diff options
Diffstat (limited to 'mesalib/src/glsl/nir/nir_lower_idiv.c')
| -rw-r--r-- | mesalib/src/glsl/nir/nir_lower_idiv.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/mesalib/src/glsl/nir/nir_lower_idiv.c b/mesalib/src/glsl/nir/nir_lower_idiv.c new file mode 100644 index 000000000..7b6803207 --- /dev/null +++ b/mesalib/src/glsl/nir/nir_lower_idiv.c @@ -0,0 +1,155 @@ +/* + * Copyright © 2015 Red Hat + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + * + * Authors: + * Rob Clark <robclark@freedesktop.org> + */ + +#include "nir.h" +#include "nir_builder.h" + +/* Lowers idiv/udiv/umod + * Based on NV50LegalizeSSA::handleDIV() + * + * Note that this is probably not enough precision for compute shaders. + * Perhaps we want a second higher precision (looping) version of this? + * Or perhaps we assume if you can do compute shaders you can also + * branch out to a pre-optimized shader library routine.. + */ + +static void +convert_instr(nir_builder *bld, nir_alu_instr *alu) +{ + nir_ssa_def *numer, *denom, *af, *bf, *a, *b, *q, *r; + nir_op op = alu->op; + bool is_signed; + + if ((op != nir_op_idiv) && + (op != nir_op_udiv) && + (op != nir_op_umod)) + return; + + is_signed = (op == nir_op_idiv); + + nir_builder_insert_before_instr(bld, &alu->instr); + + numer = nir_ssa_for_src(bld, alu->src[0].src, + nir_ssa_alu_instr_src_components(alu, 0)); + denom = nir_ssa_for_src(bld, alu->src[1].src, + nir_ssa_alu_instr_src_components(alu, 1)); + + if (is_signed) { + af = nir_i2f(bld, numer); + bf = nir_i2f(bld, denom); + af = nir_fabs(bld, af); + bf = nir_fabs(bld, bf); + a = nir_iabs(bld, numer); + b = nir_iabs(bld, denom); + } else { + af = nir_u2f(bld, numer); + bf = nir_u2f(bld, denom); + a = numer; + b = denom; + } + + /* get first result: */ + bf = nir_frcp(bld, bf); + bf = nir_isub(bld, bf, nir_imm_int(bld, 2)); /* yes, really */ + q = nir_fmul(bld, af, bf); + + if (is_signed) { + q = nir_f2i(bld, q); + } else { + q = nir_f2u(bld, q); + } + + /* get error of first result: */ + r = nir_imul(bld, q, b); + r = nir_isub(bld, a, r); + r = nir_u2f(bld, r); + r = nir_fmul(bld, r, bf); + r = nir_f2u(bld, r); + + /* add quotients: */ + q = nir_iadd(bld, q, r); + + /* correction: if modulus >= divisor, add 1 */ + r = nir_imul(bld, q, b); + r = nir_isub(bld, a, r); + + r = nir_ige(bld, r, b); + r = nir_b2i(bld, r); + + q = nir_iadd(bld, q, r); + if (is_signed) { + /* fix the sign: */ + r = nir_ixor(bld, numer, denom); + r = nir_ushr(bld, r, nir_imm_int(bld, 31)); + r = nir_i2b(bld, r); + b = nir_ineg(bld, q); + q = nir_bcsel(bld, r, b, q); + } + + if (op == nir_op_umod) { + /* division result in q */ + r = nir_imul(bld, q, b); + q = nir_isub(bld, a, r); + } + + assert(alu->dest.dest.is_ssa); + nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, + nir_src_for_ssa(q), + ralloc_parent(alu)); +} + +static bool +convert_block(nir_block *block, void *state) +{ + nir_builder *b = state; + + nir_foreach_instr_safe(block, instr) { + if (instr->type == nir_instr_type_alu) + convert_instr(b, nir_instr_as_alu(instr)); + } + + return true; +} + +static void +convert_impl(nir_function_impl *impl) +{ + nir_builder b; + nir_builder_init(&b, impl); + + nir_foreach_block(impl, convert_block, &b); + nir_metadata_preserve(impl, nir_metadata_block_index | + nir_metadata_dominance); +} + +void +nir_lower_idiv(nir_shader *shader) +{ + nir_foreach_overload(shader, overload) { + if (overload->impl) + convert_impl(overload->impl); + } +} |