[PATCH] D147256: [DebugInfo] Fix file path separator when targeting windows.

[Zequan Wu via Phabricator via cfe-commits]

zequanwu added a comment.

In D147256#4258419 <https://reviews.llvm.org/D147256#4258419>, @zequanwu wrote:

> In D147256#4257797 <https://reviews.llvm.org/D147256#4257797>, @hans wrote:
>
>> In D147256#4249527 <https://reviews.llvm.org/D147256#4249527>, @zequanwu wrote:
>>
>>> - Add a `-use-target-path-separator` flag for llc.
>>> - Add test for llc with that flag.
>>
>> But where does `TM.Options.ObjectFilenameForDebug` come from? Presumably it comes from Clang at some point, so is there any chance we can fix it "at the source" instead?
>
> `TM.Options.ObjectFilenameForDebug` either comes from llc's `-o` or clang-cl's `object-file-name=` which is translated from `/Fo[ObjectFileName]`.
>
> For Chromium, the `/Fo[ObjectFileName]` we pass to clang-cl is the same when building on Windows and targeting Windows from Linux. The problem comes `llvm::sys::path::remove_dots(PathStore, /*remove_dot_dot=*/true);` in `CodeViewDebug.cpp`. That function always convert the path to use host's path separator. And I don't think we can write a `remove_dots` function that doesn't change path separator, because `\` can only be used as path separator on Windows but is a valid path character on Linux.
>
> Or we could just not use `llvm::sys::path::remove_dots`, use the user's input as it is for object file path.

Well, MSVC cl removes redundant dots so we shouldn't remove `llvm::sys::path::remove_dots`. 
Generally, I think it's okay to use target path separator for object file path in codeview when user input is not an absolute path, because we can only generate codeview when targeting on windows.


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