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/*
* Copyright (C) 2019 Collabora, Ltd.
*
* 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 (Collabora):
* Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
*/
/**
* @file
*
* Flushes undefined SSA values to a zero vector fo the appropriate component
* count, to avoid undefined behaviour in the resulting shader. Not required
* for conformance as use of uninitialized variables is explicitly left
* undefined by the spec. Works around buggy apps, however.
*
* Call immediately after nir_opt_undef. If called before, larger optimization
* opportunities from the former pass will be missed. If called outside of an
* optimization loop, constant propagation and algebraic optimizations won't be
* able to kick in to reduce stuff consuming the zero.
*/
#include "nir_builder.h"
static bool
lower_undef_instr_to_zero(nir_builder *b, nir_instr *instr, UNUSED void *_state)
{
if (instr->type != nir_instr_type_undef)
return false;
nir_undef_instr *und = nir_instr_as_undef(instr);
b->cursor = nir_instr_remove(&und->instr);
nir_def *zero = nir_imm_zero(b, und->def.num_components,
und->def.bit_size);
nir_def_rewrite_uses(&und->def, zero);
return true;
}
bool
nir_lower_undef_to_zero(nir_shader *shader)
{
return nir_shader_instructions_pass(shader, lower_undef_instr_to_zero,
nir_metadata_control_flow,
NULL);
}
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