| Issue |
157383
|
| Summary |
Clang Apple Darwin target, __builtin_cpu_init() not supported, __built_cpu_supports() return wrong values
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
sparspare
|
Host environment: Darwin 24.6.0, latest Xcode tools installed, tried latest homebrew clang as well.
Built target is default Darwin MACH0 arm64.
First, using __built_cpu_supports("aes") returns 0 on this system, whereas is should return 1.
Second, __builtin_cpu_init() cause a compilation error "builtin is not supported on this target".
Looking at the generated binary, there was code present for "__init_cpu_features_resolver()", which indeed would initialize the cpu_supports to the proper values. However, that routine does not appear to be invoked.
Manually calling __init_cpu_features_resolver() causes subsequent __built_cpu_supports() calls to provide the correct values.
Simple test program below.
`
// clang test.c -o test
#include <stdio.h>
void __init_cpu_features_resolver(); // possibly wrong prototype
int main(void)
{
// __builtin_cpu_init(); // error: builtin is not supported on this target : __builtin_cpu_init();
printf("aes=%u\n", __builtin_cpu_supports("aes")); // 0 -- should be 1
__init_cpu_features_resolver();
printf("aes=%u\n", __builtin_cpu_supports("aes")); // now 1
return 0;
// tried with both:
// Homebrew clang version 21.1.0 Target: arm64-apple-darwin24.6.0
// Apple clang version 17.0.0 (clang-1700.0.13.5) Target: arm64-apple-darwin24.6.0
}`
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