Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp =================================================================== --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -12205,13 +12205,13 @@ // Try to infer better alignment information than the load already has. if (OptLevel != CodeGenOpt::None && LD->isUnindexed()) { if (unsigned Align = DAG.InferPtrAlignment(Ptr)) { - if (Align > LD->getMemOperand()->getBaseAlignment()) { + if (Align > LD->getAlignment() && LD->getSrcValueOffset() % Align == 0) { SDValue NewLoad = DAG.getExtLoad( LD->getExtensionType(), SDLoc(N), LD->getValueType(0), Chain, Ptr, LD->getPointerInfo(), LD->getMemoryVT(), Align, LD->getMemOperand()->getFlags(), LD->getAAInfo()); - if (NewLoad.getNode() != N) - return CombineTo(N, NewLoad, SDValue(NewLoad.getNode(), 1), true); + // NewLoad will always be N as we are only refining the alignment + assert(NewLoad.getNode() == N); } } } @@ -14212,13 +14212,13 @@ // Try to infer better alignment information than the store already has. if (OptLevel != CodeGenOpt::None && ST->isUnindexed()) { if (unsigned Align = DAG.InferPtrAlignment(Ptr)) { - if (Align > ST->getAlignment()) { + if (Align > ST->getAlignment() && ST->getSrcValueOffset() % Align == 0) { SDValue NewStore = DAG.getTruncStore(Chain, SDLoc(N), Value, Ptr, ST->getPointerInfo(), ST->getMemoryVT(), Align, ST->getMemOperand()->getFlags(), ST->getAAInfo()); - if (NewStore.getNode() != N) - return CombineTo(ST, NewStore, true); + // NewStore will always be N as we are only refining the alignment + assert(NewStore.getNode() == N); } } } Index: test/CodeGen/ARM/alias_align.ll =================================================================== --- /dev/null +++ test/CodeGen/ARM/alias_align.ll @@ -0,0 +1,25 @@ +; RUN: llc < %s | FileCheck %s + +target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64" +target triple = "armv8-arm-none-eabi" + +; Check the loads happen after the stores (note: directly returning 0 is also valid) +; CHECK-LABEL: somesortofhash +; CHECK-NOT: ldr +; CHECK: str + +define i64 @somesortofhash() { +entry: + %helper = alloca i8, i32 64, align 8 + %helper.0.4x32 = bitcast i8* %helper to <4 x i32>* + %helper.20 = getelementptr inbounds i8, i8* %helper, i32 20 + %helper.24 = getelementptr inbounds i8, i8* %helper, i32 24 + store <4 x i32> zeroinitializer, <4 x i32>* %helper.0.4x32, align 8 + %helper.20.32 = bitcast i8* %helper.20 to i32* + %helper.24.32 = bitcast i8* %helper.24 to i32* + store i32 0, i32* %helper.20.32 + store i32 0, i32* %helper.24.32, align 8 + %helper.20.64 = bitcast i8* %helper.20 to i64* + %load.helper.20.64 = load i64, i64* %helper.20.64, align 4 + ret i64 %load.helper.20.64 +}