commit ca8c72635c29993f3c79a0cf5a9918b7792e24a7
author Fangrui Song <i@maskray.me> Mon Dec 18 09:46:58 2023 -0800
committer Copybara-Service <copybara-worker@google.com> Mon Dec 18 09:50:07 2023 -0800
tree 80335f2a4f789ad20313b59791f9078f523025fc
parent aab755b3e4ad43e22e4bf6f81e5fd22fa6ea9510

[LTO] Improve diagnostics handling when parsing module-level inline assembly (#75726)

Non-LTO compiles set the buffer name to "<inline asm>"
(`AsmPrinter::addInlineAsmDiagBuffer`) and pass diagnostics to
`ClangDiagnosticHandler` (through the `MCContext` handler in
`MachineModuleInfoWrapperPass::doInitialization`) to ensure that
the exit code is 1 in the presence of errors. In contrast, LTO compiles
spuriously succeed even if error messages are printed.

```
% cat a.c
void _start() {}
asm("unknown instruction");
% clang -c a.c
<inline asm>:1:1: error: invalid instruction mnemonic 'unknown'
    1 | unknown instruction
      | ^
1 error generated.
% clang -c -flto a.c; echo $?  # -flto=thin is the same
error: invalid instruction mnemonic 'unknown'
unknown instruction
^~~~~~~
error: invalid instruction mnemonic 'unknown'
unknown instruction
^~~~~~~
0
```

`CollectAsmSymbols` parses inline assembly and is transitively called by
both `ModuleSummaryIndexAnalysis::run` and `WriteBitcodeToFile`, leading
to duplicate diagnostics.

This patch updates `CollectAsmSymbols` to be similar to non-LTO
compiles.
```
% clang -c -flto=thin a.c; echo $?
<inline asm>:1:1: error: invalid instruction mnemonic 'unknown'
    1 | unknown instruction
      | ^
1 errors generated.
1
```

The `HasErrors` check does not prevent duplicate warnings but assembler
warnings are very uncommon.

GitOrigin-RevId: 96aca7c51701f9b3c5dd8567fcddf29492008e6d