Bug Summary

File:lib/Transforms/Utils/CodeExtractor.cpp
Location:line 368, column 32
Description:Function call argument is an uninitialized value

Annotated Source Code

1//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
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 file implements the interface to tear out a code region, such as an
11// individual loop or a parallel section, into a new function, replacing it with
12// a call to the new function.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Transforms/Utils/CodeExtractor.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SetVector.h"
19#include "llvm/ADT/StringExtras.h"
20#include "llvm/Analysis/LoopInfo.h"
21#include "llvm/Analysis/RegionInfo.h"
22#include "llvm/Analysis/RegionIterator.h"
23#include "llvm/IR/Constants.h"
24#include "llvm/IR/DerivedTypes.h"
25#include "llvm/IR/Dominators.h"
26#include "llvm/IR/Instructions.h"
27#include "llvm/IR/Intrinsics.h"
28#include "llvm/IR/LLVMContext.h"
29#include "llvm/IR/Module.h"
30#include "llvm/IR/Verifier.h"
31#include "llvm/Pass.h"
32#include "llvm/Support/CommandLine.h"
33#include "llvm/Support/Debug.h"
34#include "llvm/Support/ErrorHandling.h"
35#include "llvm/Support/raw_ostream.h"
36#include "llvm/Transforms/Utils/BasicBlockUtils.h"
37#include <algorithm>
38#include <set>
39using namespace llvm;
40
41#define DEBUG_TYPE"code-extractor" "code-extractor"
42
43// Provide a command-line option to aggregate function arguments into a struct
44// for functions produced by the code extractor. This is useful when converting
45// extracted functions to pthread-based code, as only one argument (void*) can
46// be passed in to pthread_create().
47static cl::opt<bool>
48AggregateArgsOpt("aggregate-extracted-args", cl::Hidden,
49 cl::desc("Aggregate arguments to code-extracted functions"));
50
51/// \brief Test whether a block is valid for extraction.
52static bool isBlockValidForExtraction(const BasicBlock &BB) {
53 // Landing pads must be in the function where they were inserted for cleanup.
54 if (BB.isEHPad())
55 return false;
56
57 // Don't hoist code containing allocas, invokes, or vastarts.
58 for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
59 if (isa<AllocaInst>(I) || isa<InvokeInst>(I))
60 return false;
61 if (const CallInst *CI = dyn_cast<CallInst>(I))
62 if (const Function *F = CI->getCalledFunction())
63 if (F->getIntrinsicID() == Intrinsic::vastart)
64 return false;
65 }
66
67 return true;
68}
69
70/// \brief Build a set of blocks to extract if the input blocks are viable.
71template <typename IteratorT>
72static SetVector<BasicBlock *> buildExtractionBlockSet(IteratorT BBBegin,
73 IteratorT BBEnd) {
74 SetVector<BasicBlock *> Result;
75
76 assert(BBBegin != BBEnd)((BBBegin != BBEnd) ? static_cast<void> (0) : __assert_fail
("BBBegin != BBEnd", "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn250153/lib/Transforms/Utils/CodeExtractor.cpp"
, 76, __PRETTY_FUNCTION__));
77
78 // Loop over the blocks, adding them to our set-vector, and aborting with an
79 // empty set if we encounter invalid blocks.
