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llvm / llvm / ce7676b8db6bac096dad4c4ad62e9e6bb8aa1064 / . / lib / CodeGen / SelectionDAG / TargetLowering.cpp
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//===-- TargetLowering.cpp - Implement the TargetLowering class -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the TargetLowering class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Target/TargetLowering.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <cctype>
using namespace llvm;
/// NOTE: The TargetMachine owns TLOF.
TargetLowering::TargetLowering(const TargetMachine &tm)
: TargetLoweringBase(tm) {}
const char *TargetLowering::getTargetNodeName(unsigned Opcode) const {
return nullptr;
}
bool TargetLowering::isPositionIndependent() const {
return getTargetMachine().isPositionIndependent();
}
/// Check whether a given call node is in tail position within its function. If
/// so, it sets Chain to the input chain of the tail call.
bool TargetLowering::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,
SDValue &Chain) const {
const Function *F = DAG.getMachineFunction().getFunction();
// Conservatively require the attributes of the call to match those of
// the return. Ignore noalias because it doesn't affect the call sequence.
AttributeList CallerAttrs = F->getAttributes();
if (AttrBuilder(CallerAttrs, AttributeList::ReturnIndex)
.removeAttribute(Attribute::NoAlias)
.hasAttributes())
return false;
// It's not safe to eliminate the sign / zero extension of the return value.
if (CallerAttrs.hasAttribute(AttributeList::ReturnIndex, Attribute::ZExt) ||
CallerAttrs.hasAttribute(AttributeList::ReturnIndex, Attribute::SExt))
return false;
// Check if the only use is a function return node.
return isUsedByReturnOnly(Node, Chain);
}
bool TargetLowering::parametersInCSRMatch(const MachineRegisterInfo &MRI,
const uint32_t *CallerPreservedMask,
const SmallVectorImpl<CCValAssign> &ArgLocs,
const SmallVectorImpl<SDValue> &OutVals) const {
for (unsigned I = 0, E = ArgLocs.size(); I != E; ++I) {
const CCValAssign &ArgLoc = ArgLocs[I];
if (!ArgLoc.isRegLoc())
continue;
unsigned Reg = ArgLoc.getLocReg();
// Only look at callee saved registers.
if (MachineOperand::clobbersPhysReg(CallerPreservedMask, Reg))
continue;
// Check that we pass the value used for the caller.
// (We look for a CopyFromReg reading a virtual register that is used
// for the function live-in value of register Reg)
SDValue Value = OutVals[I];
if (Value->getOpcode() != ISD::CopyFromReg)
return false;
unsigned ArgReg = cast<RegisterSDNode>(Value->getOperand(1))->getReg();
if (MRI.getLiveInPhysReg(ArgReg) != Reg)
return false;
}
return true;
}
/// \brief Set CallLoweringInfo attribute flags based on a call instruction
/// and called function attributes.
void TargetLoweringBase::ArgListEntry::setAttributes(ImmutableCallSite *CS,
unsigned ArgIdx) {
IsSExt = CS->paramHasAttr(ArgIdx, Attribute::SExt);
IsZExt = CS->paramHasAttr(ArgIdx, Attribute::ZExt);
IsInReg = CS->paramHasAttr(ArgIdx, Attribute::InReg);
IsSRet = CS->paramHasAttr(ArgIdx, Attribute::StructRet);
IsNest = CS->paramHasAttr(ArgIdx, Attribute::Nest);
IsByVal = CS->paramHasAttr(ArgIdx, Attribute::ByVal);
IsInAlloca = CS->paramHasAttr(ArgIdx, Attribute::InAlloca);
IsReturned = CS->paramHasAttr(ArgIdx, Attribute::Returned);
IsSwiftSelf = CS->paramHasAttr(ArgIdx, Attribute::SwiftSelf);
IsSwiftError = CS->paramHasAttr(ArgIdx, Attribute::SwiftError);
Alignment = CS->getParamAlignment(ArgIdx);
}
/// Generate a libcall taking the given operands as arguments and returning a
/// result of type RetVT.
std::pair<SDValue, SDValue>
TargetLowering::makeLibCall(SelectionDAG &DAG, RTLIB::Libcall LC, EVT RetVT,
ArrayRef<SDValue> Ops, bool isSigned,
const SDLoc &dl, bool doesNotReturn,
bool isReturnValueUsed) const {
TargetLowering::ArgListTy Args;
Args.reserve(Ops.size());
TargetLowering::ArgListEntry Entry;
for (SDValue Op : Ops) {
Entry.Node = Op;
Entry.Ty = Entry.Node.getValueType().getTypeForEVT(*DAG.getContext());
Entry.IsSExt = shouldSignExtendTypeInLibCall(Op.getValueType(), isSigned);
Entry.IsZExt = !shouldSignExtendTypeInLibCall(Op.getValueType(), isSigned);
Args.push_back(Entry);
}
if (LC == RTLIB::UNKNOWN_LIBCALL)
report_fatal_error("Unsupported library call operation!");
SDValue Callee = DAG.getExternalSymbol(getLibcallName(LC),
getPointerTy(DAG.getDataLayout()));
Type *RetTy = RetVT.getTypeForEVT(*DAG.getContext());
TargetLowering::CallLoweringInfo CLI(DAG);
bool signExtend = shouldSignExtendTypeInLibCall(RetVT, isSigned);
CLI.setDebugLoc(dl)
.setChain(DAG.getEntryNode())
.setLibCallee(getLibcallCallingConv(LC), RetTy, Callee, std::move(Args))
.setNoReturn(doesNotReturn)
.setDiscardResult(!isReturnValueUsed)
.setSExtResult(signExtend)
.setZExtResult(!signExtend);
return LowerCallTo(CLI);
}
/// Soften the operands of a comparison. This code is shared among BR_CC,
/// SELECT_CC, and SETCC handlers.
void TargetLowering::softenSetCCOperands(SelectionDAG &DAG, EVT VT,
SDValue &NewLHS, SDValue &NewRHS,
ISD::CondCode &CCCode,
const SDLoc &dl) const {
assert((VT == MVT::f32 || VT == MVT::f64 || VT == MVT::f128 || VT == MVT::ppcf128)
&& "Unsupported setcc type!");
// Expand into one or more soft-fp libcall(s).
RTLIB::Libcall LC1 = RTLIB::UNKNOWN_LIBCALL, LC2 = RTLIB::UNKNOWN_LIBCALL;
bool ShouldInvertCC = false;
switch (CCCode) {
case ISD::SETEQ:
case ISD::SETOEQ:
LC1 = (VT == MVT::f32) ? RTLIB::OEQ_F32 :
(VT == MVT::f64) ? RTLIB::OEQ_F64 :
(VT == MVT::f128) ? RTLIB::OEQ_F128 : RTLIB::OEQ_PPCF128;
break;
case ISD::SETNE:
case ISD::SETUNE:
LC1 = (VT == MVT::f32) ? RTLIB::UNE_F32 :
(VT == MVT::f64) ? RTLIB::UNE_F64 :
(VT == MVT::f128) ? RTLIB::UNE_F128 : RTLIB::UNE_PPCF128;
break;
case ISD::SETGE:
case ISD::SETOGE:
LC1 = (VT == MVT::f32) ? RTLIB::OGE_F32 :
(VT == MVT::f64) ? RTLIB::OGE_F64 :
(VT == MVT::f128) ? RTLIB::OGE_F128 : RTLIB::OGE_PPCF128;
break;
case ISD::SETLT:
case ISD::SETOLT:
LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
(VT == MVT::f64) ? RTLIB::OLT_F64 :
(VT == MVT::f128) ? RTLIB::OLT_F128 : RTLIB::OLT_PPCF128;
break;
case ISD::SETLE:
case ISD::SETOLE:
LC1 = (VT == MVT::f32) ? RTLIB::OLE_F32 :
(VT == MVT::f64) ? RTLIB::OLE_F64 :
(VT == MVT::f128) ? RTLIB::OLE_F128 : RTLIB::OLE_PPCF128;
break;
case ISD::SETGT:
case ISD::SETOGT:
LC1 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
(VT == MVT::f64) ? RTLIB::OGT_F64 :
(VT == MVT::f128) ? RTLIB::OGT_F128 : RTLIB::OGT_PPCF128;
break;
case ISD::SETUO:
LC1 = (VT == MVT::f32) ? RTLIB::UO_F32 :
(VT == MVT::f64) ? RTLIB::UO_F64 :
(VT == MVT::f128) ? RTLIB::UO_F128 : RTLIB::UO_PPCF128;
break;
case ISD::SETO:
LC1 = (VT == MVT::f32) ? RTLIB::O_F32 :
(VT == MVT::f64) ? RTLIB::O_F64 :
(VT == MVT::f128) ? RTLIB::O_F128 : RTLIB::O_PPCF128;
break;
case ISD::SETONE:
// SETONE = SETOLT | SETOGT
LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
(VT == MVT::f64) ? RTLIB::OLT_F64 :
(VT == MVT::f128) ? RTLIB::OLT_F128 : RTLIB::OLT_PPCF128;
LC2 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
(VT == MVT::f64) ? RTLIB::OGT_F64 :
(VT == MVT::f128) ? RTLIB::OGT_F128 : RTLIB::OGT_PPCF128;
break;
case ISD::SETUEQ:
LC1 = (VT == MVT::f32) ? RTLIB::UO_F32 :
(VT == MVT::f64) ? RTLIB::UO_F64 :
(VT == MVT::f128) ? RTLIB::UO_F128 : RTLIB::UO_PPCF128;
LC2 = (VT == MVT::f32) ? RTLIB::OEQ_F32 :
(VT == MVT::f64) ? RTLIB::OEQ_F64 :
(VT == MVT::f128) ? RTLIB::OEQ_F128 : RTLIB::OEQ_PPCF128;
break;
default:
// Invert CC for unordered comparisons
ShouldInvertCC = true;
switch (CCCode) {
case ISD::SETULT:
LC1 = (VT == MVT::f32) ? RTLIB::OGE_F32 :
(VT == MVT::f64) ? RTLIB::OGE_F64 :
(VT == MVT::f128) ? RTLIB::OGE_F128 : RTLIB::OGE_PPCF128;
break;
case ISD::SETULE:
LC1 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
(VT == MVT::f64) ? RTLIB::OGT_F64 :
(VT == MVT::f128) ? RTLIB::OGT_F128 : RTLIB::OGT_PPCF128;
break;
case ISD::SETUGT:
LC1 = (VT == MVT::f32) ? RTLIB::OLE_F32 :
(VT == MVT::f64) ? RTLIB::OLE_F64 :
(VT == MVT::f128) ? RTLIB::OLE_F128 : RTLIB::OLE_PPCF128;
break;
case ISD::SETUGE:
LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
(VT == MVT::f64) ? RTLIB::OLT_F64 :
(VT == MVT::f128) ? RTLIB::OLT_F128 : RTLIB::OLT_PPCF128;
break;
default: llvm_unreachable("Do not know how to soften this setcc!");
}
}
// Use the target specific return value for comparions lib calls.
