https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104323
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Dunno how to test it in the testsuite though,
--- gcc/testsuite/gcc.dg/pch/pr104323-1.c.jj 2022-02-01 13:06:00.163192414
+0100
+++ gcc/testsuite/gcc.dg/pch/pr104323-1.c 2022-02-01 13:13:41.226712735
+0100
@@ -0,0 +1,16 @@
+/* PR target/104323 */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-maltivec -std=gnu11" } */
+
+#include "pr104323-1.h"
+
+__vector int a1 = { 100, 200, 300, 400 };
+__vector int a2 = { 500, 600, 700, 800 };
+__vector int r;
+
+int
+main ()
+{
+ r = vec_add (a1, a2);
+ return 0;
+}
--- gcc/testsuite/gcc.dg/pch/pr104323-1.hs.jj 2022-02-01 13:06:03.180149978
+0100
+++ gcc/testsuite/gcc.dg/pch/pr104323-1.hs 2022-02-01 13:12:30.175706620
+0100
@@ -0,0 +1,5 @@
+/* PR target/104323 */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-maltivec -std=gnu11" } */
+
+#include <altivec.h>
works on powerpc*-linux*, but FAILs on x86_64-linux.
