[Clang] Improve diagnostic message for loop hint pragma

[eopXD]

Summary

Originally the loop hint is not displayed correctly in the diagnostic.
This patch fixes it.

[eopXD]

Trigger upon parent revision.

[SjoerdMeijer]

clang/lib/Parse/ParsePragma.cpp

1306

We've got some duplication now, as "loop" is also checked in line 1310. Can you see if you can merge these checks, simplify things here a bit?

[eopXD]

Rebase upon latest main and simplify existing checks.

[eopXD]

clang/lib/Parse/ParsePragma.cpp

1306

Yes, the case for loop in below can now be removed. Thank you.

[SjoerdMeijer]

clang/lib/Parse/ParsePragma.cpp

1306

I was hoping that modifying the "loop" case would work:

.Case("loop", (llvm::Twine("clang loop ") + Option.getIdentifierInfo()->getName()).str());

[eopXD]

Update code based on suggestion.

[eopXD]

clang/lib/Parse/ParsePragma.cpp

1306

Your suggestion is better than mine, thank you :)

[Meinersbur]

LGTM

clang/lib/Parse/ParsePragma.cpp

1306–1308

ClangLoopStr is unused now

[eopXD]

Update code to handle when IdentifierInfo is null.
The .Case syntax seems to evaulate expression in other non-trigger cases.
The "loop" case was triggered for test case in loop unroll and jam, resulting
in segmentation fault. Anyway the updated code shall be safe now.