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-rw-r--r--llvm/lib/CodeGen/WinEHPrepare.cpp305
1 files changed, 126 insertions, 179 deletions
diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index 5b4ee17d949..c7a3ab113bd 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -21,6 +21,7 @@
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
+#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
@@ -34,6 +35,7 @@
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <memory>
using namespace llvm;
@@ -62,7 +64,7 @@ class WinEHPrepare : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(const TargetMachine *TM = nullptr)
- : FunctionPass(ID) {}
+ : FunctionPass(ID), DT(nullptr) {}
bool runOnFunction(Function &Fn) override;
@@ -77,6 +79,7 @@ public:
private:
bool prepareExceptionHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
+ void promoteLandingPadValues(LandingPadInst *LPad);
bool outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo);
@@ -89,10 +92,11 @@ private:
void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
// All fields are reset by runOnFunction.
+ DominatorTree *DT;
EHPersonality Personality;
CatchHandlerMapTy CatchHandlerMap;
CleanupHandlerMapTy CleanupHandlerMap;
- DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
+ DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
};
class WinEHFrameVariableMaterializer : public ValueMaterializer {
@@ -115,37 +119,18 @@ public:
bool isInitialized() { return OriginLPad != nullptr; }
- bool mapIfEHPtrLoad(const LoadInst *Load) {
- return mapIfEHLoad(Load, EHPtrStores, EHPtrStoreAddrs);
- }
- bool mapIfSelectorLoad(const LoadInst *Load) {
- return mapIfEHLoad(Load, SelectorStores, SelectorStoreAddrs);
- }
-
bool isOriginLandingPadBlock(const BasicBlock *BB) const;
bool isLandingPadSpecificInst(const Instruction *Inst) const;
- void remapSelector(ValueToValueMapTy &VMap, Value *MappedValue) const;
+ void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
+ Value *SelectorValue) const;
private:
- bool mapIfEHLoad(const LoadInst *Load,
- SmallVectorImpl<const StoreInst *> &Stores,
- SmallVectorImpl<const Value *> &StoreAddrs);
-
const LandingPadInst *OriginLPad;
// We will normally only see one of each of these instructions, but
// if more than one occurs for some reason we can handle that.
TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
-
- // In optimized code, there will typically be at most one instance of
- // each of the following, but in unoptimized IR it is not uncommon
- // for the values to be stored, loaded and then stored again. In that
- // case we will create a second entry for each store and store address.
- SmallVector<const StoreInst *, 2> EHPtrStores;
- SmallVector<const StoreInst *, 2> SelectorStores;
- SmallVector<const Value *, 2> EHPtrStoreAddrs;
- SmallVector<const Value *, 2> SelectorStoreAddrs;
};
class WinEHCloningDirectorBase : public CloningDirector {
@@ -298,6 +283,8 @@ bool WinEHPrepare::runOnFunction(Function &Fn) {
if (!isMSVCEHPersonality(Personality))
return false;
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+
if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
// Replace all resume instructions with unreachable.
// FIXME: Remove this once the backend can handle the prepared IR.
@@ -317,7 +304,9 @@ bool WinEHPrepare::doFinalization(Module &M) {
return false;
}
-void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
+void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<DominatorTreeWrapperPass>();
+}
bool WinEHPrepare::prepareExceptionHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
@@ -360,6 +349,10 @@ bool WinEHPrepare::prepareExceptionHandlers(
if (LPadHasActionList)
continue;
+ // If either of the values in the aggregate returned by the landing pad is
+ // extracted and stored to memory, promote the stored value to a register.
+ promoteLandingPadValues(LPad);
+
LandingPadActions Actions;
mapLandingPadBlocks(LPad, Actions);
@@ -564,6 +557,38 @@ bool WinEHPrepare::prepareExceptionHandlers(
return HandlersOutlined;
}
+void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
+ // If the return values of the landing pad instruction are extracted and
+ // stored to memory, we want to promote the store locations to reg values.
+ SmallVector<AllocaInst *, 2> EHAllocas;
+
+ // The landingpad instruction returns an aggregate value. Typically, its
+ // value will be passed to a pair of extract value instructions and the
+ // results of those extracts are often passed to store instructions.
+ // In unoptimized code the stored value will often be loaded and then stored
+ // again.
+ for (auto *U : LPad->users()) {
+ ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
+ if (!Extract)
+ continue;
+
+ for (auto *EU : Extract->users()) {
+ if (auto *Store = dyn_cast<StoreInst>(EU)) {
+ auto *AV = cast<AllocaInst>(Store->getPointerOperand());
+ EHAllocas.push_back(AV);
+ }
+ }
+ }
+
+ // We can't do this without a dominator tree.
+ assert(DT);
+
+ if (!EHAllocas.empty()) {
+ PromoteMemToReg(EHAllocas, *DT);
+ EHAllocas.clear();
+ }
+}
+
// This function examines a block to determine whether the block ends with a
// conditional branch to a catch handler based on a selector comparison.