80 for (IteratorT I = BBBegin, E = BBEnd; I != E; ++I) {
81 if (!Result.insert(*I))
82 llvm_unreachable("Repeated basic blocks in extraction input")::llvm::llvm_unreachable_internal("Repeated basic blocks in extraction input"
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn250153/lib/Transforms/Utils/CodeExtractor.cpp"
, 82);
83
84 if (!isBlockValidForExtraction(**I)) {
85 Result.clear();
86 return Result;
87 }
88 }
89
90#ifndef NDEBUG
91 for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()),
92 E = Result.end();
93 I != E; ++I)
94 for (pred_iterator PI = pred_begin(*I), PE = pred_end(*I);
95 PI != PE; ++PI)
96 assert(Result.count(*PI) &&((Result.count(*PI) && "No blocks in this region may have entries from outside the region"
" except for the first block!") ? static_cast<void> (0
) : __assert_fail ("Result.count(*PI) && \"No blocks in this region may have entries from outside the region\" \" except for the first block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn250153/lib/Transforms/Utils/CodeExtractor.cpp"
, 98, __PRETTY_FUNCTION__))
97 "No blocks in this region may have entries from outside the region"((Result.count(*PI) && "No blocks in this region may have entries from outside the region"
" except for the first block!") ? static_cast<void> (0
) : __assert_fail ("Result.count(*PI) && \"No blocks in this region may have entries from outside the region\" \" except for the first block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn250153/lib/Transforms/Utils/CodeExtractor.cpp"
, 98, __PRETTY_FUNCTION__))
98 " except for the first block!")((Result.count(*PI) && "No blocks in this region may have entries from outside the region"
" except for the first block!") ? static_cast<void> (0
) : __assert_fail ("Result.count(*PI) && \"No blocks in this region may have entries from outside the region\" \" except for the first block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn250153/lib/Transforms/Utils/CodeExtractor.cpp"
, 98, __PRETTY_FUNCTION__));
99#endif
100
101 return Result;
102}
103
104/// \brief Helper to call buildExtractionBlockSet with an ArrayRef.
105static SetVector<BasicBlock *>
106buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) {
107 return buildExtractionBlockSet(BBs.begin(), BBs.end());
108}
109
110/// \brief Helper to call buildExtractionBlockSet with a RegionNode.
111static SetVector<BasicBlock *>
112buildExtractionBlockSet(const RegionNode &RN) {
113 if (!RN.isSubRegion())
114 // Just a single BasicBlock.
115 return buildExtractionBlockSet(RN.getNodeAs<BasicBlock>());
116
117 const Region &R = *RN.getNodeAs<Region>();
118
119 return buildExtractionBlockSet(R.block_begin(), R.block_end());
120}
121
122CodeExtractor::CodeExtractor(BasicBlock *BB, bool AggregateArgs)
123 : DT(nullptr), AggregateArgs(AggregateArgs||AggregateArgsOpt),
124 Blocks(buildExtractionBlockSet(BB)), NumExitBlocks(~0U) {}
125
126CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
127 bool AggregateArgs)
128 : DT(DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
129 Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {}
130
131CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs)
132 : DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
133 Blocks(buildExtractionBlockSet(L.getBlocks())), NumExitBlocks(~0U) {}
134
135CodeExtractor::CodeExtractor(DominatorTree &DT, const RegionNode &RN,
136 bool AggregateArgs)
137 : DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
138 Blocks(buildExtractionBlockSet(RN)), NumExitBlocks(~0U) {}
139
140/// definedInRegion - Return true if the specified value is defined in the
141/// extracted region.
142static bool definedInRegion(const SetVector<BasicBlock *> &Blocks, Value *V) {
143 if (Instruction *I = dyn_cast<Instruction>(V))
144 if (Blocks.count(I->getParent()))
145 return true;
146 return false;
147}
148
149/// definedInCaller - Return true if the specified value is defined in the
150/// function being code extracted, but not in the region being extracted.
151/// These values must be passed in as live-ins to the function.
152static bool definedInCaller(const SetVector<BasicBlock *> &Blocks, Value *V) {
153 if (isa<Argument>(V)) return true;
154 if (Instruction *I = dyn_cast<Instruction>(V))
155 if (!Blocks.count(I->getParent()))
156 return true;
157 return false;
158}
159
160void CodeExtractor::findInputsOutputs(ValueSet &Inputs,
161 ValueSet &Outputs) const {
162 for (SetVector<BasicBlock *>::const_iterator I = Blocks.begin(),
163 E = Blocks.end();
164 I != E; ++I) {
165 BasicBlock *BB = *I;
166
167 // If a used value is defined outside the region, it's an input. If an
168 // instruction is used outside the region, it's an output.
