[PATCH][LTO] Fix PR48437

[Richard Guenther]

I'm testing the following patch for PR48437 - the C frontend generates
decl copies for placing them in BLOCK_VARS for

int
test (void)
{
  extern int f (void);
  return 0;
}

we currently end up putting those into the decl merging machinery,
causing DECL_CHAIN re-use and subsequent crashes.  By not indexing
them we make sure to keep them separate.

LTO bootstrap & regtest pending on x86_64-unknown-linux-gnu, ok?

[Similar fix has to be employed for VLA types]

Thanks,
Richard.

2011-12-07  Richard Guenther  <rguent...@suse.de>

        PR lto/48437
        * lto-streamer-out.c (tree_is_indexable): Exclude block-local
        extern declarations.

        * gcc.dg/lto/20111207-2_0.c: New testcase.
        * gcc.dg/guality/pr48437.c: Likewise.

Index: gcc/lto-streamer-out.c
===================================================================
*** gcc/lto-streamer-out.c      (revision 182081)
--- gcc/lto-streamer-out.c      (working copy)
*************** tree_is_indexable (tree t)
*** 129,134 ****
--- 129,144 ----
    else if (TREE_CODE (t) == VAR_DECL && decl_function_context (t)
           && !TREE_STATIC (t))
      return false;
+   /* If this is a decl generated for block local externs for
+      debug info generation, stream it unshared alongside BLOCK_VARS.  */
+   else if (VAR_OR_FUNCTION_DECL_P (t)
+          /* ???  The following tests are a literal match on what
+             c-decl.c:pop_scope does.  */
+          && TREE_PUBLIC (t)
+          && DECL_EXTERNAL (t)
+          && DECL_CONTEXT (t)
+          && TREE_CODE (DECL_CONTEXT (t)) == FUNCTION_DECL)
+     return false;
    else
      return (TYPE_P (t) || DECL_P (t) || TREE_CODE (t) == SSA_NAME);
  }
Index: gcc/testsuite/gcc.dg/lto/20111207-2_0.c
===================================================================
*** gcc/testsuite/gcc.dg/lto/20111207-2_0.c     (revision 0)
--- gcc/testsuite/gcc.dg/lto/20111207-2_0.c     (revision 0)
***************
*** 0 ****
--- 1,17 ----
+ /* { dg-lto-do run } */
+ 
+ int
+ test (void)
+ {
+   int f (void);
+   return 0;
+ }
+ 
+ int
+ main (void)
+ {
+   int f (void);
+   int test (void);
+ 
+   return test ();
+ }
Index: gcc/testsuite/gcc.dg/guality/pr48437.c
===================================================================
*** gcc/testsuite/gcc.dg/guality/pr48437.c      (revision 0)
--- gcc/testsuite/gcc.dg/guality/pr48437.c      (revision 0)
***************
*** 0 ****
--- 1,15 ----
+ /* PR lto/48437 */
+ /* { dg-do run } */
+ /* { dg-options "-g" } */
+ 
+ int i __attribute__((used));
+ int main()
+ {
+   volatile int i;
+   for (i = 3; i < 7; ++i)
+     {
+       extern int i; /* { dg-final { gdb-test 7 "i" "0" } } */
+       asm volatile ("" : : : "memory");
+     }
+   return 0;
+ }