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Simplify handling of shifts to be the same as we do for adds. Add support

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for (X * C1) + (X * C2) (where * can be mul or shl), allowing us to fold:

   Y+Y+Y+Y+Y+Y+Y+Y

into
         %tmp.8 = shl long %Y, ubyte 3           ; <long> [#uses=1]

instead of

        %tmp.4 = shl long %Y, ubyte 2           ; <long> [#uses=1]
        %tmp.12 = shl long %Y, ubyte 2          ; <long> [#uses=1]
        %tmp.8 = add long %tmp.4, %tmp.12               ; <long> [#uses=1]

This implements add.ll:test25

Also add support for (X*C1)-(X*C2) -> X*(C1-C2), implementing sub.ll:test18

llvm-svn: 17704
This commit is contained in:
Chris Lattner 2004-11-13 19:50:12 +00:00
parent 868d91e84a
commit 70e351fb1c
1 changed files with 40 additions and 45 deletions
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85
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -317,14 +317,23 @@ static inline Value *dyn_castNotVal(Value *V) {
// dyn_castFoldableMul - If this value is a multiply that can be folded into
// other computations (because it has a constant operand), return the
// non-constant operand of the multiply.
// non-constant operand of the multiply, and set CST to point to the multiplier.
// Otherwise, return null.
//
static inline Value *dyn_castFoldableMul(Value *V) {
static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
if (V->hasOneUse() && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V))
if (Instruction *I = dyn_cast<Instruction>(V)) {
if (I->getOpcode() == Instruction::Mul)
if (isa<Constant>(I->getOperand(1)))
if (CST = dyn_cast<ConstantInt>(I->getOperand(1)))
return I->getOperand(0);
if (I->getOpcode() == Instruction::Shl)
if (CST = dyn_cast<ConstantInt>(I->getOperand(1))) {
// The multiplier is really 1 << CST.
Constant *One = ConstantInt::get(V->getType(), 1);
CST = cast<ConstantInt>(ConstantExpr::getShl(One, CST));
return I->getOperand(0);
}
}
return 0;
}
@ -595,42 +604,26 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Value *V = dyn_castNegVal(RHS))
return BinaryOperator::createSub(LHS, V);
// X*C + X --> X * (C+1)
if (dyn_castFoldableMul(LHS) == RHS) {
Constant *CP1 =
ConstantExpr::getAdd(
cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
return BinaryOperator::createMul(RHS, CP1);
ConstantInt *C2;
if (Value *X = dyn_castFoldableMul(LHS, C2)) {
if (X == RHS) // X*C + X --> X * (C+1)
return BinaryOperator::createMul(RHS, AddOne(C2));
// X*C1 + X*C2 --> X * (C1+C2)
ConstantInt *C1;
if (X == dyn_castFoldableMul(RHS, C1))
return BinaryOperator::createMul(X, ConstantExpr::getAdd(C1, C2));
}
// X + X*C --> X * (C+1)
if (dyn_castFoldableMul(RHS) == LHS) {
Constant *CP1 =
ConstantExpr::getAdd(
cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
return BinaryOperator::createMul(LHS, CP1);
}
if (dyn_castFoldableMul(RHS, C2) == LHS)
return BinaryOperator::createMul(LHS, AddOne(C2));
// (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
ConstantInt *C2;
if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
// (X + (X << C2)) --> X * ((1 << C2) + 1)
// ((X << C2) + X) --> X * ((1 << C2) + 1)
Value *Tmp;
if ((RHS->hasOneUse() && match(RHS, m_Shl(m_Value(Tmp),
m_ConstantInt(C2))) && LHS == Tmp)||
(LHS->hasOneUse() && match(LHS, m_Shl(m_Value(Tmp),
m_ConstantInt(C2))) && RHS == Tmp)){
ConstantInt *One = ConstantInt::get(LHS->getType(), 1);
Constant *NewRHS =
ConstantExpr::getAdd(ConstantExpr::getShl(One, C2), One);
return BinaryOperator::createMul(Tmp, NewRHS);
}
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
Value *X;
if (match(LHS, m_Not(m_Value(X)))) { // ~X + C --> (C-1) - X
@ -800,24 +793,26 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
ConstantExpr::getNeg(DivRHS));
// X - X*C --> X * (1-C)
if (dyn_castFoldableMul(Op1I) == Op0) {
Constant *CP1 =
ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
assert(CP1 && "Couldn't constant fold 1-C?");
ConstantInt *C2;
if (dyn_castFoldableMul(Op1I, C2) == Op0) {
Constant *CP1 =
ConstantExpr::getSub(ConstantInt::get(I.getType(), 1), C2);
return BinaryOperator::createMul(Op0, CP1);
}
}
// X*C - X --> X * (C-1)
if (dyn_castFoldableMul(Op0) == Op1) {
Constant *CP1 =
ConstantExpr::getSub(cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
assert(CP1 && "Couldn't constant fold C - 1?");
return BinaryOperator::createMul(Op1, CP1);
}
ConstantInt *C1;
if (Value *X = dyn_castFoldableMul(Op0, C1)) {
if (X == Op1) { // X*C - X --> X * (C-1)
Constant *CP1 = ConstantExpr::getSub(C1, ConstantInt::get(I.getType(),1));
return BinaryOperator::createMul(Op1, CP1);
}
ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
if (X == dyn_castFoldableMul(Op1, C2))
return BinaryOperator::createMul(Op1, ConstantExpr::getSub(C1, C2));
}
return 0;
}