// This function is used both by the WinEHPrepare::findSelectorComparison() and
@@ -640,9 +665,12 @@ bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
Constant *Sel = CatchAction->getSelector();
Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap));
- LPadMap.remapSelector(VMap, ConstantInt::get(Type::getInt32Ty(Context), 1));
+ LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
+ ConstantInt::get(Type::getInt32Ty(Context), 1));
} else {
Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
+ LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
+ UndefValue::get(Type::getInt32Ty(Context)));
}
SmallVector<ReturnInst *, 8> Returns;
@@ -730,9 +758,8 @@ void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
// The landingpad instruction returns an aggregate value. Typically, its
// value will be passed to a pair of extract value instructions and the
- // results of those extracts are often passed to store instructions.
- // In unoptimized code the stored value will often be loaded and then stored
- // again.
+ // results of those extracts will have been promoted to reg values before
+ // this routine is called.
for (auto *U : LPad->users()) {
const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
if (!Extract)
@@ -743,33 +770,10 @@ void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
assert((Idx == 0 || Idx == 1) &&
"Unexpected operation: extracting an unknown landing pad element");
if (Idx == 0) {
- // Element 0 doesn't directly corresponds to anything in the WinEH
- // scheme.
- // It will be stored to a memory location, then later loaded and finally
- // the loaded value will be used as the argument to an
- // llvm.eh.begincatch
- // call. We're tracking it here so that we can skip the store and load.
ExtractedEHPtrs.push_back(Extract);
} else if (Idx == 1) {
- // Element 1 corresponds to the filter selector. We'll map it to 1 for
- // matching purposes, but it will also probably be stored to memory and
- // reloaded, so we need to track the instuction so that we can map the
- // loaded value too.
ExtractedSelectors.push_back(Extract);
}
-
- // Look for stores of the extracted values.
- for (auto *EU : Extract->users()) {
- if (auto *Store = dyn_cast<StoreInst>(EU)) {
- if (Idx == 1) {
- SelectorStores.push_back(Store);
- SelectorStoreAddrs.push_back(Store->getPointerOperand());
- } else {
- EHPtrStores.push_back(Store);
- EHPtrStoreAddrs.push_back(Store->getPointerOperand());
- }
- }
- }
}
}
@@ -788,47 +792,16 @@ bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
if (Inst == Extract)
return true;
}
- for (auto *Store : EHPtrStores) {
- if (Inst == Store)
- return true;
- }
- for (auto *Store : SelectorStores) {
- if (Inst == Store)
- return true;
- }
-
return false;
}
-void LandingPadMap::remapSelector(ValueToValueMapTy &VMap,
- Value *MappedValue) const {
- // Remap all selector extract instructions to the specified value.
+void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
+ Value *SelectorValue) const {
+ // Remap all landing pad extract instructions to the specified values.
+ for (auto *Extract : ExtractedEHPtrs)
+ VMap[Extract] = EHPtrValue;
for (auto *Extract : ExtractedSelectors)
- VMap[Extract] = MappedValue;
-}
-
-bool LandingPadMap::mapIfEHLoad(const LoadInst *Load,
- SmallVectorImpl<const StoreInst *> &Stores,
- SmallVectorImpl<const Value *> &StoreAddrs) {
- // This makes the assumption that a store we've previously seen dominates
- // this load instruction. That might seem like a rather huge assumption,
- // but given the way that landingpads are constructed its fairly safe.
- // FIXME: Add debug/assert code that verifies this.
- const Value *LoadAddr = Load->getPointerOperand();
- for (auto *StoreAddr : StoreAddrs) {
- if (LoadAddr == StoreAddr) {
- // Handle the common debug scenario where this loaded value is stored
- // to a different location.
- for (auto *U : Load->users()) {
- if (auto *Store = dyn_cast<StoreInst>(U)) {
- Stores.push_back(Store);
- StoreAddrs.push_back(Store->getPointerOperand());
- }
- }
- return true;
- }
- }
- return false;
+ VMap[Extract] = SelectorValue;
}
CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
@@ -838,25 +811,6 @@ CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
if (LPadMap.isLandingPadSpecificInst(Inst))
return CloningDirector::SkipInstruction;
- if (auto *Load = dyn_cast<LoadInst>(Inst)) {
- // Look for loads of (previously suppressed) landingpad values.
- // The EHPtr load can be mapped to an undef value as it should only be used
- // as an argument to llvm.eh.begincatch, but the selector value needs to be
- // mapped to a constant value of 1. This value will be used to simplify the
- // branching to always flow to the current handler.
- if (LPadMap.mapIfSelectorLoad(Load)) {
- VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
- return CloningDirector::SkipInstruction;
- }
- if (LPadMap.mapIfEHPtrLoad(Load)) {
- VMap[Inst] = UndefValue::get(Int8PtrType);
- return CloningDirector::SkipInstruction;
- }
-
- // Any other loads just get cloned.
- return CloningDirector::CloneInstruction;
- }
-
// Nested landing pads will be cloned as stubs, with just the
// landingpad instruction and an unreachable instruction. When
// all landingpads have been outlined, we'll replace this with the
@@ -926,20 +880,24 @@ WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
return CloningDirector::SkipInstruction;
- // If an end catch occurs anywhere else the next instruction should be an
- // unconditional branch instruction that we want to replace with a return
- // to the the address of the branch target.
