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/*
* Copyright © 2015 Red Hat
* Copyright © 2016 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.
*/
#include "nir.h"
#include "nir_builder.h"
#include "program/prog_instruction.h"
/**
* This pass adds <0.5, 0.5> to all uses of gl_FragCoord.
*
* Run before nir_lower_io().
*
* For a more full featured pass, consider using nir_lower_wpos_ytransform(),
* which can handle pixel center integer / half integer, and origin lower
* left / upper left transformations.
*
* This simple pass is primarily intended for use by Vulkan drivers on
* hardware which provides an integer pixel center. Vulkan mandates that
* the pixel center must be half-integer, and also that the coordinate
* system's origin must be upper left. This means that there's no need
* for a uniform - we can always just add a constant.
*/
static void
add_half_to_fragcoord(nir_builder *b, nir_intrinsic_instr *intr)
{
nir_ssa_def *wpos = &intr->dest.ssa;
assert(intr->dest.is_ssa);
b->cursor = nir_after_instr(&intr->instr);
wpos = nir_fadd(b, wpos, nir_imm_vec4(b, 0.5f, 0.5f, 0.0f, 0.0f));
nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, nir_src_for_ssa(wpos),
wpos->parent_instr);
}
static bool
lower_wpos_center_block(nir_builder *b, nir_block *block)
{
bool progress = false;
nir_foreach_instr(instr, block) {
if (instr->type == nir_instr_type_intrinsic) {
nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
if (intr->intrinsic == nir_intrinsic_load_var) {
nir_deref_var *dvar = intr->variables[0];
nir_variable *var = dvar->var;
if (var->data.mode == nir_var_shader_in &&
var->data.location == VARYING_SLOT_POS) {
/* gl_FragCoord should not have array/struct deref's: */
assert(dvar->deref.child == NULL);
add_half_to_fragcoord(b, intr);
progress = true;
}
}
}
}
return progress;
}
bool
nir_lower_wpos_center(nir_shader *shader)
{
bool progress = false;
nir_builder b;
assert(shader->stage == MESA_SHADER_FRAGMENT);
nir_foreach_function(function, shader) {
if (function->impl) {
nir_builder_init(&b, function->impl);
nir_foreach_block(block, function->impl) {
progress = lower_wpos_center_block(&b, block) || progress;
}
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance);
}
}
return progress;
}
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