transformed back to a
2024 // short-circuited form for code gen, and the source order may have been
2025 // optimized for the most likely conditions.
2026 if (I->getType()->isIntegerTy(1))
2027 return;
2028
2029 // If this is a subtract instruction which is not already in negate form,
2030 // see if we can convert it to X+-Y.
2031 if (I->getOpcode() == Instruction::Sub) {
2032 if (ShouldBreakUpSubtract(I)) {
2033 Instruction *NI = BreakUpSubtract(I, RedoInsts);
2034 RedoInsts.insert(I);
2035 MadeChange = true;
2036 I = NI;
2037 } else if (BinaryOperator::isNeg(I)) {
2038 // Otherwise, this is a negation. See if the operand is a multiply tree
2039 // and if this is not an inner node of a multiply tree.
2040 if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
2041 (!I->hasOneUse() ||
2042 !isReassociableOp(I->user_back(), Instruction::Mul))) {
2043 Instruction *NI = LowerNegateToMultiply(I);
2044 // If the negate was simplified, revisit the users to see if we can
2045 // reassociate further.
2046 for (User *U : NI->users()) {
2047 if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2048 RedoInsts.insert(Tmp);
2049 }
2050 RedoInsts.insert(I);
2051 MadeChange = true;
2052 I = NI;
2053 }
2054 }
2055 } else if (I->getOpcode() == Instruction::FSub) {
2056 if (ShouldBreakUpSubtract(I)) {
2057 Instruction *NI = BreakUpSubtract(I, RedoInsts);
2058 RedoInsts.insert(I);
2059 MadeChange = true;
2060 I = NI;
2061 } else if (BinaryOperator::isFNeg(I)) {
2062 // Otherwise, this is a negation. See if the operand is a multiply tree
2063 // and if this is not an inner node of a multiply tree.
2064 if (isReassociableOp(I->getOperand(1), Instruction::FMul) &&
2065 (!I->hasOneUse() ||
2066 !isReassociableOp(I->user_back(), Instruction::FMul))) {
2067 // If the negate was simplified, revisit the users to see if we can
2068 // reassociate further.
2069 Instruction *NI = LowerNegateToMultiply(I);
2070 for (User *U : NI->users()) {
2071 if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2072 RedoInsts.insert(Tmp);
2073 }
2074 RedoInsts.insert(I);
2075 MadeChange = true;
2076 I = NI;
2077 }
2078 }
2079 }
2080
2081 // If this instruction is an associative binary operator, process it.
2082 if (!I->isAssociative()) return;
2083 BinaryOperator *BO = cast<BinaryOperator>(I);
2084
2085 // If this is an interior node of a reassociable tree, ignore it until we
2086 // get to the root of the tree, to avoid N^2 analysis.
2087 unsigned Opcode = BO->getOpcode();
2088 if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
2089 // During the initial run we will get to the root of the tree.
2090 // But if we get here while we are redoing instructions, there is no
2091 // guarantee that the root will be visited. So Redo later
2092 if (BO->user_back() != BO &&
2093 BO->getParent() == BO->user_back()->getParent())
2094 RedoInsts.insert(BO->user_back());
2095 return;
2096 }
2097
2098 // If this is an add tree that is used by a sub instruction, ignore it
2099 // until we process the subtract.
2100 if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
2101 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
2102 return;
2103 if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
2104 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
2105 return;
2106
2107 ReassociateExpression(BO);
2108}
2109
2110void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
2111 // First, walk the expression tree, linearizing the tree, collecting the
2112 // operand information.
2113 SmallVector<RepeatedValue, 8> Tree;
2114 MadeChange |= LinearizeExprTree(I, Tree);
2115 SmallVector<ValueEntry, 8> Ops;
2116 Ops.reserve(Tree.size());
2117 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
2118 RepeatedValue E = Tree[i];
2119 Ops.append(E.second.getZExtValue(),
2120 ValueEntry(getRank(E.first), E.first));
2121 }
2122
2123 DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RAIn:\t"; PrintOps(I, Ops
); dbgs() << '\n'; } } while (false)
;
2124
2125 // Now that we have linearized the tree to a list and have gathered all of
2126 // the operands and their ranks, sort the operands by their rank. Use a
2127 // stable_sort so that values with equal ranks will have their relative
2128 // positions maintained (and so the compiler is deterministic). Note that
2129 // this sorts so that the highest ranking values end up at the beginning of
2130 // the vector.
