[Mesa-dev] [PATCH 2/7] i965: Adjust set_message_descriptor to handle non-sends

[Kenneth Graunke]

On Sunday, August 03, 2014 12:36:31 PM Chris Forbes wrote:
> We're about to be using this infrastructure to build descriptors in
> src1 of non-send instructions, when preparing to do an indirect send.
> 
> Don't accidentally clobber the conditionalmod field of those
> instructions with SFID bits, which aren't part of the descriptor.
> 
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/mesa/drivers/dri/i965/brw_eu_emit.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> index bc74de3..cdfc78e 100644
> --- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
> +++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> @@ -540,7 +540,19 @@ brw_set_message_descriptor(struct brw_compile *p,
>     struct brw_context *brw = p->brw;
>  
>     brw_set_src1(p, inst, brw_imm_d(0));
> -   brw_inst_set_sfid(brw, inst, sfid);
> +
> +   /* For indirect sends, `inst` will not be the SEND/SENDC instruction
> +    * itself; instead, it will be a MOV/OR into the address register.
> +    *
> +    * In this case, we avoid setting the extended message descriptor bits,
> +    * since they go on the later SEND/SENDC instead and if set here would
> +    * instead clobber the conditionalmod bits.
> +    */
> +   unsigned opcode = brw_inst_opcode(brw, inst);
> +   if (opcode == BRW_OPCODE_SEND || opcode == BRW_OPCODE_SENDC) {
> +      brw_inst_set_sfid(brw, inst, sfid);
> +   }
> +
>     brw_inst_set_mlen(brw, inst, msg_length);
>     brw_inst_set_rlen(brw, inst, response_length);
>     brw_inst_set_eot(brw, inst, end_of_thread);
> 

Hey Chris,

I was originally confused by this - setting message descriptor bits on non-SEND instructions seemed bizarre to me.  But, now that I've looked a bit more closely, I see what you're doing...the message descriptor bits are already in src1, so it actually is a convenient way to set up the right constant to copy into a0.0.

Clever - nice work :)

This series is:
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
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