llvm-project/llvm/lib/Target/TargetLowering.cpp

995 lines
41 KiB
C++

//===-- TargetLowering.cpp - Implement the TargetLowering class -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and 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/Target/TargetMachine.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/MathExtras.h"
using namespace llvm;
TargetLowering::TargetLowering(TargetMachine &tm)
: TM(tm), TD(TM.getTargetData()) {
assert(ISD::BUILTIN_OP_END <= 156 &&
"Fixed size array in TargetLowering is not large enough!");
// All operations default to being supported.
memset(OpActions, 0, sizeof(OpActions));
IsLittleEndian = TD.isLittleEndian();
ShiftAmountTy = SetCCResultTy = PointerTy = getValueType(TD.getIntPtrType());
ShiftAmtHandling = Undefined;
memset(RegClassForVT, 0,MVT::LAST_VALUETYPE*sizeof(TargetRegisterClass*));
memset(TargetDAGCombineArray, 0,
sizeof(TargetDAGCombineArray)/sizeof(TargetDAGCombineArray[0]));
maxStoresPerMemset = maxStoresPerMemcpy = maxStoresPerMemmove = 8;
allowUnalignedMemoryAccesses = false;
UseUnderscoreSetJmpLongJmp = false;
IntDivIsCheap = false;
Pow2DivIsCheap = false;
StackPointerRegisterToSaveRestore = 0;
SchedPreferenceInfo = SchedulingForLatency;
}
TargetLowering::~TargetLowering() {}
/// setValueTypeAction - Set the action for a particular value type. This
/// assumes an action has not already been set for this value type.
static void SetValueTypeAction(MVT::ValueType VT,
TargetLowering::LegalizeAction Action,
TargetLowering &TLI,
MVT::ValueType *TransformToType,
TargetLowering::ValueTypeActionImpl &ValueTypeActions) {
ValueTypeActions.setTypeAction(VT, Action);
if (Action == TargetLowering::Promote) {
MVT::ValueType PromoteTo;
if (VT == MVT::f32)
PromoteTo = MVT::f64;
else {
unsigned LargerReg = VT+1;
while (!TLI.isTypeLegal((MVT::ValueType)LargerReg)) {
++LargerReg;
assert(MVT::isInteger((MVT::ValueType)LargerReg) &&
"Nothing to promote to??");
}
PromoteTo = (MVT::ValueType)LargerReg;
}
assert(MVT::isInteger(VT) == MVT::isInteger(PromoteTo) &&
MVT::isFloatingPoint(VT) == MVT::isFloatingPoint(PromoteTo) &&
"Can only promote from int->int or fp->fp!");
assert(VT < PromoteTo && "Must promote to a larger type!");
TransformToType[VT] = PromoteTo;
} else if (Action == TargetLowering::Expand) {
assert((VT == MVT::Vector || MVT::isInteger(VT)) && VT > MVT::i8 &&
"Cannot expand this type: target must support SOME integer reg!");
// Expand to the next smaller integer type!
TransformToType[VT] = (MVT::ValueType)(VT-1);
}
}
/// computeRegisterProperties - Once all of the register classes are added,
/// this allows us to compute derived properties we expose.
void TargetLowering::computeRegisterProperties() {
assert(MVT::LAST_VALUETYPE <= 32 &&
"Too many value types for ValueTypeActions to hold!");
// Everything defaults to one.
for (unsigned i = 0; i != MVT::LAST_VALUETYPE; ++i)
NumElementsForVT[i] = 1;
// Find the largest integer register class.
unsigned LargestIntReg = MVT::i128;
for (; RegClassForVT[LargestIntReg] == 0; --LargestIntReg)
assert(LargestIntReg != MVT::i1 && "No integer registers defined!");
// Every integer value type larger than this largest register takes twice as
// many registers to represent as the previous ValueType.
unsigned ExpandedReg = LargestIntReg; ++LargestIntReg;
for (++ExpandedReg; MVT::isInteger((MVT::ValueType)ExpandedReg);++ExpandedReg)
NumElementsForVT[ExpandedReg] = 2*NumElementsForVT[ExpandedReg-1];
// Inspect all of the ValueType's possible, deciding how to process them.
for (unsigned IntReg = MVT::i1; IntReg <= MVT::i128; ++IntReg)
// If we are expanding this type, expand it!
if (getNumElements((MVT::ValueType)IntReg) != 1)
SetValueTypeAction((MVT::ValueType)IntReg, Expand, *this, TransformToType,
ValueTypeActions);
else if (!isTypeLegal((MVT::ValueType)IntReg))
// Otherwise, if we don't have native support, we must promote to a
// larger type.