2131 std::stable_sort(Ops.begin(), Ops.end());
2132
2133 // Now that we have the expression tree in a convenient
2134 // sorted form, optimize it globally if possible.
2135 if (Value *V = OptimizeExpression(I, Ops)) {
2136 if (V == I)
2137 // Self-referential expression in unreachable code.
2138 return;
2139 // This expression tree simplified to something that isn't a tree,
2140 // eliminate it.
2141 DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "Reassoc to scalar: " <<
*V << '\n'; } } while (false)
;
2142 I->replaceAllUsesWith(V);
2143 if (Instruction *VI = dyn_cast<Instruction>(V))
2144 if (I->getDebugLoc())
2145 VI->setDebugLoc(I->getDebugLoc());
2146 RedoInsts.insert(I);
2147 ++NumAnnihil;
2148 return;
2149 }
2150
2151 // We want to sink immediates as deeply as possible except in the case where
2152 // this is a multiply tree used only by an add, and the immediate is a -1.
2153 // In this case we reassociate to put the negation on the outside so that we
2154 // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
2155 if (I->hasOneUse()) {
2156 if (I->getOpcode() == Instruction::Mul &&
2157 cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
2158 isa<ConstantInt>(Ops.back().Op) &&
2159 cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
2160 ValueEntry Tmp = Ops.pop_back_val();
2161 Ops.insert(Ops.begin(), Tmp);
2162 } else if (I->getOpcode() == Instruction::FMul &&
2163 cast<Instruction>(I->user_back())->getOpcode() ==
2164 Instruction::FAdd &&
2165 isa<ConstantFP>(Ops.back().Op) &&
2166 cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
2167 ValueEntry Tmp = Ops.pop_back_val();
2168 Ops.insert(Ops.begin(), Tmp);
2169 }
2170 }
2171
2172 DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("reassociate")) { dbgs() << "RAOut:\t"; PrintOps(I, Ops
); dbgs() << '\n'; } } while (false)
;
2173
2174 if (Ops.size() == 1) {
2175 if (Ops[0].Op == I)
2176 // Self-referential expression in unreachable code.
2177 return;
2178
2179 // This expression tree simplified to something that isn't a tree,
2180 // eliminate it.
2181 I->replaceAllUsesWith(Ops[0].Op);
2182 if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
2183 OI->setDebugLoc(I->getDebugLoc());
2184 RedoInsts.insert(I);
2185 return;
2186 }
2187
2188 if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) {
2189 // Find the pair with the highest count in the pairmap and move it to the
2190 // back of the list so that it can later be CSE'd.
2191 // example:
2192 // a*b*c*d*e
2193 // if c*e is the most "popular" pair, we can express this as
2194 // (((c*e)*d)*b)*a
2195 unsigned Max = 1;
2196 unsigned BestRank = 0;
2197 std::pair<unsigned, unsigned> BestPair;
2198 unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin;
2199 for (unsigned i = 0; i < Ops.size() - 1; ++i)
2200 for (unsigned j = i + 1; j < Ops.size(); ++j) {
2201 unsigned Score = 0;
2202 Value *Op0 = Ops[i].Op;
2203 Value *Op1 = Ops[j].Op;
2204 if (std::less<Value *>()(Op1, Op0))
2205 std::swap(Op0, Op1);
2206 auto it = PairMap[Idx].find({Op0, Op1});
2207 if (it != PairMap[Idx].end())
2208 Score += it->second;
2209
2210 unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank);
2211 if (Score > Max || (Score == Max && MaxRank < BestRank)) {
2212 BestPair = {i, j};
2213 Max = Score;
2214 BestRank = MaxRank;
2215 }
2216 }
2217 if (Max > 1) {
2218 auto Op0 = Ops[BestPair.first];
2219 auto Op1 = Ops[BestPair.second];
2220 Ops.erase(&Ops[BestPair.second]);
2221 Ops.erase(&Ops[BestPair.first]);
2222 Ops.push_back(Op0);
2223 Ops.push_back(Op1);
2224 }
2225 }
2226 // Now that we ordered and optimized the expressions, splat them back into
2227 // the expression tree, removing any unneeded nodes.
