Port the recent innovations in ComputeMaskedBits to SimplifyDemandedBits.
This allows us to simplify on conditions where bits are not known, but they are not demanded either! This also fixes a couple of bugs in ComputeMaskedBits that were exposed during this work. In the future, swaths of instcombine should be removed, as this code subsumes a bunch of ad-hockery. llvm-svn: 26122
This commit is contained in:
Chris Lattner
parent
b24ce3a2a8
commit
0157e7f55b
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@ -228,7 +228,9 @@ namespace {
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// operators.
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bool SimplifyCommutative(BinaryOperator &I);
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bool SimplifyDemandedBits(Value *V, uint64_t Mask, unsigned Depth = 0);
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bool SimplifyDemandedBits(Value *V, uint64_t Mask,
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uint64_t &KnownZero, uint64_t &KnownOne,
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unsigned Depth = 0);
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// FoldOpIntoPhi - Given a binary operator or cast instruction which has a
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// PHI node as operand #0, see if we can fold the instruction into the PHI
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@ -406,6 +408,18 @@ static ConstantInt *SubOne(ConstantInt *C) {
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ConstantInt::get(C->getType(), 1)));
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}
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/// GetConstantInType - Return a ConstantInt with the specified type and value.
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///
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static ConstantInt *GetConstantInType(const Type *Ty, uint64_t Val) {
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if (Ty->isUnsigned())
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return ConstantUInt::get(Ty, Val);
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int64_t SVal = Val;
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SVal <<= 64-Ty->getPrimitiveSizeInBits();
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SVal >>= 64-Ty->getPrimitiveSizeInBits();
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return ConstantSInt::get(Ty, SVal);
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}
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/// ComputeMaskedBits - Determine which of the bits specified in Mask are
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/// known to be either zero or one and return them in the KnownZero/KnownOne
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/// bitsets. This code only analyzes bits in Mask, in order to short-circuit
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@ -420,7 +434,7 @@ static void ComputeMaskedBits(Value *V, uint64_t Mask, uint64_t &KnownZero,
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// this won't lose us code quality.
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if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V)) {
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// We know all of the bits for a constant!
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KnownOne = CI->getZExtValue();
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KnownOne = CI->getZExtValue() & Mask;
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KnownZero = ~KnownOne & Mask;
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return;
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}
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@ -430,147 +444,149 @@ static void ComputeMaskedBits(Value *V, uint64_t Mask, uint64_t &KnownZero,
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return; // Limit search depth.
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uint64_t KnownZero2, KnownOne2;
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if (Instruction *I = dyn_cast<Instruction>(V)) {
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switch (I->getOpcode()) {
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case Instruction::And:
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// If either the LHS or the RHS are Zero, the result is zero.
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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Mask &= ~KnownZero;
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-1 bits are only known if set in both the LHS & RHS.
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KnownOne &= KnownOne2;
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// Output known-0 are known to be clear if zero in either the LHS | RHS.
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KnownZero |= KnownZero2;
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return;
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case Instruction::Or:
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-0 bits are only known if clear in both the LHS & RHS.
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KnownZero &= KnownZero2;
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// Output known-1 are known to be set if set in either the LHS | RHS.
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KnownOne |= KnownOne2;
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return;
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case Instruction::Xor: {
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-0 bits are known if clear or set in both the LHS & RHS.
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uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
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// Output known-1 are known to be set if set in only one of the LHS, RHS.
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KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
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KnownZero = KnownZeroOut;
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) return;
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switch (I->getOpcode()) {
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case Instruction::And:
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// If either the LHS or the RHS are Zero, the result is zero.
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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Mask &= ~KnownZero;
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-1 bits are only known if set in both the LHS & RHS.
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KnownOne &= KnownOne2;
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// Output known-0 are known to be clear if zero in either the LHS | RHS.
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KnownZero |= KnownZero2;
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return;
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case Instruction::Or:
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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Mask &= ~KnownOne;
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-0 bits are only known if clear in both the LHS & RHS.
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KnownZero &= KnownZero2;
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// Output known-1 are known to be set if set in either the LHS | RHS.
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KnownOne |= KnownOne2;
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return;
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case Instruction::Xor: {
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Output known-0 bits are known if clear or set in both the LHS & RHS.
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uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
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// Output known-1 are known to be set if set in only one of the LHS, RHS.
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KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
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KnownZero = KnownZeroOut;
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return;
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}
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case Instruction::Select:
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ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Only known if known in both the LHS and RHS.
