[Bug debug/43516] "-fcompare-debug failure" at -O2

[jakub at gcc dot gnu dot org]

------- Comment #4 from jakub at gcc dot gnu dot org  2010-03-25 16:49 -------
Seems remove_unused_scope_block_p removes from
BLOCK #0 
  SUPERCONTEXT: re_string_skip_chars
  VARS: prev_st rawbuf_idx mbclen wc 
the prev_st variable which was unused.  But remove_unused_scope_block_p
does this only for -g0/-g1.  Then during inlining, expand_call_inline ->
remap_blocks -> remap_block -> remap_decls -> remap_decl ->
copy_decl_maybe_to_var -> copy_decl_no_change -> copy_node_stat copies
these decls, and obviously if there are more in -g2 case from -g0 case,
DECL_UIDs get out of sync and thus the -fcompare-debug failure.  There isn't
actually any code change on the #c1 testcase, at least not on x86_64-linux, but
with the DECL_UIDs being out of sync there is the possibility that some
algorithm hashing by DECL_UIDs and then traversing the hash table would lead to
code differences.  Or have we changed all such places to use bitmaps?


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |
            Summary|[4.5 Regression] "-fcompare-|"-fcompare-debug failure" at
                   |debug failure" at -O2       |-O2
   Target Milestone|4.5.0                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43516