[LLVMbugs] [Bug 18808] clang -O4 drops other -mavx2 and possibly other flags

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=18808

Eric Christopher <echristo at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #10 from Eric Christopher <echristo at gmail.com> ---
OK. Let's look at things this way:

1) Whether or not to allow changing of target-cpu/target-feature/triple at link
time code generation.

- Not convinced here of the facility to do so. Could just recompile the
individual bitcode files to get what you want, but there are some users that
are trying to ship bitcode (as crazy as that sounds).

2) How to pass other sorts of options to the backend for code generation

- -ffoo options -fno-foo options. I.e. -fno-inline, etc. I think this is really
pretty important from the user POV. It affects things at a more global level.

3) The llvm developer debugging story

- It's useful for llvm developers to be able to more accurately debug a set of
IR using bisection or being able to turn off code generation options. Should
this be done at the command level (i.e. infrastructure that clang and llc etc
could even share), or should it be done at an llvm IR rewriting level? Don't
know. I kind of want a rewriter, but I'm not wedded to any particular answer.

I'm going to go ahead and redirect this to the mailing list and close the bug
so that the rest of this discussion can go there. :)

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