EVT RetVT = getCmpLibcallReturnType();
SDValue Ops[2] = {NewLHS, NewRHS};
NewLHS = makeLibCall(DAG, LC1, RetVT, Ops, false /*sign irrelevant*/,
dl).first;
NewRHS = DAG.getConstant(0, dl, RetVT);
CCCode = getCmpLibcallCC(LC1);
if (ShouldInvertCC)
CCCode = getSetCCInverse(CCCode, /*isInteger=*/true);
if (LC2 != RTLIB::UNKNOWN_LIBCALL) {
SDValue Tmp = DAG.getNode(
ISD::SETCC, dl,
getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), RetVT),
NewLHS, NewRHS, DAG.getCondCode(CCCode));
NewLHS = makeLibCall(DAG, LC2, RetVT, Ops, false/*sign irrelevant*/,
dl).first;
NewLHS = DAG.getNode(
ISD::SETCC, dl,
getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), RetVT),
NewLHS, NewRHS, DAG.getCondCode(getCmpLibcallCC(LC2)));
NewLHS = DAG.getNode(ISD::OR, dl, Tmp.getValueType(), Tmp, NewLHS);
NewRHS = SDValue();
}
}
/// Return the entry encoding for a jump table in the current function. The
/// returned value is a member of the MachineJumpTableInfo::JTEntryKind enum.
unsigned TargetLowering::getJumpTableEncoding() const {
// In non-pic modes, just use the address of a block.
if (!isPositionIndependent())
return MachineJumpTableInfo::EK_BlockAddress;
// In PIC mode, if the target supports a GPRel32 directive, use it.
if (getTargetMachine().getMCAsmInfo()->getGPRel32Directive() != nullptr)
return MachineJumpTableInfo::EK_GPRel32BlockAddress;
// Otherwise, use a label difference.
return MachineJumpTableInfo::EK_LabelDifference32;
}
SDValue TargetLowering::getPICJumpTableRelocBase(SDValue Table,
SelectionDAG &DAG) const {
// If our PIC model is GP relative, use the global offset table as the base.
unsigned JTEncoding = getJumpTableEncoding();
if ((JTEncoding == MachineJumpTableInfo::EK_GPRel64BlockAddress) ||
(JTEncoding == MachineJumpTableInfo::EK_GPRel32BlockAddress))
return DAG.getGLOBAL_OFFSET_TABLE(getPointerTy(DAG.getDataLayout()));
return Table;
}
/// This returns the relocation base for the given PIC jumptable, the same as
/// getPICJumpTableRelocBase, but as an MCExpr.
const MCExpr *
TargetLowering::getPICJumpTableRelocBaseExpr(const MachineFunction *MF,
unsigned JTI,MCContext &Ctx) const{
// The normal PIC reloc base is the label at the start of the jump table.
return MCSymbolRefExpr::create(MF->getJTISymbol(JTI, Ctx), Ctx);
}
bool
TargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
const TargetMachine &TM = getTargetMachine();
const GlobalValue *GV = GA->getGlobal();
// If the address is not even local to this DSO we will have to load it from
// a got and then add the offset.
if (!TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
return false;
// If the code is position independent we will have to add a base register.
if (isPositionIndependent())
return false;
// Otherwise we can do it.
return true;
}
//===----------------------------------------------------------------------===//
// Optimization Methods
//===----------------------------------------------------------------------===//
/// If the specified instruction has a constant integer operand and there are
/// bits set in that constant that are not demanded, then clear those bits and
/// return true.
bool TargetLowering::ShrinkDemandedConstant(SDValue Op, const APInt &Demanded,
TargetLoweringOpt &TLO) const {
SelectionDAG &DAG = TLO.DAG;
SDLoc DL(Op);
unsigned Opcode = Op.getOpcode();
// Do target-specific constant optimization.
if (targetShrinkDemandedConstant(Op, Demanded, TLO))
return TLO.New.getNode();
// FIXME: ISD::SELECT, ISD::SELECT_CC
switch (Opcode) {
default:
break;
case ISD::XOR:
case ISD::AND:
case ISD::OR: {
auto *Op1C = dyn_cast<ConstantSDNode>(Op.getOperand(1));
if (!Op1C)
return false;
// If this is a 'not' op, don't touch it because that's a canonical form.
const APInt &C = Op1C->getAPIntValue();
if (Opcode == ISD::XOR && Demanded.isSubsetOf(C))
return false;
if (!C.isSubsetOf(Demanded)) {
EVT VT = Op.getValueType();
SDValue NewC = DAG.getConstant(Demanded & C, DL, VT);
SDValue NewOp = DAG.getNode(Opcode, DL, VT, Op.getOperand(0), NewC);
return TLO.CombineTo(Op, NewOp);
}
break;
}
}
return false;
}
/// Convert x+y to (VT)((SmallVT)x+(SmallVT)y) if the casts are free.
/// This uses isZExtFree and ZERO_EXTEND for the widening cast, but it could be
/// generalized for targets with other types of implicit widening casts.
bool TargetLowering::ShrinkDemandedOp(SDValue Op, unsigned BitWidth,
const APInt &Demanded,
TargetLoweringOpt &TLO) const {
assert(Op.getNumOperands() == 2 &&
"ShrinkDemandedOp only supports binary operators!");
assert(Op.getNode()->getNumValues() == 1 &&
"ShrinkDemandedOp only supports nodes with one result!");
SelectionDAG &DAG = TLO.DAG;
SDLoc dl(Op);
// Early return, as this function cannot handle vector types.
if (Op.getValueType().isVector())
return false;
// Don't do this if the node has another user, which may require the
// full value.
if (!Op.getNode()->hasOneUse())
return false;
// Search for the smallest integer type with free casts to and from
// Op's type. For expedience, just check power-of-2 integer types.
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
unsigned DemandedSize = Demanded.getActiveBits();
unsigned SmallVTBits = DemandedSize;
if (!isPowerOf2_32(SmallVTBits))
SmallVTBits = NextPowerOf2(SmallVTBits);
for (; SmallVTBits < BitWidth; SmallVTBits = NextPowerOf2(SmallVTBits)) {
EVT SmallVT = EVT::getIntegerVT(*DAG.getContext(), SmallVTBits);
if (TLI.isTruncateFree(Op.getValueType(), SmallVT) &&
TLI.isZExtFree(SmallVT, Op.getValueType())) {
// We found a type with free casts.
SDValue X = DAG.getNode(
Op.getOpcode(), dl, SmallVT,
DAG.getNode(ISD::TRUNCATE, dl, SmallVT, Op.getOperand(0)),
DAG.getNode(ISD::TRUNCATE, dl, SmallVT, Op.getOperand(1)));
assert(DemandedSize <= SmallVTBits && "Narrowed below demanded bits?");
SDValue Z = DAG.getNode(ISD::ANY_EXTEND, dl, Op.getValueType(), X);
return TLO.CombineTo(Op, Z);
}
}
return false;
}
bool
TargetLowering::SimplifyDemandedBits(SDNode *User, unsigned OpIdx,
const APInt &Demanded,
DAGCombinerInfo &DCI,
TargetLoweringOpt &TLO) const {
SDValue Op = User->getOperand(OpIdx);
KnownBits Known;
if (!SimplifyDemandedBits(Op, Demanded, Known, TLO, 0, true))
return false;
// Old will not always be the same as Op. For example:
//
// Demanded = 0xffffff
// Op = i64 truncate (i32 and x, 0xffffff)
// In this case simplify demand bits will want to replace the 'and' node
// with the value 'x', which will give us:
// Old = i32 and x, 0xffffff
// New = x
if (TLO.Old.hasOneUse()) {
// For the one use case, we just commit the change.
DCI.CommitTargetLoweringOpt(TLO);
return true;
}
// If Old has more than one use then it must be Op, because the
// AssumeSingleUse flag is not propogated to recursive calls of
// SimplifyDemanded bits, so the only node with multiple use that
// it will attempt to combine will be Op.
assert(TLO.Old == Op);
SmallVector <SDValue, 4> NewOps;
for (unsigned i = 0, e = User->getNumOperands(); i != e; ++i) {
if (i == OpIdx) {
NewOps.push_back(TLO.New);
continue;
}
NewOps.push_back(User->getOperand(i));
}
User = TLO.DAG.UpdateNodeOperands(User, NewOps);
// Op has less users now, so we may be able to perform additional combines
// with it.
DCI.AddToWorklist(Op.getNode());
// User's operands have been updated, so we may be able to do new combines
// with it.
DCI.AddToWorklist(User);
return true;
}
bool TargetLowering::SimplifyDemandedBits(SDValue Op, const APInt &DemandedMask,
DAGCombinerInfo &DCI) const {
SelectionDAG &DAG = DCI.DAG;
TargetLoweringOpt TLO(DAG, !DCI.isBeforeLegalize(),
!DCI.isBeforeLegalizeOps());
KnownBits Known;
bool Simplified = SimplifyDemandedBits(Op, DemandedMask, Known, TLO);
if (Simplified)
DCI.CommitTargetLoweringOpt(TLO);
return Simplified;
}
/// Look at Op. At this point, we know that only the DemandedMask bits of the
/// result of Op are ever used downstream. If we can use this information to
/// simplify Op, create a new simplified DAG node and return true, returning the
/// original and new nodes in Old and New. Otherwise, analyze the expression and
/// return a mask of Known bits for the expression (used to simplify the
/// caller). The Known bits may only be accurate for those bits in the
/// DemandedMask.
bool TargetLowering::SimplifyDemandedBits(SDValue Op,
const APInt &DemandedMask,
KnownBits &Known,
TargetLoweringOpt &TLO,
unsigned Depth,
bool AssumeSingleUse) const {
unsigned BitWidth = DemandedMask.getBitWidth();
assert(Op.getScalarValueSizeInBits() == BitWidth &&
"Mask size mismatches value type size!");
APInt NewMask = DemandedMask;
SDLoc dl(Op);
auto &DL = TLO.DAG.getDataLayout();
// Don't know anything.
Known = KnownBits(BitWidth);
if (Op.getOpcode() == ISD::Constant) {
// We know all of the bits for a constant!
Known.One = cast<ConstantSDNode>(Op)->getAPIntValue();
Known.Zero = ~Known.One;
return false;
}
// Other users may use these bits.
if (!Op.getNode()->hasOneUse() && !AssumeSingleUse) {
if (Depth != 0) {
// If not at the root, Just compute the Known bits to
// simplify things downstream.
TLO.DAG.computeKnownBits(Op, Known, Depth);
return false;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the NewMask to all bits.
NewMask = APInt::getAllOnesValue(BitWidth);
} else if (DemandedMask == 0) {
// Not demanding any bits from Op.
if (!Op.isUndef())
return TLO.CombineTo(Op, TLO.DAG.getUNDEF(Op.getValueType()));
return false;
} else if (Depth == 6) { // Limit search depth.
return false;
}
KnownBits Known2, KnownOut;
switch (Op.getOpcode()) {
case ISD::BUILD_VECTOR:
// Collect the known bits that are shared by every constant vector element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (SDValue SrcOp : Op->ops()) {
if (!isa<ConstantSDNode>(SrcOp)) {
// We can only handle all constant values - bail out with no known bits.
Known = KnownBits(BitWidth);
return false;
}
Known2.One = cast<ConstantSDNode>(SrcOp)->getAPIntValue();
Known2.Zero = ~Known2.One;
// BUILD_VECTOR can implicitly truncate sources, we must handle this.
if (Known2.One.getBitWidth() != BitWidth) {
assert(Known2.getBitWidth() > BitWidth &&
"Expected BUILD_VECTOR implicit truncation");
Known2 = Known2.trunc(BitWidth);
}
// Known bits are the values that are shared by every element.
// TODO: support per-element known bits.
