[llvm] r181125 - [XCore] Simplify code that checks for an aligned base plus a constant.
Richard Osborne
richard at xmos.com
Sat May 4 10:17:11 PDT 2013
Author: friedgold
Date: Sat May 4 12:17:10 2013
New Revision: 181125
URL: http://llvm.org/viewvc/llvm-project?rev=181125&view=rev
Log:
[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.
Modified:
llvm/trunk/lib/Target/XCore/XCoreISelLowering.cpp
llvm/trunk/lib/Target/XCore/XCoreISelLowering.h
Modified: llvm/trunk/lib/Target/XCore/XCoreISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/XCore/XCoreISelLowering.cpp?rev=181125&r1=181124&r2=181125&view=diff
==============================================================================
--- llvm/trunk/lib/Target/XCore/XCoreISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/XCore/XCoreISelLowering.cpp Sat May 4 12:17:10 2013
@@ -308,55 +308,49 @@ LowerBR_JT(SDValue Op, SelectionDAG &DAG
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;
- }
- 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;
+ if ((Offset & 0x3) == 0) {
+ return DAG.getLoad(getPointerTy(), DL, Chain, Base, MachinePointerInfo(),
+ false, false, false, 0);
+ }
+ // 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)
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) {
Modified: llvm/trunk/lib/Target/XCore/XCoreISelLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/XCore/XCoreISelLowering.h?rev=181125&r1=181124&r2=181125&view=diff
==============================================================================
--- llvm/trunk/lib/Target/XCore/XCoreISelLowering.h (original)
+++ llvm/trunk/lib/Target/XCore/XCoreISelLowering.h Sat May 4 12:17:10 2013
@@ -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;
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