[Beignet] [PATCH] Remove global barrier assert.

[Zou, Nanhai]

Per my understanding, 
barrier has included memory fence semantic, no need to insert additional mem fence message.
I think Rong has done some experiment on that.


-----Original Message-----
From: Zhigang Gong [mailto:zhigang.gong at linux.intel.com] 
Sent: Friday, June 14, 2013 1:00 PM
To: Zou, Nanhai; Yang, Rong R
Cc: beignet at lists.freedesktop.org
Subject: RE: [Beignet] [PATCH] Remove global barrier assert.

Nanhai,

I'm not worry about the barrier itself. I'm worry about the memory fence part. Please refer the following statement from Open CL spec.

The barrier CLK_LOCAL_MEM_FENCE -
function will either flush any variables stored in local memory or queue a memory fence to ensure correct ordering of memory operations to local memory.

CLK_GLOBAL_MEM_FENCE - The barrier
function will queue a memory fence to ensure correct ordering of memory operations to global memory. This can be useful when work-items, for example, write to buffer or image objects and then want to read the updated data.

And current implementation does nothing for the global memory operations.

And IMHO, if we can't make sure the implementation comply with OpenCL spec for the specified memory fence function, we can't just push the code now.
It may cause weird problem in the future which is extremely hard to debug.
Any comments? 

> -----Original Message-----
> From: Zou, Nanhai [mailto:nanhai.zou at intel.com]
> Sent: Friday, June 14, 2013 12:13 PM
> To: Zhigang Gong; Yang, Rong R
> Cc: beignet at lists.freedesktop.org
> Subject: RE: [Beignet] [PATCH] Remove global barrier assert.
> 
> From the spec, it seems that the logic is correct, the barrier is not
limited to
> SHM.
> Let's push the code till we hit bug.
> 
> Thanks
> Zou Nanhai
> 
> -----Original Message-----
> From: beignet-bounces+nanhai.zou=intel.com at lists.freedesktop.org
> [mailto:beignet-bounces+nanhai.zou=intel.com at lists.freedesktop.org] On 
> Behalf Of Zhigang Gong
> Sent: Friday, June 14, 2013 11:50 AM
> To: Yang, Rong R
> Cc: beignet at lists.freedesktop.org
> Subject: Re: [Beignet] [PATCH] Remove global barrier assert.
> 
> With this patch, you treat a global memory fence the same as a local
memory
> fence.
> I haven't check the bspec details, but I am doubt it. Need some time 
> to investigate the spec.
> 
> On Fri, Jun 14, 2013 at 11:01:09AM +0800, Yang Rong wrote:
> > Per openCL spec, Global memory barrier is consistent across 
> > work-items in a single work group, which is match the bspec's 
> > barrier. So remove global barrier assert.
> >
> > Signed-off-by: Yang Rong <rong.r.yang at intel.com>
> > ---
> >  backend/src/backend/gen_insn_selection.cpp |    4 ----
> >  1 file changed, 4 deletions(-)
> >
> > diff --git a/backend/src/backend/gen_insn_selection.cpp
> > b/backend/src/backend/gen_insn_selection.cpp
> > index 88f9e94..3a139ea 100644
> > --- a/backend/src/backend/gen_insn_selection.cpp
> > +++ b/backend/src/backend/gen_insn_selection.cpp
> > @@ -1607,10 +1607,6 @@ namespace gbe
> >      INLINE bool emitOne(Selection::Opaque &sel, const
ir::SyncInstruction
> &insn) const
> >      {
> >        using namespace ir;
> > -      const uint32_t params = insn.getParameters();
> > -      GBE_ASSERTM(params == syncLocalBarrier,
> > -                  "Only barrier(CLK_LOCAL_MEM_FENCE) is supported
> right now "
> > -                  "for the synchronization primitives");
> >        const ir::Register reg = sel.reg(FAMILY_DWORD);
> >
> >        sel.push();
> > --
> > 1.7.10.4
> >
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