- const BasicBlock *EndCatchBB = IntrinCall->getParent();
- const TerminatorInst *Terminator = EndCatchBB->getTerminator();
- const BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
- assert(Branch && Branch->isUnconditional());
- assert(std::next(BasicBlock::const_iterator(IntrinCall)) ==
- BasicBlock::const_iterator(Branch));
-
- BasicBlock *ContinueLabel = Branch->getSuccessor(0);
- ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueLabel),
- NewBB);
- ReturnTargets.push_back(ContinueLabel);
+ // If an end catch occurs anywhere else we want to terminate the handler
+ // with a return to the code that follows the endcatch call. If the
+ // next instruction is not an unconditional branch, we need to split the
+ // block to provide a clear target for the return instruction.
+ BasicBlock *ContinueBB;
+ auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
+ const BranchInst *Branch = dyn_cast<BranchInst>(Next);
+ if (!Branch || !Branch->isUnconditional()) {
+ // We're interrupting the cloning process at this location, so the
+ // const_cast we're doing here will not cause a problem.
+ ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
+ const_cast<Instruction *>(cast<Instruction>(Next)));
+ } else {
+ ContinueBB = Branch->getSuccessor(0);
+ }
+
+ ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
+ ReturnTargets.push_back(ContinueBB);
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block so that
@@ -1338,10 +1296,8 @@ CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
}
// Look for the bare resume pattern:
- // %exn2 = load i8** %exn.slot
- // %sel2 = load i32* %ehselector.slot
- // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn2, 0
- // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel2, 1
+ // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
+ // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
// resume { i8*, i32 } %lpad.val2
if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
InsertValueInst *Insert1 = nullptr;
@@ -1375,62 +1331,53 @@ CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
}
BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
- if (Branch) {
- if (Branch->isConditional()) {
- // Look for the selector dispatch.
- // %sel = load i32* %ehselector.slot
- // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
- // %matches = icmp eq i32 %sel12, %2
- // br i1 %matches, label %catch14, label %eh.resume
- CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
- if (!Compare || !Compare->isEquality())
- return createCleanupHandler(CleanupHandlerMap, BB);
- for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
- IE = BB->end();
- II != IE; ++II) {
- Instruction *Inst = II;
- if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
- continue;
- if (Inst == Compare || Inst == Branch)
- continue;
- if (!Inst->hasOneUse() || (Inst->user_back() != Compare))
- return createCleanupHandler(CleanupHandlerMap, BB);
- if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
- continue;
- if (!isa<LoadInst>(Inst))
- return createCleanupHandler(CleanupHandlerMap, BB);
- }
- // The selector dispatch block should always terminate our search.
- assert(BB == EndBB);
- return nullptr;
- } else {
- // Look for empty blocks with unconditional branches.
- for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
- IE = BB->end();
- II != IE; ++II) {
- Instruction *Inst = II;
- if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
- continue;
- if (Inst == Branch)
- continue;
- // This can happen with a catch-all handler.
- if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
- return nullptr;
- if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
- continue;
- // Anything else makes this interesting cleanup code.
- return createCleanupHandler(CleanupHandlerMap, BB);
- }
- if (BB == EndBB)
- return nullptr;
- // The branch was unconditional.
- BB = Branch->getSuccessor(0);
+ if (Branch && Branch->isConditional()) {
+ // Look for the selector dispatch.
+ // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
+ // %matches = icmp eq i32 %sel, %2
+ // br i1 %matches, label %catch14, label %eh.resume
+ CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
+ if (!Compare || !Compare->isEquality())
+ return createCleanupHandler(CleanupHandlerMap, BB);
+ for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
+ IE = BB->end();
+ II != IE; ++II) {
+ Instruction *Inst = II;
+ if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
+ continue;
+ if (Inst == Compare || Inst == Branch)
+ continue;
+ if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
+ continue;
+ return createCleanupHandler(CleanupHandlerMap, BB);
+ }
+ // The selector dispatch block should always terminate our search.
+ assert(BB == EndBB);
+ return nullptr;
+ }
+
+ // Anything else is either a catch block or interesting cleanup code.
+ for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
+ IE = BB->end();
+ II != IE; ++II) {
+ Instruction *Inst = II;
+ if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
+ continue;
+ // Unconditional branches fall through to this loop.
+ if (Inst == Branch)
continue;
- } // End else of if branch was conditional
- } // End if Branch
+ // If this is a catch block, there is no cleanup code to be found.
+ if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
+ return nullptr;
+ // Anything else makes this interesting cleanup code.
+ return createCleanupHandler(CleanupHandlerMap, BB);
+ }
- // Anything else makes this interesting cleanup code.
- return createCleanupHandler(CleanupHandlerMap, BB);
+ // Only unconditional branches in empty blocks should get this far.
+ assert(Branch && Branch->isUnconditional());
+ if (BB == EndBB)
+ return nullptr;
+ BB = Branch->getSuccessor(0);
}
return nullptr;
}
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