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* Copyright © 2018 Intel Corporation
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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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* 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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* 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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#include "nir_builder.h"
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#include "nir_deref.h"
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/* Block that has all the variable stores. All the blocks with reads
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* should be dominated by this block.
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/* If is_constant, hold the collected constant data for this var. */
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uint32_t constant_data_size;
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var_info_cmp(const void *_a, const void *_b)
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const struct var_info *a = _a;
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const struct var_info *b = _b;
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uint32_t a_size = a->constant_data_size;
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uint32_t b_size = b->constant_data_size;
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if (a->is_constant != b->is_constant) {
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return (int)a->is_constant - (int)b->is_constant;
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} else if (a_size < b_size) {
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} else if (a_size > b_size) {
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} else if (a_size == 0) {
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/* Don't call memcmp with invalid pointers. */
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return memcmp(a->constant_data, b->constant_data, a_size);
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build_constant_load(nir_builder *b, nir_deref_instr *deref,
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glsl_type_size_align_func size_align)
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nir_variable *var = nir_deref_instr_get_variable(deref);
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const unsigned bit_size = glsl_get_bit_size(deref->type);
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const unsigned num_components = glsl_get_vector_elements(deref->type);
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UNUSED unsigned var_size, var_align;
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size_align(var->type, &var_size, &var_align);
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assert(var->data.location % var_align == 0);
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UNUSED unsigned deref_size, deref_align;
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size_align(deref->type, &deref_size, &deref_align);
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nir_ssa_def *src = nir_build_deref_offset(b, deref, size_align);
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nir_load_constant(b, num_components, bit_size, src,
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.base = var->data.location,
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.align_mul = deref_align,
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if (load->bit_size < 8) {
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/* Booleans are special-cased to be 32-bit */
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assert(glsl_type_is_boolean(deref->type));
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assert(deref_size == num_components * 4);
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return nir_b2b1(b, load);
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assert(deref_size == num_components * bit_size / 8);
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handle_constant_store(void *mem_ctx, struct var_info *info,
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nir_deref_instr *deref, nir_const_value *val,
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glsl_type_size_align_func size_align)
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assert(!nir_deref_instr_has_indirect(deref));
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const unsigned bit_size = glsl_get_bit_size(deref->type);
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const unsigned num_components = glsl_get_vector_elements(deref->type);
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if (info->constant_data_size == 0) {
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unsigned var_size, var_align;
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size_align(info->var->type, &var_size, &var_align);
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info->constant_data_size = var_size;
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info->constant_data = rzalloc_size(mem_ctx, var_size);
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const unsigned offset = nir_deref_instr_get_const_offset(deref, size_align);
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if (offset >= info->constant_data_size)
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char *dst = (char *)info->constant_data + offset;
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for (unsigned i = 0; i < num_components; i++) {
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if (!(writemask & (1 << i)))
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/* Booleans are special-cased to be 32-bit */
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((int32_t *)dst)[i] = -(int)val[i].b;
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((uint8_t *)dst)[i] = val[i].u8;
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((uint16_t *)dst)[i] = val[i].u16;
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((uint32_t *)dst)[i] = val[i].u32;
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((uint64_t *)dst)[i] = val[i].u64;
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unreachable("Invalid bit size");
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/** Lower large constant variables to shader constant data
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* This pass looks for large (type_size(var->type) > threshold) variables
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* which are statically constant and moves them into shader constant data.
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* This is especially useful when large tables are baked into the shader
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* source code because they can be moved into a UBO by the driver to reduce
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* register pressure and make indirect access cheaper.
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nir_opt_large_constants(nir_shader *shader,
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glsl_type_size_align_func size_align,
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/* Default to a natural alignment if none is provided */
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if (size_align == NULL)
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size_align = glsl_get_natural_size_align_bytes;
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/* This only works with a single entrypoint */
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nir_function_impl *impl = nir_shader_get_entrypoint(shader);
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unsigned num_locals = nir_function_impl_index_vars(impl);
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if (num_locals == 0) {
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nir_shader_preserve_all_metadata(shader);
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struct var_info *var_infos = ralloc_array(NULL, struct var_info, num_locals);
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nir_foreach_function_temp_variable(var, impl) {
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var_infos[var->index] = (struct var_info) {
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nir_metadata_require(impl, nir_metadata_dominance);
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/* First, walk through the shader and figure out what variables we can
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* lower to the constant blob.
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nir_foreach_block(block, impl) {
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nir_foreach_instr(instr, block) {
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if (instr->type == nir_instr_type_deref) {
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/* If we ever see a complex use of a deref_var, we have to assume
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* that variable is non-constant because we can't guarantee we
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* will find all of the writers of that variable.