Known.One &= Known2.One;
Known.Zero &= Known2.Zero;
}
return false; // Don't fall through, will infinitely loop.
case ISD::AND:
// If the RHS is a constant, check to see if the LHS would be zero without
// using the bits from the RHS. Below, we use knowledge about the RHS to
// simplify the LHS, here we're using information from the LHS to simplify
// the RHS.
if (ConstantSDNode *RHSC = isConstOrConstSplat(Op.getOperand(1))) {
SDValue Op0 = Op.getOperand(0);
KnownBits LHSKnown;
// Do not increment Depth here; that can cause an infinite loop.
TLO.DAG.computeKnownBits(Op0, LHSKnown, Depth);
// If the LHS already has zeros where RHSC does, this and is dead.
if ((LHSKnown.Zero & NewMask) == (~RHSC->getAPIntValue() & NewMask))
return TLO.CombineTo(Op, Op0);
// If any of the set bits in the RHS are known zero on the LHS, shrink
// the constant.
if (ShrinkDemandedConstant(Op, ~LHSKnown.Zero & NewMask, TLO))
return true;
// Bitwise-not (xor X, -1) is a special case: we don't usually shrink its
// constant, but if this 'and' is only clearing bits that were just set by
// the xor, then this 'and' can be eliminated by shrinking the mask of
// the xor. For example, for a 32-bit X:
// and (xor (srl X, 31), -1), 1 --> xor (srl X, 31), 1
if (isBitwiseNot(Op0) && Op0.hasOneUse() &&
LHSKnown.One == ~RHSC->getAPIntValue()) {
SDValue Xor = TLO.DAG.getNode(ISD::XOR, dl, Op.getValueType(),
Op0.getOperand(0), Op.getOperand(1));
return TLO.CombineTo(Op, Xor);
}
}
if (SimplifyDemandedBits(Op.getOperand(1), NewMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), ~Known.Zero & NewMask,
Known2, TLO, Depth+1))
return true;
assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
// If all of the demanded bits are known one on one side, return the other.
// These bits cannot contribute to the result of the 'and'.
if (NewMask.isSubsetOf(Known2.Zero | Known.One))
return TLO.CombineTo(Op, Op.getOperand(0));
if (NewMask.isSubsetOf(Known.Zero | Known2.One))
return TLO.CombineTo(Op, Op.getOperand(1));
// If all of the demanded bits in the inputs are known zeros, return zero.
if (NewMask.isSubsetOf(Known.Zero | Known2.Zero))
return TLO.CombineTo(Op, TLO.DAG.getConstant(0, dl, Op.getValueType()));
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(Op, ~Known2.Zero & NewMask, TLO))
return true;
// If the operation can be done in a smaller type, do so.
if (ShrinkDemandedOp(Op, BitWidth, NewMask, TLO))
return true;
// Output known-1 bits are only known if set in both the LHS & RHS.
Known.One &= Known2.One;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
Known.Zero |= Known2.Zero;
break;
case ISD::OR:
if (SimplifyDemandedBits(Op.getOperand(1), NewMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), ~Known.One & NewMask,
Known2, TLO, Depth+1))
return true;
assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'or'.
if (NewMask.isSubsetOf(Known2.One | Known.Zero))
return TLO.CombineTo(Op, Op.getOperand(0));
if (NewMask.isSubsetOf(Known.One | Known2.Zero))
return TLO.CombineTo(Op, Op.getOperand(1));
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(Op, NewMask, TLO))
return true;
// If the operation can be done in a smaller type, do so.
if (ShrinkDemandedOp(Op, BitWidth, NewMask, TLO))
return true;
// Output known-0 bits are only known if clear in both the LHS & RHS.
Known.Zero &= Known2.Zero;
// Output known-1 are known to be set if set in either the LHS | RHS.
Known.One |= Known2.One;
break;
case ISD::XOR: {
if (SimplifyDemandedBits(Op.getOperand(1), NewMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), NewMask, Known2, TLO, Depth+1))
return true;
assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'xor'.
if (NewMask.isSubsetOf(Known.Zero))
return TLO.CombineTo(Op, Op.getOperand(0));
if (NewMask.isSubsetOf(Known2.Zero))
return TLO.CombineTo(Op, Op.getOperand(1));
// If the operation can be done in a smaller type, do so.
if (ShrinkDemandedOp(Op, BitWidth, NewMask, TLO))
return true;
// If all of the unknown bits are known to be zero on one side or the other
// (but not both) turn this into an *inclusive* or.
// e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
if ((NewMask & ~Known.Zero & ~Known2.Zero) == 0)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::OR, dl, Op.getValueType(),
Op.getOperand(0),
Op.getOperand(1)));
// Output known-0 bits are known if clear or set in both the LHS & RHS.
KnownOut.Zero = (Known.Zero & Known2.Zero) | (Known.One & Known2.One);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
KnownOut.One = (Known.Zero & Known2.One) | (Known.One & Known2.Zero);
// If all of the demanded bits on one side are known, and all of the set
// bits on that side are also known to be set on the other side, turn this
// into an AND, as we know the bits will be cleared.
// e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
// NB: it is okay if more bits are known than are requested
if (NewMask.isSubsetOf(Known.Zero|Known.One)) { // all known on one side
if (Known.One == Known2.One) { // set bits are the same on both sides
EVT VT = Op.getValueType();
SDValue ANDC = TLO.DAG.getConstant(~Known.One & NewMask, dl, VT);
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::AND, dl, VT,
Op.getOperand(0), ANDC));
}
}
// If the RHS is a constant, see if we can change it. Don't alter a -1
// constant because that's a 'not' op, and that is better for combining and
// codegen.
ConstantSDNode *C = isConstOrConstSplat(Op.getOperand(1));
if (C && !C->isAllOnesValue()) {
if (NewMask.isSubsetOf(C->getAPIntValue())) {
// We're flipping all demanded bits. Flip the undemanded bits too.
SDValue New = TLO.DAG.getNOT(dl, Op.getOperand(0), Op.getValueType());
return TLO.CombineTo(Op, New);
}
// If we can't turn this into a 'not', try to shrink the constant.
if (ShrinkDemandedConstant(Op, NewMask, TLO))
return true;
}
Known = std::move(KnownOut);
break;
}
case ISD::SELECT:
if (SimplifyDemandedBits(Op.getOperand(2), NewMask, Known, TLO, Depth+1))
return true;
if (SimplifyDemandedBits(Op.getOperand(1), NewMask, Known2, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (ShrinkDemandedConstant(Op, NewMask, TLO))
return true;
// Only known if known in both the LHS and RHS.
Known.One &= Known2.One;
Known.Zero &= Known2.Zero;
break;
case ISD::SELECT_CC:
if (SimplifyDemandedBits(Op.getOperand(3), NewMask, Known, TLO, Depth+1))
return true;
if (SimplifyDemandedBits(Op.getOperand(2), NewMask, Known2, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (ShrinkDemandedConstant(Op, NewMask, TLO))
return true;
// Only known if known in both the LHS and RHS.
Known.One &= Known2.One;
Known.Zero &= Known2.Zero;
break;
case ISD::SETCC: {
SDValue Op0 = Op.getOperand(0);
SDValue Op1 = Op.getOperand(1);
ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(2))->get();
// If (1) we only need the sign-bit, (2) the setcc operands are the same
// width as the setcc result, and (3) the result of a setcc conforms to 0 or
// -1, we may be able to bypass the setcc.
if (NewMask.isSignMask() && Op0.getScalarValueSizeInBits() == BitWidth &&
getBooleanContents(Op.getValueType()) ==
BooleanContent::ZeroOrNegativeOneBooleanContent) {
// If we're testing X < 0, then this compare isn't needed - just use X!
// FIXME: We're limiting to integer types here, but this should also work
// if we don't care about FP signed-zero. The use of SETLT with FP means
// that we don't care about NaNs.
if (CC == ISD::SETLT && Op1.getValueType().isInteger() &&
(isNullConstant(Op1) || ISD::isBuildVectorAllZeros(Op1.getNode())))
return TLO.CombineTo(Op, Op0);
// TODO: Should we check for other forms of sign-bit comparisons?
// Examples: X <= -1, X >= 0
}
if (getBooleanContents(Op0.getValueType()) ==
TargetLowering::ZeroOrOneBooleanContent &&
BitWidth > 1)
Known.Zero.setBitsFrom(1);
break;
}
case ISD::SHL:
if (ConstantSDNode *SA = isConstOrConstSplat(Op.getOperand(1))) {
SDValue InOp = Op.getOperand(0);
// If the shift count is an invalid immediate, don't do anything.
if (SA->getAPIntValue().uge(BitWidth))
break;
unsigned ShAmt = SA->getZExtValue();
// If this is ((X >>u C1) << ShAmt), see if we can simplify this into a
// single shift. We can do this if the bottom bits (which are shifted
// out) are never demanded.
if (InOp.getOpcode() == ISD::SRL) {
if (ConstantSDNode *SA2 = isConstOrConstSplat(InOp.getOperand(1))) {
if (ShAmt && (NewMask & APInt::getLowBitsSet(BitWidth, ShAmt)) == 0) {
if (SA2->getAPIntValue().ult(BitWidth)) {
unsigned C1 = SA2->getZExtValue();
unsigned Opc = ISD::SHL;
int Diff = ShAmt-C1;
if (Diff < 0) {
Diff = -Diff;
Opc = ISD::SRL;
}
SDValue NewSA =
TLO.DAG.getConstant(Diff, dl, Op.getOperand(1).getValueType());
EVT VT = Op.getValueType();
return TLO.CombineTo(Op, TLO.DAG.getNode(Opc, dl, VT,
InOp.getOperand(0),
NewSA));
}
}
}
}
if (SimplifyDemandedBits(InOp, NewMask.lshr(ShAmt), Known, TLO, Depth+1))
return true;
// Convert (shl (anyext x, c)) to (anyext (shl x, c)) if the high bits
// are not demanded. This will likely allow the anyext to be folded away.
if (InOp.getNode()->getOpcode() == ISD::ANY_EXTEND) {
SDValue InnerOp = InOp.getOperand(0);
EVT InnerVT = InnerOp.getValueType();
unsigned InnerBits = InnerVT.getScalarSizeInBits();
if (ShAmt < InnerBits && NewMask.getActiveBits() <= InnerBits &&
isTypeDesirableForOp(ISD::SHL, InnerVT)) {
EVT ShTy = getShiftAmountTy(InnerVT, DL);
if (!APInt(BitWidth, ShAmt).isIntN(ShTy.getSizeInBits()))
ShTy = InnerVT;
SDValue NarrowShl =
TLO.DAG.getNode(ISD::SHL, dl, InnerVT, InnerOp,
TLO.DAG.getConstant(ShAmt, dl, ShTy));
return
TLO.CombineTo(Op,
TLO.DAG.getNode(ISD::ANY_EXTEND, dl, Op.getValueType(),
NarrowShl));
}
// Repeat the SHL optimization above in cases where an extension
// intervenes: (shl (anyext (shr x, c1)), c2) to
// (shl (anyext x), c2-c1). This requires that the bottom c1 bits
// aren't demanded (as above) and that the shifted upper c1 bits of
// x aren't demanded.
if (InOp.hasOneUse() && InnerOp.getOpcode() == ISD::SRL &&
InnerOp.hasOneUse()) {
if (ConstantSDNode *SA2 = isConstOrConstSplat(InnerOp.getOperand(1))) {
unsigned InnerShAmt = SA2->getLimitedValue(InnerBits);
if (InnerShAmt < ShAmt &&
InnerShAmt < InnerBits &&
NewMask.getActiveBits() <= (InnerBits - InnerShAmt + ShAmt) &&
NewMask.countTrailingZeros() >= ShAmt) {
SDValue NewSA =
TLO.DAG.getConstant(ShAmt - InnerShAmt, dl,
Op.getOperand(1).getValueType());
EVT VT = Op.getValueType();
SDValue NewExt = TLO.DAG.getNode(ISD::ANY_EXTEND, dl, VT,
InnerOp.getOperand(0));
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SHL, dl, VT,
NewExt, NewSA));
}
}
}
}
Known.Zero <<= ShAmt;
Known.One <<= ShAmt;
// low bits known zero.
