[3.3 PATCH] PR c/11370: Backport from mainline

[Roger Sayle]

The following patch is a backport to 3.3 from mainline of my fix
for PR c/11370, which are bogus warnings following noreturn function
calls with -Wunreachable.  I realize this has very recently been
triaged for 3.3.2, but I was already testing it against 3.3 anyway.

The original patch:
http://gcc.gnu.org/ml/gcc-patches/2003-07/msg00556.html

was approved for mainline by Richard Henderson:
http://gcc.gnu.org/ml/gcc-patches/2003-07/msg00886.html

and has been on mainline for several days without problems.


The following patch has been tested against the gcc-3_3-branch on
i686-pc-linux-gnu with a complete bootstrap, all languages except
treelang, and regression tested with a top-level "make -k check"
with no new failures.

Ok for the 3.3 branch?


2003-07-13  Roger Sayle  <roger@eyesopen.com>

	PR c/11370
	* calls.c (emit_call_1): Don't bother popping the arguments off of
	the stack after a noreturn function call;  The adjustment is dead.
	(expand_call): Likewise.

	* gcc.dg/Wunreachable-6.c: New testcase.
	* gcc.dg/Wunreachable-7.c: New testcase.


Index: calls.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/calls.c,v
retrieving revision 1.244.2.8
diff -c -3 -p -r1.244.2.8 calls.c
*** calls.c	10 Jun 2003 18:34:06 -0000	1.244.2.8
--- calls.c	13 Jul 2003 13:52:16 -0000
*************** emit_call_1 (funexp, fndecl, funtype, st
*** 641,646 ****
--- 641,650 ----
       if the context of the call as a whole permits.  */
    inhibit_defer_pop = old_inhibit_defer_pop;

+   /* Don't bother cleaning up after a noreturn function.  */
+   if (ecf_flags & (ECF_NORETURN | ECF_LONGJMP))
+     return;
+
    if (n_popped > 0)
      {
        if (!already_popped)
*************** expand_call (exp, target, ignore)
*** 3098,3103 ****
--- 3102,3108 ----

        /* Verify that we've deallocated all the stack we used.  */
        if (pass
+ 	  && ! (flags & (ECF_NORETURN | ECF_LONGJMP))
  	  && old_stack_allocated != stack_pointer_delta - pending_stack_adjust)
  	abort ();

*************** expand_call (exp, target, ignore)
*** 3191,3196 ****
--- 3196,3205 ----
  	    }

  	  emit_barrier_after (last);
+
+ 	  /* Stack adjustments after a noreturn call are dead code.  */
+ 	  stack_pointer_delta = old_stack_allocated;
+ 	  pending_stack_adjust = 0;
  	}

        if (flags & ECF_LONGJMP)


/* PR c/11370  */
/* { dg-do compile } */
/* { dg-options "-Wunreachable-code" } */

int main(int argc, char *argv[])
{
  if (argc != 1)
    exit(1);

  {
    int ix;  /* { dg-bogus "will never be executed" } */
    ix = printf("hello\n");
    printf("%d\n", ix);
  }

  return 0;
}


/* PR c/11370  */
/* { dg-do compile } */
/* { dg-options "-O2 -Wunreachable-code" } */

int main(int argc, char *argv[])
{
  if (argc != 1)
    exit(1);

  {
    int ix;  /* { dg-bogus "will never be executed" } */
    ix = printf("hello\n");
    printf("%d\n", ix);
  }

  return 0;
}


Roger
--
Roger Sayle,                         E-mail: roger@eyesopen.com
OpenEye Scientific Software,         WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road,     Tel: (+1) 505-473-7385
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