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=cba6ae052b82dca8839e6e7c6e4bc5398a7a2648;hb=ba95fe05372c1934c30e21747480d401c1e5bcec;hpb=54fec07ec00b4449393a66e8e2e62fd241781f80 diff --git a/lib/Transforms/IPO/PruneEH.cpp b/lib/Transforms/IPO/PruneEH.cpp index cba6ae052b8..8e126d4de4f 100644 --- a/lib/Transforms/IPO/PruneEH.cpp +++ b/lib/Transforms/IPO/PruneEH.cpp @@ -14,22 +14,27 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "prune-eh" #include "llvm/Transforms/IPO.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" +#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/Support/CFG.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"); @@ -41,7 +46,7 @@ namespace { } // 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); @@ -85,7 +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()) { @@ -94,42 +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 / resume! + 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; } } } @@ -137,21 +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) { - AttrBuilder NewAttributes; - - if (!SCCMightUnwind) - NewAttributes.addAttribute(Attribute::NoUnwind); - if (!SCCMightReturn) - NewAttributes.addAttribute(Attribute::NoReturn); - Function *F = (*I)->getFunction(); - const AttributeSet &PAL = F->getAttributes().getFnAttributes(); - const AttributeSet &NPAL = AttributeSet::get( - F->getContext(), AttributeSet::FunctionIndex, NewAttributes); - if (PAL != NPAL) { + if (!SCCMightUnwind && !F->hasFnAttribute(Attribute::NoUnwind)) { + F->addFnAttr(Attribute::NoUnwind); + MadeChange = true; + } + + if (!SCCMightReturn && !F->hasFnAttribute(Attribute::NoReturn)) { + F->addFnAttr(Attribute::NoReturn); MadeChange = true; - F->addAttributes(AttributeSet::FunctionIndex, NPAL); } } @@ -174,32 +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, "", II); - Call->takeName(II); - Call->setCallingConv(II->getCallingConv()); - Call->setAttributes(II->getAttributes()); - Call->setDebugLoc(II->getDebugLoc()); - - // 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; @@ -217,7 +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; @@ -233,7 +225,7 @@ 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!"); + assert(pred_empty(BB) && "BB is not dead!"); CallGraph &CG = getAnalysis().getCallGraph(); CallGraphNode *CGN = CG[BB->getParent()];