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Make memcpyopt TBAA-aware.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121944 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-12-16 02:51:19 +00:00
parent ad3ea3d85f
commit 387f28aff4
3 changed files with 37 additions and 16 deletions
lib
Analysis
AliasAnalysis.cpp
Transforms/Scalar
MemCpyOptimizer.cpp
test/Analysis/TypeBasedAliasAnalysis
memcpyopt.ll

14
lib/Analysis/AliasAnalysis.cpp

@ -219,8 +219,11 @@ AliasAnalysis::getLocationForSource(const MemTransferInst *MTI) {
if (ConstantInt *C = dyn_cast<ConstantInt>(MTI->getLength()))
Size = C->getValue().getZExtValue();
// FIXME: Can memcpy/memmove have TBAA tags?
return Location(MTI->getRawSource(), Size, 0);
// memcpy/memmove can have TBAA tags. For memcpy, they apply
// to both the source and the destination.
MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa);
return Location(MTI->getRawSource(), Size, TBAATag);
}
AliasAnalysis::Location
@ -228,9 +231,12 @@ AliasAnalysis::getLocationForDest(const MemIntrinsic *MTI) {
uint64_t Size = UnknownSize;
if (ConstantInt *C = dyn_cast<ConstantInt>(MTI->getLength()))
Size = C->getValue().getZExtValue();
// memcpy/memmove can have TBAA tags. For memcpy, they apply
// to both the source and the destination.
MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa);
// FIXME: Can memcpy/memmove have TBAA tags?
return Location(MTI->getRawDest(), Size, 0);
return Location(MTI->getRawDest(), Size, TBAATag);
}

16
lib/Transforms/Scalar/MemCpyOptimizer.cpp

@ -688,10 +688,6 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
if (!C1) return false;
uint64_t DepSize = C1->getValue().getZExtValue();
if (DepSize < MSize)
return false;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// Verify that the copied-from memory doesn't change in between the two
@ -716,7 +712,8 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
// source and dest might overlap. We still want to eliminate the intermediate
// value, but we have to generate a memmove instead of memcpy.
Intrinsic::ID ResultFn = Intrinsic::memcpy;
if (!AA.isNoAlias(M->getRawDest(), MSize, MDep->getRawSource(), DepSize))
if (AA.alias(AA.getLocationForDest(M), AA.getLocationForSource(MDep)) !=
AliasAnalysis::NoAlias)
ResultFn = Intrinsic::memmove;
// If all checks passed, then we can transform M.
@ -795,14 +792,9 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
bool MemCpyOpt::processMemMove(MemMoveInst *M) {
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// If the memmove is a constant size, use it for the alias query, this allows
// us to optimize things like: memmove(P, P+64, 64);
uint64_t MemMoveSize = AliasAnalysis::UnknownSize;
if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength()))
MemMoveSize = Len->getZExtValue();
// See if the pointers alias.
if (AA.alias(M->getRawDest(), MemMoveSize, M->getRawSource(), MemMoveSize) !=
if (AA.alias(AA.getLocationForDest(M),
AA.getLocationForSource(M)) !=
AliasAnalysis::NoAlias)
return false;

23
test/Analysis/TypeBasedAliasAnalysis/memcpyopt.ll Normal file

@ -0,0 +1,23 @@
; RUN: opt -S -tbaa -basicaa -memcpyopt -instcombine < %s | FileCheck %s
target datalayout = "e-p:64:64:64"
; The second memcpy is redundant and can be deleted. There's an intervening store, but
; it has a TBAA tag which declares that it is unrelated.
; CHECK: @foo
; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %p, i8* %q, i64 16, i32 1, i1 false), !tbaa !0
; CHECK-NEXT: store i8 2, i8* %s, align 1, !tbaa !2
; CHECK-NEXT: ret void
define void @foo(i8* nocapture %p, i8* nocapture %q, i8* nocapture %s) nounwind {
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %p, i8* %q, i64 16, i32 1, i1 false), !tbaa !2
store i8 2, i8* %s, align 1, !tbaa !1
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %q, i8* %p, i64 16, i32 1, i1 false), !tbaa !2
ret void
}
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
!0 = metadata !{metadata !"tbaa root", null}
!1 = metadata !{metadata !"A", metadata !0}
!2 = metadata !{metadata !"B", metadata !0}