SetValueTypeAction((MVT::ValueType)IntReg, Promote, *this,
TransformToType, ValueTypeActions);
else
TransformToType[(MVT::ValueType)IntReg] = (MVT::ValueType)IntReg;
// If the target does not have native support for F32, promote it to F64.
if (!isTypeLegal(MVT::f32))
SetValueTypeAction(MVT::f32, Promote, *this,
TransformToType, ValueTypeActions);
else
TransformToType[MVT::f32] = MVT::f32;
// Set MVT::Vector to always be Expanded
SetValueTypeAction(MVT::Vector, Expand, *this, TransformToType,
ValueTypeActions);
assert(isTypeLegal(MVT::f64) && "Target does not support FP?");
TransformToType[MVT::f64] = MVT::f64;
}
const char *TargetLowering::getTargetNodeName(unsigned Opcode) const {
return NULL;
}
//===----------------------------------------------------------------------===//
// Optimization Methods
//===----------------------------------------------------------------------===//
/// ShrinkDemandedConstant - Check to see if the specified operand of the
/// specified instruction is a constant integer. If so, check to see if there
/// are any bits set in the constant that are not demanded. If so, shrink the
/// constant and return true.
bool TargetLowering::TargetLoweringOpt::ShrinkDemandedConstant(SDOperand Op,
uint64_t Demanded) {
// FIXME: ISD::SELECT, ISD::SELECT_CC
switch(Op.getOpcode()) {
default: break;
case ISD::AND:
case ISD::OR:
case ISD::XOR:
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1)))
if ((~Demanded & C->getValue()) != 0) {
MVT::ValueType VT = Op.getValueType();
SDOperand New = DAG.getNode(Op.getOpcode(), VT, Op.getOperand(0),
DAG.getConstant(Demanded & C->getValue(),
VT));
return CombineTo(Op, New);
}
break;
}
return false;
}
/// SimplifyDemandedBits - 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 KnownOne and KnownZero bits for
/// the expression (used to simplify the caller). The KnownZero/One bits may
/// only be accurate for those bits in the DemandedMask.
bool TargetLowering::SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask,
uint64_t &KnownZero,
uint64_t &KnownOne,
TargetLoweringOpt &TLO,
unsigned Depth) const {
KnownZero = KnownOne = 0; // Don't know anything.
// Other users may use these bits.
if (!Op.Val->hasOneUse()) {
if (Depth != 0) {
// If not at the root, Just compute the KnownZero/KnownOne bits to
// simplify things downstream.
ComputeMaskedBits(Op, DemandedMask, KnownZero, KnownOne, Depth);
return false;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the DemandedMask to all bits.
DemandedMask = MVT::getIntVTBitMask(Op.getValueType());
} else if (DemandedMask == 0) {
// Not demanding any bits from Op.
if (Op.getOpcode() != ISD::UNDEF)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::UNDEF, Op.getValueType()));
return false;
} else if (Depth == 6) { // Limit search depth.
return false;
}
uint64_t KnownZero2, KnownOne2, KnownZeroOut, KnownOneOut;
switch (Op.getOpcode()) {
case ISD::Constant:
// We know all of the bits for a constant!
