[InstCombine] Add pre-commit tests. NFC.

Author: dtcxzyw

llvm/test/Transforms/InstCombine/select-divrem.ll

@@ -322,6 +322,23 @@ define i8 @rem_euclid_non_const_pow2(i8 %0, i8 %1) {
   ret i8 %sel
 }
 
+define i8 @rem_euclid_non_const_pow2_commuted(i8 %0, i8 %1) {
+; CHECK-LABEL: @rem_euclid_non_const_pow2_commuted(
+; CHECK-NEXT:    [[POW2:%.*]] = shl nuw i8 1, [[TMP0:%.*]]
+; CHECK-NEXT:    [[REM:%.*]] = srem i8 [[TMP1:%.*]], [[POW2]]
+; CHECK-NEXT:    [[COND:%.*]] = icmp slt i8 [[REM]], 0
+; CHECK-NEXT:    [[ADD:%.*]] = select i1 [[COND]], i8 [[POW2]], i8 0
+; CHECK-NEXT:    [[SEL:%.*]] = add i8 [[REM]], [[ADD]]
+; CHECK-NEXT:    ret i8 [[SEL]]
+;
+  %pow2 = shl i8 1, %0
+  %rem = srem i8 %1, %pow2
+  %cond = icmp slt i8 %rem, 0
+  %add = add i8 %pow2, %rem
+  %sel = select i1 %cond, i8 %add, i8 %rem
+  ret i8 %sel
+}
+
 define i32 @rem_euclid_pow2_true_arm_folded(i32 %n) {
 ; CHECK-LABEL: @rem_euclid_pow2_true_arm_folded(
 ; CHECK-NEXT:    [[RES:%.*]] = and i32 [[N:%.*]], 1