[llvm-branch-commits] [openmp] [openmp] __kmp_x86_cpuid fix for i386/PIC builds. (#84626) (PR #85053)

[David CARLIER via llvm-branch-commits]

https://github.com/devnexen created https://github.com/llvm/llvm-project/pull/85053

None

>From 783bda15597707c0a4022024aa8661e0cae176ad Mon Sep 17 00:00:00 2001
From: David CARLIER <devnexen at gmail.com>
Date: Mon, 11 Mar 2024 13:15:43 +0000
Subject: [PATCH] [openmp] __kmp_x86_cpuid fix for i386/PIC builds. (#84626)

---
 openmp/runtime/src/kmp.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/openmp/runtime/src/kmp.h b/openmp/runtime/src/kmp.h
index e3a1e20731bbe0..d51ec886cfe556 100644
--- a/openmp/runtime/src/kmp.h
+++ b/openmp/runtime/src/kmp.h
@@ -1403,9 +1403,19 @@ extern void __kmp_query_cpuid(kmp_cpuinfo_t *p);
 // 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) {