[PATCH] D134337: [clang] [Driver] More flexible rules for loading default configs

[Serge Pavlov via Phabricator via cfe-commits]

sepavloff added inline comments.


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Comment at: clang/lib/Driver/Driver.cpp:1098
+  // Try loading separate config for the target (variants 3. and 4.)
+  CfgFileName = RealTriple.str() + ".cfg";
+  if (searchForFile(CfgFilePath, CfgFileSearchDirs, CfgFileName, getVFS()) &&
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mgorny wrote:
> sepavloff wrote:
> > Loading driver-mode config should take place before loading target config, it allows to override default settings set by driver mode config in target config. Also a test is need for such case.
> Do you have any specific option in mind? The main idea was that you use full triple+driver config when you need overrides because — as we pretty much established before — the options accepted by different drivers are too different for them to be meaningfully used with a single config file shared between targets.
I mean we can have several driver-mode configs like `tool.cfg`, where some default settings are set (maybe by using @file constructs`) and several `target.cfg` which may override options defined in `tool.cfg`. Due to different target and driver configs loaded separately, we can avoid creating separate config for each target+driver combination. Not a killer feature, but it is convenient.

As I understand, it is enough to swap code that tries loading driver config below with this piece of code, no?


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Comment at: clang/test/Driver/config-file3.c:27
 
-//--- Invocation qqq-clang-g++ tries to find config file qqq-clang-g++.cfg first.
+//--- Invocation x86_64-unknown-linux-gnu-clang-g++ tries x86_64-unknown-linux-gnu-clang++.cfg first.
 //
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mgorny wrote:
> arichardson wrote:
> > sepavloff wrote:
> > > Tests must check the case when target prefix is not a real triple as in the original test (qqq-clang).
> > It would be quite important for me that this continues to work. I made use of that in the CheriBSD toolchain when creating [[ https://github.com/CTSRD-CHERI/cheribuild/blob/master/pycheribuild/projects/cross/llvm.py#L499 | symlinked binaries to easily build for different ABIs]] such as `cheribsd-riscv64-hybrid-clang++` and `cheribsd-riscv64-purecap-clang-cpp`. It appears this previously only worked if the prefix did not start with a valid triple (which is why I put the OS before the architecture). I think it would also be nice if the whole prefix was checked even if it starts with a valid triple, but this does not need to be changed in this patch (haven't looked at it in detail so this might actually work).
> If the prefix is not a valid triple, then clang ignores it and uses host triple instead. And now we're back to square one. If I check both variants, it's too complex. If I don't, it's bad too.
Our customers use this feature. Target prefix may designate, for example, debug build or build with specific framework.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134337/new/

https://reviews.llvm.org/D134337