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[XCore] Simplify code that checks for an aligned base plus a constant. 

The code now makes use of ComputeMaskedBits,
SelectionDAG::isBaseWithConstantOffset and TargetLowering::isGAPlusOffset
where appropriate reducing the amount of logic needed in XCoreISelLowering.
No intended functionality change.

llvm-svn: 181125
This commit is contained in:
Richard Osborne 2013-05-04 17:17:10 +00:00
parent 8bbea9cde7
commit a282fa5b60
2 changed files with 56 additions and 81 deletions
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134
llvm/lib/Target/XCore/XCoreISelLowering.cpp
View File

@ -308,55 +308,49 @@ LowerBR_JT(SDValue Op, SelectionDAG &DAG) const
ScaledIndex);
}
static bool
IsWordAlignedBasePlusConstantOffset(SDValue Addr, SDValue &AlignedBase,
int64_t &Offset)
SDValue XCoreTargetLowering::
lowerLoadWordFromAlignedBasePlusOffset(DebugLoc DL, SDValue Chain, SDValue Base,
int64_t Offset, SelectionDAG &DAG) const
{
if (Addr.getOpcode() != ISD::ADD) {
return false;
if ((Offset & 0x3) == 0) {
return DAG.getLoad(getPointerTy(), DL, Chain, Base, MachinePointerInfo(),
false, false, false, 0);
}
ConstantSDNode *CN = 0;
if (!(CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1)))) {
return false;
}
int64_t off = CN->getSExtValue();
const SDValue &Base = Addr.getOperand(0);
const SDValue *Root = &Base;
if (Base.getOpcode() == ISD::ADD &&
Base.getOperand(1).getOpcode() == ISD::SHL) {
ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Base.getOperand(1)
.getOperand(1));
if (CN && (CN->getSExtValue() >= 2)) {
Root = &Base.getOperand(0);
}
}
if (isa<FrameIndexSDNode>(*Root)) {
// All frame indicies are word aligned
AlignedBase = Base;
Offset = off;
return true;
}
if (Root->getOpcode() == XCoreISD::DPRelativeWrapper ||
Root->getOpcode() == XCoreISD::CPRelativeWrapper) {
// All dp / cp relative addresses are word aligned
AlignedBase = Base;
Offset = off;
return true;
}
// Check for an aligned global variable.
if (GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(*Root)) {
const GlobalValue *GV = GA->getGlobal();
if (GA->getOffset() == 0 && GV->getAlignment() >= 4) {
AlignedBase = Base;
Offset = off;
return true;
}
}
return false;
// Lower to pair of consecutive word aligned loads plus some bit shifting.
int32_t HighOffset = RoundUpToAlignment(Offset, 4);
int32_t LowOffset = HighOffset - 4;
SDValue LowAddr = DAG.getNode(ISD::ADD, DL, MVT::i32, Base,
DAG.getConstant(LowOffset, MVT::i32));
SDValue HighAddr = DAG.getNode(ISD::ADD, DL, MVT::i32, Base,
DAG.getConstant(HighOffset, MVT::i32));
SDValue LowShift = DAG.getConstant((Offset - LowOffset) * 8, MVT::i32);
SDValue HighShift = DAG.getConstant((HighOffset - Offset) * 8, MVT::i32);
SDValue Low = DAG.getLoad(getPointerTy(), DL, Chain,
LowAddr, MachinePointerInfo(),
false, false, false, 0);
SDValue High = DAG.getLoad(getPointerTy(), DL, Chain,
HighAddr, MachinePointerInfo(),
false, false, false, 0);
SDValue LowShifted = DAG.getNode(ISD::SRL, DL, MVT::i32, Low, LowShift);
SDValue HighShifted = DAG.getNode(ISD::SHL, DL, MVT::i32, High, HighShift);
SDValue Result = DAG.getNode(ISD::OR, DL, MVT::i32, LowShifted, HighShifted);
Chain = DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Low.getValue(1),
High.getValue(1));
SDValue Ops[] = { Result, Chain };
