[llvm] [InstCombine] Simplify fractions when there is no overflow (PR #92949)

[Craig Topper via llvm-commits]

================
@@ -1678,6 +1678,17 @@ define i32 @sdiv_sdiv_mul_nsw_exact_use(i32 %x, i32 %y, i32 %z) {
   ret i32 %r
 }
 
+define i32 @x_times_150_over_100(i32 %x) {
+; CHECK-LABEL: @x_times_150_over_100(
+; CHECK-NEXT:    [[TMP1:%.*]] = mul nuw nsw i32 [[X:%.*]], 3
+; CHECK-NEXT:    [[D1:%.*]] = lshr i32 [[TMP1]], 1
+; CHECK-NEXT:    ret i32 [[D1]]
+;
+  %m = mul nuw nsw i32 %x, 150
----------------
topperc wrote:

Don't we need tests to cover all 3 cases here

```
          if (IsSigned && C1->isNegative() && C2->isNegative()) {
            NewC1 = C1->abs().udiv(GCD);
            NewC2 = C2->abs().udiv(GCD);
          } else if (IsSigned) {
            NewC1 = C1->sdiv(GCD);
            NewC2 = C2->sdiv(GCD);
          } else {
            NewC1 = C1->udiv(GCD);
            NewC2 = C2->udiv(GCD);
          }
```

https://github.com/llvm/llvm-project/pull/92949