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Reorganization of code, no functional changes.

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Now it shoudl be a bit more efficient


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7292 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-07-24 17:52:58 +00:00
parent 3d8d9f7e72
commit 08fd7abb42
1 changed files with 48 additions and 47 deletions
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95
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -876,51 +876,10 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
Op0 == Constant::getNullValue(Op0->getType()))
return ReplaceInstUsesWith(I, Op0);
// If this is a shift of a shift, see if we can fold the two together...
if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
if (isa<Constant>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
unsigned ShiftAmt1 = ShiftAmt1C->getValue();
unsigned ShiftAmt2 = cast<ConstantUInt>(Op1)->getValue();
// Check for (A << c1) << c2 and (A >> c1) >> c2
if (I.getOpcode() == Op0SI->getOpcode()) {
unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
ConstantUInt::get(Type::UByteTy, Amt));
}
if (I.getType()->isUnsigned()) { // Check for (A << c1) >> c2 or visaversa
// Calculate bitmask for what gets shifted off the edge...
Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
if (I.getOpcode() == Instruction::Shr)
C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
else
C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
Instruction *Mask =
BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
C, Op0SI->getOperand(0)->getName()+".mask",&I);
WorkList.push_back(Mask);
// Figure out what flavor of shift we should use...
if (ShiftAmt1 == ShiftAmt2)
return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
else if (ShiftAmt1 < ShiftAmt2) {
return new ShiftInst(I.getOpcode(), Mask,
ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
} else {
return new ShiftInst(Op0SI->getOpcode(), Mask,
ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
}
}
}
}
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr of
// a signed value.
//
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.
//
unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
if (CUI->getValue() >= TypeBits &&
(!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
@ -932,12 +891,54 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
// Convert 'shl int %X, 1' to 'add int %X, %X'
return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
// If this is a shift of a shift, see if we can fold the two together...
if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
if (isa<ConstantUInt>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
unsigned ShiftAmt1 = ShiftAmt1C->getValue();
unsigned ShiftAmt2 = CUI->getValue();
// Check for (A << c1) << c2 and (A >> c1) >> c2
if (I.getOpcode() == Op0SI->getOpcode()) {
unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
ConstantUInt::get(Type::UByteTy, Amt));
}
// Check for (A << c1) >> c2 or visaversa
if (I.getType()->isUnsigned()) {
// Calculate bitmask for what gets shifted off the edge...
Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
if (I.getOpcode() == Instruction::Shr)
C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
else
C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
Instruction *Mask =
BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
C, Op0SI->getOperand(0)->getName()+".mask");
InsertNewInstBefore(Mask, I);
// Figure out what flavor of shift we should use...
if (ShiftAmt1 == ShiftAmt2)
return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
else if (ShiftAmt1 < ShiftAmt2) {
return new ShiftInst(I.getOpcode(), Mask,
ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
} else {
return new ShiftInst(Op0SI->getOpcode(), Mask,
ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
}
}
}
}
}
// shr int -1, X = -1 (for any arithmetic shift rights of ~0)
if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
if (I.getOpcode() == Instruction::Shr && CSI->isAllOnesValue())
return ReplaceInstUsesWith(I, CSI);
if (I.getOpcode() == Instruction::Shr)
if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
if (CSI->isAllOnesValue())
return ReplaceInstUsesWith(I, CSI);
return 0;
}