diff options
| -rw-r--r-- | lib/IR/ConstantFold.cpp | 38 | ||||
| -rw-r--r-- | test/Transforms/GVN/pr17732.ll | 30 |
2 files changed, 67 insertions, 1 deletions
diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp index 8c5a983..46e391a 100644 --- a/lib/IR/ConstantFold.cpp +++ b/lib/IR/ConstantFold.cpp @@ -1940,7 +1940,43 @@ static Constant *ConstantFoldGetElementPtrImpl(Constant *C, I != E; ++I) LastTy = *I; - if ((LastTy && isa<SequentialType>(LastTy)) || Idx0->isNullValue()) { + // We cannot combine indices if doing so would take us outside of an + // array or vector. Doing otherwise could trick us if we evaluated such a + // GEP as part of a load. + // + // e.g. Consider if the original GEP was: + // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, + // i32 0, i32 0, i64 0) + // + // If we then tried to offset it by '8' to get to the third element, + // an i8, we should *not* get: + // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, + // i32 0, i32 0, i64 8) + // + // This GEP tries to index array element '8 which runs out-of-bounds. + // Subsequent evaluation would get confused and produce erroneous results. + // + // The following prohibits such a GEP from being formed by checking to see + // if the index is in-range with respect to an array or vector. + bool IsSequentialAccessInRange = false; + if (LastTy && isa<SequentialType>(LastTy)) { + uint64_t NumElements = 0; + if (ArrayType *ATy = dyn_cast<ArrayType>(LastTy)) + NumElements = ATy->getNumElements(); + else if (VectorType *VTy = dyn_cast<VectorType>(LastTy)) + NumElements = VTy->getNumElements(); + + if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0)) { + int64_t Idx0Val = CI->getSExtValue(); + if (NumElements > 0 && Idx0Val >= 0 && + (uint64_t)Idx0Val < NumElements) + IsSequentialAccessInRange = true; + } else if (PointerType *PTy = dyn_cast<PointerType>(LastTy)) + // Only handle pointers to sized types, not pointers to functions. + if (PTy->getElementType()->isSized()) + IsSequentialAccessInRange = true; + } + if (IsSequentialAccessInRange || Idx0->isNullValue()) { SmallVector<Value*, 16> NewIndices; NewIndices.reserve(Idxs.size() + CE->getNumOperands()); for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) diff --git a/test/Transforms/GVN/pr17732.ll b/test/Transforms/GVN/pr17732.ll new file mode 100644 index 0000000..606a195 --- /dev/null +++ b/test/Transforms/GVN/pr17732.ll @@ -0,0 +1,30 @@ +; RUN: opt -gvn -S -o - < %s | FileCheck %s + +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +%struct.with_array = type { [2 x i8], i32, i8 } +%struct.with_vector = type { <2 x i8>, i32, i8 } + +@main.obj_with_array = private unnamed_addr constant { [2 x i8], i32, i8, [3 x i8] } { [2 x i8] zeroinitializer, i32 0, i8 1, [3 x i8] undef }, align 4 +@array_with_zeroinit = common global %struct.with_array zeroinitializer, align 4 + +@main.obj_with_vector = private unnamed_addr constant { <2 x i8>, i32, i8, [3 x i8] } { <2 x i8> zeroinitializer, i32 0, i8 1, [3 x i8] undef }, align 4 +@vector_with_zeroinit = common global %struct.with_vector zeroinitializer, align 4 + +define i32 @main() { +entry: + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* getelementptr inbounds (%struct.with_array* @array_with_zeroinit, i64 0, i32 0, i64 0), i8* getelementptr inbounds ({ [2 x i8], i32, i8, [3 x i8] }* @main.obj_with_array, i64 0, i32 0, i64 0), i64 12, i32 4, i1 false) + %0 = load i8* getelementptr inbounds (%struct.with_array* @array_with_zeroinit, i64 0, i32 2), align 4 + + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* getelementptr inbounds (%struct.with_vector* @vector_with_zeroinit, i64 0, i32 0, i64 0), i8* getelementptr inbounds ({ <2 x i8>, i32, i8, [3 x i8] }* @main.obj_with_vector, i64 0, i32 0, i64 0), i64 12, i32 4, i1 false) + %1 = load i8* getelementptr inbounds (%struct.with_vector* @vector_with_zeroinit, i64 0, i32 2), align 4 + %conv0 = sext i8 %0 to i32 + %conv1 = sext i8 %1 to i32 + %and = and i32 %conv0, %conv1 + ret i32 %and +; CHECK-LABEL: define i32 @main( +; CHECK: ret i32 1 +} + +declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) |