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nir_deref_instr *deref = nir_instr_as_deref(instr);
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if (deref->deref_type == nir_deref_type_var &&
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deref->var->data.mode == nir_var_function_temp &&
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nir_deref_instr_has_complex_use(deref))
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var_infos[deref->var->index].is_constant = false;
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if (instr->type != nir_instr_type_intrinsic)
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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bool src_is_const = false;
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nir_deref_instr *src_deref = NULL, *dst_deref = NULL;
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unsigned writemask = 0;
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switch (intrin->intrinsic) {
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case nir_intrinsic_store_deref:
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dst_deref = nir_src_as_deref(intrin->src[0]);
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src_is_const = nir_src_is_const(intrin->src[1]);
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writemask = nir_intrinsic_write_mask(intrin);
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case nir_intrinsic_load_deref:
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src_deref = nir_src_as_deref(intrin->src[0]);
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case nir_intrinsic_copy_deref:
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assert(!"Lowering of copy_deref with large constants is prohibited");
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if (dst_deref && nir_deref_mode_must_be(dst_deref, nir_var_function_temp)) {
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nir_variable *var = nir_deref_instr_get_variable(dst_deref);
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assert(var->data.mode == nir_var_function_temp);
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struct var_info *info = &var_infos[var->index];
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if (!info->is_constant)
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/* We only consider variables constant if they only have constant
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* stores, all the stores come before any reads, and all stores
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* come from the same block. We also can't handle indirect stores.
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if (!src_is_const || info->found_read || block != info->block ||
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nir_deref_instr_has_indirect(dst_deref)) {
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info->is_constant = false;
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nir_const_value *val = nir_src_as_const_value(intrin->src[1]);
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handle_constant_store(var_infos, info, dst_deref, val, writemask,
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if (src_deref && nir_deref_mode_must_be(src_deref, nir_var_function_temp)) {
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nir_variable *var = nir_deref_instr_get_variable(src_deref);
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assert(var->data.mode == nir_var_function_temp);
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/* We only consider variables constant if all the reads are
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* dominated by the block that writes to it.
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struct var_info *info = &var_infos[var->index];
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if (!info->is_constant)
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if (!info->block || !nir_block_dominates(info->block, block))
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info->is_constant = false;
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info->found_read = true;
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/* Allocate constant data space for each variable that just has constant
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* data. We sort them by size and content so we can easily find
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const unsigned old_constant_data_size = shader->constant_data_size;
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qsort(var_infos, num_locals, sizeof(struct var_info), var_info_cmp);
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for (int i = 0; i < num_locals; i++) {
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struct var_info *info = &var_infos[i];
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/* Fix up indices after we sorted. */
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info->var->index = i;
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if (!info->is_constant)
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unsigned var_size, var_align;
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size_align(info->var->type, &var_size, &var_align);
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if (var_size <= threshold || !info->found_read) {
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/* Don't bother lowering small stuff or data that's never read */
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info->is_constant = false;
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if (i > 0 && var_info_cmp(info, &var_infos[i - 1]) == 0) {
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info->var->data.location = var_infos[i - 1].var->data.location;
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info->duplicate = true;
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info->var->data.location = ALIGN_POT(shader->constant_data_size, var_align);
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shader->constant_data_size = info->var->data.location + var_size;
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if (shader->constant_data_size == old_constant_data_size) {
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nir_shader_preserve_all_metadata(shader);
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ralloc_free(var_infos);
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assert(shader->constant_data_size > old_constant_data_size);
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shader->constant_data = rerzalloc_size(shader, shader->constant_data,
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old_constant_data_size,
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shader->constant_data_size);
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for (int i = 0; i < num_locals; i++) {
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struct var_info *info = &var_infos[i];
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if (!info->duplicate && info->is_constant) {
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memcpy((char *)shader->constant_data + info->var->data.location,
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info->constant_data, info->constant_data_size);
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nir_builder_init(&b, impl);
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nir_foreach_block(block, impl) {
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nir_foreach_instr_safe(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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switch (intrin->intrinsic) {
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case nir_intrinsic_load_deref: {
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nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
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if (!nir_deref_mode_is(deref, nir_var_function_temp))
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nir_variable *var = nir_deref_instr_get_variable(deref);
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struct var_info *info = &var_infos[var->index];
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if (info->is_constant) {
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b.cursor = nir_after_instr(&intrin->instr);
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nir_ssa_def *val = build_constant_load(&b, deref, size_align);
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nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
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nir_instr_remove(&intrin->instr);
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nir_deref_instr_remove_if_unused(deref);
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case nir_intrinsic_store_deref: {
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nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
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if (!nir_deref_mode_is(deref, nir_var_function_temp))
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nir_variable *var = nir_deref_instr_get_variable(deref);
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struct var_info *info = &var_infos[var->index];
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if (info->is_constant) {
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nir_instr_remove(&intrin->instr);
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nir_deref_instr_remove_if_unused(deref);
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case nir_intrinsic_copy_deref:
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/* Clean up the now unused variables */
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for (int i = 0; i < num_locals; i++) {
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struct var_info *info = &var_infos[i];
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if (info->is_constant)
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exec_node_remove(&info->var->node);
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ralloc_free(var_infos);
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nir_metadata_preserve(impl, nir_metadata_block_index |
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nir_metadata_dominance);