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[ConstantRange] Split makeICmpRegion in two.

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Summary:
This change splits `makeICmpRegion` into `makeAllowedICmpRegion` and
`makeSatisfyingICmpRegion` with slightly different contracts.  The first
one is useful for determining what values some expression //may// take,
given that a certain `icmp` evaluates to true.  The second one is useful
for determining what values are guaranteed to //satisfy// a given
`icmp`.

Reviewers: nlewycky

Reviewed By: nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8345

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232575 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-03-18 00:41:24 +00:00
parent 8f01b96d93
commit da5f3a3ca5
6 changed files with 96 additions and 20 deletions
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17
lib/IR/ConstantRange.cpp
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@ -49,14 +49,15 @@ ConstantRange::ConstantRange(APIntMoveTy L, APIntMoveTy U)
"Lower == Upper, but they aren't min or max value!");
}
ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
const ConstantRange &CR) {
ConstantRange ConstantRange::makeAllowedICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &CR) {
if (CR.isEmptySet())
return CR;
uint32_t W = CR.getBitWidth();
switch (Pred) {
default: llvm_unreachable("Invalid ICmp predicate to makeICmpRegion()");
default:
llvm_unreachable("Invalid ICmp predicate to makeAllowedICmpRegion()");
case CmpInst::ICMP_EQ:
return CR;
case CmpInst::ICMP_NE:
@ -114,6 +115,16 @@ ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
}
}
ConstantRange ConstantRange::makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &CR) {
// Follows from De-Morgan's laws:
//
// ~(~A union ~B) == A intersect B.
//
return makeAllowedICmpRegion(CmpInst::getInversePredicate(Pred), CR)
.inverse();
}
/// isFullSet - Return true if this set contains all of the elements possible
/// for this data-type
bool ConstantRange::isFullSet() const {