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/*
* Copyright © 2020 Mike Blumenkrantz
*
* 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:
* Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
*/
#include "nir.h"
#include "nir_builder.h"
/**
* This pass uses the enabled clip planes from the rasterizer state to rewrite
* vertex shader store operations and store an undef to the corresponding gl_ClipDistance[n]
* value if the plane is disabled
*/
/* recursively nest if/else blocks until we get to an array index,
* then overwrite it if that plane isn't enabled
*/
static void
recursive_if_chain(nir_builder *b, nir_deref_instr *deref, nir_ssa_def *value, unsigned clip_plane_enable, nir_ssa_def *index, unsigned start, unsigned end)
{
if (start == end - 1) {
/* store the original value again if the clip plane is enabled */
if (clip_plane_enable & (1 << start))
nir_store_deref(b, deref, value, 1 << start);
else
nir_store_deref(b, deref, nir_ssa_undef(b, 1, 32), 1 << start);
return;
}
unsigned mid = start + (end - start) / 2;
nir_push_if(b, nir_ilt(b, index, nir_imm_int(b, mid)));
recursive_if_chain(b, deref, value, clip_plane_enable, index, start, mid);
nir_push_else(b, NULL);
recursive_if_chain(b, deref, value, clip_plane_enable, index, mid, end);
nir_pop_if(b, NULL);
}
/* vulkan (and some drivers) provides no concept of enabling clip planes through api,
* so we rewrite disabled clip planes to an undefined value in order to disable them
*/
static bool
lower_clip_plane_store(nir_intrinsic_instr *instr, unsigned clip_plane_enable, nir_builder *b)
{
nir_variable *out;
unsigned plane;
if (instr->intrinsic != nir_intrinsic_store_deref)
return false;
nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
out = nir_deref_instr_get_variable(deref);
if ((out->data.location != VARYING_SLOT_CLIP_DIST0) ||
out->data.mode != nir_var_shader_out)
return false;
b->cursor = nir_after_instr(&instr->instr);
if (nir_src_is_const(deref->arr.index)) {
/* storing using a constant index */
plane = nir_src_as_uint(deref->arr.index);
/* no need to make changes if the clip plane is enabled */
if (clip_plane_enable & (1 << plane))
return false;
nir_store_deref(b, deref, nir_ssa_undef(b, 1, 32), 1 << plane);
} else {
/* storing using a variable index */
nir_ssa_def *index = nir_ssa_for_src(b, deref->arr.index, 1);
unsigned length = glsl_get_length(nir_deref_instr_parent(deref)->type);
recursive_if_chain(b, deref, instr->src[1].ssa, clip_plane_enable, index, 0, length);
}
nir_instr_remove(&instr->instr);
return true;
}
bool
nir_lower_clip_disable(nir_shader *shader, unsigned clip_plane_enable)
{
bool progress = false;
nir_foreach_shader_out_variable(var, shader) {
if (var->data.location == VARYING_SLOT_CLIP_DIST0) {
unsigned size = glsl_get_length(var->type);
/* if currently-enabled planes match used planes then no-op */
if (clip_plane_enable == (1u << size) - 1)
return false;
}
}
nir_foreach_function(function, shader) {
if (function->impl) {
nir_builder builder;
nir_builder_init(&builder, function->impl);
nir_foreach_block(block, function->impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type == nir_instr_type_intrinsic)
progress |= lower_clip_plane_store(nir_instr_as_intrinsic(instr),
clip_plane_enable,
&builder);
}
}
nir_metadata_preserve(function->impl, nir_metadata_block_index | nir_metadata_dominance);
}
}
return progress;
}
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