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RE: [PATCH ARM]Handle REG addressing mode in output_move_neon explicitly



> -----Original Message-----
> From: Bin.Cheng [mailto:amker.cheng@gmail.com]
> Sent: Wednesday, July 02, 2014 1:46 PM
> To: Ramana Radhakrishnan
> Cc: Bin Cheng; Richard Earnshaw; gcc-patches
> Subject: Re: [PATCH ARM]Handle REG addressing mode in
> output_move_neon explicitly
> 
> On Wed, Jul 2, 2014 at 7:48 AM, Ramana Radhakrishnan
> <ramana.gcc@googlemail.com> wrote:
> > On Mon, May 5, 2014 at 8:21 AM, bin.cheng <bin.cheng@arm.com> wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: Richard Earnshaw
> >>> Sent: Thursday, May 01, 2014 10:03 PM
> >>> To: Bin Cheng
> >>> Cc: gcc-patches@gcc.gnu.org
> >>> Subject: Re: [PATCH ARM]Handle REG addressing mode in
> >>> output_move_neon explicitly
> >>>
> >>> On 29/04/14 04:02, bin.cheng wrote:
> >>> > Hi,
> >>> > Function output_move_neon now generates vld1.64 for memory ref
> >>> > like "dx <- [r1:SI]", this is bogus because it requires at least
> >>> > 64-bit alignment for 32-bit aligned memory ref.  It works now
> >>> > because GCC doesn't generate such insns in the first place, but
> >>> > things are going to change if memset/memcpy calls are inlined by
using
> neon instructions.
> >>> >
> >>>
> >>> V[LD/ST]1.64 only need to be 64-bit aligned if strict alignment is
> >> enabled.  We
> >>> normally assume that not to be the case.  The exception to this is
> >>> when an
> >> theoretically, this doesn't make the problem go away, right?
> >>
> >>> explicit alignment check is used in the address expression (the :64
> >> suffix),
> >>> which causes the address to be checked for strict alignment at all
times.
> >>>
> >>> Do you have a testcase?
> >> I can't provide a test case without the memset inlining patch.
> >>
> > Are the tests in the memset inlining patch now sufficient to expose
> > the problem or do we need another test ?
> 
> Yes, it's covered by the 4th/7th test cases in memset inlining patch.
> 
This is the rebased patch, though the original one doesn't conflict with
latest trunk.  Is it OK?

Thanks,
bin

Attachment: output_move_neon-20140704.txt
Description: Text document


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