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Correctly lower memset / memcpy of undef. It should be a nop. PR6767.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100208 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2010-04-02 19:36:14 +00:00
parent cf5862d8ac
commit f28f8bc40e
8 changed files with 94 additions and 55 deletions
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lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+23 -11
View File
@@ -3094,6 +3094,8 @@ SDValue SelectionDAG::getStackArgumentTokenFactor(SDValue Chain) {
/// operand.
static SDValue getMemsetValue(SDValue Value, EVT VT, SelectionDAG &DAG,
DebugLoc dl) {
assert(Value.getOpcode() != ISD::UNDEF);
unsigned NumBits = VT.getScalarType().getSizeInBits();
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Value)) {
APInt Val = APInt(NumBits, C->getZExtValue() & 255);
@@ -3197,7 +3199,7 @@ static bool isMemSrcFromString(SDValue Src, std::string &Str) {
static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
unsigned Limit, uint64_t Size,
unsigned DstAlign, unsigned SrcAlign,
bool SafeToUseFP,
bool NonScalarIntSafe,
SelectionDAG &DAG,
const TargetLowering &TLI) {
assert((SrcAlign == 0 || SrcAlign >= DstAlign) &&
@@ -3207,7 +3209,8 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
// the inferred alignment of the source. 'DstAlign', on the other hand, is the
// specified alignment of the memory operation. If it is zero, that means
// it's possible to change the alignment of the destination.
EVT VT = TLI.getOptimalMemOpType(Size, DstAlign, SrcAlign, SafeToUseFP, DAG);
EVT VT = TLI.getOptimalMemOpType(Size, DstAlign, SrcAlign,
NonScalarIntSafe, DAG);
if (VT == MVT::Other) {
VT = TLI.getPointerTy();
@@ -3266,10 +3269,13 @@ static SDValue getMemcpyLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
unsigned Align, bool AlwaysInline,
const Value *DstSV, uint64_t DstSVOff,
const Value *SrcSV, uint64_t SrcSVOff) {
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
// Turn a memcpy of undef to nop.
if (Src.getOpcode() == ISD::UNDEF)
return Chain;
// Expand memcpy to a series of load and store ops if the size operand falls
// below a certain threshold.
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
std::vector<EVT> MemOps;
uint64_t Limit = -1ULL;
if (!AlwaysInline)
@@ -3352,10 +3358,13 @@ static SDValue getMemmoveLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
unsigned Align,bool AlwaysInline,
const Value *DstSV, uint64_t DstSVOff,
const Value *SrcSV, uint64_t SrcSVOff) {
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
// Turn a memmove of undef to nop.
if (Src.getOpcode() == ISD::UNDEF)
return Chain;
// Expand memmove to a series of load and store ops if the size operand falls
// below a certain threshold.
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
std::vector<EVT> MemOps;
uint64_t Limit = -1ULL;
if (!AlwaysInline)
@@ -3426,21 +3435,24 @@ static SDValue getMemsetStores(SelectionDAG &DAG, DebugLoc dl,
SDValue Src, uint64_t Size,
unsigned Align,
const Value *DstSV, uint64_t DstSVOff) {
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
// Turn a memset of undef to nop.
if (Src.getOpcode() == ISD::UNDEF)
return Chain;
// Expand memset to a series of load/store ops if the size operand
// falls below a certain threshold.
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
std::vector<EVT> MemOps;
bool DstAlignCanChange = false;
MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Dst);
if (FI && !MFI->isFixedObjectIndex(FI->getIndex()))
DstAlignCanChange = true;
bool IsZero = isa<ConstantSDNode>(Src) &&
cast<ConstantSDNode>(Src)->isNullValue();
bool NonScalarIntSafe =
isa<ConstantSDNode>(Src) && cast<ConstantSDNode>(Src)->isNullValue();
if (!FindOptimalMemOpLowering(MemOps, TLI.getMaxStoresPerMemset(),
Size, (DstAlignCanChange ? 0 : Align), 0,
IsZero, DAG, TLI))
NonScalarIntSafe, DAG, TLI))
return SDValue();
if (DstAlignCanChange) {
@@ -3592,9 +3604,9 @@ SDValue SelectionDAG::getMemset(SDValue Chain, DebugLoc dl, SDValue Dst,
if (ConstantSize->isNullValue())
return Chain;
SDValue Result =
getMemsetStores(*this, dl, Chain, Dst, Src, ConstantSize->getZExtValue(),
Align, DstSV, DstSVOff);
SDValue Result = getMemsetStores(*this, dl, Chain, Dst, Src,
ConstantSize->getZExtValue(),
Align, DstSV, DstSVOff);
if (Result.getNode())
return Result;
}