[Mesa-dev] [PATCH 01/22] i965/disasm: also print nibctrl in IVB for execsize=8

[Matt Turner]

On 01/05, Samuel Iglesias Gonsálvez wrote:
>From: Iago Toral Quiroga <itoral at igalia.com>
>
>4-wide DF operations where NibCtrl applies require and execsize of 8
>in IvyBridge/Valleyview.

Wow, the documentation is bad in this area. The QtrCtrl description in
IVB's Vol4 Part3 explicitly says "NibCtrl is only allowed for SIMD4
instructions with (DF) double precision source and/or destination." and
shows NibCtrl only being enabled with ExecSize=4. That's very unclear
and I hope that didn't trip you guys up.

>---
> src/mesa/drivers/dri/i965/brw_disasm.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
>diff --git a/src/mesa/drivers/dri/i965/brw_disasm.c b/src/mesa/drivers/dri/i965/brw_disasm.c
>index 167067a..7c3791d 100644
>--- a/src/mesa/drivers/dri/i965/brw_disasm.c
>+++ b/src/mesa/drivers/dri/i965/brw_disasm.c
>@@ -1209,6 +1209,13 @@ qtr_ctrl(FILE *file, const struct gen_device_info *devinfo, brw_inst *inst)
>          string(file, " 4Q");
>          break;
>       }
>+      if (devinfo->gen == 7 && !devinfo->is_haswell) {
>+         int nib_ctl = brw_inst_nib_control(devinfo, inst);
>+         if (nib_ctl == 0)
>+            string(file, " 1N");
>+         else
>+            string(file, " 2N");
>+      }

This looks like it will print 1N/2N in addition to the 1Q/2Q/3Q/4Q from
immediately before. I don't think that's the intention.

Perhaps we can do a slight refactor and change the structure to 

	const unsigned nib_ctrl = devinfo->gen < 7 ? 0 :
				  brw_inst_nib_control(devinfo, inst);
	if (nib_ctrl) {
		format(file, " %dN", qtr_ctl * 2 + nib_ctl + 1);
	} else if (exec_size == 8) {
		...
	} else if (exec_size == 16) {
		...
	}

this is just the disassembler, so we don't need to implement logic that
decides when NibCtrl is valid and when it's not -- just disassemble
what's there :)

(I renamed nib_ctl -> nib_ctrl in the above block intentionally to match
the field name).

You can preemptively put a

Reviewed-by: Matt Turner <mattst88 at gmail.com>

on such a patch.
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