[llvm-commits] [llvm] r47776 - in /llvm/trunk: include/llvm/Transforms/IPO.h lib/Transforms/IPO/StructRetPromotion.cpp
Devang Patel
dpatel at apple.com
Fri Feb 29 15:34:12 PST 2008
Author: dpatel
Date: Fri Feb 29 17:34:08 2008
New Revision: 47776
URL: http://llvm.org/viewvc/llvm-project?rev=47776&view=rev
Log:
Add pass to promote sret.
This pass transforms
%struct._Point = type { i32, i32, i32, i32, i32, i32 }
define internal void @foo(%struct._Point* sret %agg.result)
into
%struct._Point = type { i32, i32, i32, i32, i32, i32 }
define internal %struct._Point @foo()
This pass updates foo() clients appropriately to use
getresult instruction to extract return values.
This pass is not yet ready for prime time.
Added:
llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp
Modified:
llvm/trunk/include/llvm/Transforms/IPO.h
Modified: llvm/trunk/include/llvm/Transforms/IPO.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/IPO.h?rev=47776&r1=47775&r2=47776&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/IPO.h (original)
+++ llvm/trunk/include/llvm/Transforms/IPO.h Fri Feb 29 17:34:08 2008
@@ -125,6 +125,7 @@
/// be passed by value.
///
Pass *createArgumentPromotionPass();
+Pass *createStructRetPromotionPass();
//===----------------------------------------------------------------------===//
/// createIPConstantPropagationPass - This pass propagates constants from call
Added: llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp?rev=47776&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp (added)
+++ llvm/trunk/lib/Transforms/IPO/StructRetPromotion.cpp Fri Feb 29 17:34:08 2008
@@ -0,0 +1,292 @@
+//===-- StructRetPromotion.cpp - Promote sret arguments -000000------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass promotes "by reference" arguments to be "by value" arguments. In
+// practice, this means looking for internal functions that have pointer
+// arguments. If it can prove, through the use of alias analysis, that an
+// argument is *only* loaded, then it can pass the value into the function
+// instead of the address of the value. This can cause recursive simplification
+// of code and lead to the elimination of allocas (especially in C++ template
+// code like the STL).
+//
+// This pass also handles aggregate arguments that are passed into a function,
+// scalarizing them if the elements of the aggregate are only loaded. Note that
+// it refuses to scalarize aggregates which would require passing in more than
+// three operands to the function, because passing thousands of operands for a
+// large array or structure is unprofitable!
+//
+// Note that this transformation could also be done for arguments that are only
+// stored to (returning the value instead), but does not currently. This case
+// would be best handled when and if LLVM begins supporting multiple return
+// values from functions.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "sretpromotion"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/CallGraphSCCPass.h"
+#include "llvm/Instructions.h"
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Compiler.h"
+using namespace llvm;
+
+namespace {
+ /// SRETPromotion - This pass removes sret parameter and updates
+ /// function to use multiple return value.
+ ///
+ struct VISIBILITY_HIDDEN SRETPromotion : public CallGraphSCCPass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ CallGraphSCCPass::getAnalysisUsage(AU);
+ }
+
+ virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
+ static char ID; // Pass identification, replacement for typeid
+ SRETPromotion() : CallGraphSCCPass((intptr_t)&ID) {}
+
+ private:
+ bool PromoteReturn(CallGraphNode *CGN);
+ bool isSafeToUpdateAllCallers(Function *F);
+ Function *cloneFunctionBody(Function *F, const StructType *STy);
+ void updateCallSites(Function *F, Function *NF);
+ };
+
+ char SRETPromotion::ID = 0;
+ RegisterPass<SRETPromotion> X("sretpromotion",
+ "Promote sret arguments to multiple ret values");
+}
+
+Pass *llvm::createStructRetPromotionPass() {
+ return new SRETPromotion();
+}
+
+bool SRETPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
+ bool Changed = false;
+
+ for (unsigned i = 0, e = SCC.size(); i != e; ++i)
+ Changed |= PromoteReturn(SCC[i]);
+
+ return Changed;
+}
+
+/// PromoteReturn - This method promotes function that uses StructRet paramater
+/// into a function that uses mulitple return value.
+bool SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
+ Function *F = CGN->getFunction();
+
+ // Make sure that it is local to this module.
+ if (!F || !F->hasInternalLinkage())
+ return false;
+
+ // Make sure that function returns struct.
+ if (F->arg_size() == 0 || !F->isStructReturn() || F->doesNotReturn())
+ return false;
+
+ assert (F->getReturnType() == Type::VoidTy && "Invalid function return type");
+ Function::arg_iterator AI = F->arg_begin();
+ const llvm::PointerType *FArgType = dyn_cast<PointerType>(AI->getType());
+ assert (FArgType && "Invalid sret paramater type");
+ const llvm::StructType *STy =
+ dyn_cast<StructType>(FArgType->getElementType());
+ assert (STy && "Invalid sret parameter element type");
+
+ // Check if it is ok to perform this promotion.
+ if (isSafeToUpdateAllCallers(F) == false)
+ return false;
+
+ // [1] Replace use of sret parameter
+ AllocaInst *TheAlloca = new AllocaInst (STy, NULL, "mrv", F->getEntryBlock().begin());
+ Value *NFirstArg = F->arg_begin();
+ NFirstArg->replaceAllUsesWith(TheAlloca);
+
+ // Find and replace ret instructions
+ SmallVector<Value *,4> RetVals;
+ for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
+ for(BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
+ Instruction *I = BI;
+ ++BI;
+ if (isa<ReturnInst>(I)) {
+ RetVals.clear();
+ for (unsigned idx = 0; idx < STy->getNumElements(); ++idx) {
+ SmallVector<Value*, 2> GEPIdx;
+ GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, 0));
+ GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, idx));
+ Value *NGEPI = new GetElementPtrInst(TheAlloca, GEPIdx.begin(), GEPIdx.end(),
+ "mrv.gep", I);
+ Value *NV = new LoadInst(NGEPI, "mrv.ld", I);
+ RetVals.push_back(NV);
+ }
+
+ ReturnInst *NR = new ReturnInst(&RetVals[0], RetVals.size(), I);
+ I->replaceAllUsesWith(NR);
+ I->eraseFromParent();
+ }
+ }
+
+ // Create the new function body and insert it into the module.