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KnownOne &= KnownOne2;
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KnownZero &= KnownZero2;
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return;
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case Instruction::Cast: {
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const Type *SrcTy = I->getOperand(0)->getType();
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if (!SrcTy->isIntegral()) return;
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// If this is an integer truncate or noop, just look in the input.
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if (SrcTy->getPrimitiveSizeInBits() >=
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I->getType()->getPrimitiveSizeInBits()) {
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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return;
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}
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case Instruction::Select:
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ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
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// Only known if known in both the LHS and RHS.
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KnownOne &= KnownOne2;
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KnownZero &= KnownZero2;
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return;
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case Instruction::Cast: {
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const Type *SrcTy = I->getOperand(0)->getType();
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if (!SrcTy->isIntegral()) return;
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// Sign or Zero extension. Compute the bits in the result that are not
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// present in the input.
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uint64_t NotIn = ~SrcTy->getIntegralTypeMask();
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uint64_t NewBits = I->getType()->getIntegralTypeMask() & NotIn;
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// If this is an integer truncate or noop, just look in the input.
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if (SrcTy->getPrimitiveSizeInBits() >=
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I->getType()->getPrimitiveSizeInBits()) {
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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return;
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}
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// Handle zero extension.
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if (!SrcTy->isSigned()) {
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Mask &= SrcTy->getIntegralTypeMask();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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// The top bits are known to be zero.
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KnownZero |= NewBits;
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} else {
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// Sign extension.
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Mask &= SrcTy->getIntegralTypeMask();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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// Sign or Zero extension. Compute the bits in the result that are not
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// present in the input.
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uint64_t NotIn = ~SrcTy->getIntegralTypeMask();
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uint64_t NewBits = I->getType()->getIntegralTypeMask() & NotIn;
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// Handle zero extension.
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if (!SrcTy->isSigned()) {
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Mask &= SrcTy->getIntegralTypeMask();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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// The top bits are known to be zero.
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// If the sign bit of the input is known set or clear, then we know the
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// top bits of the result.
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uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1);
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if (KnownZero & InSignBit) { // Input sign bit known zero
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KnownZero |= NewBits;
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KnownOne &= ~NewBits;
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} else if (KnownOne & InSignBit) { // Input sign bit known set
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KnownOne |= NewBits;
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KnownZero &= ~NewBits;
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} else { // Input sign bit unknown
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KnownZero &= ~NewBits;
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KnownOne &= ~NewBits;
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}
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}
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return;
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}
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case Instruction::Shl:
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// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
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if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
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Mask >>= SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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KnownZero <<= SA->getValue();
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KnownOne <<= SA->getValue();
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KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero.
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return;
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}
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break;
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case Instruction::Shr:
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// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
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if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
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// Compute the new bits that are at the top now.
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uint64_t HighBits = (1ULL << SA->getValue())-1;
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HighBits <<= I->getType()->getPrimitiveSizeInBits()-SA->getValue();
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if (I->getType()->isUnsigned()) { // Unsigned shift right.
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Mask <<= SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
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assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
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KnownZero >>= SA->getValue();
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KnownOne >>= SA->getValue();
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KnownZero |= HighBits; // high bits known zero.
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} else {
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// Sign extension.
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Mask &= SrcTy->getIntegralTypeMask();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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// If the sign bit of the input is known set or clear, then we know the
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// top bits of the result.
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uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1);
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if (KnownZero & InSignBit) { // Input sign bit known zero
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KnownZero |= NewBits;
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KnownOne &= ~NewBits;
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} else if (KnownOne & InSignBit) { // Input sign bit known set
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KnownOne |= NewBits;
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KnownZero &= ~NewBits;
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} else { // Input sign bit unknown
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KnownZero &= ~NewBits;
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KnownOne &= ~NewBits;
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Mask <<= SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
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assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
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KnownZero >>= SA->getValue();
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KnownOne >>= SA->getValue();
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// Handle the sign bits.
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uint64_t SignBit = 1ULL << (I->getType()->getPrimitiveSizeInBits()-1);
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SignBit >>= SA->getValue(); // Adjust to where it is now in the mask.
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if (KnownZero & SignBit) { // New bits are known zero.
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KnownZero |= HighBits;
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} else if (KnownOne & SignBit) { // New bits are known one.
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KnownOne |= HighBits;
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}
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}
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return;
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}
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case Instruction::Shl:
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// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
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if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
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Mask >> SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
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assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
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KnownZero <<= SA->getValue();
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KnownOne <<= SA->getValue();
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KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero.
