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make some fairly meaty internal changes to how SimplifyDemandedBits works.

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Now, if it detects that "V" is the same as some other value, 
SimplifyDemandedBits returns the new value instead of RAUW'ing it immediately.
This has two benefits:
1) simpler code in the recursive SimplifyDemandedBits routine.
2) it allows future fun stuff in instcombine where an operation has multiple
   uses and can be simplified in one context, but not all.

#2 isn't implemented yet, this patch should have no functionality change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63479 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-01-31 08:15:18 +00:00
parent bda9dfd5ab
commit 886ab6c49c
1 changed files with 172 additions and 206 deletions
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378
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -303,23 +303,6 @@ namespace {
}
}
// UpdateValueUsesWith - This method is to be used when an value is
// found to be replacable with another preexisting expression or was
// updated. Here we add all uses of I to the worklist, replace all uses of
// I with the new value (unless the instruction was just updated), then
// return true, so that the inst combiner will know that I was modified.
//
bool UpdateValueUsesWith(Value *Old, Value *New) {
AddUsersToWorkList(*Old); // Add all modified instrs to worklist
if (Old != New)
Old->replaceAllUsesWith(New);
if (Instruction *I = dyn_cast<Instruction>(Old))
AddToWorkList(I);
if (Instruction *I = dyn_cast<Instruction>(New))
AddToWorkList(I);
return true;
}
// EraseInstFromFunction - When dealing with an instruction that has side
// effects or produces a void value, we can't rely on DCE to delete the
// instruction. Instead, visit methods should return the value returned by
@ -355,12 +338,20 @@ namespace {
/// most-complex to least-complex order.
bool SimplifyCompare(CmpInst &I);
/// SimplifyDemandedBits - Attempts to replace V with a simpler value based
/// on the demanded bits.
bool SimplifyDemandedBits(Value *V, APInt DemandedMask,
/// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
/// based on the demanded bits.
Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
APInt& KnownZero, APInt& KnownOne,
unsigned Depth);
bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
APInt& KnownZero, APInt& KnownOne,
unsigned Depth = 0);
unsigned Depth=0);
/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
/// SimplifyDemandedBits knows about. See if the instruction has any
/// properties that allow us to simplify its operands.
bool SimplifyDemandedInstructionBits(Instruction &Inst);
Value *SimplifyDemandedVectorElts(Value *V, uint64_t DemandedElts,
uint64_t &UndefElts, unsigned Depth = 0);
@ -750,14 +741,44 @@ static void ComputeUnsignedMinMaxValuesFromKnownBits(const Type *Ty,
Max = KnownOne|UnknownBits;
}
/// SimplifyDemandedBits - This function attempts to replace V with a simpler
/// value based on the demanded bits. When this function is called, it is known
/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
/// SimplifyDemandedBits knows about. See if the instruction has any
/// properties that allow us to simplify its operands.
bool InstCombiner::SimplifyDemandedInstructionBits(Instruction &Inst) {
unsigned BitWidth = cast<IntegerType>(Inst.getType())->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
APInt DemandedMask(APInt::getAllOnesValue(BitWidth));
Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask,
KnownZero, KnownOne, 0);
if (V == 0) return false;
if (V == &Inst) return true;
ReplaceInstUsesWith(Inst, V);
return true;
}
/// SimplifyDemandedBits - This form of SimplifyDemandedBits simplifies the
/// specified instruction operand if possible, updating it in place. It returns
/// true if it made any change and false otherwise.
bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask,
APInt &KnownZero, APInt &KnownOne,
unsigned Depth) {
Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask,
KnownZero, KnownOne, Depth);
if (NewVal == 0) return false;
U.set(NewVal);
return true;
}
/// SimplifyDemandedUseBits - This function attempts to replace V with a simpler
/// value based on the demanded bits. When this function is called, it is known
/// that only the bits set in DemandedMask of the result of V are ever used
/// downstream. Consequently, depending on the mask and V, it may be possible
/// to replace V with a constant or one of its operands. In such cases, this
/// function does the replacement and returns true. In all other cases, it
/// returns false after analyzing the expression and setting KnownOne and known
/// to be one in the expression. KnownZero contains all the bits that are known
/// to be one in the expression. KnownZero contains all the bits that are known
/// to be zero in the expression. These are provided to potentially allow the
/// caller (which might recursively be SimplifyDemandedBits itself) to simplify
/// the expression. KnownOne and KnownZero always follow the invariant that
@ -765,9 +786,15 @@ static void ComputeUnsignedMinMaxValuesFromKnownBits(const Type *Ty,
/// the bits in KnownOne and KnownZero may only be accurate for those bits set
/// in DemandedMask. Note also that the bitwidth of V, DemandedMask, KnownZero
/// and KnownOne must all be the same.
bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
APInt &KnownZero, APInt &KnownOne,
unsigned Depth) {
///
/// This returns null if it did not change anything and it permits no
/// simplification. This returns V itself if it did some simplification of V's
/// operands based on the information about what bits are demanded. This returns
/// some other non-null value if it found out that V is equal to another value
/// in the context where the specified bits are demanded, but not for all users.
Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
APInt &KnownZero, APInt &KnownOne,
unsigned Depth) {
assert(V != 0 && "Null pointer of Value???");
assert(Depth <= 6 && "Limit Search Depth");
uint32_t BitWidth = DemandedMask.getBitWidth();
@ -781,69 +808,63 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// We know all of the bits for a constant!
KnownOne = CI->getValue() & DemandedMask;
KnownZero = ~KnownOne & DemandedMask;
return false;
return 0;
}
KnownZero.clear();
KnownOne.clear();
if (!V->hasOneUse()) { // Other users may use these bits.
if (DemandedMask == 0) { // Not demanding any bits from V.
if (isa<UndefValue>(V))
return 0;
return UndefValue::get(VTy);
} else if (!V->hasOneUse()) { // Other users may use these bits.
if (Depth != 0) { // Not at the root.
// Just compute the KnownZero/KnownOne bits to simplify things downstream.
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
return false;
return 0;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the DemandedMask to all bits.
DemandedMask = APInt::getAllOnesValue(BitWidth);
} else if (DemandedMask == 0) { // Not demanding any bits from V.
if (!isa<UndefValue>(V))
return UpdateValueUsesWith(V, UndefValue::get(VTy));
return false;
} else if (Depth == 6) { // Limit search depth.
return false;
return 0;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false; // Only analyze instructions.
if (!I) return 0; // Only analyze instructions.
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
APInt &RHSKnownZero = KnownZero, &RHSKnownOne = KnownOne;
switch (I->getOpcode()) {
default:
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
ComputeMaskedBits(I, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
break;
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 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 & ~RHSKnownZero,
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownZero,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
assert((LHSKnownZero & LHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
// If all of the demanded bits are known 1 on one side, return the other.
// These bits cannot contribute to the result of the 'and'.
if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
(DemandedMask & ~LHSKnownZero))
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
(DemandedMask & ~RHSKnownZero))
return UpdateValueUsesWith(I, I->getOperand(1));
return I->getOperand(1);
// If all of the demanded bits in the inputs are known zeros, return zero.
if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
return UpdateValueUsesWith(I, Constant::getNullValue(VTy));
return Constant::getNullValue(VTy);
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnownZero))
return UpdateValueUsesWith(I, I);
return I;
// Output known-1 bits are only known if set in both the LHS & RHS.
RHSKnownOne &= LHSKnownOne;
@ -852,40 +873,35 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
break;
case Instruction::Or:
// If either the LHS or the RHS are One, the result is One.
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
// If something is known one on the RHS, the bits aren't demanded on the
// LHS.
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~RHSKnownOne,
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownOne,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
assert((LHSKnownZero & LHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "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 & ~LHSKnownOne & RHSKnownZero) ==
(DemandedMask & ~LHSKnownOne))
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
(DemandedMask & ~RHSKnownOne))
return UpdateValueUsesWith(I, I->getOperand(1));
return I->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 & (~RHSKnownZero) & LHSKnownOne) ==
(DemandedMask & (~RHSKnownZero)))
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
(DemandedMask & (~LHSKnownZero)))
return UpdateValueUsesWith(I, I->getOperand(1));
return I->getOperand(1);
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return UpdateValueUsesWith(I, I);
return I;
// Output known-0 bits are only known if clear in both the LHS & RHS.
