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must be called in the pass's constructor. This function uses static dependency declarations to recursively initialize the pass's dependencies. Clients that only create passes through the createFooPass() APIs will require no changes. Clients that want to use the CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h before parsing commandline arguments. I have tested this with all standard configurations of clang and llvm-gcc on Darwin. It is possible that there are problems with the static dependencies that will only be visible with non-standard options. If you encounter any crash in pass registration/creation, please send the testcase to me directly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116820 91177308-0d34-0410-b5e6-96231b3b80d8
358 lines
12 KiB
C++
358 lines
12 KiB
C++
//===-- StructRetPromotion.cpp - Promote sret arguments -------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass finds functions that return a struct (using a pointer to the struct
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// as the first argument of the function, marked with the 'sret' attribute) and
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// replaces them with a new function that simply returns each of the elements of
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// that struct (using multiple return values).
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//
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// This pass works under a number of conditions:
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// 1. The returned struct must not contain other structs
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// 2. The returned struct must only be used to load values from
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// 3. The placeholder struct passed in is the result of an alloca
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "sretpromotion"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/CallGraphSCCPass.h"
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#include "llvm/Instructions.h"
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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STATISTIC(NumRejectedSRETUses , "Number of sret rejected due to unexpected uses");
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STATISTIC(NumSRET , "Number of sret promoted");
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namespace {
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/// SRETPromotion - This pass removes sret parameter and updates
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/// function to use multiple return value.
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///
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struct SRETPromotion : public CallGraphSCCPass {
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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CallGraphSCCPass::getAnalysisUsage(AU);
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}
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virtual bool runOnSCC(CallGraphSCC &SCC);
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static char ID; // Pass identification, replacement for typeid
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SRETPromotion() : CallGraphSCCPass(ID) {
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initializeSRETPromotionPass(*PassRegistry::getPassRegistry());
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}
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private:
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CallGraphNode *PromoteReturn(CallGraphNode *CGN);
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bool isSafeToUpdateAllCallers(Function *F);
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Function *cloneFunctionBody(Function *F, const StructType *STy);
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CallGraphNode *updateCallSites(Function *F, Function *NF);
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};
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}
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char SRETPromotion::ID = 0;
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INITIALIZE_PASS_BEGIN(SRETPromotion, "sretpromotion",
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"Promote sret arguments to multiple ret values", false, false)
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INITIALIZE_AG_DEPENDENCY(CallGraph)
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INITIALIZE_PASS_END(SRETPromotion, "sretpromotion",
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"Promote sret arguments to multiple ret values", false, false)
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Pass *llvm::createStructRetPromotionPass() {
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return new SRETPromotion();
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}
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bool SRETPromotion::runOnSCC(CallGraphSCC &SCC) {
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bool Changed = false;
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for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
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if (CallGraphNode *NewNode = PromoteReturn(*I)) {
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SCC.ReplaceNode(*I, NewNode);
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Changed = true;
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}
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return Changed;
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}
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/// PromoteReturn - This method promotes function that uses StructRet paramater
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/// into a function that uses multiple return values.
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CallGraphNode *SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
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Function *F = CGN->getFunction();
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if (!F || F->isDeclaration() || !F->hasLocalLinkage())
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return 0;
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// Make sure that function returns struct.
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if (F->arg_size() == 0 || !F->hasStructRetAttr() || F->doesNotReturn())
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return 0;
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DEBUG(dbgs() << "SretPromotion: Looking at sret function "
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<< F->getName() << "\n");
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assert(F->getReturnType()->isVoidTy() && "Invalid function return type");
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Function::arg_iterator AI = F->arg_begin();
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const llvm::PointerType *FArgType = dyn_cast<PointerType>(AI->getType());
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assert(FArgType && "Invalid sret parameter type");
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const llvm::StructType *STy =
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dyn_cast<StructType>(FArgType->getElementType());
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assert(STy && "Invalid sret parameter element type");
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// Check if it is ok to perform this promotion.
