diff options
Diffstat (limited to 'src/compiler/nir/nir_move_vec_src_uses_to_dest.c')
| -rw-r--r-- | src/compiler/nir/nir_move_vec_src_uses_to_dest.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_move_vec_src_uses_to_dest.c b/src/compiler/nir/nir_move_vec_src_uses_to_dest.c new file mode 100644 index 0000000..b5186e6 --- /dev/null +++ b/src/compiler/nir/nir_move_vec_src_uses_to_dest.c @@ -0,0 +1,197 @@ +/* + * Copyright © 2014 Intel Corporation + * + * 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: + * Jason Ekstrand (jason@jlekstrand.net) + * + */ + +#include "nir.h" + +/* + * Implements a pass that tries to move uses vecN sources to their + * destinations. This is kind of like an inverse copy-propagation pass. + * For instance, if you have + * + * ssa_1 = vec4(a, b, c, d) + * ssa_2 = fadd(a, b) + * + * This will be turned into + * + * ssa_1 = vec4(a, b, c, d) + * ssa_2 = fadd(ssa_1.x, ssa_1.y) + * + * While this is "worse" because it adds a bunch of unneeded dependencies, it + * actually makes it much easier for vec4-based backends to coalesce the MOV's + * that result from the vec4 operation because it doesn't have to worry about + * quite as many reads. + */ + +/* Returns true if the given SSA def dominates the instruction. An SSA def is + * considered to *not* dominate the instruction that defines it. + */ +static bool +ssa_def_dominates_instr(nir_ssa_def *def, nir_instr *instr) +{ + if (instr->index <= def->parent_instr->index) { + return false; + } else if (def->parent_instr->block == instr->block) { + return def->parent_instr->index < instr->index; + } else { + return nir_block_dominates(def->parent_instr->block, instr->block); + } +} + +static bool +move_vec_src_uses_to_dest_block(nir_block *block, void *shader) +{ + nir_foreach_instr(block, instr) { + if (instr->type != nir_instr_type_alu) + continue; + + nir_alu_instr *vec = nir_instr_as_alu(instr); + + switch (vec->op) { + case nir_op_vec2: + case nir_op_vec3: + case nir_op_vec4: + break; + default: + continue; /* The loop */ + } + + /* Can't handle non-SSA vec operations */ + if (!vec->dest.dest.is_ssa) + continue; + + /* Can't handle saturation */ + if (vec->dest.saturate) + continue; + + /* First, mark all of the sources we are going to consider for rewriting + * to the destination + */ + int srcs_remaining = 0; + for (unsigned i = 0; i < nir_op_infos[vec->op].num_inputs; i++) { + /* We can't rewrite a source if it's not in SSA form */ + if (!vec->src[i].src.is_ssa) + continue; + + /* We can't rewrite a source if it has modifiers */ + if (vec->src[i].abs || vec->src[i].negate) + continue; + + srcs_remaining |= 1 << i; + } + + /* We can't actually do anything with this instruction */ + if (srcs_remaining == 0) + continue; + + for (unsigned i; i = ffs(srcs_remaining) - 1, srcs_remaining;) { + int8_t swizzle[4] = { -1, -1, -1, -1 }; + + for (unsigned j = i; j < nir_op_infos[vec->op].num_inputs; j++) { + if (vec->src[j].src.ssa != vec->src[i].src.ssa) + continue; + + /* Mark the given chanle as having been handled */ + srcs_remaining &= ~(1 << j); + + /* Mark the appropreate channel as coming from src j */ + swizzle[vec->src[j].swizzle[0]] = j; + } + + nir_foreach_use_safe(vec->src[i].src.ssa, use) { + if (use->parent_instr == &vec->instr) + continue; + + /* We need to dominate the use if we are going to rewrite it */ + if (!ssa_def_dominates_instr(&vec->dest.dest.ssa, use->parent_instr)) + continue; + + /* For now, we'll just rewrite ALU instructions */ + if (use->parent_instr->type != nir_instr_type_alu) + continue; + + assert(use->is_ssa); + + nir_alu_instr *use_alu = nir_instr_as_alu(use->parent_instr); + + /* Figure out which source we're actually looking at */ + nir_alu_src *use_alu_src = exec_node_data(nir_alu_src, use, src); + unsigned src_idx = use_alu_src - use_alu->src; + assert(src_idx < nir_op_infos[use_alu->op].num_inputs); + + bool can_reswizzle = true; + for (unsigned j = 0; j < 4; j++) { + if (!nir_alu_instr_channel_used(use_alu, src_idx, j)) + continue; + + if (swizzle[use_alu_src->swizzle[j]] == -1) { + can_reswizzle = false; + break; + } + } + + if (!can_reswizzle) + continue; + + /* At this point, we have determined that the given use can be + * reswizzled to actually use the destination of the vecN operation. + * Go ahead and rewrite it as needed. + */ + nir_instr_rewrite_src(use->parent_instr, use, + nir_src_for_ssa(&vec->dest.dest.ssa)); + for (unsigned j = 0; j < 4; j++) { + if (!nir_alu_instr_channel_used(use_alu, src_idx, j)) + continue; + + use_alu_src->swizzle[j] = swizzle[use_alu_src->swizzle[j]]; + } + } + } + } + + return true; +} + +static void +nir_move_vec_src_uses_to_dest_impl(nir_shader *shader, nir_function_impl *impl) +{ + nir_metadata_require(impl, nir_metadata_dominance); + + nir_index_instrs(impl); + nir_foreach_block(impl, move_vec_src_uses_to_dest_block, shader); + + nir_metadata_preserve(impl, nir_metadata_block_index | + nir_metadata_dominance); +} + +void +nir_move_vec_src_uses_to_dest(nir_shader *shader) +{ + nir_foreach_function(shader, function) { + if (function->impl) + nir_move_vec_src_uses_to_dest_impl(shader, function->impl); + } +} |