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Implement InstCombine/and.ll:test(15|16) 

llvm-svn: 8607
This commit is contained in:
Chris Lattner 2003-09-19 19:05:02 +00:00
parent d441d407cf
commit 2da29177ba
1 changed files with 27 additions and 0 deletions
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27
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -798,6 +798,33 @@ Instruction *InstCombiner::OptAndOp(Instruction *Op,
}
}
break;
case Instruction::Shl: {
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now!
//
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *CI = *AndRHS & *(*AllOne << *OpRHS);
if (CI != AndRHS) {
TheAnd.setOperand(1, CI);
return &TheAnd;
}
break;
}
case Instruction::Shr:
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now! This only applies to
// unsigned shifts, because a signed shr may bring in set bits!
//
if (AndRHS->getType()->isUnsigned()) {
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *CI = *AndRHS & *(*AllOne >> *OpRHS);
if (CI != AndRHS) {
TheAnd.setOperand(1, CI);
return &TheAnd;
}
}
break;
}
return 0;
}