Re: [PATCH] Fix recent thinko in operand_equal_p

[Richard Biener via Gcc-patches]

> Am 04.11.2022 um 10:29 schrieb Eric Botcazou via Gcc-patches 
> <gcc-patches@gcc.gnu.org>:
> 
> Hi,
> 
> there is a thinko in the recent improvement by Jan:
> 
> 2020-11-19  Jan Hubicka  <j...@suse.cz>
> 
>    * fold-const.c (operand_compare::operand_equal_p): Fix thinko in
>    COMPONENT_REF handling and guard types_same_for_odr by
>    virtual_method_call_p.
>    (operand_compare::hash_operand): Likewise.
> 
> where the code just looks at operand 2 of COMPONENT_REF, if it is present, to 
> compare addresses.  That's wrong because operand 2 contains the number of 
> DECL_OFFSET_ALIGN-bit-sized words so, when DECL_OFFSET_ALIGN > 8, not all the 
> bytes are included and some of them are in DECL_FIELD_BIT_OFFSET instead, see 
> get_inner_reference for the model computation.
> 
> In other words, you would need to compare operand 2 and DECL_OFFSET_ALIGN and 
> DECL_FIELD_BIT_OFFSET in this situation, but I'm not sure this is worth the 
> hassle in practice so the attached fix just removes this alternate handling.

> Tested on x86-64/Linux, OK for mainline, 12 and 11 branches?

Ok.

Thanks,
Richard 

> 
> 2022-11-04  Eric Botcazou  <ebotca...@adacore.com>
> 
>    * fold-const.cc (operand_compare::operand_equal_p) <COMPONENT_REF>:
>    Do not take into account operand 2.
>    (operand_compare::hash_operand) <COMPONENT_REF>: Likewise.
> 
> 
> 2022-11-04  Eric Botcazou  <ebotca...@adacore.com>
> 
>    * gnat.dg/opt99.adb: New test.
>    * gnat.dg/opt99_pkg1.ads, gnat.dg/opt99_pkg1.adb: New helper.
>    * gnat.dg/opt99_pkg2.ads: Likewise.
> 
> -- 
> Eric Botcazou
> <p.diff>
> <opt99.adb>
> <opt99_pkg1.adb>
> <opt99_pkg2.ads>
> <opt99_pkg1.ads>