Known.Zero.setLowBits(ShAmt);
}
break;
case ISD::SRL:
if (ConstantSDNode *SA = isConstOrConstSplat(Op.getOperand(1))) {
SDValue InOp = Op.getOperand(0);
// If the shift count is an invalid immediate, don't do anything.
if (SA->getAPIntValue().uge(BitWidth))
break;
unsigned ShAmt = SA->getZExtValue();
APInt InDemandedMask = (NewMask << ShAmt);
// If the shift is exact, then it does demand the low bits (and knows that
// they are zero).
if (Op->getFlags().hasExact())
InDemandedMask.setLowBits(ShAmt);
// If this is ((X << C1) >>u ShAmt), see if we can simplify this into a
// single shift. We can do this if the top bits (which are shifted out)
// are never demanded.
if (InOp.getOpcode() == ISD::SHL) {
if (ConstantSDNode *SA2 = isConstOrConstSplat(InOp.getOperand(1))) {
if (ShAmt &&
(NewMask & APInt::getHighBitsSet(BitWidth, ShAmt)) == 0) {
if (SA2->getAPIntValue().ult(BitWidth)) {
unsigned C1 = SA2->getZExtValue();
unsigned Opc = ISD::SRL;
int Diff = ShAmt-C1;
if (Diff < 0) {
Diff = -Diff;
Opc = ISD::SHL;
}
SDValue NewSA =
TLO.DAG.getConstant(Diff, dl, Op.getOperand(1).getValueType());
EVT VT = Op.getValueType();
return TLO.CombineTo(Op, TLO.DAG.getNode(Opc, dl, VT,
InOp.getOperand(0),
NewSA));
}
}
}
}
// Compute the new bits that are at the top now.
if (SimplifyDemandedBits(InOp, InDemandedMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known.Zero.lshrInPlace(ShAmt);
Known.One.lshrInPlace(ShAmt);
Known.Zero.setHighBits(ShAmt); // High bits known zero.
}
break;
case ISD::SRA:
// If this is an arithmetic shift right and only the low-bit is set, we can
// always convert this into a logical shr, even if the shift amount is
// variable. The low bit of the shift cannot be an input sign bit unless
// the shift amount is >= the size of the datatype, which is undefined.
if (NewMask.isOneValue())
return TLO.CombineTo(Op,
TLO.DAG.getNode(ISD::SRL, dl, Op.getValueType(),
Op.getOperand(0), Op.getOperand(1)));
if (ConstantSDNode *SA = isConstOrConstSplat(Op.getOperand(1))) {
EVT VT = Op.getValueType();
// If the shift count is an invalid immediate, don't do anything.
if (SA->getAPIntValue().uge(BitWidth))
break;
unsigned ShAmt = SA->getZExtValue();
APInt InDemandedMask = (NewMask << ShAmt);
// If the shift is exact, then it does demand the low bits (and knows that
// they are zero).
if (Op->getFlags().hasExact())
InDemandedMask.setLowBits(ShAmt);
// If any of the demanded bits are produced by the sign extension, we also
// demand the input sign bit.
if (NewMask.countLeadingZeros() < ShAmt)
InDemandedMask.setSignBit();
if (SimplifyDemandedBits(Op.getOperand(0), InDemandedMask, Known, TLO,
Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known.Zero.lshrInPlace(ShAmt);
Known.One.lshrInPlace(ShAmt);
// If the input sign bit is known to be zero, or if none of the top bits
// are demanded, turn this into an unsigned shift right.
if (Known.Zero[BitWidth - ShAmt - 1] ||
NewMask.countLeadingZeros() >= ShAmt) {
SDNodeFlags Flags;
Flags.setExact(Op->getFlags().hasExact());
return TLO.CombineTo(Op,
TLO.DAG.getNode(ISD::SRL, dl, VT, Op.getOperand(0),
Op.getOperand(1), Flags));
}
int Log2 = NewMask.exactLogBase2();
if (Log2 >= 0) {
// The bit must come from the sign.
SDValue NewSA =
TLO.DAG.getConstant(BitWidth - 1 - Log2, dl,
Op.getOperand(1).getValueType());
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SRL, dl, VT,
Op.getOperand(0), NewSA));
}
if (Known.One[BitWidth - ShAmt - 1])
// New bits are known one.
Known.One.setHighBits(ShAmt);
}
break;
case ISD::SIGN_EXTEND_INREG: {
EVT ExVT = cast<VTSDNode>(Op.getOperand(1))->getVT();
unsigned ExVTBits = ExVT.getScalarSizeInBits();
// If we only care about the highest bit, don't bother shifting right.
if (NewMask.isSignMask()) {
SDValue InOp = Op.getOperand(0);
bool AlreadySignExtended =
TLO.DAG.ComputeNumSignBits(InOp) >= BitWidth-ExVTBits+1;
// However if the input is already sign extended we expect the sign
// extension to be dropped altogether later and do not simplify.
if (!AlreadySignExtended) {
// Compute the correct shift amount type, which must be getShiftAmountTy
// for scalar types after legalization.
EVT ShiftAmtTy = Op.getValueType();
if (TLO.LegalTypes() && !ShiftAmtTy.isVector())
ShiftAmtTy = getShiftAmountTy(ShiftAmtTy, DL);
SDValue ShiftAmt = TLO.DAG.getConstant(BitWidth - ExVTBits, dl,
ShiftAmtTy);
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SHL, dl,
Op.getValueType(), InOp,
ShiftAmt));
}
}
// If none of the extended bits are demanded, eliminate the sextinreg.
if (NewMask.getActiveBits() <= ExVTBits)
return TLO.CombineTo(Op, Op.getOperand(0));
APInt InputDemandedBits = NewMask.getLoBits(ExVTBits);
// Since the sign extended bits are demanded, we know that the sign
// bit is demanded.
InputDemandedBits.setBit(ExVTBits - 1);
if (SimplifyDemandedBits(Op.getOperand(0), InputDemandedBits,
Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
// If the input sign bit is known zero, convert this into a zero extension.
if (Known.Zero[ExVTBits - 1])
return TLO.CombineTo(Op, TLO.DAG.getZeroExtendInReg(
Op.getOperand(0), dl, ExVT.getScalarType()));
APInt Mask = APInt::getLowBitsSet(BitWidth, ExVTBits);
if (Known.One[ExVTBits - 1]) { // Input sign bit known set
Known.One.setBitsFrom(ExVTBits);
Known.Zero &= Mask;
} else { // Input sign bit unknown
Known.Zero &= Mask;
Known.One &= Mask;
}
break;
}
case ISD::BUILD_PAIR: {
EVT HalfVT = Op.getOperand(0).getValueType();
unsigned HalfBitWidth = HalfVT.getScalarSizeInBits();
APInt MaskLo = NewMask.getLoBits(HalfBitWidth).trunc(HalfBitWidth);
APInt MaskHi = NewMask.getHiBits(HalfBitWidth).trunc(HalfBitWidth);
KnownBits KnownLo, KnownHi;
if (SimplifyDemandedBits(Op.getOperand(0), MaskLo, KnownLo, TLO, Depth + 1))
return true;
if (SimplifyDemandedBits(Op.getOperand(1), MaskHi, KnownHi, TLO, Depth + 1))
return true;
Known.Zero = KnownLo.Zero.zext(BitWidth) |
KnownHi.Zero.zext(BitWidth).shl(HalfBitWidth);
Known.One = KnownLo.One.zext(BitWidth) |
KnownHi.One.zext(BitWidth).shl(HalfBitWidth);
break;
}
case ISD::ZERO_EXTEND: {
unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits();
// If none of the top bits are demanded, convert this into an any_extend.
if (NewMask.getActiveBits() <= OperandBitWidth)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND, dl,
Op.getValueType(),
Op.getOperand(0)));
APInt InMask = NewMask.trunc(OperandBitWidth);
if (SimplifyDemandedBits(Op.getOperand(0), InMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known = Known.zext(BitWidth);
Known.Zero.setBitsFrom(OperandBitWidth);
break;
}
case ISD::SIGN_EXTEND: {
unsigned InBits = Op.getOperand(0).getValueType().getScalarSizeInBits();
// If none of the top bits are demanded, convert this into an any_extend.
if (NewMask.getActiveBits() <= InBits)
return TLO.CombineTo(Op,TLO.DAG.getNode(ISD::ANY_EXTEND, dl,
Op.getValueType(),
Op.getOperand(0)));
// Since some of the sign extended bits are demanded, we know that the sign
// bit is demanded.
APInt InDemandedBits = NewMask.trunc(InBits);
InDemandedBits.setBit(InBits - 1);
if (SimplifyDemandedBits(Op.getOperand(0), InDemandedBits, Known, TLO,
Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
// If the sign bit is known one, the top bits match.
Known = Known.sext(BitWidth);
// If the sign bit is known zero, convert this to a zero extend.
if (Known.isNonNegative())
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ZERO_EXTEND, dl,
Op.getValueType(),
Op.getOperand(0)));
break;
}
case ISD::ANY_EXTEND: {
unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits();
APInt InMask = NewMask.trunc(OperandBitWidth);
if (SimplifyDemandedBits(Op.getOperand(0), InMask, Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known = Known.zext(BitWidth);
break;
}
case ISD::TRUNCATE: {
// Simplify the input, using demanded bit information, and compute the known
// zero/one bits live out.
unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits();
APInt TruncMask = NewMask.zext(OperandBitWidth);
if (SimplifyDemandedBits(Op.getOperand(0), TruncMask, Known, TLO, Depth+1))
return true;
Known = Known.trunc(BitWidth);
// If the input is only used by this truncate, see if we can shrink it based
// on the known demanded bits.
if (Op.getOperand(0).getNode()->hasOneUse()) {
SDValue In = Op.getOperand(0);
switch (In.getOpcode()) {
default: break;
case ISD::SRL:
// Shrink SRL by a constant if none of the high bits shifted in are
// demanded.
if (TLO.LegalTypes() &&
!isTypeDesirableForOp(ISD::SRL, Op.getValueType()))
// Do not turn (vt1 truncate (vt2 srl)) into (vt1 srl) if vt1 is
// undesirable.
break;
ConstantSDNode *ShAmt = dyn_cast<ConstantSDNode>(In.getOperand(1));
if (!ShAmt)
break;
SDValue Shift = In.getOperand(1);
if (TLO.LegalTypes()) {
uint64_t ShVal = ShAmt->getZExtValue();
Shift = TLO.DAG.getConstant(ShVal, dl,
getShiftAmountTy(Op.getValueType(), DL));
}
if (ShAmt->getZExtValue() < BitWidth) {
APInt HighBits = APInt::getHighBitsSet(OperandBitWidth,
OperandBitWidth - BitWidth);
HighBits.lshrInPlace(ShAmt->getZExtValue());
HighBits = HighBits.trunc(BitWidth);
if (!(HighBits & NewMask)) {
// None of the shifted in bits are needed. Add a truncate of the
// shift input, then shift it.
