[llvm-bugs] [Bug 41035] Linux kernel build: Regression due memcmp to bcmp optimization

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Apr 8 11:28:57 PDT 2019


Nick Desaulniers <ndesaulniers at google.com> changed:

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

--- Comment #28 from Nick Desaulniers <ndesaulniers at google.com> ---
The fix for this is on the kernel side is now in mainline (I expect LTS
backports this week).

Next time a "compiler optimization" that relies on library support is written,
please ensure that relevant libraries for environments that use LLVM actually
have the proper support.  Otherwise such "compiler optimizations" will regress
builds for environments that don't have the library support.

Specifically in this case, I think it would have been better to ship the
optimized version in glibc first thus proving why such a compiler optimization
would be worthwhile, then verify that all relevant targets support bcmp, then
ship the optimization in LLVM.

Closing this issue now as fixed (it was originally filed because of the kernel
regression).  Please reopen if there's more to do here.

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