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Date: Tue, 13 Oct 2015 10:30:00 -0000
Message-ID: <CAFULd4Zvrh1Qd+_NyJqY2EUrqnKW2sW3titJ1Ghe1qjtdFB8zg@mail.gmail.com>
Subject: Re: [PATCH, sparc]: Use ROUND_UP and ROUND_DOWN macros
From: Uros Bizjak <ubizjak@gmail.com>
To: Eric Botcazou <ebotcazou@adacore.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
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X-SW-Source: 2015-10/txt/msg01207.txt.bz2

On Tue, Oct 13, 2015 at 12:10 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> Two functional changes I'd like to point out:
>>
>>  /* ALIGN FRAMES on double word boundaries */
>> -#define SPARC_STACK_ALIGN(LOC) \
>> -  (TARGET_ARCH64 ? (((LOC)+15) & ~15) : (((LOC)+7) & ~7))
>> +#define SPARC_STACK_ALIGN(LOC) ROUND_UP ((LOC), UNITS_PER_WORD * 2)
>>
>> The one above uses UNITS_PER_WORD in stack alignment calculation
>
> OK.
>
>>        /* Always preserve double-word alignment.  */
>> -      offset = (offset + 8) & -8;
>> +      offset = ROUND_UP (offset, 8);
>>
>> The one above looks like off-by-one bug, but this needs a confirmation.
>
> No, it's correct, it's a bump of 8 followed by a ROUND_DOWN (the offset may or
> may not have been bumped by 4 already in the code just above).

In this case, I think it is better to write this part as:

--cut here--
offset += 8;

/* Always preserve double-word alignment.  */
offset = ROUND_DOWN (offset, 8);
--cut here--

WDYT?

Uros.