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Optimize div/rem + select combinations more.

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In particular, implement div.ll:test10 and rem.ll:test4.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18838 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-12-12 21:48:58 +00:00
parent cb8e9c94ff
commit 857e8cdd65
1 changed files with 90 additions and 25 deletions
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115
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -952,21 +952,23 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
}
Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
if (isa<UndefValue>(I.getOperand(0))) // undef / X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(I.getOperand(1)))
return ReplaceInstUsesWith(I, I.getOperand(1)); // X / undef -> undef
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
if (isa<UndefValue>(Op0)) // undef / X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X / undef -> undef
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// div X, 1 == X
if (RHS->equalsInt(1))
return ReplaceInstUsesWith(I, I.getOperand(0));
return ReplaceInstUsesWith(I, Op0);
// div X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::createNeg(I.getOperand(0));
return BinaryOperator::createNeg(Op0);
if (Instruction *LHS = dyn_cast<Instruction>(I.getOperand(0)))
if (Instruction *LHS = dyn_cast<Instruction>(Op0))
if (LHS->getOpcode() == Instruction::Div)
if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
// (X / C1) / C2 -> X / (C1*C2)
@ -979,21 +981,54 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
if (uint64_t Val = C->getValue()) // Don't break X / 0
if (uint64_t C = Log2(Val))
return new ShiftInst(Instruction::Shr, I.getOperand(0),
return new ShiftInst(Instruction::Shr, Op0,
ConstantUInt::get(Type::UByteTy, C));
// -X/C -> X/-C
if (RHS->getType()->isSigned())
if (Value *LHSNeg = dyn_castNegVal(I.getOperand(0)))
if (Value *LHSNeg = dyn_castNegVal(Op0))
return BinaryOperator::createDiv(LHSNeg, ConstantExpr::getNeg(RHS));
if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
if (!RHS->isNullValue()) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
}
// If this is 'udiv X, (Cond ? C1, C2)' where C1&C2 are powers of two,
// transform this into: '(Cond ? (udiv X, C1) : (udiv X, C2))'.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
if (STO->getValue() == 0) { // Couldn't be this argument.
I.setOperand(1, SFO);
return &I;
} else if (SFO->getValue() == 0) {
I.setOperand(1, STO);
return &I;
}
if (uint64_t TSA = Log2(STO->getValue()))
if (uint64_t FSA = Log2(SFO->getValue())) {
Constant *TC = ConstantUInt::get(Type::UByteTy, TSA);
Instruction *TSI = new ShiftInst(Instruction::Shr, Op0,
TC, SI->getName()+".t");
TSI = InsertNewInstBefore(TSI, I);
Constant *FC = ConstantUInt::get(Type::UByteTy, FSA);
Instruction *FSI = new ShiftInst(Instruction::Shr, Op0,
FC, SI->getName()+".f");
FSI = InsertNewInstBefore(FSI, I);
return new SelectInst(SI->getOperand(0), TSI, FSI);
}
}
// 0 / X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
@ -1002,8 +1037,9 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (I.getType()->isSigned())
if (Value *RHSNeg = dyn_castNegVal(I.getOperand(1)))
if (Value *RHSNeg = dyn_castNegVal(Op1))
if (!isa<ConstantSInt>(RHSNeg) ||
cast<ConstantSInt>(RHSNeg)->getValue() > 0) {
// X % -Y -> X % Y
@ -1012,12 +1048,12 @@ Instruction *InstCombiner::visitRem(BinaryOperator &I) {
return &I;
}
if (isa<UndefValue>(I.getOperand(0))) // undef % X -> 0
if (isa<UndefValue>(Op0)) // undef % X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(I.getOperand(1)))
return ReplaceInstUsesWith(I, I.getOperand(1)); // X % undef -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
if (RHS->equalsInt(1)) // X % 1 == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
@ -1026,15 +1062,44 @@ Instruction *InstCombiner::visitRem(BinaryOperator &I) {
if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
if (!(Val & (Val-1))) // Power of 2
return BinaryOperator::createAnd(I.getOperand(0),
ConstantUInt::get(I.getType(), Val-1));
if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
return BinaryOperator::createAnd(Op0,
ConstantUInt::get(I.getType(), Val-1));
if (!RHS->isNullValue()) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
}
// If this is 'urem X, (Cond ? C1, C2)' where C1&C2 are powers of two,
// transform this into: '(Cond ? (urem X, C1) : (urem X, C2))'.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
if (STO->getValue() == 0) { // Couldn't be this argument.
I.setOperand(1, SFO);
return &I;
} else if (SFO->getValue() == 0) {
I.setOperand(1, STO);
return &I;
}
if (!(STO->getValue() & (STO->getValue()-1)) &&
!(SFO->getValue() & (SFO->getValue()-1))) {
Value *TrueAnd = InsertNewInstBefore(BinaryOperator::createAnd(Op0,
SubOne(STO), SI->getName()+".t"), I);
Value *FalseAnd = InsertNewInstBefore(BinaryOperator::createAnd(Op0,
SubOne(SFO), SI->getName()+".f"), I);
return new SelectInst(SI->getOperand(0), TrueAnd, FalseAnd);
}
}
// 0 % X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));