[FileCheck] Support comment directives

Sometimes you want to disable a FileCheck directive without removing
it entirely, or you want to write comments that mention a directive by
name.  The `COM:` directive makes it easy to do this.  For example,
you might have:

```
; X32: pinsrd_1:
; X32:    pinsrd $1, 4(%esp), %xmm0

; COM: FIXME: X64 isn't working correctly yet for this part of codegen, but
; COM: X64 will have something similar to X32:
; COM:
; COM:   X64: pinsrd_1:
; COM:   X64:    pinsrd $1, %edi, %xmm0
```

Without this patch, you need to use some combination of rewording and
directive syntax mangling to prevent FileCheck from recognizing the
commented occurrences of `X32:` and `X64:` above as directives.
Moreover, FileCheck diagnostics have been proposed that might complain
about the occurrences of `X64` that don't have the trailing `:`
because they look like directive typos:

  <http://lists.llvm.org/pipermail/llvm-dev/2020-April/140610.html>

I think dodging all these problems can prove tedious for test authors,
and directive syntax mangling already makes the purpose of existing
test code unclear.  `COM:` can avoid all these problems.

This patch also updates the small set of existing tests that define
`COM` as a check prefix:

- clang/test/CodeGen/default-address-space.c
- clang/test/CodeGenOpenCL/addr-space-struct-arg.cl
- clang/test/Driver/hip-device-libs.hip
- llvm/test/Assembler/drop-debug-info-nonzero-alloca.ll

I think lit should support `COM:` as well.  Perhaps `clang -verify`
should too.

Reviewed By: jhenderson, thopre

Differential Revision: https://reviews.llvm.org/D79276

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/utils/FileCheck/FileCheck.cpp b/llvm/utils/FileCheck/FileCheck.cpp
index 46821ec..3ee7c5a 100644
--- a/llvm/utils/FileCheck/FileCheck.cpp
+++ b/llvm/utils/FileCheck/FileCheck.cpp
@@ -44,6 +44,14 @@ static cl::alias CheckPrefixesAlias(
     cl::desc(
         "Alias for -check-prefix permitting multiple comma separated values"));
 
+static cl::list<std::string> CommentPrefixes(
+    "comment-prefixes", cl::CommaSeparated, cl::Hidden,
+    cl::desc("Comma-separated list of comment prefixes to use from check file\n"
+             "(defaults to 'COM,RUN'). Please avoid using this feature in\n"
+             "LLVM's LIT-based test suites, which should be easier to\n"
+             "maintain if they all follow a consistent comment style. This\n"
+             "feature is meant for non-LIT test suites using FileCheck."));
+
 static cl::opt<bool> NoCanonicalizeWhiteSpace(
     "strict-whitespace",
     cl::desc("Do not treat all horizontal whitespace as equivalent"));
@@ -279,6 +287,8 @@ std::string GetCheckTypeAbbreviation(Check::FileCheckType Ty) {
     return "label";
   case Check::CheckEmpty:
     return "empty";
+  case Check::CheckComment:
+    return "com";
   case Check::CheckEOF:
     return "eof";
   case Check::CheckBadNot:
@@ -565,6 +575,9 @@ int main(int argc, char **argv) {
   for (StringRef Prefix : CheckPrefixes)
     Req.CheckPrefixes.push_back(Prefix);
 
+  for (StringRef Prefix : CommentPrefixes)
+    Req.CommentPrefixes.push_back(Prefix);
+
   for (StringRef CheckNot : ImplicitCheckNot)
     Req.ImplicitCheckNot.push_back(CheckNot);