mirror of https://gitlab.freedesktop.org/mesa/mesa
104 lines
3.3 KiB
C
104 lines
3.3 KiB
C
/*
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* Copyright 2018 Collabora Ltd.
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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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* on the rights to use, copy, modify, merge, publish, distribute, sub
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* license, and/or sell copies of the Software, and to permit persons to whom
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* the 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 NON-INFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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* USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "nir.h"
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#include "compiler/nir/nir_builder.h"
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static bool
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lower_discard_if_instr(nir_builder *b, nir_instr *instr_, UNUSED void *cb_data)
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{
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if (instr_->type != nir_instr_type_intrinsic)
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return false;
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nir_intrinsic_instr *instr = nir_instr_as_intrinsic(instr_);
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if (instr->intrinsic == nir_intrinsic_discard_if) {
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b->cursor = nir_before_instr(&instr->instr);
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nir_if *if_stmt = nir_push_if(b, nir_ssa_for_src(b, instr->src[0], 1));
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nir_discard(b);
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nir_pop_if(b, if_stmt);
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nir_instr_remove(&instr->instr);
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return true;
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} else if (instr->intrinsic == nir_intrinsic_terminate_if ||
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instr->intrinsic == nir_intrinsic_demote_if) {
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unreachable("todo: handle terminates and demotes for Vulkan");
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}
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/* a shader like this (shaders@glsl-fs-discard-04):
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uniform int j, k;
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void main()
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{
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for (int i = 0; i < j; i++) {
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if (i > k)
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continue;
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discard;
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}
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gl_FragColor = vec4(0.0, 1.0, 0.0, 0.0);
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}
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will generate nir like:
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loop {
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//snip
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if ssa_11 {
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block block_5:
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/ preds: block_4 /
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vec1 32 ssa_17 = iadd ssa_50, ssa_31
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/ succs: block_7 /
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} else {
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block block_6:
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/ preds: block_4 /
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intrinsic discard () () <-- not last instruction
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vec1 32 ssa_23 = iadd ssa_50, ssa_31 <-- dead code loop itr increment
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/ succs: block_7 /
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}
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//snip
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}
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which means that we can't assert like this:
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assert(instr->intrinsic != nir_intrinsic_discard ||
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nir_block_last_instr(instr->instr.block) == &instr->instr);
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and it's unnecessary anyway since later optimizations will dce the
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instructions following the discard
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*/
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return false;
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}
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bool
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nir_lower_discard_if(nir_shader *shader)
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{
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return nir_shader_instructions_pass(shader,
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lower_discard_if_instr,
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nir_metadata_none,
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NULL);
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}
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