AVX-512: Unable to copy EFLAGS physical register! #38151
Description
| Bugzilla Link | 38803 |
| Resolution | FIXED |
| Resolved on | Oct 19, 2018 12:14 |
| Version | 7.0 |
| OS | Linux |
| Blocks | #38454 |
| Attachments | tab.cpp |
| Reporter | LLVM Bugzilla Contributor |
| CC | @chandlerc,@topperc,@francisvm,@RKSimon,@tstellar |
| Fixed by commit(s) | r343443 r343428 r344804 r344805 |
Extended Description
We've got a bug report from one of our users attempting to build Chromium using clang. The build is failing for him with the following error message:
fatal error: error in backend: Unable to copy EFLAGS physical register!
x86_64-pc-linux-gnu-clang++: error: clang frontend command failed with exit code 70 (use -v to see invocation)
I'm attaching a minimal test case prepared by Sergei Trofimovich:
// $ clang++ -march=skylake-avx512 -O2 tab.cpp
// fatal error: error in backend: Unable to copy EFLAGS physical register!
bool a();
int b, c;
float d;
float fn2() {
int e = a();
double f = e ? 0.75f : 0;
if (c)
d = e ? 0 : b;
return f;
}
I was able to reproduce the issue with today's LLVM+Clang trunk.