[all-commits] [llvm/llvm-project] 3a9380: [Multilib] Custom flags processing for library sel...

[Victor Campos via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3a9380f21d05eb8ced03349c8c503dc911f22621
      https://github.com/llvm/llvm-project/commit/3a9380f21d05eb8ced03349c8c503dc911f22621
  Author: Victor Campos <victor.campos at arm.com>
  Date:   2025-01-16 (Thu, 16 Jan 2025)

  Changed paths:
    M clang/include/clang/Driver/Driver.h
    M clang/include/clang/Driver/Multilib.h
    M clang/include/clang/Driver/ToolChain.h
    M clang/lib/Driver/Driver.cpp
    M clang/lib/Driver/Multilib.cpp
    M clang/lib/Driver/ToolChains/BareMetal.cpp
    M clang/lib/Driver/ToolChains/BareMetal.h
    A clang/test/Driver/baremetal-multilib-custom-flags.yaml

  Log Message:
  -----------
  [Multilib] Custom flags processing for library selection (#110659)

This patch is the third step to extend the current multilib system to
support the selection of library variants which do not correspond to
existing command-line options.

Proposal can be found in
https://discourse.llvm.org/t/rfc-multilib-custom-flags/81058

The multilib mechanism supports libraries that target code generation or
language options such as --target, -mcpu, -mfpu, -mbranch-protection.
However, some library variants are particular to features that do not
correspond to any command-line options. Examples include variants for
multithreading and semihosting.

This work introduces a way to instruct the multilib system to consider
these features in library selection. This particular patch is comprised
of the core processing of these flags.

- Custom flags in the command-line are read and forwarded to the
multilib system. If multiple flag values are present for the same flag
declaration, the last one wins. Default flag values are inserted for
flag declarations for which no value was given.
- Feed `MacroDefines` back into the driver. Each item `<string>` in the
`MacroDefines` list is formatted as `-D<string>`.

Library variants should list their requirement on one or more custom
flags like they do for any other flag. The new command-line option is
passed as-is to the multilib system, therefore it should be listed in
the format `-fmultilib-flag=<str>`.

Moreover, a variant that does not specify a requirement on any
particular flag can be matched against any value of that flag.

If the user specifies `-fmultilib-flag=<name>` with a name that is
invalid, but close enough to any valid flag value name in terms of edit
distance, a suggesting error is shown:
```
error: unsupported option '-fmultilib-flag=invalidname'; did you mean '-fmultilib-flag=validname'?
```
The candidate with the smallest edit distance is chosen for the
suggestion, up to a certain maximum value (implementation detail), after
which a non-suggesting error is shown instead:
```
error: unsupported option '-fmultilib-flag=invalidname'
```



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