[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

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 3ed61a79478..a5d6e670f72 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1324,12 +1324,12 @@ getValueFromConditionImpl(Value *Val, Value *Cond, bool isTrueDest,
     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);