169 for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
170 II != IE; ++II) {
171 for (User::op_iterator OI = II->op_begin(), OE = II->op_end();
172 OI != OE; ++OI)
173 if (definedInCaller(Blocks, *OI))
174 Inputs.insert(*OI);
175
176 for (User *U : II->users())
177 if (!definedInRegion(Blocks, U)) {
178 Outputs.insert(&*II);
179 break;
180 }
181 }
182 }
183}
184
185/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the
186/// region, we need to split the entry block of the region so that the PHI node
187/// is easier to deal with.
188void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) {
189 unsigned NumPredsFromRegion = 0;
190 unsigned NumPredsOutsideRegion = 0;
191
192 if (Header != &Header->getParent()->getEntryBlock()) {
193 PHINode *PN = dyn_cast<PHINode>(Header->begin());
194 if (!PN) return; // No PHI nodes.
195
196 // If the header node contains any PHI nodes, check to see if there is more
197 // than one entry from outside the region. If so, we need to sever the
198 // header block into two.
199 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
200 if (Blocks.count(PN->getIncomingBlock(i)))
201 ++NumPredsFromRegion;
202 else
203 ++NumPredsOutsideRegion;
204
205 // If there is one (or fewer) predecessor from outside the region, we don't
206 // need to do anything special.
207 if (NumPredsOutsideRegion <= 1) return;
208 }
209
210 // Otherwise, we need to split the header block into two pieces: one
211 // containing PHI nodes merging values from outside of the region, and a
212 // second that contains all of the code for the block and merges back any
213 // incoming values from inside of the region.
214 BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI()->getIterator();
215 BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs,
216 Header->getName()+".ce");
217
218 // We only want to code extract the second block now, and it becomes the new
219 // header of the region.
220 BasicBlock *OldPred = Header;
221 Blocks.remove(OldPred);
222 Blocks.insert(NewBB);
223 Header = NewBB;
224
225 // Okay, update dominator sets. The blocks that dominate the new one are the
226 // blocks that dominate TIBB plus the new block itself.
227 if (DT)
228 DT->splitBlock(NewBB);
229
230 // Okay, now we need to adjust the PHI nodes and any branches from within the
231 // region to go to the new header block instead of the old header block.
232 if (NumPredsFromRegion) {
233 PHINode *PN = cast<PHINode>(OldPred->begin());
234 // Loop over all of the predecessors of OldPred that are in the region,
235 // changing them to branch to NewBB instead.
236 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
237 if (Blocks.count(PN->getIncomingBlock(i))) {
238 TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator();
239 TI->replaceUsesOfWith(OldPred, NewBB);
240 }
241
242 // Okay, everything within the region is now branching to the right block, we
243 // just have to update the PHI nodes now, inserting PHI nodes into NewBB.
244 for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) {
245 PHINode *PN = cast<PHINode>(AfterPHIs);
246 // Create a new PHI node in the new region, which has an incoming value
247 // from OldPred of PN.
248 PHINode *NewPN = PHINode::Create(PN->getType(), 1 + NumPredsFromRegion,
249 PN->getName() + ".ce", &NewBB->front());
250 NewPN->addIncoming(PN, OldPred);
251
252 // Loop over all of the incoming value in PN, moving them to NewPN if they
253 // are from the extracted region.
254 for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) {
255 if (Blocks.count(PN->getIncomingBlock(i))) {
256 NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i));
257 PN->removeIncomingValue(i);
258 --i;
259 }
260 }
261 }
262 }
263}
264
265void CodeExtractor::splitReturnBlocks() {
266 for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end();
267 I != E; ++I)
268 if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) {
269 BasicBlock *New =
270 (*I)->splitBasicBlock(RI->getIterator(), (*I)->getName() + ".ret");
271 if (DT) {
272 // Old dominates New. New node dominates all other nodes dominated
273 // by Old.
