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Enhance GVN to do more precise alias queries for non-local memory

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references. For example, this allows gvn to eliminate the load in
this example:

  void foo(int n, int* p, int *q) {
    p[0] = 0;
    p[1] = 1;
    if (n) {
      *q = p[0];
    }
  }


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118714 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-11-10 20:37:15 +00:00
parent af3d38f70e
commit 075fb5d68f
6 changed files with 129 additions and 27 deletions
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lib/Analysis/MemDepPrinter.cpp
+17 -6
View File
@@ -11,6 +11,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/LLVMContext.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CallSite.h"
@@ -40,7 +41,8 @@ namespace {
void print(raw_ostream &OS, const Module * = 0) const;
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MemoryDependenceAnalysis>();
AU.addRequiredTransitive<AliasAnalysis>();
AU.addRequiredTransitive<MemoryDependenceAnalysis>();
AU.setPreservesAll();
}
@@ -64,6 +66,7 @@ FunctionPass *llvm::createMemDepPrinter() {
bool MemDepPrinter::runOnFunction(Function &F) {
this->F = &F;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
MemoryDependenceAnalysis &MDA = getAnalysis<MemoryDependenceAnalysis>();
// All this code uses non-const interfaces because MemDep is not
@@ -99,15 +102,23 @@ bool MemDepPrinter::runOnFunction(Function &F) {
SmallVector<NonLocalDepResult, 4> NLDI;
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
// FIXME: Volatile is not handled properly here.
MDA.getNonLocalPointerDependency(LI->getPointerOperand(), !LI->isVolatile(),
AliasAnalysis::Location Loc(LI->getPointerOperand(),
AA.getTypeStoreSize(LI->getType()),
LI->getMetadata(LLVMContext::MD_tbaa));
MDA.getNonLocalPointerDependency(Loc, !LI->isVolatile(),
LI->getParent(), NLDI);
} else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// FIXME: Volatile is not handled properly here.
MDA.getNonLocalPointerDependency(SI->getPointerOperand(), false,
SI->getParent(), NLDI);
AliasAnalysis::Location Loc(SI->getPointerOperand(),
AA.getTypeStoreSize(SI->getValueOperand()
->getType()),
SI->getMetadata(LLVMContext::MD_tbaa));
MDA.getNonLocalPointerDependency(Loc, false, SI->getParent(), NLDI);
} else if (VAArgInst *VI = dyn_cast<VAArgInst>(Inst)) {
MDA.getNonLocalPointerDependency(VI->getPointerOperand(), false,
VI->getParent(), NLDI);
AliasAnalysis::Location Loc(SI->getPointerOperand(),
AliasAnalysis::UnknownSize,
SI->getMetadata(LLVMContext::MD_tbaa));
MDA.getNonLocalPointerDependency(Loc, false, VI->getParent(), NLDI);
} else {
llvm_unreachable("Unknown memory instruction!");
}