nir: Add an ALU lowering pass for mul_high.
This is based on the glsl/lower_instructions.cpp implementation, but should be much more readable. Reviewed-by: Matt Turner <mattst88@gmail.com> Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Eric Anholt
parent
6a0db5f08f
commit
6e1597c2d9
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@ -214,6 +214,7 @@ NIR_FILES = \
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nir/nir_loop_analyze.c \
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nir/nir_loop_analyze.h \
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nir/nir_lower_alpha_test.c \
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nir/nir_lower_alu.c \
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nir/nir_lower_alu_to_scalar.c \
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nir/nir_lower_atomics_to_ssbo.c \
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nir/nir_lower_bitmap.c \
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@ -104,6 +104,7 @@ files_libnir = files(
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'nir_liveness.c',
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'nir_loop_analyze.c',
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'nir_loop_analyze.h',
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'nir_lower_alu.c',
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'nir_lower_alu_to_scalar.c',
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'nir_lower_alpha_test.c',
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'nir_lower_atomics_to_ssbo.c',
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@ -1919,6 +1919,8 @@ typedef struct nir_shader_compiler_options {
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bool lower_find_lsb;
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bool lower_uadd_carry;
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bool lower_usub_borrow;
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/** Lowers imul_high/umul_high to 16-bit multiplies and carry operations. */
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bool lower_mul_high;
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/** lowers fneg and ineg to fsub and isub. */
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bool lower_negate;
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/** lowers fsub and isub to fadd+fneg and iadd+ineg. */
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@ -2628,6 +2630,7 @@ bool nir_move_vec_src_uses_to_dest(nir_shader *shader);
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bool nir_lower_vec_to_movs(nir_shader *shader);
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void nir_lower_alpha_test(nir_shader *shader, enum compare_func func,
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bool alpha_to_one);
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bool nir_lower_alu(nir_shader *shader);
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bool nir_lower_alu_to_scalar(nir_shader *shader);
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bool nir_lower_load_const_to_scalar(nir_shader *shader);
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bool nir_lower_read_invocation_to_scalar(nir_shader *shader);
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@ -0,0 +1,165 @@
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/*
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* Copyright © 2010 Intel Corporation
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* Copyright © 2018 Broadcom
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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#include "nir.h"
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#include "nir_builder.h"
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/** nir_lower_alu.c
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*
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* NIR's home for miscellaneous ALU operation lowering implementations.
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*
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* Most NIR ALU lowering occurs in nir_opt_algebraic.py, since it's generally
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* easy to write them there. However, if terms appear multiple times in the
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* lowered code, it can get very verbose and cause a lot of work for CSE, so
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* it may end up being easier to write out in C code.
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*
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* The shader must be in SSA for this pass.
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*/
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#define LOWER_MUL_HIGH (1 << 0)
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static bool
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lower_alu_instr(nir_alu_instr *instr, nir_builder *b)
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{
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nir_ssa_def *lowered = NULL;
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assert(instr->dest.dest.is_ssa);
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b->cursor = nir_before_instr(&instr->instr);
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b->exact = instr->exact;
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switch (instr->op) {
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case nir_op_imul_high:
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case nir_op_umul_high:
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if (b->shader->options->lower_mul_high) {
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nir_ssa_def *c1 = nir_imm_int(b, 1);
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nir_ssa_def *c16 = nir_imm_int(b, 16);
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nir_ssa_def *src0 = nir_ssa_for_alu_src(b, instr, 0);
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nir_ssa_def *src1 = nir_ssa_for_alu_src(b, instr, 1);
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nir_ssa_def *different_signs = NULL;
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if (instr->op == nir_op_imul_high) {
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nir_ssa_def *c0 = nir_imm_int(b, 0);
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different_signs = nir_ixor(b,
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nir_ilt(b, src0, c0),
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nir_ilt(b, src1, c0));
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src0 = nir_iabs(b, src0);
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src1 = nir_iabs(b, src1);
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}
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/* ABCD
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* * EFGH
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* ======
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* (GH * CD) + (GH * AB) << 16 + (EF * CD) << 16 + (EF * AB) << 32
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*
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* Start by splitting into the 4 multiplies.
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*/
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nir_ssa_def *src0l = nir_iand(b, src0, nir_imm_int(b, 0xffff));
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nir_ssa_def *src1l = nir_iand(b, src1, nir_imm_int(b, 0xffff));
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nir_ssa_def *src0h = nir_ushr(b, src0, c16);
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nir_ssa_def *src1h = nir_ushr(b, src1, c16);
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nir_ssa_def *lo = nir_imul(b, src0l, src1l);
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nir_ssa_def *m1 = nir_imul(b, src0l, src1h);
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nir_ssa_def *m2 = nir_imul(b, src0h, src1l);
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nir_ssa_def *hi = nir_imul(b, src0h, src1h);
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nir_ssa_def *tmp;
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tmp = nir_ishl(b, m1, c16);
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hi = nir_iadd(b, hi, nir_iand(b, nir_uadd_carry(b, lo, tmp), c1));
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lo = nir_iadd(b, lo, tmp);
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hi = nir_iadd(b, hi, nir_ushr(b, m1, c16));
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tmp = nir_ishl(b, m2, c16);
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hi = nir_iadd(b, hi, nir_iand(b, nir_uadd_carry(b, lo, tmp), c1));
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lo = nir_iadd(b, lo, tmp);
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hi = nir_iadd(b, hi, nir_ushr(b, m2, c16));
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if (instr->op == nir_op_imul_high) {
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/* For channels where different_signs is set we have to perform a
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* 64-bit negation. This is *not* the same as just negating the
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* high 32-bits. Consider -3 * 2. The high 32-bits is 0, but the
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* desired result is -1, not -0! Recall -x == ~x + 1.
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*/
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hi = nir_bcsel(b, different_signs,
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nir_iadd(b,
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nir_inot(b, hi),
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nir_iand(b,
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nir_uadd_carry(b,
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nir_inot(b, lo),
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c1),
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nir_imm_int(b, 1))),
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hi);
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}
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lowered = hi;
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}
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break;
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default:
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break;
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}
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if (lowered) {
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nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, nir_src_for_ssa(lowered));
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nir_instr_remove(&instr->instr);
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return true;
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} else {
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return false;
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}
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}
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bool
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nir_lower_alu(nir_shader *shader)
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{
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bool progress = false;
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if (!shader->options->lower_mul_high)
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return false;
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nir_foreach_function(function, shader) {
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if (function->impl) {
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nir_builder builder;
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nir_builder_init(&builder, function->impl);
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nir_foreach_block(block, function->impl) {
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nir_foreach_instr_safe(instr, block) {
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if (instr->type == nir_instr_type_alu) {
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progress = lower_alu_instr(nir_instr_as_alu(instr),
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&builder) || progress;
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}
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}
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}
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if (progress) {
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nir_metadata_preserve(function->impl,
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nir_metadata_block_index |
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nir_metadata_dominance);
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}
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}
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}
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return progress;
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}
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@ -325,6 +325,7 @@ st_nir_opts(nir_shader *nir)
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NIR_PASS_V(nir, nir_lower_alu_to_scalar);
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NIR_PASS_V(nir, nir_lower_phis_to_scalar);
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NIR_PASS_V(nir, nir_lower_alu);
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NIR_PASS_V(nir, nir_lower_pack);
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NIR_PASS(progress, nir, nir_copy_prop);
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NIR_PASS(progress, nir, nir_opt_remove_phis);
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