274 DomTreeNode *OldNode = DT->getNode(*I);
275 SmallVector<DomTreeNode*, 8> Children;
276 for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end();
277 DI != DE; ++DI)
278 Children.push_back(*DI);
279
280 DomTreeNode *NewNode = DT->addNewBlock(New, *I);
281
282 for (SmallVectorImpl<DomTreeNode *>::iterator I = Children.begin(),
283 E = Children.end(); I != E; ++I)
284 DT->changeImmediateDominator(*I, NewNode);
285 }
286 }
287}
288
289/// constructFunction - make a function based on inputs and outputs, as follows:
290/// f(in0, ..., inN, out0, ..., outN)
291///
292Function *CodeExtractor::constructFunction(const ValueSet &inputs,
293 const ValueSet &outputs,
294 BasicBlock *header,
295 BasicBlock *newRootNode,
296 BasicBlock *newHeader,
297 Function *oldFunction,
298 Module *M) {
299 DEBUG(dbgs() << "inputs: " << inputs.size() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << "inputs: " << inputs
.size() << "\n"; } } while (0);
300 DEBUG(dbgs() << "outputs: " << outputs.size() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << "outputs: " << outputs
.size() << "\n"; } } while (0);
301
302 // This function returns unsigned, outputs will go back by reference.
303 switch (NumExitBlocks) {
1
Control jumps to the 'default' case at line 307
→
304 case 0:
305 case 1: RetTy = Type::getVoidTy(header->getContext()); break;
306 case 2: RetTy = Type::getInt1Ty(header->getContext()); break;
307 default: RetTy = Type::getInt16Ty(header->getContext()); break;
2
←
 Execution continues on line 310
→
308 }
309
310 std::vector<Type*> paramTy;
311
312 // Add the types of the input values to the function's argument list
313 for (ValueSet::const_iterator i = inputs.begin(), e = inputs.end();
3
←
Loop condition is false. Execution continues on line 321
→
314 i != e; ++i) {
315 const Value *value = *i;
316 DEBUG(dbgs() << "value used in func: " << *value << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << "value used in func: " <<
*value << "\n"; } } while (0);
317 paramTy.push_back(value->getType());
318 }
319
320 // Add the types of the output values to the function's argument list.
321 for (ValueSet::const_iterator I = outputs.begin(), E = outputs.end();
4
←
Loop condition is false. Execution continues on line 330
→
322 I != E; ++I) {
323 DEBUG(dbgs() << "instr used in func: " << **I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << "instr used in func: " <<
**I << "\n"; } } while (0);
324 if (AggregateArgs)
325 paramTy.push_back((*I)->getType());
326 else
327 paramTy.push_back(PointerType::getUnqual((*I)->getType()));
328 }
329
330 DEBUG(dbgs() << "Function type: " << *RetTy << " f(")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << "Function type: " <<
*RetTy << " f("; } } while (0);
331 for (std::vector<Type*>::iterator i = paramTy.begin(),
5
←
Loop condition is false. Execution continues on line 334
→
332 e = paramTy.end(); i != e; ++i)
333 DEBUG(dbgs() << **i << ", ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << **i << ", "; } } while
(0);
334 DEBUG(dbgs() << ")\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { dbgs() << ")\n"; } } while (0);
335
336 StructType *StructTy;
6
←
'StructTy' declared without an initial value
→
337 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
338 StructTy = StructType::get(M->getContext(), paramTy);
339 paramTy.clear();
340 paramTy.push_back(PointerType::getUnqual(StructTy));
341 }
342 FunctionType *funcType =
343 FunctionType::get(RetTy, paramTy, false);
344
345 // Create the new function
346 Function *newFunction = Function::Create(funcType,
347 GlobalValue::InternalLinkage,
348 oldFunction->getName() + "_" +
349 header->getName(), M);
350 // If the old function is no-throw, so is the new one.
351 if (oldFunction->doesNotThrow())
7
←
Taking false branch
→
352 newFunction->setDoesNotThrow();
353
354 newFunction->getBasicBlockList().push_back(newRootNode);
355
356 // Create an iterator to name all of the arguments we inserted.
357 Function::arg_iterator AI = newFunction->arg_begin();
358
359 // Rewrite all users of the inputs in the extracted region to use the
360 // arguments (or appropriate addressing into struct) instead.
