tests/codegen/README.md

   1 The files here use the LLVM FileCheck framework, documented at
   2 <https://llvm.org/docs/CommandGuide/FileCheck.html>.
   3
   4 One extension worth noting is the use of revisions as custom prefixes for
   5 FileCheck. If your codegen test has different behavior based on the chosen
   6 target or different compiler flags that you want to exercise, you can use a
   7 revisions annotation, like so:
   8
   9 ```rust
  10 // revisions: aaa bbb
  11 // [bbb] compile-flags: --flags-for-bbb
  12 ```
  13
  14 After specifying those variations, you can write different expected, or
  15 explicitly *unexpected* output by using `<prefix>-SAME:` and `<prefix>-NOT:`,
  16 like so:
  17
  18 ```rust
  19 // CHECK: expected code
  20 // aaa-SAME: emitted-only-for-aaa
  21 // aaa-NOT:                        emitted-only-for-bbb
  22 // bbb-NOT:  emitted-only-for-aaa
  23 // bbb-SAME:                       emitted-only-for-bbb
  24 ```