X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FIPO%2FPruneEH.cpp;h=8e126d4de4fcb017d418ff16303827fdf007cb3e;hp=46e11280b0e1d49734c699aa91b9ffce7ac4db27;hb=ba95fe05372c1934c30e21747480d401c1e5bcec;hpb=58d74910c6b82e622ecbb57d6644d48fec5a5c0f diff --git a/lib/Transforms/IPO/PruneEH.cpp b/lib/Transforms/IPO/PruneEH.cpp index 46e11280b0e..8e126d4de4f 100644 --- a/lib/Transforms/IPO/PruneEH.cpp +++ b/lib/Transforms/IPO/PruneEH.cpp @@ -14,131 +14,164 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "prune-eh" #include "llvm/Transforms/IPO.h" -#include "llvm/CallGraphSCCPass.h" -#include "llvm/Constants.h" -#include "llvm/Function.h" -#include "llvm/Instructions.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 "llvm/Support/Compiler.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"); -STATISTIC(NumBBUnwind, "Number of unwind dest removed from blocks"); namespace { - struct VISIBILITY_HIDDEN PruneEH : public CallGraphSCCPass { + struct PruneEH : public CallGraphSCCPass { static char ID; // Pass identification, replacement for typeid - PruneEH() : CallGraphSCCPass((intptr_t)&ID) {} + PruneEH() : CallGraphSCCPass(ID) { + initializePruneEHPass(*PassRegistry::getPassRegistry()); + } // runOnSCC - Analyze the SCC, performing the transformation if possible. - bool runOnSCC(const std::vector &SCC); + bool runOnSCC(CallGraphSCC &SCC) override; bool SimplifyFunction(Function *F); void DeleteBasicBlock(BasicBlock *BB); }; - - char PruneEH::ID = 0; - RegisterPass X("prune-eh", "Remove unused exception handling info"); } +char PruneEH::ID = 0; +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(); } -bool PruneEH::runOnSCC(const std::vector &SCC) { - CallGraph &CG = getAnalysis(); +bool PruneEH::runOnSCC(CallGraphSCC &SCC) { + SmallPtrSet SCCNodes; + CallGraph &CG = getAnalysis().getCallGraph(); bool MadeChange = false; + // Fill SCCNodes with the elements of the SCC. Used for quickly + // looking up whether a given CallGraphNode is in this SCC. + for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) + SCCNodes.insert(*I); + // First pass, scan all of the functions in the SCC, simplifying them // according to what we know. - for (unsigned i = 0, e = SCC.size(); i != e; ++i) - if (Function *F = SCC[i]->getFunction()) + for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) + if (Function *F = (*I)->getFunction()) MadeChange |= SimplifyFunction(F); // Next, check to see if any callees might throw or if there are any external // functions in this SCC: if so, we cannot prune any functions in this SCC. + // Definitions that are weak and not declared non-throwing might be + // overridden at linktime with something that throws, so assume that. // If this SCC includes the unwind instruction, we KNOW it throws, so // obviously the SCC might throw. // bool SCCMightUnwind = false, SCCMightReturn = false; - for (unsigned i = 0, e = SCC.size(); - (!SCCMightUnwind || !SCCMightReturn) && i != e; ++i) { - Function *F = SCC[i]->getFunction(); - if (F == 0) { + for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); + (!SCCMightUnwind || !SCCMightReturn) && I != E; ++I) { + Function *F = (*I)->getFunction(); + if (!F) { SCCMightUnwind = true; SCCMightReturn = true; - } else if (F->isDeclaration()) { + } else if (F->isDeclaration() || F->mayBeOverridden()) { SCCMightUnwind |= !F->doesNotThrow(); SCCMightReturn |= !F->doesNotReturn(); } 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 (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()){ - 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; } } } // If the SCC doesn't unwind or doesn't throw, note this fact. if (!SCCMightUnwind || !SCCMightReturn) - for (unsigned i = 0, e = SCC.size(); i != e; ++i) { - ParameterAttributes NewAttributes = ParamAttr::None; + for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) { + Function *F = (*I)->getFunction(); - if (!SCCMightUnwind) - NewAttributes |= ParamAttr::NoUnwind; - if (!SCCMightReturn) - NewAttributes |= ParamAttr::NoReturn; + if (!SCCMightUnwind && !F->hasFnAttribute(Attribute::NoUnwind)) { + F->addFnAttr(Attribute::NoUnwind); + MadeChange = true; + } - const PAListPtr &PAL = SCC[i]->getFunction()->getParamAttrs(); - SCC[i]->getFunction()->setParamAttrs(PAL.addAttr(0, NewAttributes)); + if (!SCCMightReturn && !F->hasFnAttribute(Attribute::NoReturn)) { + F->addFnAttr(Attribute::NoReturn); + MadeChange = true; + } } - for (unsigned i = 0, e = SCC.size(); i != e; ++i) { + for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) { // Convert any invoke instructions to non-throwing functions in this node // into call instructions with a branch. This makes the exception blocks // dead. - if (Function *F = SCC[i]->getFunction()) + if (Function *F = (*I)->getFunction()) MadeChange |= SimplifyFunction(F); } @@ -152,43 +185,21 @@ bool PruneEH::runOnSCC(const std::vector &SCC) { bool PruneEH::SimplifyFunction(Function *F) { bool MadeChange = false; for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { - bool couldUnwind = false; - if (InvokeInst *II = dyn_cast(BB->getTerminator())) - if (II->doesNotThrow()) { - SmallVector Args(II->op_begin()+3, II->op_end()); - // Insert a call instruction before the invoke. - CallInst *Call = new CallInst(II->getCalledValue(), - Args.begin(), Args.end(), "", II); - Call->takeName(II); - Call->setCallingConv(II->getCallingConv()); - Call->setParamAttrs(II->getParamAttrs()); - - // Anything that used the value produced by the invoke instruction - // now uses the value produced by the call instruction. - 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. - new BranchInst(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; MadeChange = true; - } else { - couldUnwind = true; } for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) - if (CallInst *CI = dyn_cast(I++)) { + if (CallInst *CI = dyn_cast(I++)) if (CI->doesNotReturn() && !isa(I)) { // This call calls a function that cannot return. Insert an // unreachable instruction after it and simplify the code. Do this @@ -198,25 +209,15 @@ bool PruneEH::SimplifyFunction(Function *F) { // Remove the uncond branch and add an unreachable. BB->getInstList().pop_back(); - new UnreachableInst(BB); + new UnreachableInst(BB->getContext(), &*BB); DeleteBasicBlock(New); // Delete the new BB. MadeChange = true; ++NumUnreach; break; - } else if (!CI->doesNotThrow()) { - couldUnwind = true; } - } - - // Strip 'unwindTo' off of BBs that have no calls/invokes without nounwind. - if (!couldUnwind && BB->getUnwindDest()) { - MadeChange = true; - ++NumBBUnwind; - BB->getUnwindDest()->removePredecessor(BB, false, true); - BB->setUnwindDest(NULL); - } } + return MadeChange; } @@ -224,19 +225,17 @@ 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(); CallGraphNode *CGN = CG[BB->getParent()]; for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; ) { --I; if (CallInst *CI = dyn_cast(I)) { - if (Function *Callee = CI->getCalledFunction()) - CGN->removeCallEdgeTo(CG[Callee]); - } else if (InvokeInst *II = dyn_cast(I)) { - if (Function *Callee = II->getCalledFunction()) - CGN->removeCallEdgeTo(CG[Callee]); - } + if (!isa(I)) + CGN->removeCallEdgeFor(CI); + } else if (InvokeInst *II = dyn_cast(I)) + CGN->removeCallEdgeFor(II); if (!I->use_empty()) I->replaceAllUsesWith(UndefValue::get(I->getType())); }