If we mark clean-ups as clean-ups, then it could break when inlining through an
'invoke' instruction. You will get a situation like this: bb: %ehptr = eh.exception() %sel = eh.selector(%ehptr, @per, 0); ... bb2: invoke _Unwind_Resume_or_Rethrow(%ehptr) %normal unwind to %lpad lpad: ... The unwinder will see the %sel call as a clean-up and, if it doesn't have a catch further up the call stack, it will skip running it. But there *is* another catch up the stack -- the catch for the %lpad. However, we can't see that. This is fixed in code-gen, where we detect this situation, and convert the "clean-up" selector call into a "catch-all" selector call. This gives us the correct semantics. llvm-svn: 99671
This commit is contained in:
Bill Wendling
parent
0785d92cae
commit
d1aa77c37d
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@ -8,19 +8,19 @@
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//===----------------------------------------------------------------------===//
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//
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// This pass mulches exception handling code into a form adapted to code
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// generation. Required if using dwarf exception handling.
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// generation. Required if using dwarf exception handling.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "dwarfehprepare"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Function.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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@ -40,6 +40,15 @@ namespace {
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// The eh.exception intrinsic.
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Function *ExceptionValueIntrinsic;
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// The eh.selector intrinsic.
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Function *SelectorIntrinsic;
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// _Unwind_Resume_or_Rethrow call.
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Constant *URoR;
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// The EH language-specific catch-all type.
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GlobalVariable *EHCatchAllValue;
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// _Unwind_Resume or the target equivalent.
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Constant *RewindFunction;
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@ -67,18 +76,77 @@ namespace {
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Instruction *CreateValueLoad(BasicBlock *BB);
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/// CreateReadOfExceptionValue - Return the result of the eh.exception
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/// intrinsic by calling the intrinsic if in a landing pad, or loading
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/// it from the exception value variable otherwise.
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/// intrinsic by calling the intrinsic if in a landing pad, or loading it
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/// from the exception value variable otherwise.
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Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
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return LandingPads.count(BB) ?
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CreateExceptionValueCall(BB) : CreateValueLoad(BB);
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}
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/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
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/// calls. The "unwind" part of these invokes jump to a landing pad within
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/// the current function. This is a candidate to merge the selector
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/// associated with the URoR invoke with the one from the URoR's landing
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/// pad.
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bool HandleURoRInvokes();
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/// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
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/// with the eh.exception call. This recursively looks past instructions
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/// which don't change the EH pointer value, like casts or PHI nodes.
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bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
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SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
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/// DoMem2RegPromotion - Take an alloca call and promote it from memory to a
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/// register.
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bool DoMem2RegPromotion(Value *V) {
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AllocaInst *AI = dyn_cast<AllocaInst>(V);
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if (!AI || !isAllocaPromotable(AI)) return false;
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// Turn the alloca into a register.
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std::vector<AllocaInst*> Allocas(1, AI);
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PromoteMemToReg(Allocas, *DT, *DF);
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return true;
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}
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/// PromoteStoreInst - Perform Mem2Reg on a StoreInst.
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bool PromoteStoreInst(StoreInst *SI) {
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if (!SI || !DT || !DF) return false;
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if (DoMem2RegPromotion(SI->getOperand(1)))
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return true;
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return false;
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}
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/// PromoteEHPtrStore - Promote the storing of an EH pointer into a
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/// register. This should get rid of the store and subsequent loads.
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bool PromoteEHPtrStore(IntrinsicInst *II) {
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if (!DT || !DF) return false;
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bool Changed = false;
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StoreInst *SI;
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while (1) {
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SI = 0;
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for (Value::use_iterator
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I = II->use_begin(), E = II->use_end(); I != E; ++I) {
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SI = dyn_cast<StoreInst>(I);
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if (SI) break;
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}
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if (!PromoteStoreInst(SI))
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break;
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Changed = true;
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}
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return false;
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}
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public:
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static char ID; // Pass identification, replacement for typeid.
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DwarfEHPrepare(const TargetLowering *tli, bool fast) :
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FunctionPass(&ID), TLI(tli), CompileFast(fast),
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ExceptionValueIntrinsic(0), RewindFunction(0) {}
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ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
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URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
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virtual bool runOnFunction(Function &Fn);
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@ -105,6 +173,144 @@ FunctionPass *llvm::createDwarfEHPass(const TargetLowering *tli, bool fast) {
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return new DwarfEHPrepare(tli, fast);
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}
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/// FindSelectorAndURoR - Find the eh.selector call associated with the
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/// eh.exception call. And indicate if there is a URoR "invoke" associated with
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/// the eh.exception call. This recursively looks past instructions which don't
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/// change the EH pointer value, like casts or PHI nodes.