KnownOne = cast<ConstantSDNode>(Op)->getValue() & DemandedMask;
KnownZero = ~KnownOne & DemandedMask;
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 = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
uint64_t LHSZero, LHSOne;
ComputeMaskedBits(Op.getOperand(0), DemandedMask,
LHSZero, LHSOne, Depth+1);
// If the LHS already has zeros where RHSC does, this and is dead.
if ((LHSZero & DemandedMask) == (~RHSC->getValue() & DemandedMask))
return TLO.CombineTo(Op, Op.getOperand(0));
// If any of the set bits in the RHS are known zero on the LHS, shrink
// the constant.
if (TLO.ShrinkDemandedConstant(Op, ~LHSZero & DemandedMask))
return true;
}
if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & ~KnownZero,
KnownZero2, KnownOne2, TLO, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "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 ((DemandedMask & ~KnownZero2 & KnownOne)==(DemandedMask & ~KnownZero2))
return TLO.CombineTo(Op, Op.getOperand(0));
if ((DemandedMask & ~KnownZero & KnownOne2)==(DemandedMask & ~KnownZero))
return TLO.CombineTo(Op, Op.getOperand(1));
// If all of the demanded bits in the inputs are known zeros, return zero.
if ((DemandedMask & (KnownZero|KnownZero2)) == DemandedMask)
return TLO.CombineTo(Op, TLO.DAG.getConstant(0, Op.getValueType()));
// If the RHS is a constant, see if we can simplify it.
if (TLO.ShrinkDemandedConstant(Op, DemandedMask & ~KnownZero2))
return true;
// Output known-1 bits are only known if set in both the LHS & RHS.
KnownOne &= KnownOne2;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
KnownZero |= KnownZero2;
break;
case ISD::OR:
if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & ~KnownOne,
KnownZero2, KnownOne2, TLO, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "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 ((DemandedMask & ~KnownOne2 & KnownZero) == (DemandedMask & ~KnownOne2))
return TLO.CombineTo(Op, Op.getOperand(0));
if ((DemandedMask & ~KnownOne & KnownZero2) == (DemandedMask & ~KnownOne))
return TLO.CombineTo(Op, Op.getOperand(1));
// If all of the potentially set bits on one side are known to be set on
// the other side, just use the 'other' side.
if ((DemandedMask & (~KnownZero) & KnownOne2) ==
(DemandedMask & (~KnownZero)))
return TLO.CombineTo(Op, Op.getOperand(0));
if ((DemandedMask & (~KnownZero2) & KnownOne) ==
(DemandedMask & (~KnownZero2)))
return TLO.CombineTo(Op, Op.getOperand(1));
// If the RHS is a constant, see if we can simplify it.
if (TLO.ShrinkDemandedConstant(Op, DemandedMask))
return true;
// Output known-0 bits are only known if clear in both the LHS & RHS.
KnownZero &= KnownZero2;
// Output known-1 are known to be set if set in either the LHS | RHS.
KnownOne |= KnownOne2;
break;
case ISD::XOR:
if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask, KnownZero2,
KnownOne2, TLO, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "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 ((DemandedMask & KnownZero) == DemandedMask)
return TLO.CombineTo(Op, Op.getOperand(0));
if ((DemandedMask & KnownZero2) == DemandedMask)
return TLO.CombineTo(Op, Op.getOperand(1));
// Output known-0 bits are known if clear or set in both the LHS & RHS.
KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
KnownOneOut = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
// 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 (uint64_t UnknownBits = DemandedMask & ~(KnownZeroOut|KnownOneOut))
if ((UnknownBits & (KnownZero|KnownZero2)) == UnknownBits)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::OR, Op.getValueType(),
Op.getOperand(0),
Op.getOperand(1)));
// 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
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) { // all known
if ((KnownOne & KnownOne2) == KnownOne) {
MVT::ValueType VT = Op.getValueType();
SDOperand ANDC = TLO.DAG.getConstant(~KnownOne & DemandedMask, VT);
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::AND, VT, Op.getOperand(0),
ANDC));
}
}
// If the RHS is a constant, see if we can simplify it.
// FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
if (TLO.ShrinkDemandedConstant(Op, DemandedMask))
return true;
KnownZero = KnownZeroOut;
KnownOne = KnownOneOut;
break;
case ISD::SETCC:
// If we know the result of a setcc has the top bits zero, use this info.
if (getSetCCResultContents() == TargetLowering::ZeroOrOneSetCCResult)
KnownZero |= (MVT::getIntVTBitMask(Op.getValueType()) ^ 1ULL);
break;
case ISD::SELECT:
if (SimplifyDemandedBits(Op.getOperand(2), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero2,
KnownOne2, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (TLO.ShrinkDemandedConstant(Op, DemandedMask))
return true;
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
break;
case ISD::SELECT_CC:
if (SimplifyDemandedBits(Op.getOperand(3), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
if (SimplifyDemandedBits(Op.getOperand(2), DemandedMask, KnownZero2,
KnownOne2, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (TLO.ShrinkDemandedConstant(Op, DemandedMask))
return true;
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
break;
case ISD::SHL:
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask >> SA->getValue(),
KnownZero, KnownOne, TLO, Depth+1))
return true;
KnownZero <<= SA->getValue();
KnownOne <<= SA->getValue();
KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero.
}
break;
case ISD::SRL:
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
MVT::ValueType VT = Op.getValueType();
unsigned ShAmt = SA->getValue();
// Compute the new bits that are at the top now.
uint64_t HighBits = (1ULL << ShAmt)-1;
HighBits <<= MVT::getSizeInBits(VT) - ShAmt;
uint64_t TypeMask = MVT::getIntVTBitMask(VT);
if (SimplifyDemandedBits(Op.getOperand(0),
(DemandedMask << ShAmt) & TypeMask,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero &= TypeMask;
KnownOne &= TypeMask;
KnownZero >>= ShAmt;
KnownOne >>= ShAmt;
KnownZero |= HighBits; // high bits known zero.
}
break;
case ISD::SRA:
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
MVT::ValueType VT = Op.getValueType();
unsigned ShAmt = SA->getValue();
// Compute the new bits that are at the top now.
uint64_t HighBits = (1ULL << ShAmt)-1;
HighBits <<= MVT::getSizeInBits(VT) - ShAmt;
uint64_t TypeMask = MVT::getIntVTBitMask(VT);
if (SimplifyDemandedBits(Op.getOperand(0),
(DemandedMask << ShAmt) & TypeMask,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero &= TypeMask;
KnownOne &= TypeMask;
KnownZero >>= SA->getValue();
KnownOne >>= SA->getValue();
// Handle the sign bits.
uint64_t SignBit = MVT::getIntVTSignBit(VT);
SignBit >>= SA->getValue(); // Adjust to where it is now in the mask.
// 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 ((KnownZero & SignBit) || (HighBits & ~DemandedMask) == HighBits) {
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SRL, VT, Op.getOperand(0),
Op.getOperand(1)));
} else if (KnownOne & SignBit) { // New bits are known one.
KnownOne |= HighBits;
}
}
break;
case ISD::SIGN_EXTEND_INREG: {
MVT::ValueType VT = Op.getValueType();
MVT::ValueType EVT = cast<VTSDNode>(Op.getOperand(1))->getVT();
// Sign extension. Compute the demanded bits in the result that are not
// present in the input.
uint64_t NewBits = ~MVT::getIntVTBitMask(EVT) & DemandedMask;
// If none of the extended bits are demanded, eliminate the sextinreg.
if (NewBits == 0)
return TLO.CombineTo(Op, Op.getOperand(0));
uint64_t InSignBit = MVT::getIntVTSignBit(EVT);
int64_t InputDemandedBits = DemandedMask & MVT::getIntVTBitMask(EVT);
// Since the sign extended bits are demanded, we know that the sign
// bit is demanded.