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return;
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}
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break;
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case Instruction::Shr:
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// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
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if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
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// Compute the new bits that are at the top now.
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uint64_t HighBits = (1ULL << SA->getValue())-1;
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HighBits <<= I->getType()->getPrimitiveSizeInBits()-SA->getValue();
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if (I->getType()->isUnsigned()) { // Unsigned shift right.
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Mask << SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
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assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
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KnownZero >>= SA->getValue();
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KnownOne >>= SA->getValue();
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KnownZero |= HighBits; // high bits known zero.
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} else {
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Mask << SA->getValue();
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ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
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assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
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KnownZero >>= SA->getValue();
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KnownOne >>= SA->getValue();
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// Handle the sign bits.
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uint64_t SignBit = 1ULL << (I->getType()->getPrimitiveSizeInBits()-1);
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SignBit >>= SA->getValue(); // Adjust to where it is now in the mask.
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if (KnownZero & SignBit) { // New bits are known zero.
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KnownZero |= HighBits;
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} else if (KnownOne & SignBit) { // New bits are known one.
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KnownOne |= HighBits;
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}
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}
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return;
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}
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break;
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}
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break;
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}
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}
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@ -584,19 +600,54 @@ static bool MaskedValueIsZero(Value *V, uint64_t Mask, unsigned Depth = 0) {
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return (KnownZero & Mask) == Mask;
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}
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/// SimplifyDemandedBits - Look at V. At this point, we know that only the Mask
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/// bits of the result of V are ever used downstream. If we can use this
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/// information to simplify V, return V and set NewVal to the new value we
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/// should use in V's place.
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bool InstCombiner::SimplifyDemandedBits(Value *V, uint64_t Mask,
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/// ShrinkDemandedConstant - Check to see if the specified operand of the
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/// specified instruction is a constant integer. If so, check to see if there
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/// are any bits set in the constant that are not demanded. If so, shrink the
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/// constant and return true.
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static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
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uint64_t Demanded) {
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ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
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if (!OpC) return false;
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// If there are no bits set that aren't demanded, nothing to do.
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if ((~Demanded & OpC->getZExtValue()) == 0)
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return false;
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// This is producing any bits that are not needed, shrink the RHS.
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uint64_t Val = Demanded & OpC->getZExtValue();
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I->setOperand(OpNo, GetConstantInType(OpC->getType(), Val));
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return true;
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}
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/// SimplifyDemandedBits - Look at V. At this point, we know that only the
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/// DemandedMask bits of the result of V are ever used downstream. If we can
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/// use this information to simplify V, do so and return true. Otherwise,
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/// analyze the expression and return a mask of KnownOne and KnownZero bits for
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/// the expression (used to simplify the caller). The KnownZero/One bits may
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/// only be accurate for those bits in the DemandedMask.
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bool InstCombiner::SimplifyDemandedBits(Value *V, uint64_t DemandedMask,
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uint64_t &KnownZero, uint64_t &KnownOne,
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unsigned Depth) {
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if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V)) {
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// We know all of the bits for a constant!
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KnownOne = CI->getZExtValue() & DemandedMask;
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KnownZero = ~KnownOne & DemandedMask;
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return false;
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}
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KnownZero = KnownOne = 0;
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if (!V->hasOneUse()) { // Other users may use these bits.
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if (Depth != 0) // Not at the root.
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if (Depth != 0) { // Not at the root.
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// Just compute the KnownZero/KnownOne bits to simplify things downstream.
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ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
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return false;
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}
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// If this is the root being simplified, allow it to have multiple uses,
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// just set the Mask to all bits.
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Mask = V->getType()->getIntegralTypeMask();
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} else if (Mask == 0) { // Not demanding any bits from V.
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// just set the DemandedMask to all bits.
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DemandedMask = V->getType()->getIntegralTypeMask();
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} else if (DemandedMask == 0) { // Not demanding any bits from V.
