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[InstCombine] Don't widen metadata on store-to-load forwarding

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The original check for load CSE or store-to-load forwarding is wrong
when the forwarded stored value happened to be a load.

Ref https://github.com/JuliaLang/julia/issues/16894

Differential Revision: http://reviews.llvm.org/D21271

Patch by Yichao Yu!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272868 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2016-06-16 02:33:42 +00:00
parent 3cf4eef2a1
commit 3c80c26580
4 changed files with 27 additions and 4 deletions
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3
include/llvm/Analysis/Loads.h
View File

@ -82,7 +82,8 @@ Value *FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan = DefMaxInstsToScan,
AliasAnalysis *AA = nullptr,
AAMDNodes *AATags = nullptr);
AAMDNodes *AATags = nullptr,
bool *IsLoadCSE = nullptr);
}

5
lib/Analysis/Loads.cpp
View File

@ -322,7 +322,8 @@ llvm::DefMaxInstsToScan("available-load-scan-limit", cl::init(6), cl::Hidden,
Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan,
AliasAnalysis *AA, AAMDNodes *AATags) {
AliasAnalysis *AA, AAMDNodes *AATags,
bool *IsLoadCSE) {
if (MaxInstsToScan == 0)
MaxInstsToScan = ~0U;
@ -374,6 +375,8 @@ Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
if (AATags)
LI->getAAMetadata(*AATags);
if (IsLoadCSE)
*IsLoadCSE = true;
return LI;
}

6
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -819,10 +819,12 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// separated by a few arithmetic operations.
BasicBlock::iterator BBI(LI);
AAMDNodes AATags;
bool IsLoadCSE = false;
if (Value *AvailableVal =
FindAvailableLoadedValue(&LI, LI.getParent(), BBI,
DefMaxInstsToScan, AA, &AATags)) {
if (LoadInst *NLI = dyn_cast<LoadInst>(AvailableVal)) {
DefMaxInstsToScan, AA, &AATags, &IsLoadCSE)) {
if (IsLoadCSE) {
LoadInst *NLI = cast<LoadInst>(AvailableVal);
unsigned KnownIDs[] = {
LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
LLVMContext::MD_noalias, LLVMContext::MD_range,

17
test/Transforms/InstCombine/tbaa-store-to-load.ll Normal file
View File

@ -0,0 +1,17 @@
; RUN: opt -S -instcombine < %s 2>&1 | FileCheck %s
define i64 @f(i64* %p1, i64* %p2) {
top:
; check that the tbaa is preserved
; CHECK-LABEL: @f(
; CHECK: %v1 = load i64, i64* %p1, align 8, !tbaa !0
; CHECK: store i64 %v1, i64* %p2, align 8
; CHECK: ret i64 %v1
%v1 = load i64, i64* %p1, align 8, !tbaa !0
store i64 %v1, i64* %p2, align 8
%v2 = load i64, i64* %p2, align 8
ret i64 %v2
}
!0 = !{!1, !1, i64 0}
!1 = !{!"load_tbaa"}