PATCH: PR lto/55466: Revision 191466 destroyed DWARF debug info

[H.J. Lu]

Hi,

Since revision 191466, LTO no longer maintains its own symbol table and
it uses varpool for variables instead.  As the result, debug info on
variables is lost when GCC is configured with

--enable-bootstrap --with-build-config=bootstrap-lto

This patch record the global variables if WPA isn't enabled.  It
works when GCC is configured with

--enable-bootstrap --with-build-config=bootstrap-lto 
--enable-languages=c,c++,fortran,java,lto,objc,obj-c++ 

However, when go is added, I got

lto1: internal compiler error: in add_AT_specification, at
dwarf2out.c:3985
0x629ad9 add_AT_specification
        /export/gnu/import/git/gcc/gcc/dwarf2out.c:3985
0x64dabb gen_variable_die
        /export/gnu/import/git/gcc/gcc/dwarf2out.c:18327
0x65336b gen_decl_die
        /export/gnu/import/git/gcc/gcc/dwarf2out.c:20033
0x653fcd dwarf2out_decl(tree_node*)
        /export/gnu/import/git/gcc/gcc/dwarf2out.c:20348
0x6535f9 dwarf2out_global_decl
        /export/gnu/import/git/gcc/gcc/dwarf2out.c:20083
0x997703 emit_debug_global_declarations(tree_node**, int)
        /export/gnu/import/git/gcc/gcc/toplev.c:530
0x521aaa lto_write_globals
        /export/gnu/import/git/gcc/gcc/lto/lto-lang.c:1067
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
make[6]: *** [/tmp/cc3yYR7d.ltrans4.ltrans.o] Error 1
lto-wrapper: make returned 2 exit status
/usr/local/x86_64-unknown-linux-gnu/bin/ld: lto-wrapper failed
collect2: error: ld returned 1 exit status
make[5]: *** [go1] Error 1

This is latent without my patch since no DWARF info on varaibles are
 generated.  OK to install?

Thanks.


H.J.
---
2012-12-07  H.J. Lu  <hongjiu...@intel.com>

        PR lto/55466
        * lto-symtab.c (lto_symtab_merge_decls_1): Don't record
        the prevailing variable.
        * lto.c (lto_main): Record the global variables if WPA isn't
        enabled.

diff --git a/gcc/lto-symtab.c b/gcc/lto-symtab.c
index 0b0cdac..295fd37 100644
--- a/gcc/lto-symtab.c
+++ b/gcc/lto-symtab.c
@@ -443,10 +443,6 @@ lto_symtab_merge_decls_1 (symtab_node first)
 
   symtab_prevail_in_asm_name_hash (prevailing);
 
-  /* Record the prevailing variable.  */
-  if (TREE_CODE (prevailing->symbol.decl) == VAR_DECL)
-    vec_safe_push (lto_global_var_decls, prevailing->symbol.decl);
-
   /* Diagnose mismatched objects.  */
   for (e = prevailing->symbol.next_sharing_asm_name;
        e; e = e->symbol.next_sharing_asm_name)
diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c
index 376af85..e567cb0 100644
--- a/gcc/lto/lto.c
+++ b/gcc/lto/lto.c
@@ -3380,6 +3380,8 @@ lto_main (void)
        do_whole_program_analysis ();
       else
        {
+         struct varpool_node *vnode;
+
          timevar_start (TV_PHASE_OPT_GEN);
 
          materialize_cgraph ();
@@ -3397,6 +3399,10 @@ lto_main (void)
             this.  */
          if (flag_lto_report)
            print_lto_report_1 ();
+
+         /* Record the global variables.  */
+         FOR_EACH_DEFINED_VARIABLE (vnode)
+           vec_safe_push (lto_global_var_decls, vnode->symbol.decl);
        }
     }