[llvm] Simplify `(a % b) lt/ge (b-1)` into `(a % b) eq/ne (b-1)` (PR #72504)

[Yingwei Zheng via llvm-commits]

================
@@ -10,6 +10,315 @@ declare void @use_i8(i8)
 declare void @use_i32(i32)
 declare void @use_i64(i64)
 
+; tests for (x % c) >=/ < (c - 1), where c >= 0
+define i1 @srem_sge_test1(i64 %x) {
+; CHECK-LABEL: @srem_sge_test1(
+; CHECK-NEXT:    [[Y:%.*]] = srem i64 [[X:%.*]], 34360750831
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[Y]], 34360750830
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %Cminus1 = add i64 34360750831, -1
+  %y = srem i64 %x, 34360750831
+  %cmp = icmp sge i64 %y, %Cminus1
----------------
dtcxzyw wrote:

```suggestion
  %y = srem i64 %x, 34360750831
  %cmp = icmp sge i64 %y, 34360750830
```
Please fold all the constant expressions.


https://github.com/llvm/llvm-project/pull/72504