[InstCombine] Handle constant expression result in tryFactorization()

If IRBuilder folds the result to a constant expression, don't try
to set nowrap flags on it.

Fixes #124526.

Author: nikic

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -732,7 +732,7 @@ static Value *tryFactorization(BinaryOperator &I, const SimplifyQuery &SQ,
   RetVal->takeName(&I);
 
   // Try to add no-overflow flags to the final value.
-  if (isa<OverflowingBinaryOperator>(RetVal)) {
+  if (isa<BinaryOperator>(RetVal)) {
     bool HasNSW = false;
     bool HasNUW = false;
     if (isa<OverflowingBinaryOperator>(&I)) {

llvm/test/Transforms/InstCombine/add2.ll

@@ -321,6 +321,17 @@ define i16 @mul_add_to_mul_9(i16 %a) {
   ret i16 %add
 }
 
+@g = external global i8
+
+define i32 @shl_add_to_shl_constexpr() {
+; CHECK-LABEL: @shl_add_to_shl_constexpr(
+; CHECK-NEXT:    ret i32 mul (i32 ptrtoint (ptr @g to i32), i32 4)
+;
+  %shl = shl i32 ptrtoint (ptr @g to i32), 1
+  %add = add i32 %shl, %shl
+  ret i32 %add
+}
+
 ; This test and the next test verify that when a range metadata is attached to
 ; llvm.cttz, ValueTracking correctly intersects the range specified by the
 ; metadata and the range implied by the intrinsic.