RHSKnownZero &= LHSKnownZero;
@ -893,23 +909,20 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
RHSKnownOne |= LHSKnownOne;
break;
case Instruction::Xor: {
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
assert((LHSKnownZero & LHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "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 & RHSKnownZero) == DemandedMask)
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
if ((DemandedMask & LHSKnownZero) == DemandedMask)
return UpdateValueUsesWith(I, I->getOperand(1));
return I->getOperand(1);
// Output known-0 bits are known if clear or set in both the LHS & RHS.
APInt KnownZeroOut = (RHSKnownZero & LHSKnownZero) |
@ -925,8 +938,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
Instruction *Or =
BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
I->getName());
InsertNewInstBefore(Or, *I);
return UpdateValueUsesWith(I, Or);
return InsertNewInstBefore(Or, *I);
}
// If all of the demanded bits on one side are known, and all of the set
@ -939,92 +951,80 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
Constant *AndC = ConstantInt::get(~RHSKnownOne & DemandedMask);
Instruction *And =
BinaryOperator::CreateAnd(I->getOperand(0), AndC, "tmp");
InsertNewInstBefore(And, *I);
return UpdateValueUsesWith(I, And);
return InsertNewInstBefore(And, *I);
}
}
// 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);
return I;
RHSKnownZero = KnownZeroOut;
RHSKnownOne = KnownOneOut;
break;
}
case Instruction::Select:
if (SimplifyDemandedBits(I->getOperand(2), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
if (SimplifyDemandedBits(I->getOperandUse(2), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
assert((LHSKnownZero & LHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "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);
if (ShrinkDemandedConstant(I, 1, DemandedMask) ||
ShrinkDemandedConstant(I, 2, DemandedMask))
return I;
// Only known if known in both the LHS and RHS.
RHSKnownOne &= LHSKnownOne;
RHSKnownZero &= LHSKnownZero;
break;
case Instruction::Trunc: {
uint32_t truncBf =
cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
unsigned truncBf = I->getOperand(0)->getType()->getPrimitiveSizeInBits();
DemandedMask.zext(truncBf);
RHSKnownZero.zext(truncBf);
RHSKnownOne.zext(truncBf);
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
return I;
DemandedMask.trunc(BitWidth);
RHSKnownZero.trunc(BitWidth);
RHSKnownOne.trunc(BitWidth);
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
break;
}
case Instruction::BitCast:
if (!I->getOperand(0)->getType()->isInteger())
return false;
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
return false; // vector->int or fp->int?
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
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());
uint32_t SrcBitWidth = SrcTy->getBitWidth();
unsigned SrcBitWidth =I->getOperand(0)->getType()->getPrimitiveSizeInBits();
DemandedMask.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
return I;
DemandedMask.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
// The top bits are known to be zero.
RHSKnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
break;
}
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());
uint32_t SrcBitWidth = SrcTy->getBitWidth();
unsigned SrcBitWidth =I->getOperand(0)->getType()->getPrimitiveSizeInBits();
APInt InputDemandedBits = DemandedMask &
APInt::getLowBitsSet(BitWidth, SrcBitWidth);
@ -1038,25 +1038,23 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
InputDemandedBits.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits,
if (SimplifyDemandedBits(I->getOperandUse(0), InputDemandedBits,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
return I;
InputDemandedBits.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
assert(!(RHSKnownZero & RHSKnownOne) && "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, or if the NewBits are not demanded
// convert this into a zero extension.
if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits)
{
if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) {
// Convert to ZExt cast
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName(), I);
return UpdateValueUsesWith(I, NewCast);
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName());
return InsertNewInstBefore(NewCast, *I);
} else if (RHSKnownOne[SrcBitWidth-1]) { // Input sign bit known set
RHSKnownOne |= NewBits;
}
@ -1066,7 +1064,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// Figure out what the input bits are. If the top bits of the and result
// are not demanded, then the add doesn't demand them from its input
// either.
uint32_t NLZ = DemandedMask.countLeadingZeros();
unsigned NLZ = DemandedMask.countLeadingZeros();
// If there is a constant on the RHS, there are a variety of xformations
// we can do.
