[LVI] Handle constant value lattice in `getEdgeValueLocal` (#161410)

Closes https://github.com/llvm/llvm-project/issues/161367.

In https://github.com/llvm/llvm-project/pull/157614, we ignored cases
where OpLatticeVal might be a constant or notconstant. Directly
returning the result causes a type mismatch. I apologize for the
oversight in the previous code review.

This patch applies the cast op to constants. For notconstant value
lattices, I'd leave it as a todo (it is similar to the constant case,
except for trunc without nsw/nuw).

1 files changed, 17 insertions, 11 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 6fb2807..0e5bc48 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1632,19 +1632,25 @@ LazyValueInfoImpl::getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
                 *getValueFromCondition(Usr->getOperand(0), Condition,
                                        isTrueDest, /*UseBlockValue*/ false);
 
-            if (!OpLatticeVal.isConstantRange())
-              return OpLatticeVal;
+            if (OpLatticeVal.isConstantRange()) {
+              const unsigned ResultBitWidth =
+                  Usr->getType()->getScalarSizeInBits();
+              if (auto *Trunc = dyn_cast<TruncInst>(Usr))
+                return ValueLatticeElement::getRange(
+                    OpLatticeVal.getConstantRange().truncate(
+                        ResultBitWidth, Trunc->getNoWrapKind()));
 
-            const unsigned ResultBitWidth =
-                Usr->getType()->getScalarSizeInBits();
-            if (auto *Trunc = dyn_cast<TruncInst>(Usr))
               return ValueLatticeElement::getRange(
-                  OpLatticeVal.getConstantRange().truncate(
-                      ResultBitWidth, Trunc->getNoWrapKind()));
-
-            return ValueLatticeElement::getRange(
-                OpLatticeVal.getConstantRange().castOp(
-                    cast<CastInst>(Usr)->getOpcode(), ResultBitWidth));
+                  OpLatticeVal.getConstantRange().castOp(
+                      cast<CastInst>(Usr)->getOpcode(), ResultBitWidth));
+            }
+            if (OpLatticeVal.isConstant()) {
+              Constant *C = OpLatticeVal.getConstant();
+              if (auto *CastC = ConstantFoldCastOperand(
+                      cast<CastInst>(Usr)->getOpcode(), C, Usr->getType(), DL))
+                return ValueLatticeElement::get(CastC);
+            }
+            return ValueLatticeElement::getOverdefined();
           } else {
             // If one of Val's operand has an inferred value, we may be able to
             // infer the value of Val.