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

[Yingwei Zheng via llvm-commits]

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@@ -10,6 +10,296 @@ 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]]
+;
+  %y = srem i64 %x, 34360750831
+  %cmp = icmp sge i64 %y, 34360750830
+  ret i1 %cmp
+}
+
+define i1 @srem_slt_test1(i64 %x) {
+; CHECK-LABEL: @srem_slt_test1(
+; CHECK-NEXT:    [[Y:%.*]] = srem i64 [[X:%.*]], 34360750831
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i64 [[Y]], 34360750830
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %y = srem i64 %x, 34360750831
+  %cmp = icmp slt i64 %y, 34360750830
+  ret i1 %cmp
+}
+
+define i1 @srem_sge_test2(i32 %x) {
+; CHECK-LABEL: @srem_sge_test2(
+; CHECK-NEXT:    [[Y:%.*]] = srem i32 [[X:%.*]], 1074977277
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[Y]], 1074977276
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %y = srem i32 %x, 1074977277
+  %cmp = icmp sge i32 %y, 1074977276
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dtcxzyw wrote:

Same as above.

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