361 for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
8
←
Assuming 'i' is not equal to 'e'
→
9
←
Loop condition is true. Entering loop body
→
12
←
Assuming 'i' is not equal to 'e'
→
13
←
Loop condition is true. Entering loop body
→
20
←
Assuming 'i' is not equal to 'e'
→
21
←
Loop condition is true. Entering loop body
→
362 Value *RewriteVal;
363 if (AggregateArgs) {
10
←
Taking false branch
→
14
←
Taking false branch
→
22
←
Taking true branch
→
364 Value *Idx[2];
365 Idx[0] = Constant::getNullValue(Type::getInt32Ty(header->getContext()));
366 Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i);
367 TerminatorInst *TI = newFunction->begin()->getTerminator();
368 GetElementPtrInst *GEP = GetElementPtrInst::Create(
23
←
Function call argument is an uninitialized value
369 StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI);
370 RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI);
371 } else
372 RewriteVal = &*AI++;
373
374 std::vector<User*> Users(inputs[i]->user_begin(), inputs[i]->user_end());
375 for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
11
←
Loop condition is false. Execution continues on line 361
→
15
←
Loop condition is true. Entering loop body
→
19
←
Loop condition is false. Execution continues on line 361
→
376 use != useE; ++use)
377 if (Instruction* inst = dyn_cast<Instruction>(*use))
16
←
Assuming 'inst' is non-null
→
17
←
Taking true branch
→
378 if (Blocks.count(inst->getParent()))
18
←
Taking false branch
→
379 inst->replaceUsesOfWith(inputs[i], RewriteVal);
380 }
381
382 // Set names for input and output arguments.
383 if (!AggregateArgs) {
384 AI = newFunction->arg_begin();
385 for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI)
386 AI->setName(inputs[i]->getName());
387 for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
388 AI->setName(outputs[i]->getName()+".out");
389 }
390
391 // Rewrite branches to basic blocks outside of the loop to new dummy blocks
392 // within the new function. This must be done before we lose track of which
393 // blocks were originally in the code region.
394 std::vector<User*> Users(header->user_begin(), header->user_end());
395 for (unsigned i = 0, e = Users.size(); i != e; ++i)
396 // The BasicBlock which contains the branch is not in the region
397 // modify the branch target to a new block
398 if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i]))
399 if (!Blocks.count(TI->getParent()) &&
400 TI->getParent()->getParent() == oldFunction)
401 TI->replaceUsesOfWith(header, newHeader);
402
403 return newFunction;
404}
405
406/// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI
407/// that uses the value within the basic block, and return the predecessor
408/// block associated with that use, or return 0 if none is found.
409static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) {
410 for (Use &U : Used->uses()) {
411 PHINode *P = dyn_cast<PHINode>(U.getUser());
412 if (P && P->getParent() == BB)
413 return P->getIncomingBlock(U);
414 }
415
416 return nullptr;
417}
418
419/// emitCallAndSwitchStatement - This method sets up the caller side by adding
420/// the call instruction, splitting any PHI nodes in the header block as
421/// necessary.
422void CodeExtractor::
423emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer,
424 ValueSet &inputs, ValueSet &outputs) {
425 // Emit a call to the new function, passing in: *pointer to struct (if
426 // aggregating parameters), or plan inputs and allocated memory for outputs
427 std::vector<Value*> params, StructValues, ReloadOutputs, Reloads;
428
429 LLVMContext &Context = newFunction->getContext();
430
431 // Add inputs as params, or to be filled into the struct
432 for (ValueSet::iterator i = inputs.begin(), e = inputs.end(); i != e; ++i)
433 if (AggregateArgs)
434 StructValues.push_back(*i);
435 else
436 params.push_back(*i);
437
438 // Create allocas for the outputs
439 for (ValueSet::iterator i = outputs.begin(), e = outputs.end(); i != e; ++i) {
440 if (AggregateArgs) {
441 StructValues.push_back(*i);
442 } else {
443 AllocaInst *alloca =
444 new AllocaInst((*i)->getType(), nullptr, (*i)->getName() + ".loc",
445 &codeReplacer->getParent()->front().front());
446 ReloadOutputs.push_back(alloca);
447 params.push_back(alloca);
448 }
