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compiler/spirv: implement 16-bit frexp

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Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
This commit is contained in:
Iago Toral Quiroga 2018-05-15 10:25:10 +02:00
parent 7d3c34197a
commit fda3f6d424
1 changed files with 46 additions and 2 deletions
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48
src/compiler/spirv/vtn_glsl450.c
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@ -371,6 +371,45 @@ build_atan2(nir_builder *b, nir_ssa_def *y, nir_ssa_def *x)
nir_fneg(b, arc), arc);
}
static nir_ssa_def *
build_frexp16(nir_builder *b, nir_ssa_def *x, nir_ssa_def **exponent)
{
assert(x->bit_size == 16);
nir_ssa_def *abs_x = nir_fabs(b, x);
nir_ssa_def *zero = nir_imm_floatN_t(b, 0, 16);
/* Half-precision floating-point values are stored as
* 1 sign bit;
* 5 exponent bits;
* 10 mantissa bits.
*
* An exponent shift of 10 will shift the mantissa out, leaving only the
* exponent and sign bit (which itself may be zero, if the absolute value
* was taken before the bitcast and shift).
*/
nir_ssa_def *exponent_shift = nir_imm_int(b, 10);
nir_ssa_def *exponent_bias = nir_imm_intN_t(b, -14, 16);
nir_ssa_def *sign_mantissa_mask = nir_imm_intN_t(b, 0x83ffu, 16);
/* Exponent of floating-point values in the range [0.5, 1.0). */
nir_ssa_def *exponent_value = nir_imm_intN_t(b, 0x3800u, 16);
nir_ssa_def *is_not_zero = nir_fne(b, abs_x, zero);
/* Significand return must be of the same type as the input, but the
* exponent must be a 32-bit integer.
*/
*exponent =
nir_i2i32(b,
nir_iadd(b, nir_ushr(b, abs_x, exponent_shift),
nir_bcsel(b, is_not_zero, exponent_bias, zero)));
return nir_ior(b, nir_iand(b, x, sign_mantissa_mask),
nir_bcsel(b, is_not_zero, exponent_value, zero));
}
static nir_ssa_def *
build_frexp32(nir_builder *b, nir_ssa_def *x, nir_ssa_def **exponent)
{
@ -732,8 +771,10 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint,
nir_ssa_def *exponent;
if (src[0]->bit_size == 64)
val->ssa->def = build_frexp64(nb, src[0], &exponent);
else
else if (src[0]->bit_size == 32)
val->ssa->def = build_frexp32(nb, src[0], &exponent);
else
val->ssa->def = build_frexp16(nb, src[0], &exponent);
nir_store_deref(nb, vtn_nir_deref(b, w[6]), exponent, 0xf);
return;
}
@ -743,9 +784,12 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint,
if (src[0]->bit_size == 64)
val->ssa->elems[0]->def = build_frexp64(nb, src[0],
&val->ssa->elems[1]->def);
else
else if (src[0]->bit_size == 32)
val->ssa->elems[0]->def = build_frexp32(nb, src[0],
&val->ssa->elems[1]->def);
else
val->ssa->elems[0]->def = build_frexp16(nb, src[0],
&val->ssa->elems[1]->def);
return;
}