2228 RewriteExprTree(I, Ops);
2229}
2230
2231void
2232ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
2233 // Make a "pairmap" of how often each operand pair occurs.
2234 for (BasicBlock *BI : RPOT) {
2235 for (Instruction &I : *BI) {
2236 if (!I.isAssociative())
2237 continue;
2238
2239 // Ignore nodes that aren't at the root of trees.
2240 if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode())
2241 continue;
2242
2243 // Collect all operands in a single reassociable expression.
2244 // Since Reassociate has already been run once, we can assume things
2245 // are already canonical according to Reassociation's regime.
2246 SmallVector<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) };
2247 SmallVector<Value *, 8> Ops;
2248 while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) {
2249 Value *Op = Worklist.pop_back_val();
2250 Instruction *OpI = dyn_cast<Instruction>(Op);
2251 if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) {
2252 Ops.push_back(Op);
2253 continue;
2254 }
2255 // Be paranoid about self-referencing expressions in unreachable code.
2256 if (OpI->getOperand(0) != OpI)
2257 Worklist.push_back(OpI->getOperand(0));
2258 if (OpI->getOperand(1) != OpI)
2259 Worklist.push_back(OpI->getOperand(1));
2260 }
2261 // Skip extremely long expressions.
2262 if (Ops.size() > GlobalReassociateLimit)
2263 continue;
2264
2265 // Add all pairwise combinations of operands to the pair map.
2266 unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin;
2267 SmallSet<std::pair<Value *, Value*>, 32> Visited;
2268 for (unsigned i = 0; i < Ops.size() - 1; ++i) {
2269 for (unsigned j = i + 1; j < Ops.size(); ++j) {
2270 // Canonicalize operand orderings.
2271 Value *Op0 = Ops[i];
2272 Value *Op1 = Ops[j];
2273 if (std::less<Value *>()(Op1, Op0))
2274 std::swap(Op0, Op1);
2275 if (!Visited.insert({Op0, Op1}).second)
2276 continue;
2277 auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, 1});
2278 if (!res.second)
2279 ++res.first->second;
2280 }
2281 }
2282 }
2283 }
2284}
2285
2286PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) {
2287 // Get the functions basic blocks in Reverse Post Order. This order is used by
2288 // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
2289 // blocks (it has been seen that the analysis in this pass could hang when
2290 // analysing dead basic blocks).
2291 ReversePostOrderTraversal<Function *> RPOT(&F);
2292
2293 // Calculate the rank map for F.
2294 BuildRankMap(F, RPOT);
4
Calling 'ReassociatePass::BuildRankMap'
2295
2296 // Build the pair map before running reassociate.
2297 // Technically this would be more accurate if we did it after one round
2298 // of reassociation, but in practice it doesn't seem to help much on
2299 // real-world code, so don't waste the compile time running reassociate
2300 // twice.
2301 // If a user wants, they could expicitly run reassociate twice in their
2302 // pass pipeline for further potential gains.
2303 // It might also be possible to update the pair map during runtime, but the
2304 // overhead of that may be large if there's many reassociable chains.
2305 BuildPairMap(RPOT);
2306
2307 MadeChange = false;
2308
2309 // Traverse the same blocks that were analysed by BuildRankMap.
2310 for (BasicBlock *BI : RPOT) {
2311 assert(RankMap.count(&*BI) && "BB should be ranked.")(static_cast <bool> (RankMap.count(&*BI) &&
"BB should be ranked.") ? void (0) : __assert_fail ("RankMap.count(&*BI) && \"BB should be ranked.\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 2311, __extension__ __PRETTY_FUNCTION__))
;
2312 // Optimize every instruction in the basic block.