SDValue NewTrunc = TLO.DAG.getNode(ISD::TRUNCATE, dl,
Op.getValueType(),
In.getOperand(0));
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SRL, dl,
Op.getValueType(),
NewTrunc,
Shift));
}
}
break;
}
}
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
break;
}
case ISD::AssertZext: {
// AssertZext demands all of the high bits, plus any of the low bits
// demanded by its users.
EVT VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
APInt InMask = APInt::getLowBitsSet(BitWidth,
VT.getSizeInBits());
if (SimplifyDemandedBits(Op.getOperand(0), ~InMask | NewMask,
Known, TLO, Depth+1))
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known.Zero |= ~InMask;
break;
}
case ISD::BITCAST:
// If this is an FP->Int bitcast and if the sign bit is the only
// thing demanded, turn this into a FGETSIGN.
if (!TLO.LegalOperations() &&
!Op.getValueType().isVector() &&
!Op.getOperand(0).getValueType().isVector() &&
NewMask == APInt::getSignMask(Op.getValueSizeInBits()) &&
Op.getOperand(0).getValueType().isFloatingPoint()) {
bool OpVTLegal = isOperationLegalOrCustom(ISD::FGETSIGN, Op.getValueType());
bool i32Legal = isOperationLegalOrCustom(ISD::FGETSIGN, MVT::i32);
if ((OpVTLegal || i32Legal) && Op.getValueType().isSimple() &&
Op.getOperand(0).getValueType() != MVT::f128) {
// Cannot eliminate/lower SHL for f128 yet.
EVT Ty = OpVTLegal ? Op.getValueType() : MVT::i32;
// Make a FGETSIGN + SHL to move the sign bit into the appropriate
// place. We expect the SHL to be eliminated by other optimizations.
SDValue Sign = TLO.DAG.getNode(ISD::FGETSIGN, dl, Ty, Op.getOperand(0));
unsigned OpVTSizeInBits = Op.getValueSizeInBits();
if (!OpVTLegal && OpVTSizeInBits > 32)
Sign = TLO.DAG.getNode(ISD::ZERO_EXTEND, dl, Op.getValueType(), Sign);
unsigned ShVal = Op.getValueSizeInBits() - 1;
SDValue ShAmt = TLO.DAG.getConstant(ShVal, dl, Op.getValueType());
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SHL, dl,
Op.getValueType(),
Sign, ShAmt));
}
}
break;
case ISD::ADD:
case ISD::MUL:
case ISD::SUB: {
// Add, Sub, and Mul don't demand any bits in positions beyond that
// of the highest bit demanded of them.
APInt LoMask = APInt::getLowBitsSet(BitWidth,
BitWidth - NewMask.countLeadingZeros());
if (SimplifyDemandedBits(Op.getOperand(0), LoMask, Known2, TLO, Depth+1) ||
SimplifyDemandedBits(Op.getOperand(1), LoMask, Known2, TLO, Depth+1) ||
// See if the operation should be performed at a smaller bit width.
ShrinkDemandedOp(Op, BitWidth, NewMask, TLO)) {
SDNodeFlags Flags = Op.getNode()->getFlags();
if (Flags.hasNoSignedWrap() || Flags.hasNoUnsignedWrap()) {
// Disable the nsw and nuw flags. We can no longer guarantee that we
// won't wrap after simplification.
Flags.setNoSignedWrap(false);
Flags.setNoUnsignedWrap(false);
SDValue NewOp = TLO.DAG.getNode(Op.getOpcode(), dl, Op.getValueType(),
Op.getOperand(0), Op.getOperand(1),
Flags);
return TLO.CombineTo(Op, NewOp);
}
return true;
}
LLVM_FALLTHROUGH;
}
default:
// Just use computeKnownBits to compute output bits.
TLO.DAG.computeKnownBits(Op, Known, Depth);
break;
}
// If we know the value of all of the demanded bits, return this as a
// constant.
if (NewMask.isSubsetOf(Known.Zero|Known.One)) {
// Avoid folding to a constant if any OpaqueConstant is involved.
const SDNode *N = Op.getNode();
for (SDNodeIterator I = SDNodeIterator::begin(N),
E = SDNodeIterator::end(N); I != E; ++I) {
SDNode *Op = *I;
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op))
if (C->isOpaque())
return false;
}
return TLO.CombineTo(Op,
TLO.DAG.getConstant(Known.One, dl, Op.getValueType()));
}
return false;
}
/// Determine which of the bits specified in Mask are known to be either zero or
/// one and return them in the Known.
void TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
KnownBits &Known,
const APInt &DemandedElts,
const SelectionDAG &DAG,
unsigned Depth) const {
assert((Op.getOpcode() >= ISD::BUILTIN_OP_END ||
Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN ||
Op.getOpcode() == ISD::INTRINSIC_W_CHAIN ||
Op.getOpcode() == ISD::INTRINSIC_VOID) &&
"Should use MaskedValueIsZero if you don't know whether Op"
" is a target node!");
Known.resetAll();
}
/// This method can be implemented by targets that want to expose additional
/// information about sign bits to the DAG Combiner.
unsigned TargetLowering::ComputeNumSignBitsForTargetNode(SDValue Op,
const APInt &,
const SelectionDAG &,
unsigned Depth) const {
assert((Op.getOpcode() >= ISD::BUILTIN_OP_END ||
Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN ||
Op.getOpcode() == ISD::INTRINSIC_W_CHAIN ||
Op.getOpcode() == ISD::INTRINSIC_VOID) &&
"Should use ComputeNumSignBits if you don't know whether Op"
" is a target node!");
return 1;
}
// FIXME: Ideally, this would use ISD::isConstantSplatVector(), but that must
// work with truncating build vectors and vectors with elements of less than
// 8 bits.
bool TargetLowering::isConstTrueVal(const SDNode *N) const {
if (!N)
return false;
APInt CVal;
if (auto *CN = dyn_cast<ConstantSDNode>(N)) {
CVal = CN->getAPIntValue();
} else if (auto *BV = dyn_cast<BuildVectorSDNode>(N)) {
auto *CN = BV->getConstantSplatNode();
if (!CN)
return false;
// If this is a truncating build vector, truncate the splat value.
// Otherwise, we may fail to match the expected values below.
unsigned BVEltWidth = BV->getValueType(0).getScalarSizeInBits();
CVal = CN->getAPIntValue();
if (BVEltWidth < CVal.getBitWidth())
CVal = CVal.trunc(BVEltWidth);
} else {
return false;
}
switch (getBooleanContents(N->getValueType(0))) {
case UndefinedBooleanContent:
return CVal[0];
case ZeroOrOneBooleanContent:
return CVal.isOneValue();
case ZeroOrNegativeOneBooleanContent:
return CVal.isAllOnesValue();
}
llvm_unreachable("Invalid boolean contents");
}
SDValue TargetLowering::getConstTrueVal(SelectionDAG &DAG, EVT VT,
const SDLoc &DL) const {
unsigned ElementWidth = VT.getScalarSizeInBits();
APInt TrueInt =
getBooleanContents(VT) == TargetLowering::ZeroOrOneBooleanContent
? APInt(ElementWidth, 1)
: APInt::getAllOnesValue(ElementWidth);
return DAG.getConstant(TrueInt, DL, VT);
}
bool TargetLowering::isConstFalseVal(const SDNode *N) const {
if (!N)
return false;
const ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N);
if (!CN) {
const BuildVectorSDNode *BV = dyn_cast<BuildVectorSDNode>(N);
if (!BV)
return false;
// Only interested in constant splats, we don't care about undef
// elements in identifying boolean constants and getConstantSplatNode
// returns NULL if all ops are undef;
CN = BV->getConstantSplatNode();
if (!CN)
return false;
}
if (getBooleanContents(N->getValueType(0)) == UndefinedBooleanContent)
return !CN->getAPIntValue()[0];
return CN->isNullValue();
}
bool TargetLowering::isExtendedTrueVal(const ConstantSDNode *N, EVT VT,
bool SExt) const {
if (VT == MVT::i1)
return N->isOne();
TargetLowering::BooleanContent Cnt = getBooleanContents(VT);
switch (Cnt) {
case TargetLowering::ZeroOrOneBooleanContent:
// An extended value of 1 is always true, unless its original type is i1,
// in which case it will be sign extended to -1.
return (N->isOne() && !SExt) || (SExt && (N->getValueType(0) != MVT::i1));
case TargetLowering::UndefinedBooleanContent:
case TargetLowering::ZeroOrNegativeOneBooleanContent:
return N->isAllOnesValue() && SExt;
}
llvm_unreachable("Unexpected enumeration.");
}
/// This helper function of SimplifySetCC tries to optimize the comparison when
/// either operand of the SetCC node is a bitwise-and instruction.
SDValue TargetLowering::simplifySetCCWithAnd(EVT VT, SDValue N0, SDValue N1,
ISD::CondCode Cond,
DAGCombinerInfo &DCI,
const SDLoc &DL) const {
// Match these patterns in any of their permutations:
// (X & Y) == Y
// (X & Y) != Y
if (N1.getOpcode() == ISD::AND && N0.getOpcode() != ISD::AND)
std::swap(N0, N1);
EVT OpVT = N0.getValueType();
if (N0.getOpcode() != ISD::AND || !OpVT.isInteger() ||
(Cond != ISD::SETEQ && Cond != ISD::SETNE))
return SDValue();
SDValue X, Y;
if (N0.getOperand(0) == N1) {
X = N0.getOperand(1);
Y = N0.getOperand(0);
} else if (N0.getOperand(1) == N1) {
X = N0.getOperand(0);
Y = N0.getOperand(1);
} else {
return SDValue();
}
SelectionDAG &DAG = DCI.DAG;
SDValue Zero = DAG.getConstant(0, DL, OpVT);
if (DAG.isKnownToBeAPowerOfTwo(Y)) {
// Simplify X & Y == Y to X & Y != 0 if Y has exactly one bit set.
// Note that where Y is variable and is known to have at most one bit set
// (for example, if it is Z & 1) we cannot do this; the expressions are not
// equivalent when Y == 0.
Cond = ISD::getSetCCInverse(Cond, /*isInteger=*/true);
if (DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(Cond, N0.getSimpleValueType()))
return DAG.getSetCC(DL, VT, N0, Zero, Cond);
} else if (N0.hasOneUse() && hasAndNotCompare(Y)) {
// If the target supports an 'and-not' or 'and-complement' logic operation,
// try to use that to make a comparison operation more efficient.
// But don't do this transform if the mask is a single bit because there are
// more efficient ways to deal with that case (for example, 'bt' on x86 or
// 'rlwinm' on PPC).
// Bail out if the compare operand that we want to turn into a zero is
// already a zero (otherwise, infinite loop).
auto *YConst = dyn_cast<ConstantSDNode>(Y);
if (YConst && YConst->isNullValue())
return SDValue();
// Transform this into: ~X & Y == 0.
SDValue NotX = DAG.getNOT(SDLoc(X), X, OpVT);
SDValue NewAnd = DAG.getNode(ISD::AND, SDLoc(N0), OpVT, NotX, Y);
return DAG.getSetCC(DL, VT, NewAnd, Zero, Cond);
}
return SDValue();
}
/// Try to simplify a setcc built with the specified operands and cc. If it is
/// unable to simplify it, return a null SDValue.
SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
ISD::CondCode Cond, bool foldBooleans,
DAGCombinerInfo &DCI,
const SDLoc &dl) const {
SelectionDAG &DAG = DCI.DAG;
// These setcc operations always fold.
switch (Cond) {
default: break;
case ISD::SETFALSE:
case ISD::SETFALSE2: return DAG.getConstant(0, dl, VT);
case ISD::SETTRUE:
case ISD::SETTRUE2: {
TargetLowering::BooleanContent Cnt =
getBooleanContents(N0->getValueType(0));
return DAG.getConstant(
Cnt == TargetLowering::ZeroOrNegativeOneBooleanContent ? -1ULL : 1, dl,
VT);
}
}
// Ensure that the constant occurs on the RHS and fold constant comparisons.
