Looks like a known fail:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101674

diff --git a/gcc/testsuite/gcc.dg/uninit-pred-9_b.c b/gcc/testsuite/gcc.dg/uninit-pred-9_b.c

index 53c4a5399ea..c2b043f5019 100644

--- a/gcc/testsuite/gcc.dg/uninit-pred-9_b.c

+++ b/gcc/testsuite/gcc.dg/uninit-pred-9_b.c

@@ -17,7 +17,7 @@ int foo (int n, int l, int m, int r)

   if (l > 100)

     if ( (n <= 9) &&  (m < 100)  && (r < 19) )

-      blah(v); /* { dg-bogus "uninitialized" "bogus warning" { xfail powerpc64*-*-* cris-*-* } } */

+      blah(v); /* { dg-bogus "uninitialized" "bogus warning" { xfail powerpc64*-*-* cris-*-* s390*-*-* } } */

   if ( (n <= 8) &&  (m < 99)  && (r < 19) )

       blah(v); /* { dg-bogus "uninitialized" "pr101674" { xfail mmix-*-* } } */