On Tue, Dec 4, 2018 at 1:17 AM Iago Toral Quiroga <ito...@igalia.com> wrote:
> ---
> src/compiler/spirv/vtn_glsl450.c | 36 +++++++++++++++++++++-----------
> 1 file changed, 24 insertions(+), 12 deletions(-)
>
> diff --git a/src/compiler/spirv/vtn_glsl450.c
> b/src/compiler/spirv/vtn_glsl450.c
> index 4345c9c61a3..9cda80c5137 100644
> --- a/src/compiler/spirv/vtn_glsl450.c
> +++ b/src/compiler/spirv/vtn_glsl450.c
> @@ -238,8 +238,10 @@ build_fsum(nir_builder *b, nir_ssa_def **xs, int
> terms)
> static nir_ssa_def *
> build_atan(nir_builder *b, nir_ssa_def *y_over_x)
> {
> + const uint32_t bit_size = y_over_x->bit_size;
> +
> nir_ssa_def *abs_y_over_x = nir_fabs(b, y_over_x);
> - nir_ssa_def *one = nir_imm_float(b, 1.0f);
> + nir_ssa_def *one = nir_imm_floatN_t(b, 1.0f, bit_size);
>
> /*
> * range-reduction, first step:
> @@ -265,25 +267,35 @@ build_atan(nir_builder *b, nir_ssa_def *y_over_x)
> nir_ssa_def *x_9 = nir_fmul(b, x_7, x_2);
> nir_ssa_def *x_11 = nir_fmul(b, x_9, x_2);
>
> + const float coef[] = {
> + 0.9999793128310355f,
> + -0.3326756418091246f,
> + 0.1938924977115610f,
> + -0.1173503194786851f,
> + 0.0536813784310406f,
> + -0.0121323213173444f,
> + };
> +
> nir_ssa_def *polynomial_terms[] = {
> - nir_fmul(b, x, nir_imm_float(b, 0.9999793128310355f)),
> - nir_fmul(b, x_3, nir_imm_float(b, -0.3326756418091246f)),
> - nir_fmul(b, x_5, nir_imm_float(b, 0.1938924977115610f)),
> - nir_fmul(b, x_7, nir_imm_float(b, -0.1173503194786851f)),
> - nir_fmul(b, x_9, nir_imm_float(b, 0.0536813784310406f)),
> - nir_fmul(b, x_11, nir_imm_float(b, -0.0121323213173444f)),
> + nir_fmul(b, x, nir_imm_floatN_t(b, coef[0], bit_size)),
> + nir_fmul(b, x_3, nir_imm_floatN_t(b, coef[1], bit_size)),
> + nir_fmul(b, x_5, nir_imm_floatN_t(b, coef[2], bit_size)),
> + nir_fmul(b, x_7, nir_imm_floatN_t(b, coef[3], bit_size)),
> + nir_fmul(b, x_9, nir_imm_floatN_t(b, coef[4], bit_size)),
> + nir_fmul(b, x_11, nir_imm_floatN_t(b, coef[5], bit_size)),
>
Any reason why you split the coefficients out into their own array? Just
to avoid line wrapping?
In a recent commit, I added nir_iadd_imm and nir_imul_imm helpers for
multiplying by or adding an immediate. It might be worth doing the same
thing for multiplying and add by floats for these kinds of computations.
> };
>
> nir_ssa_def *tmp =
> build_fsum(b, polynomial_terms, ARRAY_SIZE(polynomial_terms));
>
> /* range-reduction fixup */
> + nir_ssa_def *minus_2 = nir_imm_floatN_t(b, -2.0f, bit_size);
> + nir_ssa_def *m_pi_2 = nir_imm_floatN_t(b, M_PI_2f, bit_size);
> + nir_ssa_def *b2f = nir_b2f(b, nir_flt(b, one, abs_y_over_x));
> + b2f->bit_size = bit_size; /* do we prefer b2f<bitsize> opcodes? */
>
I have patches which will fix this at least somewhat. For right now, what
you did there is fine.
> tmp = nir_fadd(b, tmp,
> - nir_fmul(b,
> - nir_b2f(b, nir_flt(b, one, abs_y_over_x)),
> - nir_fadd(b, nir_fmul(b, tmp,
> - nir_imm_float(b, -2.0f)),
> - nir_imm_float(b, M_PI_2f))));
> + nir_fmul(b, b2f,
> + nir_fadd(b, nir_fmul(b, tmp, minus_2),
> m_pi_2)));
>
> /* sign fixup */
> return nir_fmul(b, tmp, nir_fsign(b, y_over_x));
> --
> 2.17.1
>
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