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Implement Transforms/InstCombine/and.ll:test18, a case that occurs 20 times

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in perlbmk


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16504 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-09-23 21:46:38 +00:00
parent 7502ae6640
commit b20ba0a83f
1 changed files with 45 additions and 0 deletions
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45
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -897,6 +897,32 @@ static bool isOneBitSet(const ConstantInt *CI) {
return V && (V & (V-1)) == 0;
}
#if 0 // Currently unused
// isLowOnes - Return true if the constant is of the form 0+1+.
static bool isLowOnes(const ConstantInt *CI) {
uint64_t V = CI->getRawValue();
// There won't be bits set in parts that the type doesn't contain.
V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
uint64_t U = V+1; // If it is low ones, this should be a power of two.
return U && V && (U & V) == 0;
}
#endif
// isHighOnes - Return true if the constant is of the form 1+0+.
// This is the same as lowones(~X).
static bool isHighOnes(const ConstantInt *CI) {
uint64_t V = ~CI->getRawValue();
// There won't be bits set in parts that the type doesn't contain.
V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
uint64_t U = V+1; // If it is low ones, this should be a power of two.
return U && V && (U & V) == 0;
}
/// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
/// are carefully arranged to allow folding of expressions such as:
///
@ -1620,6 +1646,25 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
Instruction::SetGE, X,
Constant::getNullValue(X->getType()));
}
// ((X & ~7) == 0) --> X < 7
if (CI->isNullValue() && isHighOnes(BOC)) {
Value *X = BO->getOperand(0);
Constant *NotX = ConstantExpr::getNot(BOC);
// If 'X' is signed, insert a cast now.
if (!NotX->getType()->isSigned()) {
const Type *DestTy = NotX->getType()->getUnsignedVersion();
CastInst *NewCI = new CastInst(X, DestTy, X->getName()+".uns");
InsertNewInstBefore(NewCI, I);
X = NewCI;
NotX = ConstantExpr::getCast(NotX, DestTy);
}
return new SetCondInst(isSetNE ? Instruction::SetGE :
Instruction::SetLT, X, NotX);
}
}
default: break;
}