target/s390x: Fix determination of overflow condition code after addition

target/s390x: Fix determination of overflow condition code after addition

This program currently prints different results when run with TCG instead
of running on real s390x hardware:

 #include <stdio.h>

 int overflow_32 (int x, int y)
 {
   int sum;
   return ! __builtin_add_overflow (x, y, &sum);
 }

 int overflow_64 (long long x, long long y)
 {
   long sum;
   return ! __builtin_add_overflow (x, y, &sum);
 }

 int a1 = -2147483648;
 int b1 = -2147483648;
 long long a2 = -9223372036854775808L;
 long long b2 = -9223372036854775808L;

 int main ()
 {
   {
     int a = a1;
     int b = b1;
     printf ("a = 0x%x, b = 0x%x\n", a, b);
     printf ("no_overflow = %d\n", overflow_32 (a, b));
   }
   {
     long long a = a2;
     long long b = b2;
     printf ("a = 0x%llx, b = 0x%llx\n", a, b);
     printf ("no_overflow = %d\n", overflow_64 (a, b));
   }
 }

Signed-off-by: Bruno Haible <bruno@clisp.org>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/616
Message-Id: <20220323162621.139313-2-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>