[Mesa-dev] [PATCH 2/6] i965/fs: Enumerate logical fb writes arguments

[Ben Widawsky]

On Tue, Oct 20, 2015 at 02:57:24PM -0700, Matt Turner wrote:
> On Tue, Oct 20, 2015 at 2:54 PM, Ben Widawsky <ben at bwidawsk.net> wrote:
> > On Tue, Oct 20, 2015 at 02:52:29PM -0700, Matt Turner wrote:
> >> On Tue, Oct 20, 2015 at 2:29 PM, Ben Widawsky
> >> <benjamin.widawsky at intel.com> wrote:
> >> > Gen9 adds the ability to write out a stencil value, so we need to expand the
> >> > virtual payload by one. Abstracting this now makes that change easier to read.
> >> >
> >> > I was admittedly confused early on about some of the hardcoding. If people
> >> > believe the resulting code is inferior, I am not super attached to the patch.
> >> >
> >> > Cc: Francisco Jerez <currojerez at riseup.net>
> >> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> >> > ---
> >> >  src/mesa/drivers/dri/i965/brw_defines.h | 18 ++++++++++--------
> >> >  src/mesa/drivers/dri/i965/brw_fs.cpp    | 21 +++++++++++----------
> >> >  2 files changed, 21 insertions(+), 18 deletions(-)
> >> >
> >> > diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
> >> > index 7a5ee1b..e06c9d6 100644
> >> > --- a/src/mesa/drivers/dri/i965/brw_defines.h
> >> > +++ b/src/mesa/drivers/dri/i965/brw_defines.h
> >> > @@ -912,14 +912,6 @@ enum opcode {
> >> >     /**
> >> >      * Same as FS_OPCODE_FB_WRITE but expects its arguments separately as
> >> >      * individual sources instead of as a single payload blob:
> >> > -    *
> >> > -    * Source 0: [required] Color 0.
> >> > -    * Source 1: [optional] Color 1 (for dual source blend messages).
> >> > -    * Source 2: [optional] Src0 Alpha.
> >> > -    * Source 3: [optional] Source Depth (gl_FragDepth)
> >> > -    * Source 4: [optional (gen4-5)] Destination Depth passthrough from thread
> >> > -    * Source 5: [optional] Sample Mask (gl_SampleMask).
> >> > -    * Source 6: [required] Number of color components (as a UD immediate).
> >> >      */
> >> >     FS_OPCODE_FB_WRITE_LOGICAL,
> >> >
> >> > @@ -1318,6 +1310,16 @@ enum brw_urb_write_flags {
> >> >        BRW_URB_WRITE_ALLOCATE | BRW_URB_WRITE_COMPLETE,
> >> >  };
> >> >
> >> > +enum fb_write_logical_args {
> >> > +   FB_WRITE_COLOR0 = 0,      /* REQUIRED */
> >> > +   FB_WRITE_COLOR1 = 1,      /* for dual source blend messages */
> >> > +   FB_WRITE_SRC0_ALPHA = 2,
> >> > +   FB_WRITE_SRC_DEPTH = 3,   /* gl_FragDepth */
> >> > +   FB_WRITE_DST_DEPTH = 4,   /* GEN4-5: passthrough from thread */
> >> > +   FB_WRITE_OMASK = 5,       /* Sample Mask (gl_SampleMask) */
> >> > +   FB_WRITE_COMPONENTS = 6,  /* REQUIRED */
> >>
> >> Do we gain anything by assigning values explicitly?
> >
> > Just code readability. As a noob coming into the code, seeing a random "6" or
> > "4" in places was strange and it took a bit to figure out where to get the
> > sensible value from.
> >
> > Is there any specific opposition toward doing this, or some reason it wasn't
> > done in the first place? I honestly don't care too much...
> 
> If everything just uses the new enum values (and their values don't
> matter per se), we shouldn't assign them specifically. Patch 4/6 would
> be simpler if you didn't have to renumber some of the enums, for
> instance.

Yes, I suppose patch 4/6 does end up without the first hunk in the patch if I
did away with this, but I still think the readability gained outweighs that.
However, I admit my knowledge in this part of the codebase is likely the
minority (in between 0 and expert).