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Fold binary operators with a constant operand into select instructions 

that have a constant operand.  This implements
add.ll:test19, shift.ll:test15*, and others that are not tested

llvm-svn: 12794
This commit is contained in:
Chris Lattner 2004-04-09 19:05:30 +00:00
parent cf7baf3519
commit 183b336a54
1 changed files with 94 additions and 15 deletions
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109
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -489,7 +489,50 @@ struct AddMaskingAnd {
}
};
static Value *FoldOperationIntoSelectOperand(Instruction &BI, Value *SO,
InstCombiner *IC) {
// Figure out if the constant is the left or the right argument.
bool ConstIsRHS = isa<Constant>(BI.getOperand(1));
Constant *ConstOperand = cast<Constant>(BI.getOperand(ConstIsRHS));
if (Constant *SOC = dyn_cast<Constant>(SO)) {
if (ConstIsRHS)
return ConstantExpr::get(BI.getOpcode(), SOC, ConstOperand);
return ConstantExpr::get(BI.getOpcode(), ConstOperand, SOC);
}
Value *Op0 = SO, *Op1 = ConstOperand;
if (!ConstIsRHS)
std::swap(Op0, Op1);
Instruction *New;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&BI))
New = BinaryOperator::create(BO->getOpcode(), Op0, Op1);
else if (ShiftInst *SI = dyn_cast<ShiftInst>(&BI))
New = new ShiftInst(SI->getOpcode(), Op0, Op1);
else
assert(0 && "Unknown binary instruction type!");
return IC->InsertNewInstBefore(New, BI);
}
// FoldBinOpIntoSelect - Given an instruction with a select as one operand and a
// constant as the other operand, try to fold the binary operator into the
// select arguments.
static Instruction *FoldBinOpIntoSelect(Instruction &BI, SelectInst *SI,
InstCombiner *IC) {
// Don't modify shared select instructions
if (!SI->hasOneUse()) return 0;
Value *TV = SI->getOperand(1);
Value *FV = SI->getOperand(2);
if (isa<Constant>(TV) || isa<Constant>(FV)) {
Value *SelectTrueVal = FoldOperationIntoSelectOperand(BI, TV, IC);
Value *SelectFalseVal = FoldOperationIntoSelectOperand(BI, FV, IC);
return new SelectInst(SI->getCondition(), SelectTrueVal,
SelectFalseVal);
}
return 0;
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
@ -547,6 +590,11 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
CRHS, ConstantInt::get(I.getType(), 1)),
ILHS->getOperand(0));
break;
case Instruction::Select:
// Try to fold constant add into select arguments.
if (Instruction *R = FoldBinOpIntoSelect(I,cast<SelectInst>(ILHS),this))
return R;
default: break;
}
}
@ -632,6 +680,11 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
}
}
}
// Try to fold constant sub into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
}
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
@ -740,6 +793,11 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (Op1F->getValue() == 1.0)
return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
}
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
@ -1093,6 +1151,11 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
return Res;
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
}
Value *Op0NotVal = dyn_castNotVal(Op0);
@ -1158,6 +1221,11 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
NotConstant(RHS)));
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
}
// (A & C1)|(A & C2) == A & (C1|C2)
@ -1268,6 +1336,11 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
default: break;
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
}
if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
@ -1668,6 +1741,12 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
if (CSI->isAllOnesValue())
return ReplaceInstUsesWith(I, CSI);
// Try to fold constant and into select arguments.
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
// of a signed value.
@ -1689,6 +1768,10 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
ConstantExpr::get(Instruction::Shl, BOOp, CUI));
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
// If the operand is an bitwise operator with a constant RHS, and the
// shift is the only use, we can pull it out of the shift.
@ -2052,22 +2135,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
}
}
// Selecting between two constants?
if (Constant *TrueValC = dyn_cast<Constant>(TrueVal))
if (Constant *FalseValC = dyn_cast<Constant>(FalseVal)) {
if (SI.getType()->isInteger()) {
// select C, 1, 0 -> cast C to int
if (FalseValC->isNullValue() && isa<ConstantInt>(TrueValC) &&
cast<ConstantInt>(TrueValC)->getRawValue() == 1) {
return new CastInst(CondVal, SI.getType());
} else if (TrueValC->isNullValue() && isa<ConstantInt>(FalseValC) &&
cast<ConstantInt>(FalseValC)->getRawValue() == 1) {
// select C, 0, 1 -> cast !C to int
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
// Selecting between two integer constants?
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
// select C, 1, 0 -> cast C to int
if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
return new CastInst(CondVal, SI.getType());
} else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
// select C, 0, 1 -> cast !C to int
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
"not."+CondVal->getName()), SI);
return new CastInst(NotCond, SI.getType());
}
return new CastInst(NotCond, SI.getType());
}
}