[IPSCCP] Add getCompare which returns either true, false, undef or null.

getCompare returns true, false or undef constants if the comparison can
be evaluated, or nullptr if it cannot. This is in line with what
ConstantExpr::getCompare returns. It also allows us to use
ConstantExpr::getCompare for comparing constants.

Reviewers: davide, mssimpso, dberlin, anna

Reviewed By: davide

Differential Revision: https://reviews.llvm.org/D43761

llvm-svn: 326720

1 files changed, 1 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
index 329c7570b45..da8b6cfda5f 100644
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1644,12 +1644,7 @@ static bool tryToReplaceWithConstantRange(SCCPSolver &Solver, Value *V) {
     ValueLatticeElement A = getIcmpLatticeValue(Icmp->getOperand(0));
     ValueLatticeElement B = getIcmpLatticeValue(Icmp->getOperand(1));
 
-    Constant *C = nullptr;
-    if (A.satisfiesPredicate(Icmp->getPredicate(), B))
-      C = ConstantInt::getTrue(Icmp->getType());
-    else if (A.satisfiesPredicate(Icmp->getInversePredicate(), B))
-      C = ConstantInt::getFalse(Icmp->getType());
-
+    Constant *C = A.getCompare(Icmp->getPredicate(), Icmp->getType(), B);
     if (C) {
       Icmp->replaceAllUsesWith(C);
       DEBUG(dbgs() << "Replacing " << *Icmp << " with " << *C