[Mesa-dev] [PATCH 7/8] i965/vec4: Allow constant propagation of VF immediates.

[Ian Romanick]

On 12/21/2014 03:24 PM, Matt Turner wrote:
> total instructions in shared programs: 5877951 -> 5877012 (-0.02%)
> instructions in affected programs:     155923 -> 154984 (-0.60%)
> 
> Helps 1233, hurts 156 shaders. The hurt shaders are addressed in the
> next commit.
> ---
>  .../drivers/dri/i965/brw_vec4_copy_propagation.cpp | 28 +++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
> index 9deaffa..9e47dd9 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
> @@ -50,7 +50,9 @@ is_direct_copy(vec4_instruction *inst)
>  	   inst->dst.file == GRF &&
>  	   !inst->dst.reladdr &&
>  	   !inst->src[0].reladdr &&
> -	   inst->dst.type == inst->src[0].type);
> +	   (inst->dst.type == inst->src[0].type ||
> +            (inst->dst.type == BRW_REGISTER_TYPE_F &&
> +             inst->src[0].type == BRW_REGISTER_TYPE_VF)));
>  }
>  
>  static bool
> @@ -77,6 +79,22 @@ is_channel_updated(vec4_instruction *inst, src_reg *values[4], int ch)
>  	   inst->dst.writemask & (1 << BRW_GET_SWZ(src->swizzle, ch)));
>  }
>  
> +static unsigned
> +swizzle_vf_imm(unsigned vf4, unsigned swizzle)
> +{
> +   union {
> +      unsigned vf4;
> +      uint8_t vf[4];
> +   } v = { vf4 }, ret;
> +
> +   ret.vf[0] = v.vf[BRW_GET_SWZ(swizzle, 0)];
> +   ret.vf[1] = v.vf[BRW_GET_SWZ(swizzle, 1)];
> +   ret.vf[2] = v.vf[BRW_GET_SWZ(swizzle, 2)];
> +   ret.vf[3] = v.vf[BRW_GET_SWZ(swizzle, 3)];
> +
> +   return ret.vf4;
> +}
> +
>  static bool
>  try_constant_propagate(struct brw_context *brw, vec4_instruction *inst,
>                         int arg, struct copy_entry *entry)
> @@ -98,6 +116,8 @@ try_constant_propagate(struct brw_context *brw, vec4_instruction *inst,
>     if (inst->src[arg].abs) {
>        if (value.type == BRW_REGISTER_TYPE_F) {
>  	 value.fixed_hw_reg.dw1.f = fabs(value.fixed_hw_reg.dw1.f);
> +      } else if (value.type == BRW_REGISTER_TYPE_VF) {
> +         value.fixed_hw_reg.dw1.ud &= ~0x80808080;

What's the magic constant?  Sign bits of all the vector float values?

>        } else if (value.type == BRW_REGISTER_TYPE_D) {
>  	 if (value.fixed_hw_reg.dw1.d < 0)
>  	    value.fixed_hw_reg.dw1.d = -value.fixed_hw_reg.dw1.d;
> @@ -107,10 +127,16 @@ try_constant_propagate(struct brw_context *brw, vec4_instruction *inst,
>     if (inst->src[arg].negate) {
>        if (value.type == BRW_REGISTER_TYPE_F)
>  	 value.fixed_hw_reg.dw1.f = -value.fixed_hw_reg.dw1.f;
> +      else if (value.type == BRW_REGISTER_TYPE_VF)
> +         value.fixed_hw_reg.dw1.ud ^= 0x80808080;
>        else
>  	 value.fixed_hw_reg.dw1.ud = -value.fixed_hw_reg.dw1.ud;
>     }
>  
> +   if (value.type == BRW_REGISTER_TYPE_VF)
> +      value.fixed_hw_reg.dw1.ud = swizzle_vf_imm(value.fixed_hw_reg.dw1.ud,
> +                                                 inst->src[arg].swizzle);
> +
>     switch (inst->opcode) {
>     case BRW_OPCODE_MOV:
>        inst->src[arg] = value;
>