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if (isSafeToUpdateAllCallers(F) == false) {
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DEBUG(dbgs() << "SretPromotion: Not all callers can be updated\n");
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++NumRejectedSRETUses;
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return 0;
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}
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DEBUG(dbgs() << "SretPromotion: sret argument will be promoted\n");
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++NumSRET;
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// [1] Replace use of sret parameter
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AllocaInst *TheAlloca = new AllocaInst(STy, NULL, "mrv",
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F->getEntryBlock().begin());
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Value *NFirstArg = F->arg_begin();
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NFirstArg->replaceAllUsesWith(TheAlloca);
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// [2] Find and replace ret instructions
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for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
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for(BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
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Instruction *I = BI;
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++BI;
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if (isa<ReturnInst>(I)) {
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Value *NV = new LoadInst(TheAlloca, "mrv.ld", I);
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ReturnInst *NR = ReturnInst::Create(F->getContext(), NV, I);
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I->replaceAllUsesWith(NR);
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I->eraseFromParent();
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}
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}
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// [3] Create the new function body and insert it into the module.
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Function *NF = cloneFunctionBody(F, STy);
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// [4] Update all call sites to use new function
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CallGraphNode *NF_CFN = updateCallSites(F, NF);
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CallGraph &CG = getAnalysis<CallGraph>();
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NF_CFN->stealCalledFunctionsFrom(CG[F]);
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delete CG.removeFunctionFromModule(F);
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return NF_CFN;
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}
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// Check if it is ok to perform this promotion.
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bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
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if (F->use_empty())
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// No users. OK to modify signature.
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return true;
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for (Value::use_iterator FnUseI = F->use_begin(), FnUseE = F->use_end();
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FnUseI != FnUseE; ++FnUseI) {
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// The function is passed in as an argument to (possibly) another function,
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// we can't change it!
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CallSite CS(*FnUseI);
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Instruction *Call = CS.getInstruction();
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// The function is used by something else than a call or invoke instruction,
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// we can't change it!
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if (!Call || !CS.isCallee(FnUseI))
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return false;
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CallSite::arg_iterator AI = CS.arg_begin();
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Value *FirstArg = *AI;
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if (!isa<AllocaInst>(FirstArg))
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return false;
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// Check FirstArg's users.
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for (Value::use_iterator ArgI = FirstArg->use_begin(),
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ArgE = FirstArg->use_end(); ArgI != ArgE; ++ArgI) {
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User *U = *ArgI;
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// If FirstArg user is a CallInst that does not correspond to current
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// call site then this function F is not suitable for sret promotion.
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if (CallInst *CI = dyn_cast<CallInst>(U)) {
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if (CI != Call)
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return false;
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}
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// If FirstArg user is a GEP whose all users are not LoadInst then
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// this function F is not suitable for sret promotion.
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else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
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// TODO : Use dom info and insert PHINodes to collect get results
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// from multiple call sites for this GEP.
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if (GEP->getParent() != Call->getParent())
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return false;
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for (Value::use_iterator GEPI = GEP->use_begin(), GEPE = GEP->use_end();
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GEPI != GEPE; ++GEPI)
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if (!isa<LoadInst>(*GEPI))
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return false;
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}
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// Any other FirstArg users make this function unsuitable for sret
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// promotion.
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else
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return false;
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}
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}
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return true;
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}
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/// cloneFunctionBody - Create a new function based on F and
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/// insert it into module. Remove first argument. Use STy as
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/// the return type for new function.
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Function *SRETPromotion::cloneFunctionBody(Function *F,
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const StructType *STy) {
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const FunctionType *FTy = F->getFunctionType();
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std::vector<const Type*> Params;
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// Attributes - Keep track of the parameter attributes for the arguments.
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SmallVector<AttributeWithIndex, 8> AttributesVec;
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const AttrListPtr &PAL = F->getAttributes();
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// Add any return attributes.
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if (Attributes attrs = PAL.getRetAttributes())
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AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
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// Skip first argument.
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Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
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++I;
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// 0th parameter attribute is reserved for return type.
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// 1th parameter attribute is for first 1st sret argument.
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unsigned ParamIndex = 2;
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while (I != E) {
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Params.push_back(I->getType());
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if (Attributes Attrs = PAL.getParamAttributes(ParamIndex))
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AttributesVec.push_back(AttributeWithIndex::get(ParamIndex - 1, Attrs));
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++I;
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++ParamIndex;
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}
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// Add any fn attributes.
