Hi All,
I'm trying to implement DImode shifts using ARM NEON instructions. This
wouldn't be difficult in itself, but making it play nice with the
existing implementation is causing me problems. I'd like a few
suggestions/pointers/comments to help me get this right, please.
The existing shift
On 02/12/11 12:42, Andrew Stubbs wrote:
> Hi All,
>
> I'm trying to implement DImode shifts using ARM NEON instructions. This
> wouldn't be difficult in itself, but making it play nice with the
> existing implementation is causing me problems. I'd like a few
> suggestions/pointers/comments to h
On Wed 07 Dec 2011 13:42:37 GMT, Richard Earnshaw wrote:
So it looks like the code generated for core registers with thumb2 is
pretty rubbish (no real surprise there -- to get the best code you need
to make use of the fact that on ARM a shift by a small negative number
(< -128) will give zero.
On 07/12/11 14:03, Andrew Stubbs wrote:
> On Wed 07 Dec 2011 13:42:37 GMT, Richard Earnshaw wrote:
>> So it looks like the code generated for core registers with thumb2 is
>> pretty rubbish (no real surprise there -- to get the best code you need
>> to make use of the fact that on ARM a shift by a
On Wed 07 Dec 2011 14:20:43 GMT, Richard Earnshaw wrote:
Would it not require an unspec to prevent 'clever things' happening to
the negative shift, if we were to encode these in the machine
description? I'm not too clear on what these 'clever things' might be in
the case of shift-by-register (pre
On 07/12/11 13:42, Richard Earnshaw wrote:
So it looks like the code generated for core registers with thumb2 is
pretty rubbish (no real surprise there -- to get the best code you need
to make use of the fact that on ARM a shift by a small negative number
(< -128) will give zero. This gives us
On 12/12/11 16:28, Andrew Stubbs wrote:
> On 07/12/11 13:42, Richard Earnshaw wrote:
>> So it looks like the code generated for core registers with thumb2 is
>> pretty rubbish (no real surprise there -- to get the best code you need
>> to make use of the fact that on ARM a shift by a small negative
