diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/compiler/nir/nir_lower_double_ops.c | 56 |
1 files changed, 12 insertions, 44 deletions
diff --git a/src/compiler/nir/nir_lower_double_ops.c b/src/compiler/nir/nir_lower_double_ops.c index 4d4cdf635ea..054fce9c168 100644 --- a/src/compiler/nir/nir_lower_double_ops.c +++ b/src/compiler/nir/nir_lower_double_ops.c @@ -392,50 +392,18 @@ lower_fract(nir_builder *b, nir_ssa_def *src) static nir_ssa_def * lower_round_even(nir_builder *b, nir_ssa_def *src) { - /* If fract(src) == 0.5, then we will have to decide the rounding direction. - * We will do this by computing the mod(abs(src), 2) and testing if it - * is < 1 or not. - * - * We compute mod(abs(src), 2) as: - * abs(src) - 2.0 * floor(abs(src) / 2.0) - */ - nir_ssa_def *two = nir_imm_double(b, 2.0); - nir_ssa_def *abs_src = nir_fabs(b, src); - nir_ssa_def *mod = - nir_fsub(b, - abs_src, - nir_fmul(b, - two, - nir_ffloor(b, - nir_fmul(b, - abs_src, - nir_imm_double(b, 0.5))))); - - /* - * If fract(src) != 0.5, then we round as floor(src + 0.5) - * - * If fract(src) == 0.5, then we have to check the modulo: - * - * if it is < 1 we need a trunc operation so we get: - * 0.5 -> 0, -0.5 -> -0 - * 2.5 -> 2, -2.5 -> -2 - * - * otherwise we need to check if src >= 0, in which case we need to round - * upwards, or not, in which case we need to round downwards so we get: - * 1.5 -> 2, -1.5 -> -2 - * 3.5 -> 4, -3.5 -> -4 - */ - nir_ssa_def *fract = nir_ffract(b, src); - return nir_bcsel(b, - nir_fne(b, fract, nir_imm_double(b, 0.5)), - nir_ffloor(b, nir_fadd(b, src, nir_imm_double(b, 0.5))), - nir_bcsel(b, - nir_flt(b, mod, nir_imm_double(b, 1.0)), - nir_ftrunc(b, src), - nir_bcsel(b, - nir_fge(b, src, nir_imm_double(b, 0.0)), - nir_fadd(b, src, nir_imm_double(b, 0.5)), - nir_fsub(b, src, nir_imm_double(b, 0.5))))); + /* Add and subtract 2**52 to round off any fractional bits. */ + nir_ssa_def *two52 = nir_imm_double(b, (double)(1ull << 52)); + nir_ssa_def *sign = nir_iand(b, nir_unpack_64_2x32_split_y(b, src), + nir_imm_int(b, 1ull << 31)); + + b->exact = true; + nir_ssa_def *res = nir_fsub(b, nir_fadd(b, nir_fabs(b, src), two52), two52); + b->exact = false; + + return nir_bcsel(b, nir_flt(b, nir_fabs(b, src), two52), + nir_pack_64_2x32_split(b, nir_unpack_64_2x32_split_x(b, res), + nir_ior(b, nir_unpack_64_2x32_split_y(b, res), sign)), src); } static nir_ssa_def * |