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if (Attributes attrs = PAL.getFnAttributes())
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AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
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FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
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Function *NF = Function::Create(NFTy, F->getLinkage());
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NF->takeName(F);
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NF->copyAttributesFrom(F);
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NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
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F->getParent()->getFunctionList().insert(F, NF);
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NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
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// Replace arguments
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I = F->arg_begin();
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E = F->arg_end();
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Function::arg_iterator NI = NF->arg_begin();
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++I;
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while (I != E) {
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I->replaceAllUsesWith(NI);
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NI->takeName(I);
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++I;
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++NI;
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}
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return NF;
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}
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/// updateCallSites - Update all sites that call F to use NF.
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CallGraphNode *SRETPromotion::updateCallSites(Function *F, Function *NF) {
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CallGraph &CG = getAnalysis<CallGraph>();
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SmallVector<Value*, 16> Args;
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// Attributes - Keep track of the parameter attributes for the arguments.
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SmallVector<AttributeWithIndex, 8> ArgAttrsVec;
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// Get a new callgraph node for NF.
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CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
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while (!F->use_empty()) {
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CallSite CS(*F->use_begin());
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Instruction *Call = CS.getInstruction();
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const AttrListPtr &PAL = F->getAttributes();
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// Add any return attributes.
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if (Attributes attrs = PAL.getRetAttributes())
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ArgAttrsVec.push_back(AttributeWithIndex::get(0, attrs));
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// Copy arguments, however skip first one.
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CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
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Value *FirstCArg = *AI;
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++AI;
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// 0th parameter attribute is reserved for return type.
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// 1th parameter attribute is for first 1st sret argument.
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unsigned ParamIndex = 2;
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while (AI != AE) {
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Args.push_back(*AI);
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if (Attributes Attrs = PAL.getParamAttributes(ParamIndex))
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ArgAttrsVec.push_back(AttributeWithIndex::get(ParamIndex - 1, Attrs));
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++ParamIndex;
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++AI;
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}
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// Add any function attributes.
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if (Attributes attrs = PAL.getFnAttributes())
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ArgAttrsVec.push_back(AttributeWithIndex::get(~0, attrs));
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AttrListPtr NewPAL = AttrListPtr::get(ArgAttrsVec.begin(), ArgAttrsVec.end());
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// Build new call instruction.
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Instruction *New;
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if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
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New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
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Args.begin(), Args.end(), "", Call);
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cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
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cast<InvokeInst>(New)->setAttributes(NewPAL);
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} else {
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New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
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cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
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cast<CallInst>(New)->setAttributes(NewPAL);
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if (cast<CallInst>(Call)->isTailCall())
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cast<CallInst>(New)->setTailCall();
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}
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Args.clear();
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ArgAttrsVec.clear();
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New->takeName(Call);
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// Update the callgraph to know that the callsite has been transformed.
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CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
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CalleeNode->removeCallEdgeFor(Call);
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CalleeNode->addCalledFunction(New, NF_CGN);
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// Update all users of sret parameter to extract value using extractvalue.
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for (Value::use_iterator UI = FirstCArg->use_begin(),
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UE = FirstCArg->use_end(); UI != UE; ) {
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User *U2 = *UI++;
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CallInst *C2 = dyn_cast<CallInst>(U2);
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if (C2 && (C2 == Call))
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continue;
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GetElementPtrInst *UGEP = cast<GetElementPtrInst>(U2);
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ConstantInt *Idx = cast<ConstantInt>(UGEP->getOperand(2));
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Value *GR = ExtractValueInst::Create(New, Idx->getZExtValue(),
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"evi", UGEP);
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while(!UGEP->use_empty()) {
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// isSafeToUpdateAllCallers has checked that all GEP uses are
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// LoadInsts
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LoadInst *L = cast<LoadInst>(*UGEP->use_begin());
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L->replaceAllUsesWith(GR);
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L->eraseFromParent();
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}
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UGEP->eraseFromParent();
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continue;
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}
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Call->eraseFromParent();
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}
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return NF_CGN;
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}
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