@ -1081,14 +1079,14 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ));
// Find information about known zero/one bits in the input.
if (SimplifyDemandedBits(I->getOperand(0), InDemandedBits,
if (SimplifyDemandedBits(I->getOperandUse(0), InDemandedBits,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
return I;
// If the RHS of the add has bits set that can't affect the input, reduce
// the constant.
if (ShrinkDemandedConstant(I, 1, InDemandedBits))
return UpdateValueUsesWith(I, I);
return I;
// Avoid excess work.
if (LHSKnownZero == 0 && LHSKnownOne == 0)
@ -1099,8 +1097,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
Instruction *Or =
BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
I->getName());
InsertNewInstBefore(Or, *I);
return UpdateValueUsesWith(I, Or);
return InsertNewInstBefore(Or, *I);
}
// We can say something about the output known-zero and known-one bits,
@ -1112,7 +1109,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// To compute this, we first compute the potential carry bits. These are
// the bits which may be modified. I'm not aware of a better way to do
// this scan.
const APInt& RHSVal = RHS->getValue();
const APInt &RHSVal = RHS->getValue();
APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal));
// Now that we know which bits have carries, compute the known-1/0 sets.
@ -1132,12 +1129,11 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// Right fill the mask of bits for this ADD to demand the most
// significant bit and all those below it.
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
if (SimplifyDemandedBits(I->getOperand(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
return I;
}
}
break;
@ -1150,12 +1146,11 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// significant bit and all those below it.
uint32_t NLZ = DemandedMask.countLeadingZeros();
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
if (SimplifyDemandedBits(I->getOperand(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
return I;
}
// Otherwise just hand the sub off to ComputeMaskedBits to fill in
// the known zeros and ones.
@ -1165,11 +1160,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero <<= ShiftAmt;
RHSKnownOne <<= ShiftAmt;
// low bits known zero.
@ -1184,11 +1178,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// Unsigned shift right.
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
if (ShiftAmt) {
@ -1205,16 +1198,15 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// the shift amount is >= the size of the datatype, which is undefined.
if (DemandedMask == 1) {
// Perform the logical shift right.
Value *NewVal = BinaryOperator::CreateLShr(
Instruction *NewVal = BinaryOperator::CreateLShr(
I->getOperand(0), I->getOperand(1), I->getName());
InsertNewInstBefore(cast<Instruction>(NewVal), *I);
return UpdateValueUsesWith(I, NewVal);
return InsertNewInstBefore(NewVal, *I);
}
// If the sign bit is the only bit demanded by this ashr, then there is no
// need to do it, the shift doesn't change the high bit.
if (DemandedMask.isSignBit())
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t ShiftAmt = SA->getLimitedValue(BitWidth);
@ -1225,12 +1217,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// demanded.
if (DemandedMask.countLeadingZeros() <= ShiftAmt)
DemandedMaskIn.set(BitWidth-1);
if (SimplifyDemandedBits(I->getOperand(0),
DemandedMaskIn,
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
@ -1246,10 +1236,9 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
if (BitWidth <= ShiftAmt || RHSKnownZero[BitWidth-ShiftAmt-1] ||
(HighBits & ~DemandedMask) == HighBits) {
// Perform the logical shift right.
Value *NewVal = BinaryOperator::CreateLShr(
Instruction *NewVal = BinaryOperator::CreateLShr(
I->getOperand(0), SA, I->getName());
InsertNewInstBefore(cast<Instruction>(NewVal), *I);
return UpdateValueUsesWith(I, NewVal);
return InsertNewInstBefore(NewVal, *I);
} else if ((RHSKnownOne & SignBit) != 0) { // New bits are known one.