449 }
450
451 StructType *StructArgTy = nullptr;
452 AllocaInst *Struct = nullptr;
453 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
454 std::vector<Type*> ArgTypes;
455 for (ValueSet::iterator v = StructValues.begin(),
456 ve = StructValues.end(); v != ve; ++v)
457 ArgTypes.push_back((*v)->getType());
458
459 // Allocate a struct at the beginning of this function
460 StructArgTy = StructType::get(newFunction->getContext(), ArgTypes);
461 Struct = new AllocaInst(StructArgTy, nullptr, "structArg",
462 &codeReplacer->getParent()->front().front());
463 params.push_back(Struct);
464
465 for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
466 Value *Idx[2];
467 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
468 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), i);
469 GetElementPtrInst *GEP = GetElementPtrInst::Create(
470 StructArgTy, Struct, Idx, "gep_" + StructValues[i]->getName());
471 codeReplacer->getInstList().push_back(GEP);
472 StoreInst *SI = new StoreInst(StructValues[i], GEP);
473 codeReplacer->getInstList().push_back(SI);
474 }
475 }
476
477 // Emit the call to the function
478 CallInst *call = CallInst::Create(newFunction, params,
479 NumExitBlocks > 1 ? "targetBlock" : "");
480 codeReplacer->getInstList().push_back(call);
481
482 Function::arg_iterator OutputArgBegin = newFunction->arg_begin();
483 unsigned FirstOut = inputs.size();
484 if (!AggregateArgs)
485 std::advance(OutputArgBegin, inputs.size());
486
487 // Reload the outputs passed in by reference
488 for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
489 Value *Output = nullptr;
490 if (AggregateArgs) {
491 Value *Idx[2];
492 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
493 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), FirstOut + i);
494 GetElementPtrInst *GEP = GetElementPtrInst::Create(
495 StructArgTy, Struct, Idx, "gep_reload_" + outputs[i]->getName());
496 codeReplacer->getInstList().push_back(GEP);
497 Output = GEP;
498 } else {
499 Output = ReloadOutputs[i];
500 }
501 LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload");
502 Reloads.push_back(load);
503 codeReplacer->getInstList().push_back(load);
504 std::vector<User*> Users(outputs[i]->user_begin(), outputs[i]->user_end());
505 for (unsigned u = 0, e = Users.size(); u != e; ++u) {
506 Instruction *inst = cast<Instruction>(Users[u]);
507 if (!Blocks.count(inst->getParent()))
508 inst->replaceUsesOfWith(outputs[i], load);
509 }
510 }
511
512 // Now we can emit a switch statement using the call as a value.
513 SwitchInst *TheSwitch =
514 SwitchInst::Create(Constant::getNullValue(Type::getInt16Ty(Context)),
515 codeReplacer, 0, codeReplacer);
516
517 // Since there may be multiple exits from the original region, make the new
518 // function return an unsigned, switch on that number. This loop iterates
519 // over all of the blocks in the extracted region, updating any terminator
520 // instructions in the to-be-extracted region that branch to blocks that are
521 // not in the region to be extracted.
522 std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
523
524 unsigned switchVal = 0;
525 for (SetVector<BasicBlock*>::const_iterator i = Blocks.begin(),
526 e = Blocks.end(); i != e; ++i) {
527 TerminatorInst *TI = (*i)->getTerminator();
528 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
529 if (!Blocks.count(TI->getSuccessor(i))) {
530 BasicBlock *OldTarget = TI->getSuccessor(i);
531 // add a new basic block which returns the appropriate value
532 BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
533 if (!NewTarget) {
534 // If we don't already have an exit stub for this non-extracted
535 // destination, create one now!
536 NewTarget = BasicBlock::Create(Context,
537 OldTarget->getName() + ".exitStub",
538 newFunction);
539 unsigned SuccNum = switchVal++;
540
541 Value *brVal = nullptr;
542 switch (NumExitBlocks) {
543 case 0:
544 case 1: break; // No value needed.
545 case 2: // Conditional branch, return a bool
546 brVal = ConstantInt::get(Type::getInt1Ty(Context), !SuccNum);
547 break;
548 default:
549 brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum);
550 break;
551 }
552
553 ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget);
554
555 // Update the switch instruction.
