Re: [PATCH] Limit alignment on error_mark_node variable

[Richard Biener <richard dot guenther at gmail dot com>]

On Thu, Jul 9, 2015 at 1:08 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Jul 9, 2015 at 2:54 AM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Thu, Jul 9, 2015 at 11:52 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Thu, Jul 09, 2015 at 10:16:38AM +0200, Richard Biener wrote:
>>>> On Wed, Jul 8, 2015 at 5:32 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>>>> > There is no need to try different alignment on variable of
>>>> > error_mark_node.
>>>> >
>>>> > OK for trunk if there is no regression?
>>>>
>>>> Can't we avoid calling align_variable on error_mark_node type decls
>>>> completely?  That is, punt earlier when we try to emit it.
>>>>
>>>
>>> How about this?  OK for trunk?
>>
>> Heh, you now get the obvious question why we can't simply avoid
>> adding the varpool node in the first place ;)
>>
>
> When it was first added to varpool, its type was OK:
>
> (gdb) bt
> #0  varpool_node::get_create (decl=<var_decl 0x7ffff1506900 vv>)
>     at /export/gnu/import/git/sources/gcc/gcc/varpool.c:150
> #1  0x0000000000e1c3e8 in rest_of_decl_compilation (
>     decl=<var_decl 0x7ffff1506900 vv>, top_level=1, at_end=0)
>     at /export/gnu/import/git/sources/gcc/gcc/passes.c:271
> #2  0x0000000000731d39 in finish_decl (decl=<var_decl 0x7ffff1506900 vv>,
>     init_loc=0, init=<tree 0x0>, origtype=<tree 0x0>, asmspec_tree=<tree 0x0>)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-decl.c:4863
> #3  0x000000000078d1ed in c_parser_declaration_or_fndef (
>     parser=0x7ffff15050a8, fndef_ok=false, static_assert_ok=true,
>     empty_ok=true, nested=false, start_attr_ok=true,
>     objc_foreach_object_declaration=0x0, omp_declare_simd_clauses=...)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1855
> #4  0x000000000078c234 in c_parser_external_declaration (parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1435
> #5  0x000000000078be45 in c_parser_translation_unit (parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1322
> #6  0x00000000007b3271 in c_parse_file ()
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:15440
> #7  0x000000000081cb97 in c_common_parse_file ()
>     at /export/gnu/import/git/sources/gcc/gcc/c-family/c-opts.c:1059
> #8  0x0000000000f27662 in compile_file ()
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:543
> ---Type <return> to continue, or q <return> to quit---
> #9  0x0000000000f29baa in do_compile ()
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:2041
> #10 0x0000000000f29df9 in toplev::main (this=0x7fffffffdc90, argc=17,
>     argv=0x7fffffffdd98)
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:2142
> #11 0x00000000017d8228 in main (argc=17, argv=0x7fffffffdd98)
>     at /export/gnu/import/git/sources/gcc/gcc/main.c:39
>
> Later, it was turned into error_mark_node:
>
> Old value = <array_type 0x7ffff15ee150>
> New value = <error_mark 0x7ffff14fac90>
> finish_decl (decl=<var_decl 0x7ffff1506990 a>, init_loc=0, init=<tree 0x0>,
>     origtype=<tree 0x0>, asmspec_tree=<tree 0x0>)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-decl.c:4802
> 4802      if (TREE_USED (type))
> (gdb) bt
> #0  finish_decl (decl=<var_decl 0x7ffff1506990 a>, init_loc=0,
>     init=<tree 0x0>, origtype=<tree 0x0>, asmspec_tree=<tree 0x0>)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-decl.c:4802
> #1  0x000000000078d1ed in c_parser_declaration_or_fndef (
>     parser=0x7ffff15050a8, fndef_ok=false, static_assert_ok=true,
>     empty_ok=true, nested=true, start_attr_ok=true,
>     objc_foreach_object_declaration=0x0, omp_declare_simd_clauses=...)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1855
> #2  0x0000000000792a23 in c_parser_compound_statement_nostart (
>     parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:4621
> #3  0x0000000000792688 in c_parser_compound_statement (parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:4532
> #4  0x000000000078d5a3 in c_parser_declaration_or_fndef (
>     parser=0x7ffff15050a8, fndef_ok=true, static_assert_ok=true,
>     empty_ok=true, nested=false, start_attr_ok=true,
>     objc_foreach_object_declaration=0x0, omp_declare_simd_clauses=...)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1965
> #5  0x000000000078c234 in c_parser_external_declaration (parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1435
> #6  0x000000000078be45 in c_parser_translation_unit (parser=0x7ffff15050a8)
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:1322
> #7  0x00000000007b3271 in c_parse_file ()
> ---Type <return> to continue, or q <return> to quit---
>     at /export/gnu/import/git/sources/gcc/gcc/c/c-parser.c:15440
> #8  0x000000000081cb97 in c_common_parse_file ()
>     at /export/gnu/import/git/sources/gcc/gcc/c-family/c-opts.c:1059
> #9  0x0000000000f27662 in compile_file ()
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:543
> #10 0x0000000000f29baa in do_compile ()
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:2041
> #11 0x0000000000f29df9 in toplev::main (this=0x7fffffffdc90, argc=17,
>     argv=0x7fffffffdd98)
>     at /export/gnu/import/git/sources/gcc/gcc/toplev.c:2142
> #12 0x00000000017d8228 in main (argc=17, argv=0x7fffffffdd98)
>     at /export/gnu/import/git/sources/gcc/gcc/main.c:39
> (gdb)
>
> I guess it isn't worth to take it out of varpool.
>
> Is my patch OK for trunk?

I don't see why the C FE would need to invoke finish_decl twice here.
So I'd rather
have the C frontend not invoke rest_of_decl_compilation on this in the
first place.

Your patch still feels like a hack in the wrong place.

Richard.

> --
> H.J.