InputDemandedBits |= InSignBit;
if (SimplifyDemandedBits(Op.getOperand(0), InputDemandedBits,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "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 (KnownZero & InSignBit)
return TLO.CombineTo(Op,
TLO.DAG.getZeroExtendInReg(Op.getOperand(0), EVT));
if (KnownOne & InSignBit) { // Input sign bit known set
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Input sign bit unknown
KnownZero &= ~NewBits;
KnownOne &= ~NewBits;
}
break;
}
case ISD::CTTZ:
case ISD::CTLZ:
case ISD::CTPOP: {
MVT::ValueType VT = Op.getValueType();
unsigned LowBits = Log2_32(MVT::getSizeInBits(VT))+1;
KnownZero = ~((1ULL << LowBits)-1) & MVT::getIntVTBitMask(VT);
KnownOne = 0;
break;
}
case ISD::ZEXTLOAD: {
MVT::ValueType VT = cast<VTSDNode>(Op.getOperand(3))->getVT();
KnownZero |= ~MVT::getIntVTBitMask(VT) & DemandedMask;
break;
}
case ISD::ZERO_EXTEND: {
uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType());
// If none of the top bits are demanded, convert this into an any_extend.
uint64_t NewBits = (~InMask) & DemandedMask;
if (NewBits == 0)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND,
Op.getValueType(),
Op.getOperand(0)));
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero |= NewBits;
break;
}
case ISD::SIGN_EXTEND: {
MVT::ValueType InVT = Op.getOperand(0).getValueType();
uint64_t InMask = MVT::getIntVTBitMask(InVT);
uint64_t InSignBit = MVT::getIntVTSignBit(InVT);
uint64_t NewBits = (~InMask) & DemandedMask;
// If none of the top bits are demanded, convert this into an any_extend.
if (NewBits == 0)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND,Op.getValueType(),
Op.getOperand(0)));
// Since some of the sign extended bits are demanded, we know that the sign
// bit is demanded.
uint64_t InDemandedBits = DemandedMask & InMask;
InDemandedBits |= InSignBit;
if (SimplifyDemandedBits(Op.getOperand(0), InDemandedBits, KnownZero,
KnownOne, TLO, Depth+1))
return true;
// If the sign bit is known zero, convert this to a zero extend.
if (KnownZero & InSignBit)
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ZERO_EXTEND,
Op.getValueType(),
Op.getOperand(0)));
// If the sign bit is known one, the top bits match.
if (KnownOne & InSignBit) {
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Otherwise, top bits aren't known.
KnownOne &= ~NewBits;
KnownZero &= ~NewBits;
}
break;
}
case ISD::ANY_EXTEND: {
uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType());
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
break;
}
case ISD::AssertZext: {
MVT::ValueType VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
uint64_t InMask = MVT::getIntVTBitMask(VT);
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask,
KnownZero, KnownOne, TLO, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero |= ~InMask & DemandedMask;
break;
}
case ISD::ADD:
if (ConstantSDNode *AA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask, KnownZero,
KnownOne, TLO, Depth+1))
return true;
// Compute the KnownOne/KnownZero masks for the constant, so we can set
// KnownZero appropriately if we're adding a constant that has all low
// bits cleared.
ComputeMaskedBits(Op.getOperand(1),
MVT::getIntVTBitMask(Op.getValueType()),
KnownZero2, KnownOne2, Depth+1);
uint64_t KnownZeroOut = std::min(CountTrailingZeros_64(~KnownZero),
CountTrailingZeros_64(~KnownZero2));
KnownZero = (1ULL << KnownZeroOut) - 1;
KnownOne = 0;
}
break;
case ISD::SUB:
// Just use ComputeMaskedBits to compute output bits, there are no
// simplifications that can be done here, and sub always demands all input
// bits.
ComputeMaskedBits(Op, DemandedMask, KnownZero, KnownOne, Depth);
break;
}
// If we know the value of all of the demanded bits, return this as a
// constant.