556 TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context),
557 SuccNum),
558 OldTarget);
559
560 // Restore values just before we exit
561 Function::arg_iterator OAI = OutputArgBegin;
562 for (unsigned out = 0, e = outputs.size(); out != e; ++out) {
563 // For an invoke/catchpad, the normal destination is the only one
564 // that is dominated by the result of the invocation
565 BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent();
566
567 bool DominatesDef = true;
568
569 BasicBlock *NormalDest = nullptr;
570 if (auto *Invoke = dyn_cast<InvokeInst>(outputs[out]))
571 NormalDest = Invoke->getNormalDest();
572 if (auto *CatchPad = dyn_cast<CatchPadInst>(outputs[out]))
573 NormalDest = CatchPad->getNormalDest();
574
575 if (NormalDest) {
576 DefBlock = NormalDest;
577
578 // Make sure we are looking at the original successor block, not
579 // at a newly inserted exit block, which won't be in the dominator
580 // info.
581 for (std::map<BasicBlock*, BasicBlock*>::iterator I =
582 ExitBlockMap.begin(), E = ExitBlockMap.end(); I != E; ++I)
583 if (DefBlock == I->second) {
584 DefBlock = I->first;
585 break;
586 }
587
588 // In the extract block case, if the block we are extracting ends
589 // with an invoke instruction, make sure that we don't emit a
590 // store of the invoke value for the unwind block.
591 if (!DT && DefBlock != OldTarget)
592 DominatesDef = false;
593 }
594
595 if (DT) {
596 DominatesDef = DT->dominates(DefBlock, OldTarget);
597
598 // If the output value is used by a phi in the target block,
599 // then we need to test for dominance of the phi's predecessor
600 // instead. Unfortunately, this a little complicated since we
601 // have already rewritten uses of the value to uses of the reload.
602 BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out],
603 OldTarget);
604 if (pred && DT && DT->dominates(DefBlock, pred))
605 DominatesDef = true;
606 }
607
608 if (DominatesDef) {
609 if (AggregateArgs) {
610 Value *Idx[2];
611 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
612 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context),
613 FirstOut+out);
614 GetElementPtrInst *GEP = GetElementPtrInst::Create(
615 StructArgTy, &*OAI, Idx, "gep_" + outputs[out]->getName(),
616 NTRet);
617 new StoreInst(outputs[out], GEP, NTRet);
618 } else {
619 new StoreInst(outputs[out], &*OAI, NTRet);
620 }
621 }
622 // Advance output iterator even if we don't emit a store
623 if (!AggregateArgs) ++OAI;
624 }
625 }
626
627 // rewrite the original branch instruction with this new target
628 TI->setSuccessor(i, NewTarget);
629 }
630 }
631
632 // Now that we've done the deed, simplify the switch instruction.
633 Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType();
634 switch (NumExitBlocks) {
635 case 0:
636 // There are no successors (the block containing the switch itself), which
637 // means that previously this was the last part of the function, and hence
638 // this should be rewritten as a `ret'
639
640 // Check if the function should return a value
641 if (OldFnRetTy->isVoidTy()) {
642 ReturnInst::Create(Context, nullptr, TheSwitch); // Return void
643 } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) {
644 // return what we have
645 ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch);
646 } else {
647 // Otherwise we must have code extracted an unwind or something, just
648 // return whatever we want.
649 ReturnInst::Create(Context,
650 Constant::getNullValue(OldFnRetTy), TheSwitch);
651 }
652
653 TheSwitch->eraseFromParent();
654 break;
655 case 1:
656 // Only a single destination, change the switch into an unconditional
657 // branch.
658 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch);
659 TheSwitch->eraseFromParent();
660 break;
661 case 2:
662 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2),
663 call, TheSwitch);
664 TheSwitch->eraseFromParent();
665 break;
666 default:
667 // Otherwise, make the default destination of the switch instruction be one
668 // of the other successors.
