Hi,
On Mon, May 17 2021, Eric Botcazou wrote:
>> sorry for breaking Ada over the weekend, however...
>
> No problem.
>
>> None of the non-ACATS tests fail for me without doing a bootstrap, but I
>> did manage to reproduce this one (by the way, there really should be a
>> documentation on how to run ACATS tests manually, I should not need to
>> spend an hour and half figuring it out).
>
> https://gcc.gnu.org/wiki/DebuggingGCC
I missed that. I'll try to put the string ACATS there so that people
can search for it.
>
>> The problem is that before (early) SRA, there is a TREE_READONLY decl
>> that is being written to and my patch eliminated those writes.
>> Specifically, I see:
>>
>> <bb 183> :
>> var_ara_5D.5012.FD.4868[1]{lb: 1 sz: 4}[1]{lb: 1 sz: 1} = _877;
>> _880 = report.ident_bool (1);
>>
>> <bb 184> :
>> var_ara_5D.5012.FD.4868[1]{lb: 1 sz: 4}[2]{lb: 1 sz: 1} = _880;
>> _883 = report.ident_bool (1);
>>
>> <bb 185> :
>> var_ara_5D.5012.FD.4868[1]{lb: 1 sz: 4}[3]{lb: 1 sz: 1} = _883;
>> _886 = report.ident_bool (1);
>>
>> <bb 186> :
>> var_ara_5D.5012.FD.4868[1]{lb: 1 sz: 4}[4]{lb: 1 sz: 1} = _886;
>> _889 = report.ident_bool (1);
>>
>> [...and many more.] Note that this is an -fdump-tree-all-uid dump, the
>> DECL that is being assigned to has DECL_UID 5012 and when I dump it:
>>
>> DECL_UID of racc->base is: 5012
>> print_node (dump_file, "", racc->base, 0):
>> <var_decl 0x7fc249fbc5a0 var_ara_5
>> type <record_type 0x7fc249faf690 c41325a__p__p__obj_ara_5___PAD
>> sizes-gimplified type_5 TI size <integer_cst 0x7fc24b13dc00 constant 128>
>> unit-size <integer_cst 0x7fc24b13dc18 constant 16>
>> align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
>> 0x7fc249faf690 fields <field_decl 0x7fc249fb02f8 F type <array_type
>> 0x7fc249faf1f8 c41325a__p__array_5> decl_3 TI c41325a.adb:57:11
>> size <integer_cst 0x7fc24b13dc00 constant 128>
>> unit-size <integer_cst 0x7fc24b13dc18 constant 16>
>> align:8 warn_if_not_align:0 offset_align 128
>> offset <integer_cst 0x7fc24b13dbe8 constant 0>
>> bit-offset <integer_cst 0x7fc24b13dc30 constant 0> context
>> <record_type 0x7fc249faf690 c41325a__p__p__obj_ara_5___PAD>> context
>> <function_decl 0x7fc249f89d00 c41325a> Ada size <integer_cst 0x7fc24b13dc00
>> constant 128>
>> pointer_to_this <pointer_type 0x7fc249d4e7e0> chain <type_decl
>> 0x7fc249fb0390 c41325a__p__p__obj_ara_5___PAD>> --> readonly TI
>> c41325a.adb:70:6
>> size <integer_cst 0x7fc24b13dc00 type <integer_type 0x7fc24b1520a8
>> bitsizetype> constant 128> unit-size <integer_cst 0x7fc24b13dc18 type
>> <integer_type 0x7fc24b152000 sizetype> constant 16> align:64
>> warn_if_not_align:0 context <function_decl 0x7fc249f89d00 c41325a> chain
>> <var_decl 0x7fc249fbc630 var_ara_6>>
>>
>> I can see that base is TREE_READONLY.
>>
>> Am I right that this is a bug happening at some point earlier in the Ada
>> compiler?
>
> Yes, in the gimplifier apparently, so try with:
>
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index e790f08b23f..52cef6f8bff 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -1822,6 +1822,7 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
> if (!TREE_STATIC (decl))
> {
> DECL_INITIAL (decl) = NULL_TREE;
> + TREE_READONLY (decl) = 0;
> init = build2 (INIT_EXPR, void_type_node, decl, init);
> gimplify_and_add (init, seq_p);
> ggc_free (init);
The problem with this patch is that it causes:
FAIL: gnat.dg/opt94.adb scan-tree-dump-times optimized "worker" 1
which is exactly the testcase from the commit which caused the bug I am
trying to address.
I have given up attempting to clean IL we get from Ada testcases from
writes to TREE_READONLY decls, at least for now. I spent a bigger part
of today trying to handle those cases gracefully in SRA but I still
cannot make it work, always some Ada testcase breaks. I'll try again
next week.
Martin
