X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FIPO%2FPruneEH.cpp;h=c2f55d896ba783cd4f160f3019b9ea5950fc6de0;hp=e71344b215877e33621d5b82a30ef0a4e4371485;hb=9f25a0678ed9f06088a09649a040a6bef362e6af;hpb=ce665bd2e2b581ab0858d1afe359192bac96b868 diff --git a/lib/Transforms/IPO/PruneEH.cpp b/lib/Transforms/IPO/PruneEH.cpp index e71344b2158..c2f55d896ba 100644 --- a/lib/Transforms/IPO/PruneEH.cpp +++ b/lib/Transforms/IPO/PruneEH.cpp @@ -14,33 +14,39 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "prune-eh" #include "llvm/Transforms/IPO.h" -#include "llvm/CallGraphSCCPass.h" -#include "llvm/Constants.h" -#include "llvm/Function.h" -#include "llvm/LLVMContext.h" -#include "llvm/Instructions.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/Analysis/CallGraph.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" -#include "llvm/Support/CFG.h" -#include +#include "llvm/Support/raw_ostream.h" +#include "llvm/Analysis/CallGraph.h" +#include "llvm/Analysis/CallGraphSCCPass.h" +#include "llvm/Analysis/EHPersonalities.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/InlineAsm.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/Transforms/Utils/Local.h" #include using namespace llvm; +#define DEBUG_TYPE "prune-eh" + STATISTIC(NumRemoved, "Number of invokes removed"); STATISTIC(NumUnreach, "Number of noreturn calls optimized"); namespace { struct PruneEH : public CallGraphSCCPass { static char ID; // Pass identification, replacement for typeid - PruneEH() : CallGraphSCCPass(ID) {} + PruneEH() : CallGraphSCCPass(ID) { + initializePruneEHPass(*PassRegistry::getPassRegistry()); + } // runOnSCC - Analyze the SCC, performing the transformation if possible. - bool runOnSCC(CallGraphSCC &SCC); + bool runOnSCC(CallGraphSCC &SCC) override; bool SimplifyFunction(Function *F); void DeleteBasicBlock(BasicBlock *BB); @@ -48,7 +54,10 @@ namespace { } char PruneEH::ID = 0; -INITIALIZE_PASS(PruneEH, "prune-eh", +INITIALIZE_PASS_BEGIN(PruneEH, "prune-eh", + "Remove unused exception handling info", false, false) +INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass) +INITIALIZE_PASS_END(PruneEH, "prune-eh", "Remove unused exception handling info", false, false) Pass *llvm::createPruneEHPass() { return new PruneEH(); } @@ -56,7 +65,7 @@ Pass *llvm::createPruneEHPass() { return new PruneEH(); } bool PruneEH::runOnSCC(CallGraphSCC &SCC) { SmallPtrSet SCCNodes; - CallGraph &CG = getAnalysis(); + CallGraph &CG = getAnalysis().getCallGraph(); bool MadeChange = false; // Fill SCCNodes with the elements of the SCC. Used for quickly @@ -81,7 +90,7 @@ bool PruneEH::runOnSCC(CallGraphSCC &SCC) { for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); (!SCCMightUnwind || !SCCMightReturn) && I != E; ++I) { Function *F = (*I)->getFunction(); - if (F == 0) { + if (!F) { SCCMightUnwind = true; SCCMightReturn = true; } else if (F->isDeclaration() || F->mayBeOverridden()) { @@ -90,42 +99,54 @@ bool PruneEH::runOnSCC(CallGraphSCC &SCC) { } else { bool CheckUnwind = !SCCMightUnwind && !F->doesNotThrow(); bool CheckReturn = !SCCMightReturn && !F->doesNotReturn(); + // Determine if we should scan for InlineAsm in a naked function as it + // is the only way to return without a ReturnInst. Only do this for + // no-inline functions as functions which may be inlined cannot + // meaningfully return via assembly. + bool CheckReturnViaAsm = CheckReturn && + F->hasFnAttribute(Attribute::Naked) && + F->hasFnAttribute(Attribute::NoInline); if (!CheckUnwind && !CheckReturn) continue; - // Check to see if this function performs an unwind or calls an - // unwinding function. - for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { - if (CheckUnwind && isa(BB->getTerminator())) { - // Uses unwind! + for (const BasicBlock &BB : *F) { + const TerminatorInst *TI = BB.getTerminator(); + if (CheckUnwind && TI->mayThrow()) { SCCMightUnwind = true; - } else if (CheckReturn && isa(BB->getTerminator())) { + } else if (CheckReturn && isa(TI)) { SCCMightReturn = true; } - // Invoke instructions don't allow unwinding to continue, so we are - // only interested in call instructions. - if (CheckUnwind && !SCCMightUnwind) - for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) - if (CallInst *CI = dyn_cast(I)) { - if (CI->doesNotThrow()) { - // This call cannot throw. - } else if (Function *Callee = CI->getCalledFunction()) { + for (const Instruction &I : BB) { + if ((!CheckUnwind || SCCMightUnwind) && + (!CheckReturnViaAsm || SCCMightReturn)) + break; + + // Check to see if this function performs an unwind or calls an + // unwinding function. + if (CheckUnwind && !SCCMightUnwind && I.mayThrow()) { + bool InstMightUnwind = true; + if (const auto *CI = dyn_cast(&I)) { + if (Function *Callee = CI->getCalledFunction()) { CallGraphNode *CalleeNode = CG[Callee]; - // If the callee is outside our current SCC then we may - // throw because it might. - if (!SCCNodes.count(CalleeNode)) { - SCCMightUnwind = true; - break; - } - } else { - // Indirect call, it might throw. - SCCMightUnwind = true; - break; + // If the callee is outside our current SCC then we may throw + // because it might. If it is inside, do nothing. + if (SCCNodes.count(CalleeNode) > 0) + InstMightUnwind = false; } } - if (SCCMightUnwind && SCCMightReturn) break; + SCCMightUnwind |= InstMightUnwind; + } + if (CheckReturnViaAsm && !SCCMightReturn) + if (auto ICS = ImmutableCallSite(&I)) + if (const auto *IA = dyn_cast(ICS.getCalledValue())) + if (IA->hasSideEffects()) + SCCMightReturn = true; + } + + if (SCCMightUnwind && SCCMightReturn) + break; } } } @@ -133,19 +154,16 @@ bool PruneEH::runOnSCC(CallGraphSCC &SCC) { // If the SCC doesn't unwind or doesn't throw, note this fact. if (!SCCMightUnwind || !SCCMightReturn) for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) { - Attributes NewAttributes = Attribute::None; + Function *F = (*I)->getFunction(); - if (!SCCMightUnwind) - NewAttributes |= Attribute::NoUnwind; - if (!SCCMightReturn) - NewAttributes |= Attribute::NoReturn; + if (!SCCMightUnwind && !F->hasFnAttribute(Attribute::NoUnwind)) { + F->addFnAttr(Attribute::NoUnwind); + MadeChange = true; + } - Function *F = (*I)->getFunction(); - const AttrListPtr &PAL = F->getAttributes(); - const AttrListPtr &NPAL = PAL.addAttr(~0, NewAttributes); - if (PAL != NPAL) { + if (!SCCMightReturn && !F->hasFnAttribute(Attribute::NoReturn)) { + F->addFnAttr(Attribute::NoReturn); MadeChange = true; - F->setAttributes(NPAL); } } @@ -168,32 +186,12 @@ bool PruneEH::SimplifyFunction(Function *F) { bool MadeChange = false; for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { if (InvokeInst *II = dyn_cast(BB->getTerminator())) - if (II->doesNotThrow()) { - SmallVector Args(II->op_begin(), II->op_end() - 3); - // Insert a call instruction before the invoke. - CallInst *Call = CallInst::Create(II->getCalledValue(), - Args.begin(), Args.end(), "", II); - Call->takeName(II); - Call->setCallingConv(II->getCallingConv()); - Call->setAttributes(II->getAttributes()); - - // Anything that used the value produced by the invoke instruction - // now uses the value produced by the call instruction. Note that we - // do this even for void functions and calls with no uses so that the - // callgraph edge is updated. - II->replaceAllUsesWith(Call); + if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(F)) { BasicBlock *UnwindBlock = II->getUnwindDest(); - UnwindBlock->removePredecessor(II->getParent()); - - // Insert a branch to the normal destination right before the - // invoke. - BranchInst::Create(II->getNormalDest(), II); - - // Finally, delete the invoke instruction! - BB->getInstList().pop_back(); + removeUnwindEdge(&*BB); // If the unwind block is now dead, nuke it. - if (pred_begin(UnwindBlock) == pred_end(UnwindBlock)) + if (pred_empty(UnwindBlock)) DeleteBasicBlock(UnwindBlock); // Delete the new BB. ++NumRemoved; @@ -211,7 +209,7 @@ bool PruneEH::SimplifyFunction(Function *F) { // Remove the uncond branch and add an unreachable. BB->getInstList().pop_back(); - new UnreachableInst(BB->getContext(), BB); + new UnreachableInst(BB->getContext(), &*BB); DeleteBasicBlock(New); // Delete the new BB. MadeChange = true; @@ -227,26 +225,41 @@ bool PruneEH::SimplifyFunction(Function *F) { /// updating the callgraph to reflect any now-obsolete edges due to calls that /// exist in the BB. void PruneEH::DeleteBasicBlock(BasicBlock *BB) { - assert(pred_begin(BB) == pred_end(BB) && "BB is not dead!"); - CallGraph &CG = getAnalysis(); + assert(pred_empty(BB) && "BB is not dead!"); + CallGraph &CG = getAnalysis().getCallGraph(); + + Instruction *TokenInst = nullptr; CallGraphNode *CGN = CG[BB->getParent()]; for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; ) { --I; - if (CallInst *CI = dyn_cast(I)) { - if (!isa(I)) - CGN->removeCallEdgeFor(CI); - } else if (InvokeInst *II = dyn_cast(I)) - CGN->removeCallEdgeFor(II); + + if (I->getType()->isTokenTy()) { + TokenInst = &*I; + break; + } + + if (auto CS = CallSite (&*I)) { + const Function *Callee = CS.getCalledFunction(); + if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID())) + CGN->removeCallEdgeFor(CS); + else if (!Callee->isIntrinsic()) + CGN->removeCallEdgeFor(CS); + } + if (!I->use_empty()) I->replaceAllUsesWith(UndefValue::get(I->getType())); } - // Get the list of successors of this block. - std::vector Succs(succ_begin(BB), succ_end(BB)); + if (TokenInst) { + changeToUnreachable(TokenInst->getNextNode(), /*UseLLVMTrap=*/false); + } else { + // Get the list of successors of this block. + std::vector Succs(succ_begin(BB), succ_end(BB)); - for (unsigned i = 0, e = Succs.size(); i != e; ++i) - Succs[i]->removePredecessor(BB); + for (unsigned i = 0, e = Succs.size(); i != e; ++i) + Succs[i]->removePredecessor(BB); - BB->eraseFromParent(); + BB->eraseFromParent(); + } }