diff options
| author | Jason Ekstrand <[email protected]> | 2016-01-27 16:58:42 -0800 |
|---|---|---|
| committer | Kristian Høgsberg Kristensen <[email protected]> | 2016-01-27 19:55:21 -0800 |
| commit | 7fb35a82281c2d245c7ae421893ffa287405b975 (patch) | |
| tree | 04c31ffb944a01b0fb8db2e4fd137a79b94a27ec | |
| parent | 983db2b8042ee8ca25a3870767e0d76940011034 (diff) | |
An alternate arccosine implementation
| -rw-r--r-- | src/glsl/nir/spirv/vtn_glsl450.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/src/glsl/nir/spirv/vtn_glsl450.c b/src/glsl/nir/spirv/vtn_glsl450.c index 219a9c7dc5f..01d72a1531e 100644 --- a/src/glsl/nir/spirv/vtn_glsl450.c +++ b/src/glsl/nir/spirv/vtn_glsl450.c @@ -208,6 +208,9 @@ build_log(nir_builder *b, nir_ssa_def *x) static nir_ssa_def * build_asin(nir_builder *b, nir_ssa_def *x) { + /* + * asin(x) = sign(x) * (pi/2 - sqrt(1 - |x|) * (pi / 4 - 1 + |x| * (0.086566724 + |x| * -0.03102955))) + */ nir_ssa_def *abs_x = nir_fabs(b, x); return nir_fmul(b, nir_fsign(b, x), nir_fsub(b, nir_imm_float(b, M_PI_2f), @@ -221,6 +224,26 @@ build_asin(nir_builder *b, nir_ssa_def *x) nir_imm_float(b, -0.03102955f)))))))))); } +static nir_ssa_def * +build_acos(nir_builder *b, nir_ssa_def *x) +{ + /* + * acos(x) = sign(x) * sqrt(1 - |x|) * (pi / 4 - 1 + |x| * (0.086566724 + |x| * -0.03102955)) + */ + nir_ssa_def *abs_x = nir_fabs(b, x); + nir_ssa_def *poly = nir_fmul(b, nir_fsqrt(b, nir_fsub(b, nir_imm_float(b, 1.0f), abs_x)), + nir_fadd(b, nir_imm_float(b, M_PI_2f), + nir_fmul(b, abs_x, + nir_fadd(b, nir_imm_float(b, M_PI_4f - 1.0f), + nir_fmul(b, abs_x, + nir_fadd(b, nir_imm_float(b, 0.086566724f), + nir_fmul(b, abs_x, + nir_imm_float(b, -0.03102955f)))))))); + return nir_bcsel(b, nir_flt(b, x, nir_imm_float(b, 0)), + nir_fsub(b, nir_imm_float(b, M_PI), poly), + poly); +} + /** * Compute xs[0] + xs[1] + xs[2] + ... using fadd. */ @@ -583,8 +606,7 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint, return; case GLSLstd450Acos: - val->ssa->def = nir_fsub(nb, nir_imm_float(nb, M_PI_2f), - build_asin(nb, src[0])); + val->ssa->def = build_acos(nb, src[0]); return; case GLSLstd450Atan: |