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perform DSE through launder.invariant.group

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Summary:
Alias Analysis knows that llvm.launder.invariant.group
returns pointer that mustalias argument, but this information
wasn't used, therefor we didn't DSE through launder.invariant.group

Reviewers: chandlerc, dberlin, bogner, hfinkel, efriedma

Reviewed By: dberlin

Subscribers: amharc, llvm-commits, nlewycky, rsmith

Differential Revision: https://reviews.llvm.org/D31581

llvm-svn: 331449
This commit is contained in:
Piotr Padlewski 2018-05-03 11:03:53 +00:00
parent 1e96fe1a21
commit 997163a54e
2 changed files with 35 additions and 5 deletions
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10
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -343,7 +343,8 @@ static OverwriteResult isOverwrite(const MemoryLocation &Later,
const TargetLibraryInfo &TLI,
int64_t &EarlierOff, int64_t &LaterOff,
Instruction *DepWrite,
InstOverlapIntervalsTy &IOL) {
InstOverlapIntervalsTy &IOL,
AliasAnalysis &AA) {
// If we don't know the sizes of either access, then we can't do a comparison.
if (Later.Size == MemoryLocation::UnknownSize ||
Earlier.Size == MemoryLocation::UnknownSize)
@ -354,7 +355,7 @@ static OverwriteResult isOverwrite(const MemoryLocation &Later,
// If the start pointers are the same, we just have to compare sizes to see if
// the later store was larger than the earlier store.
if (P1 == P2) {
if (P1 == P2 || AA.isMustAlias(P1, P2)) {
// Make sure that the Later size is >= the Earlier size.
if (Later.Size >= Earlier.Size)
return OW_Complete;
@ -1162,9 +1163,8 @@ static bool eliminateDeadStores(BasicBlock &BB, AliasAnalysis *AA,
if (isRemovable(DepWrite) &&
!isPossibleSelfRead(Inst, Loc, DepWrite, *TLI, *AA)) {
int64_t InstWriteOffset, DepWriteOffset;
OverwriteResult OR =
isOverwrite(Loc, DepLoc, DL, *TLI, DepWriteOffset, InstWriteOffset,
DepWrite, IOL);
OverwriteResult OR = isOverwrite(Loc, DepLoc, DL, *TLI, DepWriteOffset,
InstWriteOffset, DepWrite, IOL, *AA);
if (OR == OW_Complete) {
DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: "
<< *DepWrite << "\n KILLER: " << *Inst << '\n');

30
test/Transforms/DeadStoreElimination/launder.invariant.group.ll Normal file
View File

@ -0,0 +1,30 @@
; RUN: opt < %s -basicaa -dse -S | FileCheck %s
; CHECK-LABEL: void @skipBarrier(i8* %ptr)
define void @skipBarrier(i8* %ptr) {
; CHECK-NOT: store i8 42
store i8 42, i8* %ptr
; CHECK: %ptr2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr)
%ptr2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr)
; CHECK: store i8 43
store i8 43, i8* %ptr2
ret void
}
; CHECK-LABEL: void @skip2Barriers(i8* %ptr)
define void @skip2Barriers(i8* %ptr) {
; CHECK-NOT: store i8 42
store i8 42, i8* %ptr
; CHECK: %ptr2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr)
%ptr2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr)
; CHECK-NOT: store i8 43
store i8 43, i8* %ptr2
%ptr3 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr2)
%ptr4 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr3)
; CHECK: store i8 44
store i8 44, i8* %ptr4
ret void
}
declare i8* @llvm.launder.invariant.group.p0i8(i8*)