mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-25 04:02:41 +01:00
For PR1205:
Add a new ComputeMaskedBits function that is APIntified. We'll slowly convert things over to use this version. When its all done, we'll remove the existing version. llvm-svn: 35018
This commit is contained in:
Reid Spencer
parent
c79408b032
commit
6a924d1a1d
@ -566,6 +566,211 @@ static ConstantInt *SubOne(ConstantInt *C) {
|
||||
ConstantInt::get(C->getType(), 1)));
|
||||
}
|
||||
|
||||
/// ComputeMaskedBits - Determine which of the bits specified in Mask are
|
||||
/// known to be either zero or one and return them in the KnownZero/KnownOne
|
||||
/// bit sets. This code only analyzes bits in Mask, in order to short-circuit
|
||||
/// processing.
|
||||
/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
|
||||
/// we cannot optimize based on the assumption that it is zero without changing
|
||||
/// it to be an explicit zero. If we don't change it to zero, other code could
|
||||
/// optimized based on the contradictory assumption that it is non-zero.
|
||||
/// Because instcombine aggressively folds operations with undef args anyway,
|
||||
/// this won't lose us code quality.
|
||||
static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
|
||||
APInt& KnownOne, unsigned Depth = 0) {
|
||||
uint32_t BitWidth = Mask.getBitWidth();
|
||||
assert(KnownZero.getBitWidth() == BitWidth &&
|
||||
KnownOne.getBitWidth() == BitWidth &&
|
||||
"Mask, KnownOne and KnownZero should have same BitWidth");
|
||||
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
|
||||
// We know all of the bits for a constant!
|
||||
APInt Tmp(CI->getValue());
|
||||
Tmp.zextOrTrunc(BitWidth);
|
||||
KnownOne = Tmp & Mask;
|
||||
KnownZero = ~KnownOne & Mask;
|
||||
return;
|
||||
}
|
||||
|
||||
KnownZero.clear(); KnownOne.clear(); // Don't know anything.
|
||||
if (Depth == 6 || Mask == 0)
|
||||
return; // Limit search depth.
|
||||
|
||||
Instruction *I = dyn_cast<Instruction>(V);
|
||||
if (!I) return;
|
||||
|
||||
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
|
||||
Mask &= APInt::getAllOnesValue(
|
||||
cast<IntegerType>(V->getType())->getBitWidth()).zextOrTrunc(BitWidth);
|
||||
|
||||
switch (I->getOpcode()) {
|
||||
case Instruction::And:
|
||||
// If either the LHS or the RHS are Zero, the result is zero.
|
||||
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
|
||||
Mask &= ~KnownZero;
|
||||
ComputeMaskedBits(I->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 Instruction::Or:
|
||||
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
|
||||
Mask &= ~KnownOne;
|
||||
ComputeMaskedBits(I->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 Instruction::Xor: {
|
||||
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
|
||||
ComputeMaskedBits(I->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.
|
||||
APInt 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 Instruction::Select:
|
||||
ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
|
||||
ComputeMaskedBits(I->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 Instruction::FPTrunc:
|
||||
case Instruction::FPExt:
|
||||
case Instruction::FPToUI:
|
||||
case Instruction::FPToSI:
|
||||
case Instruction::SIToFP:
|
||||
case Instruction::PtrToInt:
|
||||
case Instruction::UIToFP:
|
||||
case Instruction::IntToPtr:
|
||||
return; // Can't work with floating point or pointers
|
||||
case Instruction::Trunc:
|
||||
// All these have integer operands
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
|
||||
return;
|
||||
case Instruction::BitCast: {
|
||||
const Type *SrcTy = I->getOperand(0)->getType();
|
||||
if (SrcTy->isInteger()) {
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
|
||||
return;
|
||||
}
|
||||
break;
|
||||
}
|
||||
case Instruction::ZExt: {
|
||||
// Compute the bits in the result that are not present in the input.
|
||||
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
|
||||
APInt NotIn(~SrcTy->getMask());
|
||||
APInt NewBits = APInt::getAllOnesValue(BitWidth) &
|
||||
NotIn.zext(BitWidth);
|
||||
|
||||
Mask &= ~NotIn;
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
// The top bits are known to be zero.
|
||||
KnownZero |= NewBits;
|
||||
return;
|
||||
}
|
||||
case Instruction::SExt: {
|
||||
// Compute the bits in the result that are not present in the input.
|
||||
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
|
||||
APInt NotIn(~SrcTy->getMask());
|
||||
APInt NewBits = APInt::getAllOnesValue(BitWidth) &
|
||||
NotIn.zext(BitWidth);
|
||||
|
||||
Mask &= ~NotIn;
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, 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.
|
||||
APInt InSignBit(APInt::getSignedMinValue(SrcTy->getBitWidth()));
|
||||
InSignBit.zextOrTrunc(BitWidth);
|
||||
if ((KnownZero & InSignBit) != 0) { // Input sign bit known zero
|
||||
KnownZero |= NewBits;
|
||||
KnownOne &= ~NewBits;
|
||||
} else if ((KnownOne & InSignBit) != 0) { // Input sign bit known set
|
||||
KnownOne |= NewBits;
|
||||
KnownZero &= ~NewBits;
|
||||
} else { // Input sign bit unknown
|
||||
KnownZero &= ~NewBits;
|
||||
KnownOne &= ~NewBits;
|
||||
}
|
||||
return;
|
||||
}
|
||||
case Instruction::Shl:
|
||||
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
|
||||
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
||||
uint64_t ShiftAmt = SA->getZExtValue();
|
||||
Mask = APIntOps::lshr(Mask, ShiftAmt);
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
KnownZero = APIntOps::shl(KnownZero, ShiftAmt);
|
||||
KnownOne = APIntOps::shl(KnownOne, ShiftAmt);
|
||||
KnownZero |= APInt(BitWidth, 1ULL).shl(ShiftAmt)-1; // low bits known zero.
|
||||
return;
|
||||
}
|
||||
break;
|
||||
case Instruction::LShr:
|
||||
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
|
||||
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
||||
// Compute the new bits that are at the top now.
|
||||
uint64_t ShiftAmt = SA->getZExtValue();
|
||||
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth-ShiftAmt));
|
||||
|
||||
// Unsigned shift right.
|
||||
Mask = APIntOps::shl(Mask, ShiftAmt);
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
|
||||
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
|
||||
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
|
||||
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
|
||||
KnownZero |= HighBits; // high bits known zero.
|
||||
return;
|
||||
}
|
||||
break;
|
||||
case Instruction::AShr:
|
||||
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
|
||||
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
||||
// Compute the new bits that are at the top now.
|
||||
uint64_t ShiftAmt = SA->getZExtValue();
|
||||
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth-ShiftAmt));
|
||||
|
||||
// Signed shift right.
|
||||
Mask = APIntOps::shl(Mask, ShiftAmt);
|
||||
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
|
||||
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
|
||||
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
|
||||
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
|
||||
|
||||
// Handle the sign bits and adjust to where it is now in the mask.
|
||||
APInt SignBit = APInt::getSignedMinValue(BitWidth).lshr(ShiftAmt);
|
||||
|
||||
if ((KnownZero & SignBit) != 0) { // New bits are known zero.
|
||||
KnownZero |= HighBits;
|
||||
} else if ((KnownOne & SignBit) != 0) { // New bits are known one.
|
||||
KnownOne |= HighBits;
|
||||
}
|
||||
return;
|
||||
}
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
/// 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
|
||||
|
||||
Loading…
Reference in New Issue
Block a user