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9e6dc5b64d
We may find a cause to do more undef optimization in the future, but for
now this fixes up things after if flattening. vc4 was handling this
internally most of the time, but a GLB2.7 shader that did a conditional
discard and assign gl_FragColor in the else was still emitting some extra
code.
total instructions in shared programs: 100809 -> 100795 (-0.01%)
instructions in affected programs: 37 -> 23 (-37.84%)
v2: Use nir_instr_rewrite_src() to update def/use on src[0] (by Thomas
Helland).
v3: Make sure to flag metadata dirties, and copy the swizzle and abs/neg
over to src[0], too (by anholt).
Reviewed-by: Thomas Helland <thomashelland90@gmail.com> (v2)
Tested-by: Thomas Helland <thomashelland90@gmail.com> (v2)
104 lines
3.4 KiB
C
104 lines
3.4 KiB
C
/*
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* Copyright © 2015 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 DEALINGS
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* IN THE SOFTWARE.
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*/
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#include "nir.h"
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/** @file nir_opt_undef.c
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*
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* Handles optimization of operations involving ssa_undef. For now, we just
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* make sure that csels between undef and some other value just give the other
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* value (on the assumption that the condition's going to be choosing the
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* defined value). This reduces work after if flattening when each side of
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* the if is defining a variable.
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*
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* Some day, we may find some use for making other operations consuming an
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* undef arg output undef, but I don't know of any cases currently.
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*/
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static bool
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opt_undef_alu(nir_alu_instr *instr)
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{
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if (instr->op != nir_op_bcsel && instr->op != nir_op_fcsel)
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return false;
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assert(instr->dest.dest.is_ssa);
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for (int i = 1; i <= 2; i++) {
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if (!instr->src[i].src.is_ssa)
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continue;
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nir_instr *parent = instr->src[i].src.ssa->parent_instr;
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if (parent->type != nir_instr_type_ssa_undef)
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continue;
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/* We can't just use nir_alu_src_copy, because we need the def/use
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* updated.
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*/
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nir_instr_rewrite_src(&instr->instr, &instr->src[0].src,
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instr->src[i == 1 ? 2 : 1].src);
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nir_alu_src_copy(&instr->src[0], &instr->src[i == 1 ? 2 : 1],
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ralloc_parent(instr));
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nir_src empty_src;
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memset(&empty_src, 0, sizeof(empty_src));
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nir_instr_rewrite_src(&instr->instr, &instr->src[1].src, empty_src);
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nir_instr_rewrite_src(&instr->instr, &instr->src[2].src, empty_src);
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instr->op = nir_op_imov;
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return true;
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}
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return false;
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}
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static bool
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opt_undef_block(nir_block *block, void *data)
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{
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bool *progress = data;
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nir_foreach_instr_safe(block, instr) {
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if (instr->type == nir_instr_type_alu)
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if (opt_undef_alu(nir_instr_as_alu(instr)))
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(*progress) = true;
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}
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return true;
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}
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bool
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nir_opt_undef(nir_shader *shader)
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{
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bool progress = false;
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nir_foreach_overload(shader, overload) {
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if (overload->impl) {
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nir_foreach_block(overload->impl, opt_undef_block, &progress);
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if (progress)
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nir_metadata_preserve(overload->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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return progress;
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}
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