From a3c3e1bd22fef6de6d31b3a80d773d1176b4ca8c Mon Sep 17 00:00:00 2001 From: Yichao Yu Date: Sun, 12 Jun 2016 17:14:38 -0400 Subject: [PATCH] Fix `InstCombine` to not widen metadata on store-to-load forwarding. The original check for load CSE or store-to-load forwarding is wrong when the forwarded stored value happened to be a load. --- include/llvm/Analysis/Loads.h | 3 ++- lib/Analysis/Loads.cpp | 5 ++++- .../InstCombine/InstCombineLoadStoreAlloca.cpp | 6 ++++-- test/Transforms/InstCombine/tbaa-store-to-load.ll | 17 +++++++++++++++++ 4 files changed, 27 insertions(+), 4 deletions(-) create mode 100644 test/Transforms/InstCombine/tbaa-store-to-load.ll diff --git a/include/llvm/Analysis/Loads.h b/include/llvm/Analysis/Loads.h index 42667d2..5db3c2f 100644 --- a/include/llvm/Analysis/Loads.h +++ b/include/llvm/Analysis/Loads.h @@ -50,7 +50,8 @@ Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, BasicBlock::iterator &ScanFrom, unsigned MaxInstsToScan = 6, AliasAnalysis *AA = nullptr, - AAMDNodes *AATags = nullptr); + AAMDNodes *AATags = nullptr, + bool *IsLoadCSE = nullptr); } diff --git a/lib/Analysis/Loads.cpp b/lib/Analysis/Loads.cpp index 624c5a1..baecd3f 100644 --- a/lib/Analysis/Loads.cpp +++ b/lib/Analysis/Loads.cpp @@ -183,7 +183,8 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom, Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, BasicBlock::iterator &ScanFrom, unsigned MaxInstsToScan, - AliasAnalysis *AA, AAMDNodes *AATags) { + AliasAnalysis *AA, AAMDNodes *AATags, + bool *IsLoadCSE) { if (MaxInstsToScan == 0) MaxInstsToScan = ~0U; @@ -220,6 +221,8 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, DL)) { if (AATags) LI->getAAMetadata(*AATags); + if (IsLoadCSE) + *IsLoadCSE = true; return LI; } diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp index e3179db..f1af1f7 100644 --- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp +++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp @@ -750,9 +750,11 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) { // separated by a few arithmetic operations. BasicBlock::iterator BBI = &LI; AAMDNodes AATags; + bool IsLoadCSE = false; if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI, - 6, AA, &AATags)) { - if (LoadInst *NLI = dyn_cast(AvailableVal)) { + 6, AA, &AATags, &IsLoadCSE)) { + if (IsLoadCSE) { + LoadInst *NLI = cast(AvailableVal); unsigned KnownIDs[] = { LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope, diff --git a/test/Transforms/InstCombine/tbaa-store-to-load.ll b/test/Transforms/InstCombine/tbaa-store-to-load.ll new file mode 100644 index 0000000..707be73 --- /dev/null +++ b/test/Transforms/InstCombine/tbaa-store-to-load.ll @@ -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"} -- 2.8.3