RHSKnownOne |= HighBits;
}
@ -1260,35 +1249,33 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
APInt RA = Rem->getValue().abs();
if (RA.isPowerOf2()) {
if (DemandedMask.ule(RA)) // srem won't affect demanded bits
return UpdateValueUsesWith(I, I->getOperand(0));
return I->getOperand(0);
APInt LowBits = RA - 1;
APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
if (SimplifyDemandedBits(I->getOperand(0), Mask2,
if (SimplifyDemandedBits(I->getOperandUse(0), Mask2,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
return I;
if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits))
LHSKnownZero |= ~LowBits;
KnownZero |= LHSKnownZero & DemandedMask;
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
}
}
break;
case Instruction::URem: {
APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
APInt AllOnes = APInt::getAllOnesValue(BitWidth);
if (SimplifyDemandedBits(I->getOperand(0), AllOnes,
if (SimplifyDemandedBits(I->getOperandUse(0), AllOnes,
KnownZero2, KnownOne2, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), AllOnes,
KnownZero2, KnownOne2, Depth+1))
return true;
return I;
unsigned Leaders = KnownZero2.countLeadingOnes();
if (SimplifyDemandedBits(I->getOperand(1), AllOnes,
KnownZero2, KnownOne2, Depth+1))
return true;
Leaders = std::max(Leaders,
KnownZero2.countLeadingOnes());
KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask;
@ -1324,8 +1311,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
NewVal = BinaryOperator::CreateShl(I->getOperand(1),
ConstantInt::get(I->getType(), ResultBit-InputBit));
NewVal->takeName(I);
InsertNewInstBefore(NewVal, *I);
return UpdateValueUsesWith(I, NewVal);
return InsertNewInstBefore(NewVal, *I);
}
// TODO: Could compute known zero/one bits based on the input.
@ -1340,7 +1326,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// If the client is only demanding bits that we know, return the known
// constant.
if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask)
return UpdateValueUsesWith(I, ConstantInt::get(RHSKnownOne));
return ConstantInt::get(RHSKnownOne);
return false;
}
@ -1993,12 +1979,8 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
// See if SimplifyDemandedBits can simplify this. This handles stuff like
// (X & 254)+1 -> (X&254)|1
if (!isa<VectorType>(I.getType())) {
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne))
return &I;
}
if (!isa<VectorType>(I.getType()) && SimplifyDemandedInstructionBits(I))
return &I;
// zext(i1) - 1 -> select i1, 0, -1
if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
@ -3002,10 +2984,7 @@ Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
}
// See if we can fold away this rem instruction.
uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(I))
return &I;
}
}
@ -3786,10 +3765,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (!isa<VectorType>(I.getType())) {
uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(I))
return &I;
} else {
if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) {
@ -4496,10 +4472,7 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (!isa<VectorType>(I.getType())) {
uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(I))
return &I;
} else if (isa<ConstantAggregateZero>(Op1)) {
return ReplaceInstUsesWith(I, Op0); // X | <0,0> -> X
@ -4837,10 +4810,7 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (!isa<VectorType>(I.getType())) {
uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(I))
return &I;
} else if (isa<ConstantAggregateZero>(Op1)) {
return ReplaceInstUsesWith(I, Op0); // X ^ <0,0> -> X
@ -5826,7 +5796,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool UnusedBit;
bool isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
if (SimplifyDemandedBits(Op0,
if (SimplifyDemandedBits(I.getOperandUse(0),
isSignBit ? APInt::getSignBit(BitWidth)
: APInt::getAllOnesValue(BitWidth),
KnownZero, KnownOne, 0))
@ -6995,9 +6965,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint32_t TypeBits = Op0->getType()->getPrimitiveSizeInBits();
APInt KnownZero(TypeBits, 0), KnownOne(TypeBits, 0);
if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(TypeBits),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(I))
return &I;
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
@ -7828,9 +7796,7 @@ Instruction *InstCombiner::commonIntCastTransforms(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.
APInt KnownZero(DestBitSize, 0), KnownOne(DestBitSize, 0);
if (SimplifyDemandedBits(&CI, APInt::getAllOnesValue(DestBitSize),
KnownZero, KnownOne))
if (SimplifyDemandedInstructionBits(CI))
return &CI;
// If the source isn't an instruction or has more than one use then we