+ Function *NF = cloneFunctionBody(F, STy);
+
+ // Update all call sites to use new function
+ updateCallSites(F, NF);
+
+ F->eraseFromParent();
+ getAnalysis<CallGraph>().changeFunction(F, NF);
+ return true;
+}
+
+ // Check if it is ok to perform this promotion.
+bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
+
+ if (F->use_empty())
+ // No users. OK to modify signature.
+ return true;
+
+ for (Value::use_iterator FnUseI = F->use_begin(), FnUseE = F->use_end();
+ FnUseI != FnUseE; ++FnUseI) {
+
+ CallSite CS = CallSite::get(*FnUseI);
+ Instruction *Call = CS.getInstruction();
+ CallSite::arg_iterator AI = CS.arg_begin();
+ Value *FirstArg = *AI;
+
+ if (!isa<AllocaInst>(FirstArg))
+ return false;
+
+ // Check FirstArg's users.
+ for (Value::use_iterator ArgI = FirstArg->use_begin(),
+ ArgE = FirstArg->use_end(); ArgI != ArgE; ++ArgI) {
+
+ // If FirstArg user is a CallInst that does not correspond to current
+ // call site then this function F is not suitable for sret promotion.
+ if (CallInst *CI = dyn_cast<CallInst>(ArgI)) {
+ if (CI != Call)
+ return false;
+ }
+ // If FirstArg user is a GEP whose all users are not LoadInst then
+ // this function F is not suitable for sret promotion.
+ else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(ArgI)) {
+ for (Value::use_iterator GEPI = GEP->use_begin(), GEPE = GEP->use_end();
+ GEPI != GEPE; ++GEPI)
+ if (!isa<LoadInst>(GEPI))
+ return false;
+ }
+ // Any other FirstArg users make this function unsuitable for sret
+ // promotion.
+ else
+ return false;
+ }
+ }
+
+ return true;
+}
+
+/// cloneFunctionBody - Create a new function based on F and
+/// insert it into module. Remove first argument. Use STy as
+/// the return type for new function.
+Function *SRETPromotion::cloneFunctionBody(Function *F,
+ const StructType *STy) {
+
+ // FIXME : Do not drop param attributes on the floor.
+ const FunctionType *FTy = F->getFunctionType();
+ std::vector<const Type*> Params;
+
+ // Skip first argument.
+ Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ ++I;
+ while (I != E) {
+ Params.push_back(I->getType());
+ ++I;
+ }
+
+ FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
+ Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
+ NF->setCallingConv(F->getCallingConv());
+ F->getParent()->getFunctionList().insert(F, NF);
+ NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
+
+ // Replace arguments
+ I = F->arg_begin();
+ E = F->arg_end();
+ Function::arg_iterator NI = NF->arg_begin();
+ ++I;
+ while (I != E) {
+ I->replaceAllUsesWith(NI);
+ NI->takeName(I);
+ ++I;
+ ++NI;
+ }
+
+ return NF;
+}
+
+/// updateCallSites - Update all sites that call F to use NF.
+void SRETPromotion::updateCallSites(Function *F, Function *NF) {
+
+ // FIXME : Handle parameter attributes
+ SmallVector<Value*, 16> Args;
+
+ for (Value::use_iterator FUI = F->use_begin(), FUE = F->use_end(); FUI != FUE;) {
+ CallSite CS = CallSite::get(*FUI);
+ ++FUI;
+ Instruction *Call = CS.getInstruction();
+
+ // Copy arguments, however skip first one.
+ CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ Value *FirstCArg = *AI;
+ ++AI;
+ while (AI != AE) {
+ Args.push_back(*AI);
+ ++AI;
+ }
+
+ // Build new call instruction.
+ Instruction *New;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
+ New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args.begin(), Args.end(), "", Call);
+ cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
+ } else {
+ New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
+ cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
+ if (cast<CallInst>(Call)->isTailCall())
+ cast<CallInst>(New)->setTailCall();
+ }
+ Args.clear();
+ New->takeName(Call);
+
+ // Update all users of sret parameter to extract value using getresult.
+ for (Value::use_iterator UI = FirstCArg->use_begin(),
+ UE = FirstCArg->use_end(); UI != UE; ) {
+ User *U2 = *UI++;
+ CallInst *C2 = dyn_cast<CallInst>(U2);
+ if (C2 && (C2 == Call))
+ continue;
+ else if (GetElementPtrInst *UGEP = dyn_cast<GetElementPtrInst>(U2)) {
+ Value *GR = new GetResultInst(New, 5, "xxx", UGEP);
+ for (Value::use_iterator GI = UGEP->use_begin(),
+ GE = UGEP->use_end(); GI != GE; ++GI) {
+ if (LoadInst *L = dyn_cast<LoadInst>(*GI)) {
+ L->replaceAllUsesWith(GR);
+ L->eraseFromParent();
+ }
+ }
+ UGEP->eraseFromParent();
+ }
+ else assert( 0 && "Unexpected sret parameter use");
+ }
+ Call->eraseFromParent();
+ }
+}
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