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bool
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DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
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SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
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SmallPtrSet<PHINode*, 32> SeenPHIs;
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bool Changed = false;
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restart:
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for (Value::use_iterator
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I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
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Instruction *II = dyn_cast<Instruction>(I);
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if (!II || II->getParent()->getParent() != F) continue;
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if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
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if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
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SelCalls.insert(Sel);
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} else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
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if (Invoke->getCalledFunction() == URoR)
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URoRInvoke = true;
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} else if (CastInst *CI = dyn_cast<CastInst>(II)) {
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Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
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} else if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
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if (!PromoteStoreInst(SI)) continue;
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Changed = true;
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SeenPHIs.clear();
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goto restart; // Uses may have changed, restart loop.
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} else if (PHINode *PN = dyn_cast<PHINode>(II)) {
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if (SeenPHIs.insert(PN))
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// Don't process a PHI node more than once.
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Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
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}
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}
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return Changed;
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}
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/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
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/// "unwind" part of these invokes jump to a landing pad within the current
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/// function. This is a candidate to merge the selector associated with the URoR
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/// invoke with the one from the URoR's landing pad.
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bool DwarfEHPrepare::HandleURoRInvokes() {
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if (!EHCatchAllValue) {
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EHCatchAllValue =
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F->getParent()->getNamedGlobal(".llvm.eh.catch.all.value");
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if (!EHCatchAllValue) return false;
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}
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if (!URoR) {
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URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
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if (!URoR) return false;
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}
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if (!ExceptionValueIntrinsic) {
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ExceptionValueIntrinsic =
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Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
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if (!ExceptionValueIntrinsic) return false;
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}
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if (!SelectorIntrinsic) {
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SelectorIntrinsic =
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Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
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if (!SelectorIntrinsic) return false;
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}
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bool Changed = false;
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SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
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for (Value::use_iterator
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I = ExceptionValueIntrinsic->use_begin(),
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E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
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IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(I);
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if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
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Changed |= PromoteEHPtrStore(EHPtr);
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bool URoRInvoke = false;
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SmallPtrSet<IntrinsicInst*, 8> SelCalls;
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Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
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if (URoRInvoke) {
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// This EH pointer is being used by an invoke of an URoR instruction and
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// an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
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// need to convert it to a 'catch-all'.
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for (SmallPtrSet<IntrinsicInst*, 8>::iterator
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SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) {
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IntrinsicInst *II = *SI;
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unsigned NumOps = II->getNumOperands();
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if (NumOps <= 4) {
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bool IsCleanUp = (NumOps == 3);
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if (!IsCleanUp)
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if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getOperand(3)))
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IsCleanUp = (CI->getZExtValue() == 0);
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if (IsCleanUp)
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SelsToConvert.insert(II);
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}
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}
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}
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}
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if (!SelsToConvert.empty()) {
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// Convert all clean-up eh.selectors, which are associated with "invokes" of
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// URoR calls, into catch-all eh.selectors.
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Changed = true;
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for (SmallPtrSet<IntrinsicInst*, 8>::iterator
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SI = SelsToConvert.begin(), SE = SelsToConvert.end();
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SI != SE; ++SI) {
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IntrinsicInst *II = *SI;
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SmallVector<Value*, 8> Args;
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// Use the exception object pointer and the personality function
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// from the original selector.
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Args.push_back(II->getOperand(1)); // Exception object pointer.
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Args.push_back(II->getOperand(2)); // Personality function.
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Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
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CallInst *NewSelector =
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CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
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"eh.sel.catch.all", II);
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NewSelector->setTailCall(II->isTailCall());
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NewSelector->setAttributes(II->getAttributes());
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NewSelector->setCallingConv(II->getCallingConv());
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II->replaceAllUsesWith(NewSelector);
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II->eraseFromParent();
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}
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}
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return Changed;
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}
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/// NormalizeLandingPads - Normalize and discover landing pads, noting them
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/// in the LandingPads set. A landing pad is normal if the only CFG edges
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/// that end at it are unwind edges from invoke instructions. If we inlined
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@ -422,6 +628,8 @@ bool DwarfEHPrepare::runOnFunction(Function &Fn) {
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if (!CompileFast)
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Changed |= PromoteStackTemporaries();
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Changed |= HandleURoRInvokes();
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LandingPads.clear();
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return Changed;
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Loading…
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