return DAG.getMergeValues(Ops, 2, DL);
}
static bool isWordAligned(SDValue Value, SelectionDAG &DAG)
{
APInt KnownZero, KnownOne;
DAG.ComputeMaskedBits(Value, KnownZero, KnownOne);
return KnownZero.countTrailingOnes() >= 2;
}
SDValue XCoreTargetLowering::
LowerLOAD(SDValue Op, SelectionDAG &DAG) const {
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
LoadSDNode *LD = cast<LoadSDNode>(Op);
assert(LD->getExtensionType() == ISD::NON_EXTLOAD &&
"Unexpected extension type");
@ -374,45 +368,23 @@ LowerLOAD(SDValue Op, SelectionDAG &DAG) const {
SDValue BasePtr = LD->getBasePtr();
DebugLoc DL = Op.getDebugLoc();
SDValue Base;
int64_t Offset;
if (!LD->isVolatile() &&
IsWordAlignedBasePlusConstantOffset(BasePtr, Base, Offset)) {
if (Offset % 4 == 0) {
// We've managed to infer better alignment information than the load
// already has. Use an aligned load.
//
return DAG.getLoad(getPointerTy(), DL, Chain, BasePtr,
MachinePointerInfo(),
false, false, false, 0);
if (!LD->isVolatile()) {
const GlobalValue *GV;
int64_t Offset = 0;
if (DAG.isBaseWithConstantOffset(BasePtr) &&
isWordAligned(BasePtr->getOperand(0), DAG)) {
SDValue NewBasePtr = BasePtr->getOperand(0);
Offset = cast<ConstantSDNode>(BasePtr->getOperand(1))->getSExtValue();
return lowerLoadWordFromAlignedBasePlusOffset(DL, Chain, NewBasePtr,
Offset, DAG);
}
if (TLI.isGAPlusOffset(BasePtr.getNode(), GV, Offset) &&
MinAlign(GV->getAlignment(), 4) == 4) {
SDValue NewBasePtr = DAG.getGlobalAddress(GV, DL,
BasePtr->getValueType(0));
return lowerLoadWordFromAlignedBasePlusOffset(DL, Chain, NewBasePtr,
Offset, DAG);
}
// Lower to
// ldw low, base[offset >> 2]
// ldw high, base[(offset >> 2) + 1]
// shr low_shifted, low, (offset & 0x3) * 8
// shl high_shifted, high, 32 - (offset & 0x3) * 8
// or result, low_shifted, high_shifted
SDValue LowOffset = DAG.getConstant(Offset & ~0x3, MVT::i32);
SDValue HighOffset = DAG.getConstant((Offset & ~0x3) + 4, MVT::i32);
SDValue LowShift = DAG.getConstant((Offset & 0x3) * 8, MVT::i32);
SDValue HighShift = DAG.getConstant(32 - (Offset & 0x3) * 8, MVT::i32);
SDValue LowAddr = DAG.getNode(ISD::ADD, DL, MVT::i32, Base, LowOffset);
SDValue HighAddr = DAG.getNode(ISD::ADD, DL, MVT::i32, Base, HighOffset);
SDValue Low = DAG.getLoad(getPointerTy(), DL, Chain,
LowAddr, MachinePointerInfo(),
false, false, false, 0);
SDValue High = DAG.getLoad(getPointerTy(), DL, Chain,
HighAddr, MachinePointerInfo(),
false, false, false, 0);
SDValue LowShifted = DAG.getNode(ISD::SRL, DL, MVT::i32, Low, LowShift);
SDValue HighShifted = DAG.getNode(ISD::SHL, DL, MVT::i32, High, HighShift);
SDValue Result = DAG.getNode(ISD::OR, DL, MVT::i32, LowShifted, HighShifted);
Chain = DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Low.getValue(1),
High.getValue(1));
SDValue Ops[] = { Result, Chain };
return DAG.getMergeValues(Ops, 2, DL);
}
if (LD->getAlignment() == 2) {

3
llvm/lib/Target/XCore/XCoreISelLowering.h
View File

@ -135,6 +135,9 @@ namespace llvm {
SDValue getReturnAddressFrameIndex(SelectionDAG &DAG) const;
SDValue getGlobalAddressWrapper(SDValue GA, const GlobalValue *GV,
SelectionDAG &DAG) const;
SDValue lowerLoadWordFromAlignedBasePlusOffset(DebugLoc DL, SDValue Chain,
SDValue Base, int64_t Offset,
SelectionDAG &DAG) const;
// Lower Operand specifics
SDValue LowerLOAD(SDValue Op, SelectionDAG &DAG) const;