This header has long lacked a standard multiple inclusion guard
like other headers have, for no apparent reason. The GCC header
of the same name likewise lacks one up through release 10.1, but
trunk GCC (release 11, and perhaps future 10.x) has fixed it
(see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96238).
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D91226
This commit makes two changes:
- Remove the push and pop instructions that were saving and restoring %ebx
before and after cpuid in 32-bit pic mode. We were doing this to ensure we
don't lose the GOT address in pic register %ebx, but this isn't necessary
because the GOT address is kept in a virtual register.
- In 64-bit mode, preserve base register %rbx around cpuid.
This fixes PR20311 and rdar://problem/17686779.
llvm-svn: 218173
Roland McGrath