2313 for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
2314 if (isInstructionTriviallyDead(&*II)) {
2315 EraseInst(&*II++);
2316 } else {
2317 OptimizeInst(&*II);
2318 assert(II->getParent() == &*BI && "Moved to a different block!")(static_cast <bool> (II->getParent() == &*BI &&
"Moved to a different block!") ? void (0) : __assert_fail ("II->getParent() == &*BI && \"Moved to a different block!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/Reassociate.cpp"
, 2318, __extension__ __PRETTY_FUNCTION__))
;
2319 ++II;
2320 }
2321
2322 // Make a copy of all the instructions to be redone so we can remove dead
2323 // instructions.
2324 SetVector<AssertingVH<Instruction>> ToRedo(RedoInsts);
2325 // Iterate over all instructions to be reevaluated and remove trivially dead
2326 // instructions. If any operand of the trivially dead instruction becomes
2327 // dead mark it for deletion as well. Continue this process until all
2328 // trivially dead instructions have been removed.
2329 while (!ToRedo.empty()) {
2330 Instruction *I = ToRedo.pop_back_val();
2331 if (isInstructionTriviallyDead(I)) {
2332 RecursivelyEraseDeadInsts(I, ToRedo);
2333 MadeChange = true;
2334 }
2335 }
2336
2337 // Now that we have removed dead instructions, we can reoptimize the
2338 // remaining instructions.
2339 while (!RedoInsts.empty()) {
2340 Instruction *I = RedoInsts.pop_back_val();
2341 if (isInstructionTriviallyDead(I))
2342 EraseInst(I);
2343 else
2344 OptimizeInst(I);
2345 }
2346 }
2347
2348 // We are done with the rank map and pair map.
2349 RankMap.clear();
2350 ValueRankMap.clear();
2351 for (auto &Entry : PairMap)
2352 Entry.clear();
2353
2354 if (MadeChange) {
2355 PreservedAnalyses PA;
2356 PA.preserveSet<CFGAnalyses>();
2357 PA.preserve<GlobalsAA>();
2358 return PA;
2359 }
2360
2361 return PreservedAnalyses::all();
2362}
2363
2364namespace {
2365
2366 class ReassociateLegacyPass : public FunctionPass {
2367 ReassociatePass Impl;
2368
2369 public:
2370 static char ID; // Pass identification, replacement for typeid
2371
2372 ReassociateLegacyPass() : FunctionPass(ID) {
2373 initializeReassociateLegacyPassPass(*PassRegistry::getPassRegistry());
2374 }
2375
2376 bool runOnFunction(Function &F) override {
2377 if (skipFunction(F))
1
Assuming the condition is false
2
Taking false branch
2378 return false;
2379
2380 FunctionAnalysisManager DummyFAM;
2381 auto PA = Impl.run(F, DummyFAM);
3
Calling 'ReassociatePass::run'
2382 return !PA.areAllPreserved();
2383 }
2384
2385 void getAnalysisUsage(AnalysisUsage &AU) const override {
2386 AU.setPreservesCFG();
2387 AU.addPreserved<GlobalsAAWrapperPass>();
2388 }
2389 };
2390
2391} // end anonymous namespace
2392
2393char ReassociateLegacyPass::ID = 0;
2394
2395INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",static void *initializeReassociateLegacyPassPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "Reassociate expressions"
, "reassociate", &ReassociateLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<ReassociateLegacyPass>), false, false)
; Registry.registerPass(*PI, true); return PI; } static llvm::
once_flag InitializeReassociateLegacyPassPassFlag; void llvm::
initializeReassociateLegacyPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeReassociateLegacyPassPassFlag, initializeReassociateLegacyPassPassOnce
, std::ref(Registry)); }
2396 "Reassociate expressions", false, false)static void *initializeReassociateLegacyPassPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "Reassociate expressions"
, "reassociate", &ReassociateLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<ReassociateLegacyPass>), false, false)
; Registry.registerPass(*PI, true); return PI; } static llvm::
once_flag InitializeReassociateLegacyPassPassFlag; void llvm::
initializeReassociateLegacyPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeReassociateLegacyPassPassFlag, initializeReassociateLegacyPassPassOnce
, std::ref(Registry)); }
2397
2398// Public interface to the Reassociate pass
2399FunctionPass *llvm::createReassociatePass() {
2400 return new ReassociateLegacyPass();
2401}