ISD::CondCode SwappedCC = ISD::getSetCCSwappedOperands(Cond);
if (isa<ConstantSDNode>(N0.getNode()) &&
(DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(SwappedCC, N0.getSimpleValueType())))
return DAG.getSetCC(dl, VT, N1, N0, SwappedCC);
if (auto *N1C = dyn_cast<ConstantSDNode>(N1.getNode())) {
const APInt &C1 = N1C->getAPIntValue();
// If the LHS is '(srl (ctlz x), 5)', the RHS is 0/1, and this is an
// equality comparison, then we're just comparing whether X itself is
// zero.
if (N0.getOpcode() == ISD::SRL && (C1.isNullValue() || C1.isOneValue()) &&
N0.getOperand(0).getOpcode() == ISD::CTLZ &&
N0.getOperand(1).getOpcode() == ISD::Constant) {
const APInt &ShAmt
= cast<ConstantSDNode>(N0.getOperand(1))->getAPIntValue();
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
ShAmt == Log2_32(N0.getValueSizeInBits())) {
if ((C1 == 0) == (Cond == ISD::SETEQ)) {
// (srl (ctlz x), 5) == 0 -> X != 0
// (srl (ctlz x), 5) != 1 -> X != 0
Cond = ISD::SETNE;
} else {
// (srl (ctlz x), 5) != 0 -> X == 0
// (srl (ctlz x), 5) == 1 -> X == 0
Cond = ISD::SETEQ;
}
SDValue Zero = DAG.getConstant(0, dl, N0.getValueType());
return DAG.getSetCC(dl, VT, N0.getOperand(0).getOperand(0),
Zero, Cond);
}
}
SDValue CTPOP = N0;
// Look through truncs that don't change the value of a ctpop.
if (N0.hasOneUse() && N0.getOpcode() == ISD::TRUNCATE)
CTPOP = N0.getOperand(0);
if (CTPOP.hasOneUse() && CTPOP.getOpcode() == ISD::CTPOP &&
(N0 == CTPOP ||
N0.getValueSizeInBits() > Log2_32_Ceil(CTPOP.getValueSizeInBits()))) {
EVT CTVT = CTPOP.getValueType();
SDValue CTOp = CTPOP.getOperand(0);
// (ctpop x) u< 2 -> (x & x-1) == 0
// (ctpop x) u> 1 -> (x & x-1) != 0
if ((Cond == ISD::SETULT && C1 == 2) || (Cond == ISD::SETUGT && C1 == 1)){
SDValue Sub = DAG.getNode(ISD::SUB, dl, CTVT, CTOp,
DAG.getConstant(1, dl, CTVT));
SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Sub);
ISD::CondCode CC = Cond == ISD::SETULT ? ISD::SETEQ : ISD::SETNE;
return DAG.getSetCC(dl, VT, And, DAG.getConstant(0, dl, CTVT), CC);
}
// TODO: (ctpop x) == 1 -> x && (x & x-1) == 0 iff ctpop is illegal.
}
// (zext x) == C --> x == (trunc C)
// (sext x) == C --> x == (trunc C)
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
DCI.isBeforeLegalize() && N0->hasOneUse()) {
unsigned MinBits = N0.getValueSizeInBits();
SDValue PreExt;
bool Signed = false;
if (N0->getOpcode() == ISD::ZERO_EXTEND) {
// ZExt
MinBits = N0->getOperand(0).getValueSizeInBits();
PreExt = N0->getOperand(0);
} else if (N0->getOpcode() == ISD::AND) {
// DAGCombine turns costly ZExts into ANDs
if (auto *C = dyn_cast<ConstantSDNode>(N0->getOperand(1)))
if ((C->getAPIntValue()+1).isPowerOf2()) {
MinBits = C->getAPIntValue().countTrailingOnes();
PreExt = N0->getOperand(0);
}
} else if (N0->getOpcode() == ISD::SIGN_EXTEND) {
// SExt
MinBits = N0->getOperand(0).getValueSizeInBits();
PreExt = N0->getOperand(0);
Signed = true;
} else if (auto *LN0 = dyn_cast<LoadSDNode>(N0)) {
// ZEXTLOAD / SEXTLOAD
if (LN0->getExtensionType() == ISD::ZEXTLOAD) {
MinBits = LN0->getMemoryVT().getSizeInBits();
PreExt = N0;
} else if (LN0->getExtensionType() == ISD::SEXTLOAD) {
Signed = true;
MinBits = LN0->getMemoryVT().getSizeInBits();
PreExt = N0;
}
}
// Figure out how many bits we need to preserve this constant.
unsigned ReqdBits = Signed ?
C1.getBitWidth() - C1.getNumSignBits() + 1 :
C1.getActiveBits();
// Make sure we're not losing bits from the constant.
if (MinBits > 0 &&
MinBits < C1.getBitWidth() &&
MinBits >= ReqdBits) {
EVT MinVT = EVT::getIntegerVT(*DAG.getContext(), MinBits);
if (isTypeDesirableForOp(ISD::SETCC, MinVT)) {
// Will get folded away.
SDValue Trunc = DAG.getNode(ISD::TRUNCATE, dl, MinVT, PreExt);
if (MinBits == 1 && C1 == 1)
// Invert the condition.
return DAG.getSetCC(dl, VT, Trunc, DAG.getConstant(0, dl, MVT::i1),
Cond == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ);
SDValue C = DAG.getConstant(C1.trunc(MinBits), dl, MinVT);
return DAG.getSetCC(dl, VT, Trunc, C, Cond);
}
// If truncating the setcc operands is not desirable, we can still
// simplify the expression in some cases:
// setcc ([sz]ext (setcc x, y, cc)), 0, setne) -> setcc (x, y, cc)
// setcc ([sz]ext (setcc x, y, cc)), 0, seteq) -> setcc (x, y, inv(cc))
// setcc (zext (setcc x, y, cc)), 1, setne) -> setcc (x, y, inv(cc))
// setcc (zext (setcc x, y, cc)), 1, seteq) -> setcc (x, y, cc)
// setcc (sext (setcc x, y, cc)), -1, setne) -> setcc (x, y, inv(cc))
// setcc (sext (setcc x, y, cc)), -1, seteq) -> setcc (x, y, cc)
SDValue TopSetCC = N0->getOperand(0);
unsigned N0Opc = N0->getOpcode();
bool SExt = (N0Opc == ISD::SIGN_EXTEND);
if (TopSetCC.getValueType() == MVT::i1 && VT == MVT::i1 &&
TopSetCC.getOpcode() == ISD::SETCC &&
(N0Opc == ISD::ZERO_EXTEND || N0Opc == ISD::SIGN_EXTEND) &&
(isConstFalseVal(N1C) ||
isExtendedTrueVal(N1C, N0->getValueType(0), SExt))) {
bool Inverse = (N1C->isNullValue() && Cond == ISD::SETEQ) ||
(!N1C->isNullValue() && Cond == ISD::SETNE);
if (!Inverse)
return TopSetCC;
ISD::CondCode InvCond = ISD::getSetCCInverse(
cast<CondCodeSDNode>(TopSetCC.getOperand(2))->get(),
TopSetCC.getOperand(0).getValueType().isInteger());
return DAG.getSetCC(dl, VT, TopSetCC.getOperand(0),
TopSetCC.getOperand(1),
InvCond);
}
}
}
// If the LHS is '(and load, const)', the RHS is 0, the test is for
// equality or unsigned, and all 1 bits of the const are in the same
// partial word, see if we can shorten the load.
if (DCI.isBeforeLegalize() &&
!ISD::isSignedIntSetCC(Cond) &&
N0.getOpcode() == ISD::AND && C1 == 0 &&
N0.getNode()->hasOneUse() &&
isa<LoadSDNode>(N0.getOperand(0)) &&
N0.getOperand(0).getNode()->hasOneUse() &&
isa<ConstantSDNode>(N0.getOperand(1))) {
LoadSDNode *Lod = cast<LoadSDNode>(N0.getOperand(0));
APInt bestMask;
unsigned bestWidth = 0, bestOffset = 0;
if (!Lod->isVolatile() && Lod->isUnindexed()) {
unsigned origWidth = N0.getValueSizeInBits();
unsigned maskWidth = origWidth;
// We can narrow (e.g.) 16-bit extending loads on 32-bit target to
// 8 bits, but have to be careful...
if (Lod->getExtensionType() != ISD::NON_EXTLOAD)
origWidth = Lod->getMemoryVT().getSizeInBits();
const APInt &Mask =
cast<ConstantSDNode>(N0.getOperand(1))->getAPIntValue();
for (unsigned width = origWidth / 2; width>=8; width /= 2) {
APInt newMask = APInt::getLowBitsSet(maskWidth, width);
for (unsigned offset=0; offset<origWidth/width; offset++) {
if (Mask.isSubsetOf(newMask)) {
if (DAG.getDataLayout().isLittleEndian())
bestOffset = (uint64_t)offset * (width/8);
else
bestOffset = (origWidth/width - offset - 1) * (width/8);
bestMask = Mask.lshr(offset * (width/8) * 8);
bestWidth = width;
break;
}
newMask <<= width;
}
}
}
if (bestWidth) {
EVT newVT = EVT::getIntegerVT(*DAG.getContext(), bestWidth);
if (newVT.isRound()) {
EVT PtrType = Lod->getOperand(1).getValueType();
SDValue Ptr = Lod->getBasePtr();
if (bestOffset != 0)
Ptr = DAG.getNode(ISD::ADD, dl, PtrType, Lod->getBasePtr(),
DAG.getConstant(bestOffset, dl, PtrType));
unsigned NewAlign = MinAlign(Lod->getAlignment(), bestOffset);
SDValue NewLoad = DAG.getLoad(
newVT, dl, Lod->getChain(), Ptr,
Lod->getPointerInfo().getWithOffset(bestOffset), NewAlign);
return DAG.getSetCC(dl, VT,
DAG.getNode(ISD::AND, dl, newVT, NewLoad,
DAG.getConstant(bestMask.trunc(bestWidth),
dl, newVT)),
DAG.getConstant(0LL, dl, newVT), Cond);
}
}
}
// If the LHS is a ZERO_EXTEND, perform the comparison on the input.
if (N0.getOpcode() == ISD::ZERO_EXTEND) {
unsigned InSize = N0.getOperand(0).getValueSizeInBits();
// If the comparison constant has bits in the upper part, the
// zero-extended value could never match.
if (C1.intersects(APInt::getHighBitsSet(C1.getBitWidth(),
C1.getBitWidth() - InSize))) {
switch (Cond) {
case ISD::SETUGT:
case ISD::SETUGE:
case ISD::SETEQ:
return DAG.getConstant(0, dl, VT);
case ISD::SETULT:
case ISD::SETULE:
case ISD::SETNE:
return DAG.getConstant(1, dl, VT);
case ISD::SETGT:
case ISD::SETGE:
// True if the sign bit of C1 is set.
return DAG.getConstant(C1.isNegative(), dl, VT);
case ISD::SETLT:
case ISD::SETLE:
// True if the sign bit of C1 isn't set.
return DAG.getConstant(C1.isNonNegative(), dl, VT);
default:
break;
}
}
// Otherwise, we can perform the comparison with the low bits.