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask)
return TLO.CombineTo(Op, TLO.DAG.getConstant(KnownOne, Op.getValueType()));
return false;
}
/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. Mask is known to be zero
/// for bits that V cannot have.
bool TargetLowering::MaskedValueIsZero(SDOperand Op, uint64_t Mask,
unsigned Depth) const {
uint64_t KnownZero, KnownOne;
ComputeMaskedBits(Op, Mask, KnownZero, KnownOne, Depth);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
return (KnownZero & Mask) == Mask;
}
/// ComputeMaskedBits - Determine which of the bits specified in Mask are
/// known to be either zero or one and return them in the KnownZero/KnownOne
/// bitsets. This code only analyzes bits in Mask, in order to short-circuit
/// processing.
void TargetLowering::ComputeMaskedBits(SDOperand Op, uint64_t Mask,
uint64_t &KnownZero, uint64_t &KnownOne,
unsigned Depth) const {
KnownZero = KnownOne = 0; // Don't know anything.
if (Depth == 6 || Mask == 0)
return; // Limit search depth.
uint64_t KnownZero2, KnownOne2;
switch (Op.getOpcode()) {
case ISD::Constant:
// We know all of the bits for a constant!
KnownOne = cast<ConstantSDNode>(Op)->getValue() & Mask;
KnownZero = ~KnownOne & Mask;
return;
case ISD::AND:
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
Mask &= ~KnownZero;
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-1 bits are only known if set in both the LHS & RHS.
KnownOne &= KnownOne2;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
KnownZero |= KnownZero2;
return;
case ISD::OR:
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
Mask &= ~KnownOne;
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-0 bits are only known if clear in both the LHS & RHS.
KnownZero &= KnownZero2;
// Output known-1 are known to be set if set in either the LHS | RHS.
KnownOne |= KnownOne2;
return;
case ISD::XOR: {
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-0 bits are known if clear or set in both the LHS & RHS.
uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
KnownZero = KnownZeroOut;
return;
}
case ISD::SELECT:
ComputeMaskedBits(Op.getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
return;
case ISD::SELECT_CC:
ComputeMaskedBits(Op.getOperand(3), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(Op.getOperand(2), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
return;
case ISD::SETCC:
// If we know the result of a setcc has the top bits zero, use this info.
if (getSetCCResultContents() == TargetLowering::ZeroOrOneSetCCResult)
KnownZero |= (MVT::getIntVTBitMask(Op.getValueType()) ^ 1ULL);
return;
case ISD::SHL:
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
Mask >>= SA->getValue();
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero <<= SA->getValue();
KnownOne <<= SA->getValue();
KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero.
}
return;
case ISD::SRL:
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
uint64_t HighBits = (1ULL << SA->getValue())-1;
HighBits <<= MVT::getSizeInBits(Op.getValueType())-SA->getValue();
Mask <<= SA->getValue();
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero >>= SA->getValue();
KnownOne >>= SA->getValue();
KnownZero |= HighBits; // high bits known zero.
}
return;
case ISD::SRA:
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
uint64_t HighBits = (1ULL << SA->getValue())-1;
HighBits <<= MVT::getSizeInBits(Op.getValueType())-SA->getValue();
Mask <<= SA->getValue();
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
KnownZero >>= SA->getValue();
KnownOne >>= SA->getValue();
// Handle the sign bits.
uint64_t SignBit = 1ULL << (MVT::getSizeInBits(Op.getValueType())-1);
SignBit >>= SA->getValue(); // Adjust to where it is now in the mask.
if (KnownZero & SignBit) { // New bits are known zero.
KnownZero |= HighBits;
} else if (KnownOne & SignBit) { // New bits are known one.
KnownOne |= HighBits;
}
}
return;
case ISD::SIGN_EXTEND_INREG: {
MVT::ValueType VT = Op.getValueType();
MVT::ValueType EVT = cast<VTSDNode>(Op.getOperand(1))->getVT();
// Sign extension. Compute the demanded bits in the result that are not
// present in the input.
uint64_t NewBits = ~MVT::getIntVTBitMask(EVT) & Mask;
uint64_t InSignBit = MVT::getIntVTSignBit(EVT);
int64_t InputDemandedBits = Mask & MVT::getIntVTBitMask(EVT);
// If the sign extended bits are demanded, we know that the sign
// bit is demanded.
