Re: [patch RFC,PR50038]

[Ilya Enkovich <enkovich dot gnu at gmail dot com>]

2011/10/4 Richard Henderson <rth@redhat.com>:
> On 10/04/2011 08:42 AM, Joseph S. Myers wrote:
>> On Tue, 4 Oct 2011, Ilya Tocar wrote:
>>
>>> Hi everyone,
>>>
>>> This patch fixes PR 50038 (redundant zero extensions) by modifying
>>> implicit-zee pass
>>> to also remove unneeded zero extensions from QImode to SImode.
>>
>> Hardcoding particular modes like this in the target-independent parts of
>> the compiler is fundamentally ill-conceived. ?Right now it hardcodes the
>> (SImode, DImode) pair. ?You're adding hardcoding of (QImode, SImode) as
>> well. ?But really it should consider all pairs of (integer mode, wider
>> integer mode), with the machine description (or target hooks) determining
>> which pairs are relevant on a particular target. ?Changing it not to
>> hardcode particular modes would be better than adding a second pair.
>>
>
> That along with not hard-coding ZERO_EXTEND.
>
> Both MIPS and Alpha have much the same free operations, but with SIGN_EXTEND.
>
> I remember rejecting one iteration of this pass with this hard-coded, but the
> pass was apparently approved by someone else without that being corrected.
>
>
> r~
>

Hello guys,

Could you please look at my patch version? I tried to remove all
unnecessary mode restrictions and cover SIGN_EXTEND case. I did not
test this patch yet, just checked it worked on reproducer from
PR50038.

Thanks
Ilya
---
gcc/

	* implicit-zee.c (ext_cand): New.
	(ext_cand_pool): Likewise.
	(add_ext_candidate): Likewise.
	(zee_init): Likewise.
	(zee_cleanup): Likewise.
	(combine_set_zero_extend): Get extend candidate as new parameter.
	Now handle sign extend cases and all modes.
	(transform_ifelse): Likewise.
	(merge_def_and_ze): Likewise.
	(combine_reaching_defs): Change parameter type.
	(zero_extend_info): Changed insn_list type.
	(add_removable_zero_extend): Relaxed mode and code filter.
	(find_removable_zero_extends): Changed return type.
	(find_and_remove_ze): Var type changes.
	(rest_of_handle_zee): Initialization and cleanup added.

Attachment: PR50038.diff
Description: Binary data