Upon further consideration and actually seeing the patch, I think
using num_components would be better. Calling it writemask isn't
really true since it isn't the writemask for the mul. I thought about
calling it read_mask but that isn't really true either because it
isn't the components of the mul that get read either. It's only the
write/read mask when combined with the swizzle. I guess we could call
it swizzle_mask, but that just seems strange. Using the number of
components nicely side-steps the whole problem. Since this pass
fundamentally requires SSA, I don't think that's a problem.
--Jason
On Wed, May 27, 2015 at 1:10 AM, Iago Toral Quiroga <ito...@igalia.com> wrote:
> When we compute the output swizzle we want to consider the writemask of the
> add operation, not the one from the multiplication.
> ---
> src/glsl/nir/nir_opt_peephole_ffma.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/src/glsl/nir/nir_opt_peephole_ffma.c
> b/src/glsl/nir/nir_opt_peephole_ffma.c
> index b430eac..c895c22 100644
> --- a/src/glsl/nir/nir_opt_peephole_ffma.c
> +++ b/src/glsl/nir/nir_opt_peephole_ffma.c
> @@ -73,7 +73,8 @@ are_all_uses_fadd(nir_ssa_def *def)
> }
>
> static nir_alu_instr *
> -get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4], bool *negate, bool
> *abs)
> +get_mul_for_src(nir_alu_src *src, int writemask,
> + uint8_t swizzle[4], bool *negate, bool *abs)
> {
> assert(src->src.is_ssa && !src->abs && !src->negate);
>
> @@ -85,16 +86,16 @@ get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4],
> bool *negate, bool *abs)
> switch (alu->op) {
> case nir_op_imov:
> case nir_op_fmov:
> - alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
> + alu = get_mul_for_src(&alu->src[0], writemask, swizzle, negate, abs);
> break;
>
> case nir_op_fneg:
> - alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
> + alu = get_mul_for_src(&alu->src[0], writemask, swizzle, negate, abs);
> *negate = !*negate;
> break;
>
> case nir_op_fabs:
> - alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
> + alu = get_mul_for_src(&alu->src[0], writemask, swizzle, negate, abs);
> *negate = false;
> *abs = true;
> break;
> @@ -116,7 +117,7 @@ get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4],
> bool *negate, bool *abs)
> return NULL;
>
> for (unsigned i = 0; i < 4; i++) {
> - if (!(alu->dest.write_mask & (1 << i)))
> + if (!(writemask & (1 << i)))
> break;
>
> swizzle[i] = swizzle[src->swizzle[i]];
> @@ -160,7 +161,8 @@ nir_opt_peephole_ffma_block(nir_block *block, void
> *void_state)
> negate = false;
> abs = false;
>
> - mul = get_mul_for_src(&add->src[add_mul_src], swizzle, &negate,
> &abs);
> + mul = get_mul_for_src(&add->src[add_mul_src], add->dest.write_mask,
> + swizzle, &negate, &abs);
>
> if (mul != NULL)
> break;
> --
> 1.9.1
>
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