libatomic: Handle AVX+CX16 AMD like Intel for 16b atomics [PR104688]

We got a response from AMD in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104688#c10
so the following patch starts treating AMD with AVX and CMPXCHG16B
ISAs like Intel by using vmovdqa for atomic load/store in libatomic.
We still don't have confirmation from Zhaoxin and VIA (anything else
with CPUs featuring AVX and CX16?).

2022-11-15  Jakub Jelinek  <jakub@redhat.com>

	PR target/104688
	* config/x86/init.c (__libat_feat1_init): Don't clear
	bit_AVX on AMD CPUs.

(cherry picked from commit 4a7a846687e076eae58ad3ea959245b2bf7fdc07)

diff --git a/libatomic/config/x86/init.c b/libatomic/config/x86/init.c
index 36e231c68cc7a4d9204d5b64bfe3c9d314bed86f..c9b474bda796abb3edbcd8ba3613a052ad51c6d9 100644 (file)
--- a/libatomic/config/x86/init.c
+++ b/libatomic/config/x86/init.c
@@ -39,10 +39,12 @@ __libat_feat1_init (void)
       == (bit_AVX | bit_CMPXCHG16B))
     {
       /* Intel SDM guarantees that 16-byte VMOVDQA on 16-byte aligned address
-        is atomic, but so far we don't have this guarantee from AMD.  */
+        is atomic, and AMD is going to do something similar soon.
+        We don't have a guarantee from vendors of other CPUs with AVX,
+        like Zhaoxin and VIA.  */
       unsigned int ecx2 = 0;
       __get_cpuid (0, &eax, &ebx, &ecx2, &edx);
-      if (ecx2 != signature_INTEL_ecx)
+      if (ecx2 != signature_INTEL_ecx && ecx2 != signature_AMD_ecx)
        FEAT1_REGISTER &= ~bit_AVX;
     }
 #endif