https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103661
Bug ID: 103661
Summary: __builtin_cpu_supports returns a negative integer for
avx512vbmi2
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: stefan.kneifel at bluewin dot ch
Target Milestone: ---
__builtin_cpu_supports is supposed to return a positive integer if the run-time
CPU supports the requested feature and zero otherwise (see Documentation).
However, for the feature "avx512vbmi2", a negative integer (0x80000000) is
returned.
FEATURE_AVX512VBMI2 equals to 31 in gcc/common/config/i386/i386-cpuinfo.h, thus
the returned 32-bit integer has bit 31 set and is therefore negative.
This might lead to surprising errors even inside GCC (e.g. when features are
tested in automatically generated resolvers; the code seems to rely on the
positivity).
Would it be an acceptable solution to declare __builtin_cpu_supports as
unsigned, or do you see another solution?
