From patchwork Mon Oct 29 16:38:12 2012
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Subject: RFA: patch to fix PR55116
Date: Mon, 29 Oct 2012 06:38:12 -0000
From: Vladimir Makarov <vmakarov@redhat.com>
X-Patchwork-Id: 195071
Message-Id: <508EB0F4.2@redhat.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>, rdsandiford@googlemail.com

On 12-10-29 12:21 PM, Richard Sandiford wrote:
> Vladimir Makarov <vmakarov@redhat.com> writes:
>>     H.J. in
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55116
>>
>>     reported an interesting address
>>
>> (and:DI (subreg:DI (plus:SI (ashift:SI (reg:SI 96 [ glob_vol_int.22 ])
>>                   (const_int 2 [0x2]))
>>               (symbol_ref:SI ("glob_vol_int_arr") <var_decl
>> 0x7ffff03c2720 glob_vol_int_arr>)) 0)
>>       (const_int 4294967295 [0xffffffff]))
>>
>>     which can not be correctly extracted.  Here `and' with `subreg'
>> behaves as an address mutation.
>>
>>     The following patch fixes the problem.
>>
>> Ok to commit, Richard?
> Heh, I wondered if subregs might still be used like that, and was almost
> tempted to add them just in case.
>
> I think this particular case is really a failed canonicalisation and that:
>
>     (and:DI (subreg:DI (foo:SI ...) 0) (const_int 0xffffffff))
>
> ought to be:
>
>     (zero_extend:DI (foo:SI ...))
Yes, that was my thought too.
> But I know I've approved MIPS patches to accept
> (and:DI ... (const_int 0xffffffff)) as an alternative.
>
>> Index: rtlanal.c
>> ===================================================================
>> --- rtlanal.c   (revision 192942)
>> +++ rtlanal.c   (working copy)
>> @@ -5459,6 +5459,11 @@ strip_address_mutations (rtx *loc, enum
>>          else if (code == AND && CONST_INT_P (XEXP (*loc, 1)))
>>           /* (and ... (const_int -X)) is used to align to X bytes.  */
>>           loc = &XEXP (*loc, 0);
>> +      else if (code == SUBREG
>> +              && ! REG_P (XEXP (*loc, 0)) && ! MEM_P (XEXP (*loc, 0)))
>> +       /* (subreg (operator ...) ...) usually inside and is used for
>> +          mode conversion too.  */
>> +       loc = &XEXP (*loc, 0);
> I think the condition should be:
>
>        else if (code == SUBREG
>                 && !OBJECT_P (SUBREG_REG (*loc))
>                 && subreg_lowpart (*loc))
>
> OK with that change, if it works.
>
Yes, it works.
I've submitted the following patch.


Index: rtlanal.c
===================================================================
--- rtlanal.c	(revision 192942)
+++ rtlanal.c	(working copy)
@@ -5459,6 +5459,12 @@ strip_address_mutations (rtx *loc, enum
       else if (code == AND && CONST_INT_P (XEXP (*loc, 1)))
 	/* (and ... (const_int -X)) is used to align to X bytes.  */
 	loc = &XEXP (*loc, 0);
+      else if (code == SUBREG
+               && !OBJECT_P (SUBREG_REG (*loc))
+               && subreg_lowpart_p (*loc))
+	/* (subreg (operator ...) ...) inside and is used for mode
+	   conversion too.  */
+	loc = &XEXP (*loc, 0);
       else
 	return loc;
       if (outer_code)