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compiler/spirv: implement 16-bit hyperbolic trigonometric functions

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v2:
 - use nir_fadd_imm and nir_fmul_imm helpers (Jason)

v3:
 - since we need to define one for fsub use it for fdiv too (Jason)

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
This commit is contained in:
Iago Toral Quiroga
2018-04-18 10:14:11 +02:00
parent 88663ba67c
commit 7d3c34197a
1 changed files with 26 additions and 18 deletions
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src/compiler/spirv/vtn_glsl450.c
+26 -18
View File
@@ -654,17 +654,17 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint,
case GLSLstd450Sinh:
/* 0.5 * (e^x - e^(-x)) */
val->ssa->def =
nir_fmul(nb, nir_imm_float(nb, 0.5f),
nir_fsub(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))));
nir_fmul_imm(nb, nir_fsub(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))),
0.5f);
return;
case GLSLstd450Cosh:
/* 0.5 * (e^x + e^(-x)) */
val->ssa->def =
nir_fmul(nb, nir_imm_float(nb, 0.5f),
nir_fadd(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))));
nir_fmul_imm(nb, nir_fadd(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))),
0.5f);
return;
case GLSLstd450Tanh: {
@@ -675,30 +675,38 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint,
* We clamp x to (-inf, +10] to avoid precision problems. When x > 10,
* e^2x is so much larger than 1.0 that 1.0 gets flushed to zero in the
* computation e^2x +/- 1 so it can be ignored.
*
* For 16-bit precision we clamp x to (-inf, +4.2] since the maximum
* representable number is only 65,504 and e^(2*6) exceeds that. Also,
* if x > 4.2, tanh(x) will return 1.0 in fp16.
*/
nir_ssa_def *x = nir_fmin(nb, src[0], nir_imm_float(nb, 10));
nir_ssa_def *exp2x = build_exp(nb, nir_fmul(nb, x, nir_imm_float(nb, 2)));
val->ssa->def = nir_fdiv(nb, nir_fsub(nb, exp2x, nir_imm_float(nb, 1)),
nir_fadd(nb, exp2x, nir_imm_float(nb, 1)));
const uint32_t bit_size = src[0]->bit_size;
const double clamped_x = bit_size > 16 ? 10.0 : 4.2;
nir_ssa_def *x = nir_fmin(nb, src[0],
nir_imm_floatN_t(nb, clamped_x, bit_size));
nir_ssa_def *exp2x = build_exp(nb, nir_fmul_imm(nb, x, 2.0));
val->ssa->def = nir_fdiv(nb, nir_fadd_imm(nb, exp2x, -1.0),
nir_fadd_imm(nb, exp2x, 1.0));
return;
}
case GLSLstd450Asinh:
val->ssa->def = nir_fmul(nb, nir_fsign(nb, src[0]),
build_log(nb, nir_fadd(nb, nir_fabs(nb, src[0]),
nir_fsqrt(nb, nir_fadd(nb, nir_fmul(nb, src[0], src[0]),
nir_imm_float(nb, 1.0f))))));
nir_fsqrt(nb, nir_fadd_imm(nb, nir_fmul(nb, src[0], src[0]),
1.0f)))));
return;
case GLSLstd450Acosh:
val->ssa->def = build_log(nb, nir_fadd(nb, src[0],
nir_fsqrt(nb, nir_fsub(nb, nir_fmul(nb, src[0], src[0]),
nir_imm_float(nb, 1.0f)))));
nir_fsqrt(nb, nir_fadd_imm(nb, nir_fmul(nb, src[0], src[0]),
-1.0f))));
return;
case GLSLstd450Atanh: {
nir_ssa_def *one = nir_imm_float(nb, 1.0);
val->ssa->def = nir_fmul(nb, nir_imm_float(nb, 0.5f),
build_log(nb, nir_fdiv(nb, nir_fadd(nb, one, src[0]),
nir_fsub(nb, one, src[0]))));
nir_ssa_def *one = nir_imm_floatN_t(nb, 1.0, src[0]->bit_size);
val->ssa->def =
nir_fmul_imm(nb, build_log(nb, nir_fdiv(nb, nir_fadd(nb, src[0], one),
nir_fsub(nb, one, src[0]))),
0.5f);
return;
}