Skip to content

[builtins][FMV][Apple] Use builtin atomic load/store, instead of libdispatch #78807

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jan 22, 2024
Merged

[builtins][FMV][Apple] Use builtin atomic load/store, instead of libdispatch #78807

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 15 additions & 13 deletions compiler-rt/lib/builtins/cpu_model/aarch64/fmv/apple.inc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,19 +14,17 @@ static bool isKnownAndSupported(const char *name) {
void __init_cpu_features_resolver(void) {
// On Darwin platforms, this may be called concurrently by multiple threads
// because the resolvers that use it are called lazily at runtime (unlike on
// ELF platforms, where IFuncs are resolved serially at load time). This
// function's effect on __aarch64_cpu_features should be idempotent, but even
// so we need dispatch_once to resolve the race condition. Dispatch is
// available through libSystem, which we need anyway for the sysctl, so this
// does not add a new dependency.
// ELF platforms, where IFuncs are resolved serially at load time). This
// function's effect on __aarch64_cpu_features must be idempotent.

if (!__atomic_load_n(&__aarch64_cpu_features.features, __ATOMIC_RELAXED)) {
uint64_t features = 0;

static dispatch_once_t onceToken = 0;
dispatch_once(&onceToken, ^{
// https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics
static const struct {
const char *sysctl_name;
enum CPUFeatures feature;
} features[] = {
} feature_checks[] = {
{"hw.optional.arm.FEAT_FlagM", FEAT_FLAGM},
{"hw.optional.arm.FEAT_FlagM2", FEAT_FLAGM2},
{"hw.optional.arm.FEAT_FHM", FEAT_FP16FML},
Expand Down Expand Up @@ -58,12 +56,16 @@ void __init_cpu_features_resolver(void) {
{"hw.optional.arm.FEAT_BTI", FEAT_BTI},
};

for (size_t I = 0, E = sizeof(features) / sizeof(features[0]); I != E; ++I)
if (isKnownAndSupported(features[I].sysctl_name))
__aarch64_cpu_features.features |= (1ULL << features[I].feature);
for (size_t I = 0, E = sizeof(feature_checks) / sizeof(feature_checks[0]);
I != E; ++I)
if (isKnownAndSupported(feature_checks[I].sysctl_name))
features |= (1ULL << feature_checks[I].feature);

features |= (1ULL << FEAT_INIT);

__aarch64_cpu_features.features |= (1ULL << FEAT_INIT);
});
__atomic_store(&__aarch64_cpu_features.features, &features,
__ATOMIC_RELAXED);
}
}

#endif // TARGET_OS_OSX || TARGET_OS_IPHONE