[llvm] Use range attribute to constant fold comparisons with constant values. (PR #84627)

[Nikita Popov via llvm-commits]

================
@@ -160,6 +160,35 @@ define i1 @test_two_ranges2(ptr nocapture readonly %arg1, ptr nocapture readonly
   ret i1 %rval
 }
 
+; Values' ranges do not overlap each other, so it can simplified to false.
+define i1 @test_two_argument_ranges(i32 range(i32 1, 6) %arg1, i32 range(i32 8, 16) %arg2) {
+; CHECK-LABEL: @test_two_argument_ranges(
+; CHECK-NEXT:    ret i1 false
+;
+  %rval = icmp ult i32 %arg2, %arg1
+  ret i1 %rval
+}
+
+; Values' ranges do not overlap each other, so it can simplified to false.
+define i1 @test_one_range_and_one_argument_range(ptr nocapture readonly %arg1, i32 range(i32 8, 16) %arg2) {
+; CHECK-LABEL: @test_one_range_and_one_argument_range(
+; CHECK-NEXT:    ret i1 false
+;
+  %val1 = load i32, ptr %arg1, !range !0
+  %rval = icmp ult i32 %arg2, %val1
+  ret i1 %rval
+}
+
+; Values' ranges do not overlap each other, so it can simplified to false.
+define i1 @test_one_argument_range_and_one_range(i32 range(i32 1, 6) %arg1, ptr nocapture readonly %arg2) {
+; CHECK-LABEL: @test_one_argument_range_and_one_range(
+; CHECK-NEXT:    ret i1 false
+;
+  %val1 = load i32, ptr %arg2, !range !6
+  %rval = icmp ult i32 %val1, %arg1
+  ret i1 %rval
+}
----------------
nikic wrote:

Please also add a negative test (range attribute exists but no simplification possible).

https://github.com/llvm/llvm-project/pull/84627