[gcc r17-3392] mv28.C: Compile with -march=x86-64

https://gcc.gnu.org/g:1fb18207ae8aa92c2ef1b1878c1c1a87039685be

commit r17-3392-g1fb18207ae8aa92c2ef1b1878c1c1a87039685be
Author: H.J. Lu <[email protected]>
Date:   Tue Aug 18 13:15:30 2026 +0800

    mv28.C: Compile with -march=x86-64
    
    mv28.C has
    
    void __attribute__ ((target("avx512vl"))) foo () {} /* { dg-error "ISA '\[^\n\r\]*' is not supported in 'target' attribute, use 'arch=' syntax" } */
    ...
    
    to check for unsupported target attribute errors.  If AVX512 is enabled
    by default, there are no expected compiler errors.  Compile mv28.C with
    -march=x86-64 so that AVX512 isn't enabled on AVX512 machines when GCC
    is configured with
    
    --with-arch=native --with-cpu=native
    
            PR testsuite/126923
            * g++.target/i386/mv28.C (dg-additional-options): New.
    
    Signed-off-by: H.J. Lu <[email protected]>

Diff:
---
 gcc/testsuite/g++.target/i386/mv28.C | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gcc/testsuite/g++.target/i386/mv28.C b/gcc/testsuite/g++.target/i386/mv28.C
index c377d23a4241..3c566668857e 100644
--- a/gcc/testsuite/g++.target/i386/mv28.C
+++ b/gcc/testsuite/g++.target/i386/mv28.C
@@ -1,5 +1,6 @@
 /* { dg-do compile } */
 /* { dg-require-ifunc "" }  */
+/* { dg-additional-options "-march=x86-64" } */
 
 void __attribute__ ((target("avx512vl"))) foo () {} /* { dg-error "ISA '\[^\n\r\]*' is not supported in 'target' attribute, use 'arch=' syntax" } */
 void __attribute__ ((target("avx512bw"))) foo () {} /* { dg-error "ISA '\[^\n\r\]*' is not supported in 'target' attribute, use 'arch=' syntax" } */