[Mesa-dev] [PATCH 3/4] i965/vec4: Combine all the math emitters.

[Kenneth Graunke]

On Thursday, November 13, 2014 03:09:22 PM Francisco Jerez wrote:
> Kenneth Graunke <kenneth at whitecape.org> writes:
> 
> > On Wednesday, November 12, 2014 09:57:30 PM Matt Turner wrote:
> >> On Wed, Nov 12, 2014 at 9:35 PM, Kenneth Graunke <kenneth at whitecape.org> 
> > wrote:
> >> > +vec4_visitor::emit_math(enum opcode opcode,
> >> > +                       dst_reg dst, src_reg src0, src_reg src1)
> >> 
> >> I think you can make the arguments const references too?
> >
> > Yeah.  I've changed the prototype to:
> >
> > void emit_math(enum opcode opcode, const dst_reg &dst, const src_reg 
&src0,
> >                const src_reg &src1 = src_reg());
> >
> > It also meant changing the first few lines to:
> >
> >    vec4_instruction *math =
> >       emit(opcode, dst, fix_math_operand(src0), fix_math_operand(src1))
> >
> > since "src0 = fix_math_operand(src0)" doesn't work with "const src_reg &".
> >
> >> > +   if (brw->gen == 6 && dst.writemask != WRITEMASK_XYZW) {
> >> > +      /* MATH on Gen6 must be align1, so we can't do writemasks. */
> >> > +      math->dst = dst_reg(this, glsl_type::vec4_type);
> >> > +      math->dst.type = dst.type;
> >> > +      math->dst.writemask = WRITEMASK_XYZW;
> >> 
> >> I don't think you need to set the writemask (XYZW is the default).
> >
> > I do, actually - it's guaranteed to not be XYZW at this point.  The caller 
> > passed us a destination register with some writemask set.  We create the 
> > "math" instruction using dst, so it inherits that writemask.  This block 
> > executes when dst.writemask != WRITEMASK_XYZW.
> >
> > The point is to override it back to XYZW, since it isn't.
> 
> Are you sure?  You are assigning a newly created dst_reg() to math->dst,
> so it should have the default writemask for a vec4, which is XYZW
> already.  With that fixed and the change you mention above this patch
> is:
> Reviewed-by: Francisco Jerez <currojerez at riseup.net>
> 
> I had a very similar change in my tree, but you beat me to it ;).

You're both right, of course.  I've dropped the XYZW setting.
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