[LVI] Teach LVI to reason about ORs of icmps similar to how it reasons about ANDs of icmps
Summary: LVI can reason about an AND of icmps on the true dest of a branch. I believe we can do similar for the false dest of ORs. This allows us to get the same answer for the demorganed versions of some of the AND test cases as you can see.
Reviewers: anna, reames
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D34431
llvm-svn: 306076
diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 3ed61a7..a5d6e67 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1324,12 +1324,12 @@
return getValueFromICmpCondition(Val, ICI, isTrueDest);
// Handle conditions in the form of (cond1 && cond2), we know that on the
- // true dest path both of the conditions hold.
- if (!isTrueDest)
- return LVILatticeVal::getOverdefined();
-
+ // true dest path both of the conditions hold. Similarly for conditions of
+ // the form (cond1 || cond2), we know that on the false dest path neither
+ // condition holds.
BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond);
- if (!BO || BO->getOpcode() != BinaryOperator::And)
+ if (!BO || (isTrueDest && BO->getOpcode() != BinaryOperator::And) ||
+ (!isTrueDest && BO->getOpcode() != BinaryOperator::Or))
return LVILatticeVal::getOverdefined();
auto RHS = getValueFromCondition(Val, BO->getOperand(0), isTrueDest, Visited);