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if (V != UndefValue::get(V->getType()))
|
||||
return UpdateValueUsesWith(V, UndefValue::get(V->getType()));
|
||||
return false;
|
||||
|
|
@ -607,99 +658,257 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, uint64_t Mask,
|
|||
Instruction *I = dyn_cast<Instruction>(V);
|
||||
if (!I) return false; // Only analyze instructions.
|
||||
|
||||
uint64_t KnownZero2, KnownOne2;
|
||||
switch (I->getOpcode()) {
|
||||
default: break;
|
||||
case Instruction::And:
|
||||
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
||||
// Only demanding an intersection of the bits.
|
||||
if (SimplifyDemandedBits(I->getOperand(0), RHS->getRawValue() & Mask,
|
||||
Depth+1))
|
||||
return true;
|
||||
if (~Mask & RHS->getZExtValue()) {
|
||||
// If this is producing any bits that are not needed, simplify the RHS.
|
||||
uint64_t Val = Mask & RHS->getZExtValue();
|
||||
Constant *RHS =
|
||||
ConstantUInt::get(I->getType()->getUnsignedVersion(), Val);
|
||||
if (I->getType()->isSigned())
|
||||
RHS = ConstantExpr::getCast(RHS, I->getType());
|
||||
I->setOperand(1, RHS);
|
||||
return UpdateValueUsesWith(I, I);
|
||||
// If either the LHS or the RHS are Zero, the result is zero.
|
||||
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
|
||||
// If something is known zero on the RHS, the bits aren't demanded on the
|
||||
// LHS.
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~KnownZero,
|
||||
KnownZero2, KnownOne2, 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 UpdateValueUsesWith(I, I->getOperand(0));
|
||||
if ((DemandedMask & ~KnownZero & KnownOne2) == (DemandedMask & ~KnownZero))
|
||||
return UpdateValueUsesWith(I, I->getOperand(1));
|
||||
|
||||
// If the RHS is a constant, see if we can simplify it.
|
||||
if (ShrinkDemandedConstant(I, 1, DemandedMask))
|
||||
return UpdateValueUsesWith(I, I);
|
||||
|
||||
// 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 Instruction::Or:
|
||||
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~KnownOne,
|
||||
KnownZero2, KnownOne2, 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 UpdateValueUsesWith(I, I->getOperand(0));
|
||||
if ((DemandedMask & ~KnownOne & KnownZero2) == DemandedMask & ~KnownOne)
|
||||
return UpdateValueUsesWith(I, I->getOperand(1));
|
||||
|
||||
// If the RHS is a constant, see if we can simplify it.
|
||||
if (ShrinkDemandedConstant(I, 1, DemandedMask))
|
||||
return UpdateValueUsesWith(I, I);
|
||||
|
||||
// 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 Instruction::Xor: {
|
||||
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
|
||||
KnownZero2, KnownOne2, 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 UpdateValueUsesWith(I, I->getOperand(0));
|
||||
if ((DemandedMask & KnownZero2) == DemandedMask)
|
||||
return UpdateValueUsesWith(I, I->getOperand(1));
|
||||
|
||||
// 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.
|
||||
uint64_t 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.
|
||||
if (uint64_t UnknownBits = DemandedMask & ~(KnownZeroOut|KnownOneOut)) {
|
||||
if ((UnknownBits & (KnownZero|KnownZero2)) == UnknownBits) {
|
||||
Instruction *Or =
|
||||
BinaryOperator::createOr(I->getOperand(0), I->getOperand(1),
|
||||
I->getName());
|
||||
InsertNewInstBefore(Or, *I);
|
||||
return UpdateValueUsesWith(I, Or);
|
||||
}
|
||||
}
|
||||
// Walk the LHS and the RHS.
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask, Depth+1) ||
|
||||
SimplifyDemandedBits(I->getOperand(1), Mask, Depth+1);
|
||||
case Instruction::Or:
|
||||
case Instruction::Xor:
|
||||
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
||||
// If none of the [x]or'd in bits are demanded, don't both with the [x]or.
|
||||
if ((Mask & RHS->getRawValue()) == 0)
|
||||
return UpdateValueUsesWith(I, I->getOperand(0));
|
||||
|
||||
// Otherwise, for an OR, we only demand those bits not set by the OR.
|
||||
if (I->getOpcode() == Instruction::Or)
|
||||
Mask &= ~RHS->getRawValue();
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask, Depth+1);
|
||||
}
|
||||
// Walk the LHS and the RHS.