switch (Cond) {
case ISD::SETEQ:
case ISD::SETNE:
case ISD::SETUGT:
case ISD::SETUGE:
case ISD::SETULT:
case ISD::SETULE: {
EVT newVT = N0.getOperand(0).getValueType();
if (DCI.isBeforeLegalizeOps() ||
(isOperationLegal(ISD::SETCC, newVT) &&
getCondCodeAction(Cond, newVT.getSimpleVT()) == Legal)) {
EVT NewSetCCVT =
getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), newVT);
SDValue NewConst = DAG.getConstant(C1.trunc(InSize), dl, newVT);
SDValue NewSetCC = DAG.getSetCC(dl, NewSetCCVT, N0.getOperand(0),
NewConst, Cond);
return DAG.getBoolExtOrTrunc(NewSetCC, dl, VT, N0.getValueType());
}
break;
}
default:
break; // todo, be more careful with signed comparisons
}
} else if (N0.getOpcode() == ISD::SIGN_EXTEND_INREG &&
(Cond == ISD::SETEQ || Cond == ISD::SETNE)) {
EVT ExtSrcTy = cast<VTSDNode>(N0.getOperand(1))->getVT();
unsigned ExtSrcTyBits = ExtSrcTy.getSizeInBits();
EVT ExtDstTy = N0.getValueType();
unsigned ExtDstTyBits = ExtDstTy.getSizeInBits();
// If the constant doesn't fit into the number of bits for the source of
// the sign extension, it is impossible for both sides to be equal.
if (C1.getMinSignedBits() > ExtSrcTyBits)
return DAG.getConstant(Cond == ISD::SETNE, dl, VT);
SDValue ZextOp;
EVT Op0Ty = N0.getOperand(0).getValueType();
if (Op0Ty == ExtSrcTy) {
ZextOp = N0.getOperand(0);
} else {
APInt Imm = APInt::getLowBitsSet(ExtDstTyBits, ExtSrcTyBits);
ZextOp = DAG.getNode(ISD::AND, dl, Op0Ty, N0.getOperand(0),
DAG.getConstant(Imm, dl, Op0Ty));
}
if (!DCI.isCalledByLegalizer())
DCI.AddToWorklist(ZextOp.getNode());
// Otherwise, make this a use of a zext.
return DAG.getSetCC(dl, VT, ZextOp,
DAG.getConstant(C1 & APInt::getLowBitsSet(
ExtDstTyBits,
ExtSrcTyBits),
dl, ExtDstTy),
Cond);
} else if ((N1C->isNullValue() || N1C->isOne()) &&
(Cond == ISD::SETEQ || Cond == ISD::SETNE)) {
// SETCC (SETCC), [0|1], [EQ|NE] -> SETCC
if (N0.getOpcode() == ISD::SETCC &&
isTypeLegal(VT) && VT.bitsLE(N0.getValueType())) {
bool TrueWhenTrue = (Cond == ISD::SETEQ) ^ (!N1C->isOne());
if (TrueWhenTrue)
return DAG.getNode(ISD::TRUNCATE, dl, VT, N0);
// Invert the condition.
ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
CC = ISD::getSetCCInverse(CC,
N0.getOperand(0).getValueType().isInteger());
if (DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(CC, N0.getOperand(0).getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0.getOperand(0), N0.getOperand(1), CC);
}
if ((N0.getOpcode() == ISD::XOR ||
(N0.getOpcode() == ISD::AND &&
N0.getOperand(0).getOpcode() == ISD::XOR &&
N0.getOperand(1) == N0.getOperand(0).getOperand(1))) &&
isa<ConstantSDNode>(N0.getOperand(1)) &&
cast<ConstantSDNode>(N0.getOperand(1))->isOne()) {
// If this is (X^1) == 0/1, swap the RHS and eliminate the xor. We
// can only do this if the top bits are known zero.
unsigned BitWidth = N0.getValueSizeInBits();
if (DAG.MaskedValueIsZero(N0,
APInt::getHighBitsSet(BitWidth,
BitWidth-1))) {
// Okay, get the un-inverted input value.
SDValue Val;
if (N0.getOpcode() == ISD::XOR) {
Val = N0.getOperand(0);
} else {
assert(N0.getOpcode() == ISD::AND &&
N0.getOperand(0).getOpcode() == ISD::XOR);
// ((X^1)&1)^1 -> X & 1
Val = DAG.getNode(ISD::AND, dl, N0.getValueType(),
N0.getOperand(0).getOperand(0),
N0.getOperand(1));
}
return DAG.getSetCC(dl, VT, Val, N1,
Cond == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ);
}
} else if (N1C->isOne() &&
(VT == MVT::i1 ||
getBooleanContents(N0->getValueType(0)) ==
ZeroOrOneBooleanContent)) {
SDValue Op0 = N0;
if (Op0.getOpcode() == ISD::TRUNCATE)
Op0 = Op0.getOperand(0);
if ((Op0.getOpcode() == ISD::XOR) &&
Op0.getOperand(0).getOpcode() == ISD::SETCC &&
Op0.getOperand(1).getOpcode() == ISD::SETCC) {
// (xor (setcc), (setcc)) == / != 1 -> (setcc) != / == (setcc)
Cond = (Cond == ISD::SETEQ) ? ISD::SETNE : ISD::SETEQ;
return DAG.getSetCC(dl, VT, Op0.getOperand(0), Op0.getOperand(1),
Cond);
}
if (Op0.getOpcode() == ISD::AND &&
isa<ConstantSDNode>(Op0.getOperand(1)) &&
cast<ConstantSDNode>(Op0.getOperand(1))->isOne()) {
// If this is (X&1) == / != 1, normalize it to (X&1) != / == 0.
if (Op0.getValueType().bitsGT(VT))
Op0 = DAG.getNode(ISD::AND, dl, VT,
DAG.getNode(ISD::TRUNCATE, dl, VT, Op0.getOperand(0)),
DAG.getConstant(1, dl, VT));
else if (Op0.getValueType().bitsLT(VT))
Op0 = DAG.getNode(ISD::AND, dl, VT,
DAG.getNode(ISD::ANY_EXTEND, dl, VT, Op0.getOperand(0)),
DAG.getConstant(1, dl, VT));
return DAG.getSetCC(dl, VT, Op0,
DAG.getConstant(0, dl, Op0.getValueType()),
Cond == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ);
}
if (Op0.getOpcode() == ISD::AssertZext &&
cast<VTSDNode>(Op0.getOperand(1))->getVT() == MVT::i1)
return DAG.getSetCC(dl, VT, Op0,
DAG.getConstant(0, dl, Op0.getValueType()),
Cond == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ);
}
}
APInt MinVal, MaxVal;
unsigned OperandBitSize = N1C->getValueType(0).getSizeInBits();
if (ISD::isSignedIntSetCC(Cond)) {
MinVal = APInt::getSignedMinValue(OperandBitSize);
MaxVal = APInt::getSignedMaxValue(OperandBitSize);
} else {
MinVal = APInt::getMinValue(OperandBitSize);
MaxVal = APInt::getMaxValue(OperandBitSize);
}
// Canonicalize GE/LE comparisons to use GT/LT comparisons.
if (Cond == ISD::SETGE || Cond == ISD::SETUGE) {
// X >= MIN --> true
if (C1 == MinVal)
return DAG.getConstant(1, dl, VT);
// X >= C0 --> X > (C0 - 1)
APInt C = C1 - 1;
ISD::CondCode NewCC = (Cond == ISD::SETGE) ? ISD::SETGT : ISD::SETUGT;
if ((DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(NewCC, VT.getSimpleVT())) &&
(!N1C->isOpaque() || (N1C->isOpaque() && C.getBitWidth() <= 64 &&
isLegalICmpImmediate(C.getSExtValue())))) {
return DAG.getSetCC(dl, VT, N0,
DAG.getConstant(C, dl, N1.getValueType()),
NewCC);
}
}
if (Cond == ISD::SETLE || Cond == ISD::SETULE) {
// X <= MAX --> true
if (C1 == MaxVal)
return DAG.getConstant(1, dl, VT);
// X <= C0 --> X < (C0 + 1)
APInt C = C1 + 1;
ISD::CondCode NewCC = (Cond == ISD::SETLE) ? ISD::SETLT : ISD::SETULT;
if ((DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(NewCC, VT.getSimpleVT())) &&
(!N1C->isOpaque() || (N1C->isOpaque() && C.getBitWidth() <= 64 &&
isLegalICmpImmediate(C.getSExtValue())))) {
return DAG.getSetCC(dl, VT, N0,
DAG.getConstant(C, dl, N1.getValueType()),
NewCC);
}
}
if ((Cond == ISD::SETLT || Cond == ISD::SETULT) && C1 == MinVal)
return DAG.getConstant(0, dl, VT); // X < MIN --> false
if ((Cond == ISD::SETGE || Cond == ISD::SETUGE) && C1 == MinVal)
return DAG.getConstant(1, dl, VT); // X >= MIN --> true
if ((Cond == ISD::SETGT || Cond == ISD::SETUGT) && C1 == MaxVal)
return DAG.getConstant(0, dl, VT); // X > MAX --> false
if ((Cond == ISD::SETLE || Cond == ISD::SETULE) && C1 == MaxVal)
return DAG.getConstant(1, dl, VT); // X <= MAX --> true
// Canonicalize setgt X, Min --> setne X, Min
if ((Cond == ISD::SETGT || Cond == ISD::SETUGT) && C1 == MinVal)
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETNE);
// Canonicalize setlt X, Max --> setne X, Max
if ((Cond == ISD::SETLT || Cond == ISD::SETULT) && C1 == MaxVal)
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETNE);
// If we have setult X, 1, turn it into seteq X, 0
if ((Cond == ISD::SETLT || Cond == ISD::SETULT) && C1 == MinVal+1)
return DAG.getSetCC(dl, VT, N0,
DAG.getConstant(MinVal, dl, N0.getValueType()),
ISD::SETEQ);
// If we have setugt X, Max-1, turn it into seteq X, Max
if ((Cond == ISD::SETGT || Cond == ISD::SETUGT) && C1 == MaxVal-1)
return DAG.getSetCC(dl, VT, N0,
DAG.getConstant(MaxVal, dl, N0.getValueType()),
ISD::SETEQ);
// If we have "setcc X, C0", check to see if we can shrink the immediate
// by changing cc.
// SETUGT X, SINTMAX -> SETLT X, 0
if (Cond == ISD::SETUGT &&
C1 == APInt::getSignedMaxValue(OperandBitSize))
return DAG.getSetCC(dl, VT, N0,
DAG.getConstant(0, dl, N1.getValueType()),
ISD::SETLT);
// SETULT X, SINTMIN -> SETGT X, -1
if (Cond == ISD::SETULT &&
C1 == APInt::getSignedMinValue(OperandBitSize)) {
SDValue ConstMinusOne =
DAG.getConstant(APInt::getAllOnesValue(OperandBitSize), dl,
N1.getValueType());
return DAG.getSetCC(dl, VT, N0, ConstMinusOne, ISD::SETGT);
}
// Fold bit comparisons when we can.
