Make `//@ skip-filecheck` a normal compiletest directive
The `skip-filecheck` directive is currently used by mir-opt tests, to suppress the default behaviour of running LLVM's `FileCheck` tool to check MIR output against FileCheck rules in the test file.
The `skip-filecheck` directive was not included in the big migration to `//@` directive syntax (https://github.com/rust-lang/rust/pull/121370), perhaps because it was parsed and processed in the *miropt-test-tools* helper crate, not in compiletest itself.
Recently I noticed that a small number of *codegen-llvm* tests were using the `//@ build-pass` directive, which has the non-obvious effect of skipping FileCheck in codegen tests. That's quite confusing, so I decided to have the mir-opt tests migrate over to a proper `//@ skip-filecheck` directive, which could then be used by codegen tests as well.
(I also added skip-filecheck support to assembly tests, which are very similar to codegen tests, though there are currently no assembly tests that actually use `//@ skip-filecheck`.)
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Support for using `//@ build-pass` in codegen tests to skip FileCheck was introduced in https://github.com/rust-lang/rust/pull/113603. With hindsight, I think doing things that way was pretty clearly a mistake, and we'll be better off with `//@ skip-filecheck`.
r? jieyouxu
One extension worth noting is the use of revisions as custom prefixes for
FileCheck. If your codegen test has different behavior based on the chosen
target or different compiler flags that you want to exercise, you can use a
revisions annotation, like so:
After specifying those variations, you can write different expected, or
explicitly unexpected output by using <prefix>-SAME: and <prefix>-NOT:,
like so:
Jonathan Brouwer
610bfadb9b