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask, Depth+1) ||
|
||||
SimplifyDemandedBits(I->getOperand(1), Mask, Depth+1);
|
||||
|
||||
// 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 (ShrinkDemandedConstant(I, 1, DemandedMask))
|
||||
return UpdateValueUsesWith(I, I);
|
||||
|
||||
KnownZero = KnownZeroOut;
|
||||
KnownOne = KnownOneOut;
|
||||
break;
|
||||
}
|
||||
case Instruction::Select:
|
||||
if (SimplifyDemandedBits(I->getOperand(2), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
|
||||
KnownZero2, KnownOne2, 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 (ShrinkDemandedConstant(I, 1, DemandedMask))
|
||||
return UpdateValueUsesWith(I, I);
|
||||
if (ShrinkDemandedConstant(I, 2, DemandedMask))
|
||||
return UpdateValueUsesWith(I, I);
|
||||
|
||||
// Only known if known in both the LHS and RHS.
|
||||
KnownOne &= KnownOne2;
|
||||
KnownZero &= KnownZero2;
|
||||
break;
|
||||
case Instruction::Cast: {
|
||||
const Type *SrcTy = I->getOperand(0)->getType();
|
||||
if (SrcTy == Type::BoolTy)
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask&1, Depth+1);
|
||||
if (!SrcTy->isIntegral()) return false;
|
||||
|
||||
if (!SrcTy->isInteger()) return false;
|
||||
// If this is an integer truncate or noop, just look in the input.
|
||||
if (SrcTy->getPrimitiveSizeInBits() >=
|
||||
I->getType()->getPrimitiveSizeInBits()) {
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
break;
|
||||
}
|
||||
|
||||
// Sign or Zero extension. Compute the bits in the result that are not
|
||||
// present in the input.
|
||||
uint64_t NotIn = ~SrcTy->getIntegralTypeMask();
|
||||
uint64_t NewBits = I->getType()->getIntegralTypeMask() & NotIn;
|
||||
|
||||
// Handle zero extension.
|
||||
if (!SrcTy->isSigned()) {
|
||||
DemandedMask &= SrcTy->getIntegralTypeMask();
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
// The top bits are known to be zero.
|
||||
KnownZero |= NewBits;
|
||||
} else {
|
||||
// Sign extension.
|
||||
if (SimplifyDemandedBits(I->getOperand(0),
|
||||
DemandedMask & SrcTy->getIntegralTypeMask(),
|
||||
KnownZero, KnownOne, 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.
|
||||
uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1);
|
||||
|
||||
unsigned SrcBits = SrcTy->getPrimitiveSizeInBits();
|
||||
// If this is a sign-extend, treat specially.
|
||||
if (SrcTy->isSigned() &&
|
||||
SrcBits < I->getType()->getPrimitiveSizeInBits()) {
|
||||
// If none of the top bits are demanded, convert this into an unsigned
|
||||
// extend instead of a sign extend.
|
||||
if ((Mask & ((1ULL << SrcBits)-1)) == 0) {
|
||||
// If the input sign bit is known zero, or if the NewBits are not demanded
|
||||
// convert this into a zero extension.
|
||||
if ((KnownZero & InSignBit) || (NewBits & ~DemandedMask) == NewBits) {
|
||||
// Convert to unsigned first.
|
||||
Instruction *NewVal;
|
||||
NewVal = new CastInst(I->getOperand(0), SrcTy->getUnsignedVersion(),
|
||||
I->getOperand(0)->getName());
|
||||
InsertNewInstBefore(NewVal, *I);
|
||||
// Then cast that to the destination type.
|
||||
NewVal = new CastInst(NewVal, I->getType(), I->getName());
|
||||
InsertNewInstBefore(NewVal, *I);
|
||||
return UpdateValueUsesWith(I, NewVal);
|
||||
} else if (KnownOne & InSignBit) { // Input sign bit known set
|
||||
KnownOne |= NewBits;
|
||||
KnownZero &= ~NewBits;
|
||||
} else { // Input sign bit unknown
|
||||
KnownZero &= ~NewBits;
|
||||
KnownOne &= ~NewBits;
|
||||
}
|
||||
|
||||
// Otherwise, the high-bits *are* demanded. This means that the code
|
||||
// implicitly demands computation of the sign bit of the input, make sure
|
||||
// we explicitly include it in Mask.
|
||||
Mask |= 1ULL << (SrcBits-1);
|
||||
}
|
||||
|
||||
// If this is an extension, the top bits are ignored.
|
||||
Mask &= SrcTy->getIntegralTypeMask();
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask, Depth+1);
|
||||
break;
|
||||
}
|
||||
case Instruction::Select:
|
||||
// Simplify the T and F values if they are not demanded.
|
||||
return SimplifyDemandedBits(I->getOperand(2), Mask, Depth+1) ||
|
||||
SimplifyDemandedBits(I->getOperand(1), Mask, Depth+1);
|
||||
case Instruction::Shl:
|
||||
// We only demand the low bits of the input.
