[openmp] __kmp_x86_cpuid fix for i386/PIC builds. (#84626)
GitOrigin-RevId: facb89ae1228c067b2b14f32e7e70608fe50704b
diff --git a/runtime/src/kmp.h b/runtime/src/kmp.h
index 6510dd9..48d7124 100644
--- a/runtime/src/kmp.h
+++ b/runtime/src/kmp.h
@@ -1404,9 +1404,19 @@
// subleaf is only needed for cache and topology discovery and can be set to
// zero in most cases
static inline void __kmp_x86_cpuid(int leaf, int subleaf, struct kmp_cpuid *p) {
+#if KMP_ARCH_X86 && (defined(__pic__) || defined(__PIC__))
+ // on i386 arch, the ebx reg. is used by pic, thus we need to preserve from
+ // being trashed beforehand
+ __asm__ __volatile__("mov %%ebx, %%edi\n"
+ "cpuid\n"
+ "xchg %%edi, %%ebx\n"
+ : "=a"(p->eax), "=b"(p->ebx), "=c"(p->ecx), "=d"(p->edx)
+ : "a"(leaf), "c"(subleaf));
+#else
__asm__ __volatile__("cpuid"
: "=a"(p->eax), "=b"(p->ebx), "=c"(p->ecx), "=d"(p->edx)
: "a"(leaf), "c"(subleaf));
+#endif
}
// Load p into FPU control word
static inline void __kmp_load_x87_fpu_control_word(const kmp_int16 *p) {
