Created attachment 1545109 [details]
Test code with register volatile

This changed in http://gcc.gnu.org/r203303

Created attachment 1546058 [details]
experimental patch


------- Comment on attachment From Andreas.Krebbel.com 2019-03-20 08:57 EDT-------


The stack pointer needs saving and restoring even if it is a global register. This is currently not handled correctly in s390_optimize_register_info.

I'm testing the attached patch. Does this fix the problem for you?

Comment on attachment 1546058 [details]
experimental patch

Thanks, looks reasonable to me, though not sure if for the testcase it wouldn't be better to just have a runtime testcase with that global register variable, a noipa function that does something that needs stack allocation and perhaps in auxiliary source have the rest, main that calls that noipa function and have that noipa function say call some other noipa one in the auxiliary TU and do some runtime verification which would fail if the stack pointer changed in main (then it wouldn't find some variable for a check or comparison of addresses would fail etc.).

Something like:
$ cat prNNNNN-1.c
/* PR target/NNNNN */
/* { dg-do run } */
/* { dg-options "-O0 -fomit-frame-pointer" } */
/* { dg-additional-sources "prNNNNN-2.c" } */

register void *sp __asm ("15");

__attribute__((noipa)) int
foo (const char *a, const char *b)
{
  while (1)
    {
      char c = *a++;
      if (c != *b++) return 0;
      if (c == '\0') return 1;
    }
}
$ cat prNNNNN-2.c
/* PR target/NNNNN */
/* { dg-do compile } */

extern int foo (const char *, const char *);

__attribute__((noipa)) void
bar (const char *p)
{
  static const char *x;
  if (!x)
    x = p;
  else if (p != x)
    __builtin_abort ();
}

int
main ()
{
  char a[8] = "abcdefg";
  bar (a);
  if (foo (a, a) != 1)
    __builtin_abort ();
  bar (a);
  return 0;
}

with NNNNN replaced by some gcc bugzilla bug filed for this.  At least the above fails for me with the current trunk and commenting out the sp declaration makes it work.

------- Comment From Andreas.Krebbel.com 2019-03-20 11:00 EDT-------
GCC Bugzilla: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89775

------- Comment From Andreas.Krebbel.com 2019-03-20 11:29 EDT-------
Test was successful. I've committed the patch with the testcase from Jakub. I've verified that the testcase fails before and succeeds after the patch. Thanks!

Thanks for the fast analysis and fix.  Once a patched gcc is available in the Fedora repos, I'll try it out on the clisp code.

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