https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122304
Bug ID: 122304
Summary: UB MArch x86_64 v3/4 rounding Errors
Product: gcc
Version: 14.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: crange76 at gmail dot com
Target Milestone: ---
After hours of digging, I found out the reason this march build of
`opencolorio` keep failing tests is because of gcc's optimizations on x64_86v3+
binaries.
https://github.com/NixOS/nixpkgs/issues/398621#issuecomment-3411553517
This issue has good traceability between the project and the build failure, the
main problem is when I swapped the compiler to clang it worked flawlessly. It
didn't matter what I did it worked, and the following does not work on gcc 14.
DOES NOT WORK
* -march=x64_86v3
* -march=x64_86v4
* -march=x64_86v3 -fno-fast-math
* -march=x64_86v4 -fno-fast-math
since this was a rounding error test I thought explicitly disabling fastmath
might help.
WORKS
* -march=x64_86v2
WORKS ON CLANG
* -march=x64_86v2
* -march=x64_86v3
* -march=x64_86v4