if (NewBits)
InputDemandedBits |= InSignBit;
ComputeMaskedBits(Op.getOperand(0), InputDemandedBits,
KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "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 (KnownZero & InSignBit) { // Input sign bit known clear
KnownZero |= NewBits;
KnownOne &= ~NewBits;
} else if (KnownOne & InSignBit) { // Input sign bit known set
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Input sign bit unknown
KnownZero &= ~NewBits;
KnownOne &= ~NewBits;
}
return;
}
case ISD::CTTZ:
case ISD::CTLZ:
case ISD::CTPOP: {
MVT::ValueType VT = Op.getValueType();
unsigned LowBits = Log2_32(MVT::getSizeInBits(VT))+1;
KnownZero = ~((1ULL << LowBits)-1) & MVT::getIntVTBitMask(VT);
KnownOne = 0;
return;
}
case ISD::ZEXTLOAD: {
MVT::ValueType VT = cast<VTSDNode>(Op.getOperand(3))->getVT();
KnownZero |= ~MVT::getIntVTBitMask(VT) & Mask;
return;
}
case ISD::ZERO_EXTEND: {
uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType());
uint64_t NewBits = (~InMask) & Mask;
ComputeMaskedBits(Op.getOperand(0), Mask & InMask, KnownZero,
KnownOne, Depth+1);
KnownZero |= NewBits & Mask;
KnownOne &= ~NewBits;
return;
}
case ISD::SIGN_EXTEND: {
MVT::ValueType InVT = Op.getOperand(0).getValueType();
unsigned InBits = MVT::getSizeInBits(InVT);
uint64_t InMask = MVT::getIntVTBitMask(InVT);
uint64_t InSignBit = 1ULL << (InBits-1);
uint64_t NewBits = (~InMask) & Mask;
uint64_t InDemandedBits = Mask & InMask;
// If any of the sign extended bits are demanded, we know that the sign
// bit is demanded.
if (NewBits & Mask)
InDemandedBits |= InSignBit;
ComputeMaskedBits(Op.getOperand(0), InDemandedBits, KnownZero,
KnownOne, Depth+1);
// If the sign bit is known zero or one, the top bits match.
if (KnownZero & InSignBit) {
KnownZero |= NewBits;
KnownOne &= ~NewBits;
} else if (KnownOne & InSignBit) {
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Otherwise, top bits aren't known.
KnownOne &= ~NewBits;
KnownZero &= ~NewBits;
}
return;
}
case ISD::ANY_EXTEND: {
MVT::ValueType VT = Op.getOperand(0).getValueType();
ComputeMaskedBits(Op.getOperand(0), Mask & MVT::getIntVTBitMask(VT),
KnownZero, KnownOne, Depth+1);
return;
}
case ISD::AssertZext: {
MVT::ValueType VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
uint64_t InMask = MVT::getIntVTBitMask(VT);
ComputeMaskedBits(Op.getOperand(0), Mask & InMask, KnownZero,
KnownOne, Depth+1);
KnownZero |= (~InMask) & Mask;
return;
}
case ISD::ADD: {
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-0 bits are known if clear or set in both the low clear bits
// common to both LHS & RHS;
uint64_t KnownZeroOut = std::min(CountTrailingZeros_64(~KnownZero),
CountTrailingZeros_64(~KnownZero2));
KnownZero = (1ULL << KnownZeroOut) - 1;
KnownOne = 0;
return;
}
case ISD::SUB: {
ConstantSDNode *CLHS = dyn_cast<ConstantSDNode>(Op.getOperand(0));
if (!CLHS) return;
// We know that the top bits of C-X are clear if X contains less bits
// than C (i.e. no wrap-around can happen). For example, 20-X is
// positive if we can prove that X is >= 0 and < 16.
MVT::ValueType VT = CLHS->getValueType(0);
if ((CLHS->getValue() & MVT::getIntVTSignBit(VT)) == 0) { // sign bit clear
unsigned NLZ = CountLeadingZeros_64(CLHS->getValue()+1);
uint64_t MaskV = (1ULL << (63-NLZ))-1; // NLZ can't be 64 with no sign bit
MaskV = ~MaskV & MVT::getIntVTBitMask(VT);
ComputeMaskedBits(Op.getOperand(1), MaskV, KnownZero, KnownOne, Depth+1);
// If all of the MaskV bits are known to be zero, then we know the output
// top bits are zero, because we now know that the output is from [0-C].
if ((KnownZero & MaskV) == MaskV) {
unsigned NLZ2 = CountLeadingZeros_64(CLHS->getValue());
KnownZero = ~((1ULL << (64-NLZ2))-1) & Mask; // Top bits known zero.
