PATCH [mainline] fix -combine bug for parser, gzip of 2000 SPEC benchmark

[Fariborz Jahanian <fjahanian at apple dot com>]

Following patch fixes an IMA bug in two SPEC 2000 benchmarks, parser 
and gzip. Without this patch
both programs  mis-compare. This patch, along with RTH's patch for 
PR/17531 (needed to prevent
ICEing of gzip), was tested successfully in building SPEC benchmarks in 
IMA mode (-combine)
for apple-ppc-darwin platform. Patch has been bootstrapped, dejagnu 
tested on apple-ppc-darwin.

Problem can be reproduced in a trivial test case using -combine only. 
Issued
warning tells the whole story.

% cat a.h
#define MAX_WORD 60

extern int sentence[];

% cat a.c
#include "a.h"

% cat main.c
#include "a.h"

int sentence[MAX_WORD];

% cat b.c
#include "a.h"

% mygccm5o -combine a.c main.c b.c -c
a.h:3: warning: array 'sentence' assumed to have one element

OK for FSF mainline?

- Fariborz (fjahanian@apple.com)


ChangeLog:

2004-09-29  Fariborz Jahanian <fjahanian@apple.com>

        * c-decl.c (merge_decls): Preserve OLDDECL's size if newdecl is
          in another TU and its size is unspecified.


Index: c-decl.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-decl.c,v
retrieving revision 1.589
diff -c -p -r1.589 c-decl.c
*** c-decl.c    24 Sep 2004 17:22:17 -0000      1.589
--- c-decl.c    29 Sep 2004 15:49:03 -0000
*************** merge_decls (tree newdecl, tree olddecl,
*** 1517,1522 ****
--- 1517,1523 ----
  {
    int new_is_definition = (TREE_CODE (newdecl) == FUNCTION_DECL
                           && DECL_INITIAL (newdecl) != 0);
+   bool preserve_old_decl_size = false;

    /* For real parm decl following a forward decl, rechain the old decl
       in its new location and clear TREE_ASM_WRITTEN (it's not a
*************** merge_decls (tree newdecl, tree olddecl,
*** 1654,1659 ****
--- 1655,1666 ----
        TREE_PUBLIC (newdecl) = TREE_PUBLIC (olddecl);
        if (! DECL_EXTERNAL (newdecl))
        {
+           /* Preserve OLDDECL's size if newdecl is in
+              another TU and its size is unspecified. */
+           preserve_old_decl_size =
+             (DECL_SIZE (olddecl) != NULL_TREE
+            && DECL_SIZE (newdecl) == NULL_TREE
+            && !same_translation_unit_p (olddecl, newdecl));
          DECL_CONTEXT (newdecl) = DECL_CONTEXT (olddecl);
          DECL_COMMON (newdecl) = DECL_COMMON (olddecl);
        }
*************** merge_decls (tree newdecl, tree olddecl,
*** 1737,1748 ****
--- 1744,1758 ----
    {
      unsigned olddecl_uid = DECL_UID (olddecl);
      tree olddecl_context = DECL_CONTEXT (olddecl);
+     tree olddecl_decl_size = DECL_SIZE (olddecl);

      memcpy ((char *) olddecl + sizeof (struct tree_common),
            (char *) newdecl + sizeof (struct tree_common),
            sizeof (struct tree_decl) - sizeof (struct tree_common));
      DECL_UID (olddecl) = olddecl_uid;
      DECL_CONTEXT (olddecl) = olddecl_context;
+     if (preserve_old_decl_size)
+       DECL_SIZE (olddecl) = olddecl_decl_size;
    }

    /* If OLDDECL had its DECL_RTL instantiated, re-invoke make_decl_rtl