669 TheSwitch->setCondition(call);
670 TheSwitch->setDefaultDest(TheSwitch->getSuccessor(NumExitBlocks));
671 // Remove redundant case
672 TheSwitch->removeCase(SwitchInst::CaseIt(TheSwitch, NumExitBlocks-1));
673 break;
674 }
675}
676
677void CodeExtractor::moveCodeToFunction(Function *newFunction) {
678 Function *oldFunc = (*Blocks.begin())->getParent();
679 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
680 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
681
682 for (SetVector<BasicBlock*>::const_iterator i = Blocks.begin(),
683 e = Blocks.end(); i != e; ++i) {
684 // Delete the basic block from the old function, and the list of blocks
685 oldBlocks.remove(*i);
686
687 // Insert this basic block into the new function
688 newBlocks.push_back(*i);
689 }
690}
691
692Function *CodeExtractor::extractCodeRegion() {
693 if (!isEligible())
694 return nullptr;
695
696 ValueSet inputs, outputs;
697
698 // Assumption: this is a single-entry code region, and the header is the first
699 // block in the region.
700 BasicBlock *header = *Blocks.begin();
701
702 // If we have to split PHI nodes or the entry block, do so now.
703 severSplitPHINodes(header);
704
705 // If we have any return instructions in the region, split those blocks so
706 // that the return is not in the region.
707 splitReturnBlocks();
708
709 Function *oldFunction = header->getParent();
710
711 // This takes place of the original loop
712 BasicBlock *codeReplacer = BasicBlock::Create(header->getContext(),
713 "codeRepl", oldFunction,
714 header);
715
716 // The new function needs a root node because other nodes can branch to the
717 // head of the region, but the entry node of a function cannot have preds.
718 BasicBlock *newFuncRoot = BasicBlock::Create(header->getContext(),
719 "newFuncRoot");
720 newFuncRoot->getInstList().push_back(BranchInst::Create(header));
721
722 // Find inputs to, outputs from the code region.
723 findInputsOutputs(inputs, outputs);
724
725 SmallPtrSet<BasicBlock *, 1> ExitBlocks;
726 for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end();
727 I != E; ++I)
728 for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
729 if (!Blocks.count(*SI))
730 ExitBlocks.insert(*SI);
731 NumExitBlocks = ExitBlocks.size();
732
733 // Construct new function based on inputs/outputs & add allocas for all defs.
734 Function *newFunction = constructFunction(inputs, outputs, header,
735 newFuncRoot,
736 codeReplacer, oldFunction,
737 oldFunction->getParent());
738
739 emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
740
741 moveCodeToFunction(newFunction);
742
743 // Loop over all of the PHI nodes in the header block, and change any
744 // references to the old incoming edge to be the new incoming edge.
745 for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) {
746 PHINode *PN = cast<PHINode>(I);
747 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
748 if (!Blocks.count(PN->getIncomingBlock(i)))
749 PN->setIncomingBlock(i, newFuncRoot);
750 }
751
752 // Look at all successors of the codeReplacer block. If any of these blocks
753 // had PHI nodes in them, we need to update the "from" block to be the code
754 // replacer, not the original block in the extracted region.
755 std::vector<BasicBlock*> Succs(succ_begin(codeReplacer),
756 succ_end(codeReplacer));
757 for (unsigned i = 0, e = Succs.size(); i != e; ++i)
758 for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) {
759 PHINode *PN = cast<PHINode>(I);
760 std::set<BasicBlock*> ProcessedPreds;
761 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
762 if (Blocks.count(PN->getIncomingBlock(i))) {
763 if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second)
764 PN->setIncomingBlock(i, codeReplacer);
765 else {
766 // There were multiple entries in the PHI for this block, now there
767 // is only one, so remove the duplicated entries.
768 PN->removeIncomingValue(i, false);
769 --i; --e;
770 }
771 }
772 }
773
774 //cerr << "NEW FUNCTION: " << *newFunction;
775 // verifyFunction(*newFunction);
776
777 // cerr << "OLD FUNCTION: " << *oldFunction;
778 // verifyFunction(*oldFunction);
779
780 DEBUG(if (verifyFunction(*newFunction))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { if (verifyFunction(*newFunction)) report_fatal_error
("verifyFunction failed!"); } } while (0)
781 report_fatal_error("verifyFunction failed!"))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("code-extractor")) { if (verifyFunction(*newFunction)) report_fatal_error
("verifyFunction failed!"); } } while (0);
782 return newFunction;
783}