Handle some more combinations of extend and icmp. Fixes PR1940.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46431 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 5ba4857..e56b559 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -5820,18 +5820,22 @@
if (RHSCIOp->getType() != LHSCIOp->getType())
return 0;
- // If the signedness of the two compares doesn't agree (i.e. one is a sext
+ // If the signedness of the two casts doesn't agree (i.e. one is a sext
// and the other is a zext), then we can't handle this.
if (CI->getOpcode() != LHSCI->getOpcode())
return 0;
- // Likewise, if the signedness of the [sz]exts and the compare don't match,
- // then we can't handle this.
- if (isSignedExt != isSignedCmp && !ICI.isEquality())
- return 0;
-
- // Okay, just insert a compare of the reduced operands now!
- return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+ // Deal with equality cases early.
+ if (ICI.isEquality())
+ return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+
+ // A signed comparison of sign extended values simplifies into a
+ // signed comparison.
+ if (isSignedCmp && isSignedExt)
+ return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+
+ // The other three cases all fold into an unsigned comparison.
+ return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
}
// If we aren't dealing with a constant on the RHS, exit early