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
(VT == N0.getValueType() ||
(isTypeLegal(VT) && VT.bitsLE(N0.getValueType()))) &&
N0.getOpcode() == ISD::AND) {
auto &DL = DAG.getDataLayout();
if (auto *AndRHS = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
if (Cond == ISD::SETNE && C1 == 0) {// (X & 8) != 0 --> (X & 8) >> 3
// Perform the xform if the AND RHS is a single bit.
if (AndRHS->getAPIntValue().isPowerOf2()) {
return DAG.getNode(ISD::TRUNCATE, dl, VT,
DAG.getNode(ISD::SRL, dl, N0.getValueType(), N0,
DAG.getConstant(AndRHS->getAPIntValue().logBase2(), dl,
ShiftTy)));
}
} else if (Cond == ISD::SETEQ && C1 == AndRHS->getAPIntValue()) {
// (X & 8) == 8 --> (X & 8) >> 3
// Perform the xform if C1 is a single bit.
if (C1.isPowerOf2()) {
return DAG.getNode(ISD::TRUNCATE, dl, VT,
DAG.getNode(ISD::SRL, dl, N0.getValueType(), N0,
DAG.getConstant(C1.logBase2(), dl,
ShiftTy)));
}
}
}
}
if (C1.getMinSignedBits() <= 64 &&
!isLegalICmpImmediate(C1.getSExtValue())) {
// (X & -256) == 256 -> (X >> 8) == 1
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
N0.getOpcode() == ISD::AND && N0.hasOneUse()) {
if (auto *AndRHS = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
const APInt &AndRHSC = AndRHS->getAPIntValue();
if ((-AndRHSC).isPowerOf2() && (AndRHSC & C1) == C1) {
unsigned ShiftBits = AndRHSC.countTrailingZeros();
auto &DL = DAG.getDataLayout();
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
EVT CmpTy = N0.getValueType();
SDValue Shift = DAG.getNode(ISD::SRL, dl, CmpTy, N0.getOperand(0),
DAG.getConstant(ShiftBits, dl,
ShiftTy));
SDValue CmpRHS = DAG.getConstant(C1.lshr(ShiftBits), dl, CmpTy);
return DAG.getSetCC(dl, VT, Shift, CmpRHS, Cond);
}
}
} else if (Cond == ISD::SETULT || Cond == ISD::SETUGE ||
Cond == ISD::SETULE || Cond == ISD::SETUGT) {
bool AdjOne = (Cond == ISD::SETULE || Cond == ISD::SETUGT);
// X < 0x100000000 -> (X >> 32) < 1
// X >= 0x100000000 -> (X >> 32) >= 1
// X <= 0x0ffffffff -> (X >> 32) < 1
// X > 0x0ffffffff -> (X >> 32) >= 1
unsigned ShiftBits;
APInt NewC = C1;
ISD::CondCode NewCond = Cond;
if (AdjOne) {
ShiftBits = C1.countTrailingOnes();
NewC = NewC + 1;
NewCond = (Cond == ISD::SETULE) ? ISD::SETULT : ISD::SETUGE;
} else {
ShiftBits = C1.countTrailingZeros();
}
NewC.lshrInPlace(ShiftBits);
if (ShiftBits && NewC.getMinSignedBits() <= 64 &&
isLegalICmpImmediate(NewC.getSExtValue())) {
auto &DL = DAG.getDataLayout();
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
EVT CmpTy = N0.getValueType();
SDValue Shift = DAG.getNode(ISD::SRL, dl, CmpTy, N0,
DAG.getConstant(ShiftBits, dl, ShiftTy));
SDValue CmpRHS = DAG.getConstant(NewC, dl, CmpTy);
return DAG.getSetCC(dl, VT, Shift, CmpRHS, NewCond);
}
}
}
}
if (isa<ConstantFPSDNode>(N0.getNode())) {
// Constant fold or commute setcc.
SDValue O = DAG.FoldSetCC(VT, N0, N1, Cond, dl);
if (O.getNode()) return O;
} else if (auto *CFP = dyn_cast<ConstantFPSDNode>(N1.getNode())) {
// If the RHS of an FP comparison is a constant, simplify it away in
// some cases.
if (CFP->getValueAPF().isNaN()) {
// If an operand is known to be a nan, we can fold it.
switch (ISD::getUnorderedFlavor(Cond)) {
default: llvm_unreachable("Unknown flavor!");
case 0: // Known false.
return DAG.getConstant(0, dl, VT);
case 1: // Known true.
return DAG.getConstant(1, dl, VT);
case 2: // Undefined.
return DAG.getUNDEF(VT);
}
}
// Otherwise, we know the RHS is not a NaN. Simplify the node to drop the
// constant if knowing that the operand is non-nan is enough. We prefer to
// have SETO(x,x) instead of SETO(x, 0.0) because this avoids having to
// materialize 0.0.
if (Cond == ISD::SETO || Cond == ISD::SETUO)
return DAG.getSetCC(dl, VT, N0, N0, Cond);
// setcc (fneg x), C -> setcc swap(pred) x, -C
if (N0.getOpcode() == ISD::FNEG) {
ISD::CondCode SwapCond = ISD::getSetCCSwappedOperands(Cond);
if (DCI.isBeforeLegalizeOps() ||
isCondCodeLegal(SwapCond, N0.getSimpleValueType())) {
SDValue NegN1 = DAG.getNode(ISD::FNEG, dl, N0.getValueType(), N1);
return DAG.getSetCC(dl, VT, N0.getOperand(0), NegN1, SwapCond);
}
}
// If the condition is not legal, see if we can find an equivalent one
// which is legal.
if (!isCondCodeLegal(Cond, N0.getSimpleValueType())) {
// If the comparison was an awkward floating-point == or != and one of
// the comparison operands is infinity or negative infinity, convert the
// condition to a less-awkward <= or >=.
if (CFP->getValueAPF().isInfinity()) {
if (CFP->getValueAPF().isNegative()) {
if (Cond == ISD::SETOEQ &&
isCondCodeLegal(ISD::SETOLE, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETOLE);
if (Cond == ISD::SETUEQ &&
isCondCodeLegal(ISD::SETOLE, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETULE);
if (Cond == ISD::SETUNE &&
isCondCodeLegal(ISD::SETUGT, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETUGT);
if (Cond == ISD::SETONE &&
isCondCodeLegal(ISD::SETUGT, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETOGT);
} else {
if (Cond == ISD::SETOEQ &&
isCondCodeLegal(ISD::SETOGE, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETOGE);
if (Cond == ISD::SETUEQ &&
isCondCodeLegal(ISD::SETOGE, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETUGE);
if (Cond == ISD::SETUNE &&
isCondCodeLegal(ISD::SETULT, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETULT);
if (Cond == ISD::SETONE &&
isCondCodeLegal(ISD::SETULT, N0.getSimpleValueType()))
return DAG.getSetCC(dl, VT, N0, N1, ISD::SETOLT);
}
}
}
}
if (N0 == N1) {
// The sext(setcc()) => setcc() optimization relies on the appropriate
// constant being emitted.
uint64_t EqVal = 0;
switch (getBooleanContents(N0.getValueType())) {
case UndefinedBooleanContent:
case ZeroOrOneBooleanContent:
EqVal = ISD::isTrueWhenEqual(Cond);
break;
case ZeroOrNegativeOneBooleanContent:
EqVal = ISD::isTrueWhenEqual(Cond) ? -1 : 0;
break;
}
// We can always fold X == X for integer setcc's.
if (N0.getValueType().isInteger()) {
return DAG.getConstant(EqVal, dl, VT);
}
unsigned UOF = ISD::getUnorderedFlavor(Cond);
if (UOF == 2) // FP operators that are undefined on NaNs.
return DAG.getConstant(EqVal, dl, VT);
if (UOF == unsigned(ISD::isTrueWhenEqual(Cond)))
return DAG.getConstant(EqVal, dl, VT);
// Otherwise, we can't fold it. However, we can simplify it to SETUO/SETO
// if it is not already.
ISD::CondCode NewCond = UOF == 0 ? ISD::SETO : ISD::SETUO;
if (NewCond != Cond && (DCI.isBeforeLegalizeOps() ||
getCondCodeAction(NewCond, N0.getSimpleValueType()) == Legal))
return DAG.getSetCC(dl, VT, N0, N1, NewCond);
}
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
N0.getValueType().isInteger()) {
if (N0.getOpcode() == ISD::ADD || N0.getOpcode() == ISD::SUB ||
N0.getOpcode() == ISD::XOR) {
// Simplify (X+Y) == (X+Z) --> Y == Z
if (N0.getOpcode() == N1.getOpcode()) {
if (N0.getOperand(0) == N1.getOperand(0))
return DAG.getSetCC(dl, VT, N0.getOperand(1), N1.getOperand(1), Cond);
if (N0.getOperand(1) == N1.getOperand(1))
return DAG.getSetCC(dl, VT, N0.getOperand(0), N1.getOperand(0), Cond);
if (isCommutativeBinOp(N0.getOpcode())) {
// If X op Y == Y op X, try other combinations.
if (N0.getOperand(0) == N1.getOperand(1))
return DAG.getSetCC(dl, VT, N0.getOperand(1), N1.getOperand(0),
Cond);
if (N0.getOperand(1) == N1.getOperand(0))
return DAG.getSetCC(dl, VT, N0.getOperand(0), N1.getOperand(1),
Cond);
}
}
// If RHS is a legal immediate value for a compare instruction, we need
// to be careful about increasing register pressure needlessly.
bool LegalRHSImm = false;
if (auto *RHSC = dyn_cast<ConstantSDNode>(N1)) {
if (auto *LHSR = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
// Turn (X+C1) == C2 --> X == C2-C1
if (N0.getOpcode() == ISD::ADD && N0.getNode()->hasOneUse()) {
return DAG.getSetCC(dl, VT, N0.getOperand(0),
DAG.getConstant(RHSC->getAPIntValue()-
LHSR->getAPIntValue(),
dl, N0.getValueType()), Cond);
}
// Turn (X^C1) == C2 into X == C1^C2 iff X&~C1 = 0.
if (N0.getOpcode() == ISD::XOR)
// If we know that all of the inverted bits are zero, don't bother
// performing the inversion.
if (DAG.MaskedValueIsZero(N0.getOperand(0), ~LHSR->getAPIntValue()))
return
DAG.getSetCC(dl, VT, N0.getOperand(0),
DAG.getConstant(LHSR->getAPIntValue() ^
RHSC->getAPIntValue(),
dl, N0.getValueType()),
Cond);
}
// Turn (C1-X) == C2 --> X == C1-C2
if (auto *SUBC = dyn_cast<ConstantSDNode>(N0.getOperand(0))) {
if (N0.getOpcode() == ISD::SUB && N0.getNode()->hasOneUse()) {
return
DAG.getSetCC(dl, VT, N0.getOperand(1),
DAG.getConstant(SUBC->getAPIntValue() -
RHSC->getAPIntValue(),
dl, N0.getValueType()),
Cond);
}
}
// Could RHSC fold directly into a compare?
if (RHSC->getValueType(0).getSizeInBits() <= 64)
LegalRHSImm = isLegalICmpImmediate(RHSC->getSExtValue());
}
// Simplify (X+Z) == X --> Z == 0
// Don't do this if X is an immediate that can fold into a cmp
// instruction and X+Z has other uses. It could be an induction variable
// chain, and the transform would increase register pressure.
if (!LegalRHSImm || N0.getNode()->hasOneUse()) {
if (N0.getOperand(0) == N1)
return DAG.getSetCC(dl, VT, N0.getOperand(1),
DAG.getConstant(0, dl, N0.getValueType()), Cond);
if (N0.getOperand(1) == N1) {
if (isCommutativeBinOp(N0.getOpcode()))
return DAG.getSetCC(dl, VT, N0.getOperand(0),
DAG.getConstant(0, dl, N0.getValueType()),