From 9009d2905debfc210859e5d20a1fb3ec319a9ce7 Mon Sep 17 00:00:00 2001 From: John Brawn Date: Fri, 26 May 2017 13:59:12 +0000 Subject: [ARM] Fix lowering of misaligned memcpy/memset Currently getOptimalMemOpType returns i32 for large enough sizes without checking for alignment, leading to poor code generation when misaligned accesses aren't permitted as we generate a word store then later split it up into byte stores. This means we inadvertantly go over the MaxStoresPerMemcpy limit and for memset we splat the memset value into a word then immediately split it up again. Fix this by leaving it up to FindOptimalMemOpLowering to figure out which type to use, but also fix a bug there where it wasn't correctly checking if misaligned memory accesses are allowed. Differential Revision: https://reviews.llvm.org/D33442 llvm-svn: 303990 --- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) (limited to 'llvm/lib/CodeGen') diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index b26f1ce8c5e..177898e1e95 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -4779,23 +4779,23 @@ static bool FindOptimalMemOpLowering(std::vector &MemOps, DAG.getMachineFunction()); if (VT == MVT::Other) { - if (DstAlign >= DAG.getDataLayout().getPointerPrefAlignment(DstAS) || - TLI.allowsMisalignedMemoryAccesses(VT, DstAS, DstAlign)) { - VT = TLI.getPointerTy(DAG.getDataLayout(), DstAS); - } else { - switch (DstAlign & 7) { - case 0: VT = MVT::i64; break; - case 4: VT = MVT::i32; break; - case 2: VT = MVT::i16; break; - default: VT = MVT::i8; break; - } - } - + // Use the largest integer type whose alignment constraints are satisfied. + // We only need to check DstAlign here as SrcAlign is always greater or + // equal to DstAlign (or zero). + VT = MVT::i64; + while (DstAlign && DstAlign < VT.getSizeInBits() / 8 && + !TLI.allowsMisalignedMemoryAccesses(VT, DstAS, DstAlign)) + VT = (MVT::SimpleValueType)(VT.getSimpleVT().SimpleTy - 1); + assert(VT.isInteger()); + + // Find the largest legal integer type. MVT LVT = MVT::i64; while (!TLI.isTypeLegal(LVT)) LVT = (MVT::SimpleValueType)(LVT.SimpleTy - 1); assert(LVT.isInteger()); + // If the type we've chosen is larger than the largest legal integer type + // then use that instead. if (VT.bitsGT(LVT)) VT = LVT; } -- cgit v1.2.3