From 9fa11e94b5a7709cf05396420b3b3eaad6fb8e37 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 8 Jan 2011 21:07:56 +0000 Subject: [PATCH] fix an issue in IsPointerOffset that prevented us from recognizing that P and P+1 are relative to the same base pointer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123087 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/MemCpyOptimizer.cpp | 22 +++++++++++++++++++--- test/Transforms/MemCpyOpt/form-memset.ll | 12 ++++++++++++ 2 files changed, 31 insertions(+), 3 deletions(-) diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp index a4f60878e6f..c2844375c44 100644 --- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp +++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp @@ -71,13 +71,30 @@ static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx, /// be &A[42], and Ptr2 might be &A[40]. In this case offset would be -8. static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, const TargetData &TD) { + Ptr1 = Ptr1->stripPointerCasts(); + Ptr2 = Ptr2->stripPointerCasts(); + GetElementPtrInst *GEP1 = dyn_cast(Ptr1); + GetElementPtrInst *GEP2 = dyn_cast(Ptr2); + + bool VariableIdxFound = false; + + // If one pointer is a GEP and the other isn't, then see if the GEP is a + // constant offset from the base, as in "P" and "gep P, 1". + if (GEP1 && GEP2 == 0 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) { + Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, TD); + return !VariableIdxFound; + } + + if (GEP2 && GEP1 == 0 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) { + Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, TD); + return !VariableIdxFound; + } + // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical // base. After that base, they may have some number of common (and // potentially variable) indices. After that they handle some constant // offset, which determines their offset from each other. At this point, we // handle no other case. - GetElementPtrInst *GEP1 = dyn_cast(Ptr1); - GetElementPtrInst *GEP2 = dyn_cast(Ptr2); if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0)) return false; @@ -87,7 +104,6 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx)) break; - bool VariableIdxFound = false; int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD); int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD); if (VariableIdxFound) return false; diff --git a/test/Transforms/MemCpyOpt/form-memset.ll b/test/Transforms/MemCpyOpt/form-memset.ll index 04bd6742efe..523615d72d2 100644 --- a/test/Transforms/MemCpyOpt/form-memset.ll +++ b/test/Transforms/MemCpyOpt/form-memset.ll @@ -177,6 +177,18 @@ entry: ; CHECK: call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 15, i32 4, i1 false) } +define void @test4(i32* nocapture %P) nounwind ssp { +entry: + store i32 0, i32* %P, align 4 + %add.ptr = getelementptr inbounds i32* %P, i64 1 + %0 = bitcast i32* %add.ptr to i8* + tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 11, i32 1, i1 false) + ret void +; CHECK: @test4 +; CHECK-NOT: store +; CHECK: call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 15, i32 4, i1 false) +} + declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind