110 lines
3.2 KiB
C
110 lines
3.2 KiB
C
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/*
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* Copyright © 2015 Connor Abbott
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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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* Authors:
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* Connor Abbott (cwabbott0@gmail.com)
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*
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*/
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#include "nir.h"
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/*
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* This is a pass for removing phi nodes that look like:
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* a = phi(b, b, b, ...)
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*
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* Note that we can't ignore undef sources here, or else we may create a
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* situation where the definition of b isn't dominated by its uses. We're
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* allowed to do this since the definition of b must dominate all of the
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* phi node's predecessors, which means it must dominate the phi node as well
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* as all of the phi node's uses. In essence, the phi node acts as a copy
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* instruction. b can't be another phi node in the same block, since the only
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* time when phi nodes can source other phi nodes defined in the same block is
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* at the loop header, and in that case one of the sources of the phi has to
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* be from before the loop and that source can't be b.
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*/
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static bool
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remove_phis_block(nir_block *block, void *state)
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{
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bool *progress = state;
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void *mem_ctx = ralloc_parent(block);
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nir_foreach_instr_safe(block, instr) {
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if (instr->type != nir_instr_type_phi)
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break;
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nir_phi_instr *phi = nir_instr_as_phi(instr);
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nir_ssa_def *def = NULL;
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bool srcs_same = true;
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nir_foreach_phi_src(phi, src) {
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assert(src->src.is_ssa);
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if (def == NULL) {
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def = src->src.ssa;
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} else {
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if (src->src.ssa != def) {
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srcs_same = false;
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break;
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}
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}
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}
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if (!srcs_same)
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continue;
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assert(phi->dest.is_ssa);
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nir_ssa_def_rewrite_uses(&phi->dest.ssa, nir_src_for_ssa(def),
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mem_ctx);
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nir_instr_remove(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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static bool
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remove_phis_impl(nir_function_impl *impl)
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{
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bool progress = false;
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nir_foreach_block(impl, remove_phis_block, &progress);
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return progress;
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}
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bool
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nir_opt_remove_phis(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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progress = remove_phis_impl(overload->impl) || progress;
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return progress;
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}
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