Realised that this could be done with just an assert (no separate check function) so this is a much smaller patch now. This still mostly hits the assertion with the previous way of calculating duration (duration_cast). I think the extra code in end() may make it slightly less likely that this case happens, but only with assertions enabled.

Fix some style issues and remove unit test.

Added structure check on time profile and assertion.

Fixed comment

I don't know a lot about the structure of clang but it LGTM from the point of view of the code and traces coming out.

Update: https://bugs.llvm.org/show_bug.cgi?id=41279 has been fixed by https://reviews.llvm.org/D62700.

Re-added test cases using variables and added comment. This now tests both formats.

We support non immediate on these because gcc does.

I'll have a look and see if there is a reason why these don't fail in the same way (which would make the test fail in it's current form).

Then the test should be failing? Or is the current form also legal?

Is the compiler missing a check that these parameters are immediates?

I'm not sure what you mean.

https://reviews.llvm.org/D62200 has landed so -fprofile-generate and -fcs-profile-generate both add --dependent-lib (required for this patch to make sense).

I was going to suggest that maybe what we should do is just embed the basename, i.e. /nodefaultlib:clang_rt.profile-x86_64.lib ...

it looks like passing -no-canonical-prefixes makes this path relative

Hello, this embeds an absolute path into the generated .obj file, which means the output now is no longer deterministic (since it depends on the absolute path to clang_rt.profile-x86_64.lib).

1). -fprofile-generate and -fcs-profile-generate need clang_rt.profile adding with --dependent-lib in the driver (like https://reviews.llvm.org/D61742). I'll create a separate review for that.

2). Self hosting with -fprofile-generate hits a crash building CrashRecoveryContext.cpp. I'll try to report this.

Handle -fprofile-generate and -fcs-profile-generate options for self hosting as well.

In D61742#1497259, @rnk wrote:

Thanks, I would like to do this for the sanitizers as well, since this is a constant pain point for users

Prevent adding -dependent-lib on mingw32 and add tests.

We also see an assertion failure prior to the revert. At r329738:

Ping

I found a number of bugs comparing direct object emission and via assembly with the check_cfc tool. Sean I and spoke about using fuzzing in that area. I expect it would find issues but I haven't done any work on it so no objections if someone wanted to add this to llvm-mc-fuzzer.

Thanks for the review Rafael.

Thanks Rafael. I've fixed the 80 col violations and committed revision 233919.

Fixes for points raised by Rafael.

Fix line endings.

Use -via-file-asm for dash_s_no_change check.

This would be very useful to us. I tried this patch and it basically works with our CI server too.