KnownOne = 0; // No one bits known.
} else {
KnownOne = KnownOne = 0; // Otherwise, nothing known.
}
}
return;
}
default:
// Allow the target to implement this method for its nodes.
if (Op.getOpcode() >= ISD::BUILTIN_OP_END)
computeMaskedBitsForTargetNode(Op, Mask, KnownZero, KnownOne);
return;
}
}
/// computeMaskedBitsForTargetNode - Determine which of the bits specified
/// in Mask are known to be either zero or one and return them in the
/// KnownZero/KnownOne bitsets.
void TargetLowering::computeMaskedBitsForTargetNode(const SDOperand Op,
uint64_t Mask,
uint64_t &KnownZero,
uint64_t &KnownOne,
unsigned Depth) const {
assert(Op.getOpcode() >= ISD::BUILTIN_OP_END &&
"Should use MaskedValueIsZero if you don't know whether Op"
" is a target node!");
KnownZero = 0;
KnownOne = 0;
}
SDOperand TargetLowering::
PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const {
// Default implementation: no optimization.
return SDOperand();
}
//===----------------------------------------------------------------------===//
// Inline Assembler Implementation Methods
//===----------------------------------------------------------------------===//
TargetLowering::ConstraintType
TargetLowering::getConstraintType(char ConstraintLetter) const {
// FIXME: lots more standard ones to handle.
switch (ConstraintLetter) {
default: return C_Unknown;
case 'r': return C_RegisterClass;
case 'm': // memory
case 'o': // offsetable
case 'V': // not offsetable
return C_Memory;
case 'i': // Simple Integer or Relocatable Constant
case 'n': // Simple Integer
case 's': // Relocatable Constant
case 'I': // Target registers.
case 'J':
case 'K':
case 'L':
case 'M':
case 'N':
case 'O':
case 'P':
return C_Other;
}
}
bool TargetLowering::isOperandValidForConstraint(SDOperand Op,
char ConstraintLetter) {
switch (ConstraintLetter) {
default: return false;
case 'i': // Simple Integer or Relocatable Constant
case 'n': // Simple Integer
case 's': // Relocatable Constant
return true; // FIXME: not right.
}
}
std::vector<unsigned> TargetLowering::
getRegClassForInlineAsmConstraint(const std::string &Constraint,
MVT::ValueType VT) const {
return std::vector<unsigned>();
}
std::pair<unsigned, const TargetRegisterClass*> TargetLowering::
getRegForInlineAsmConstraint(const std::string &Constraint,
MVT::ValueType VT) const {
if (Constraint[0] != '{')
return std::pair<unsigned, const TargetRegisterClass*>(0, 0);
assert(*(Constraint.end()-1) == '}' && "Not a brace enclosed constraint?");
// Remove the braces from around the name.
std::string RegName(Constraint.begin()+1, Constraint.end()-1);
// Figure out which register class contains this reg.
const MRegisterInfo *RI = TM.getRegisterInfo();
for (MRegisterInfo::regclass_iterator RCI = RI->regclass_begin(),
E = RI->regclass_end(); RCI != E; ++RCI) {
const TargetRegisterClass *RC = *RCI;
// If none of the the value types for this register class are valid, we
// can't use it. For example, 64-bit reg classes on 32-bit targets.
bool isLegal = false;
for (TargetRegisterClass::vt_iterator I = RC->vt_begin(), E = RC->vt_end();
I != E; ++I) {
if (isTypeLegal(*I)) {
isLegal = true;
break;
}
}
if (!isLegal) continue;
for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
I != E; ++I) {
if (StringsEqualNoCase(RegName, RI->get(*I).Name))
return std::make_pair(*I, RC);
}
}
return std::pair<unsigned, const TargetRegisterClass*>(0, 0);
}