|
||||
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask >> SA->getValue(),
|
||||
Depth+1);
|
||||
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask >> SA->getValue(),
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
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.
|
||||
}
|
||||
break;
|
||||
case Instruction::Shr:
|
||||
// We only demand the high bits of the input.
|
||||
if (I->getType()->isUnsigned())
|
||||
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
|
||||
Mask <<= SA->getValue();
|
||||
Mask &= I->getType()->getIntegralTypeMask();
|
||||
return SimplifyDemandedBits(I->getOperand(0), Mask, Depth+1);
|
||||
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1))) {
|
||||
unsigned ShAmt = SA->getValue();
|
||||
|
||||
// Compute the new bits that are at the top now.
|
||||
uint64_t HighBits = (1ULL << ShAmt)-1;
|
||||
HighBits <<= I->getType()->getPrimitiveSizeInBits() - ShAmt;
|
||||
|
||||
if (I->getType()->isUnsigned()) { // Unsigned shift right.
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask << ShAmt,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
|
||||
KnownZero >>= ShAmt;
|
||||
KnownOne >>= ShAmt;
|
||||
KnownZero |= HighBits; // high bits known zero.
|
||||
} else { // Signed shift right.
|
||||
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask << ShAmt,
|
||||
KnownZero, KnownOne, Depth+1))
|
||||
return true;
|
||||
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 << (I->getType()->getPrimitiveSizeInBits()-1);
|
||||
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) {
|
||||
// Convert the input to unsigned.
|
||||
Instruction *NewVal;
|
||||
NewVal = new CastInst(I->getOperand(0),
|
||||
I->getType()->getUnsignedVersion(),
|
||||
I->getOperand(0)->getName());
|
||||
InsertNewInstBefore(NewVal, *I);
|
||||
// Perform the unsigned shift right.
|
||||
NewVal = new ShiftInst(Instruction::Shr, NewVal, SA, I->getName());
|
||||
InsertNewInstBefore(NewVal, *I);
|
||||
// Then cast that to the destination type.
|
||||
NewVal = new CastInst(NewVal, I->getType(), I->getName());
|
||||
InsertNewInstBefore(NewVal, *I);
|
||||
return UpdateValueUsesWith(I, NewVal);
|
||||
} else if (KnownOne & SignBit) { // New bits are known one.
|
||||
KnownOne |= HighBits;
|
||||
}
|
||||
}
|
||||
// FIXME: handle signed shr, demanding the appropriate bits. If the top
|
||||
// bits aren't demanded, strength reduce to a logical SHR instead.
|
||||
}
|
||||
break;
|
||||
}
|
||||
|
||||
// If the client is only demanding bits that we know, return the known
|
||||
// constant.
|
||||
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask)
|
||||
return UpdateValueUsesWith(I, GetConstantInType(I->getType(), KnownOne));
|
||||
return false;
|
||||
}
|
||||
|
||||
|
|
@ -2021,7 +2230,9 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
|
|||
|
||||
// See if we can simplify any instructions used by the LHS whose sole
|
||||
// purpose is to compute bits we don't care about.
|
||||
if (SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask()))
|
||||
uint64_t KnownZero, KnownOne;
|
||||
if (SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask(),
|
||||
KnownZero, KnownOne))
|
||||
return &I;
|
||||
|
||||
if (ConstantIntegral *AndRHS = dyn_cast<ConstantIntegral>(Op1)) {
|
||||
|
|
@ -4378,9 +4589,12 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
|
|||
|
||||
// See if we can simplify any instructions used by the LHS whose sole
|
||||
// purpose is to compute bits we don't care about.
|
||||
if (CI.getType()->isInteger() && CI.getOperand(0)->getType()->isIntegral() &&
|
||||
SimplifyDemandedBits(&CI, CI.getType()->getIntegralTypeMask()))
|
||||
return &CI;
|
||||
if (CI.getType()->isInteger() && CI.getOperand(0)->getType()->isIntegral()) {
|
||||
uint64_t KnownZero, KnownOne;
|
||||
if (SimplifyDemandedBits(&CI, CI.getType()->getIntegralTypeMask(),
|
||||
KnownZero, KnownOne))
|
||||
return &CI;
|
||||
}
|
||||
|
||||
// If casting the result of a getelementptr instruction with no offset, turn
|
||||
// this into a cast of the original pointer!
|
||||
|
|
|
|||
Loading…
Reference in New Issue