src/compiler/nir/nir_opt_large_constants.c - platform/external/mesa3d - Git at Google

 /*
  * Copyright © 2018 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 "nir_deref.h"

 struct var_info {
    nir_variable *var;

    bool is_constant;
    bool found_read;
    bool duplicate;

    /* Block that has all the variable stores.  All the blocks with reads
     * should be dominated by this block.
     */
    nir_block *block;

    /* If is_constant, hold the collected constant data for this var. */
    uint32_t constant_data_size;
    void *constant_data;
 };

 static int
 var_info_cmp(const void *_a, const void *_b)
 {
    const struct var_info *a = _a;
    const struct var_info *b = _b;
    uint32_t a_size = a->constant_data_size;
    uint32_t b_size = b->constant_data_size;

    if (a_size < b_size) {
       return -1;
    } else if (a_size > b_size) {
       return 1;
    } else if (a_size == 0) {
       /* Don't call memcmp with invalid pointers. */
       return 0;
    } else {
       return memcmp(a->constant_data, b->constant_data, a_size);
    }
 }

 static nir_ssa_def *
 build_constant_load(nir_builder *b, nir_deref_instr *deref,
                     glsl_type_size_align_func size_align)
 {
    nir_variable *var = nir_deref_instr_get_variable(deref);

    const unsigned bit_size = glsl_get_bit_size(deref->type);
    const unsigned num_components = glsl_get_vector_elements(deref->type);

    UNUSED unsigned var_size, var_align;
    size_align(var->type, &var_size, &var_align);
    assert(var->data.location % var_align == 0);

    UNUSED unsigned deref_size, deref_align;
    size_align(deref->type, &deref_size, &deref_align);

    nir_intrinsic_instr *load =
       nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_constant);
    load->num_components = num_components;
    nir_intrinsic_set_base(load, var->data.location);
    nir_intrinsic_set_range(load, var_size);
    nir_intrinsic_set_align(load, deref_align, 0);
    load->src[0] = nir_src_for_ssa(nir_build_deref_offset(b, deref, size_align));
    nir_ssa_dest_init(&load->instr, &load->dest,
                      num_components, bit_size, NULL);
    nir_builder_instr_insert(b, &load->instr);

    if (load->dest.ssa.bit_size < 8) {
       /* Booleans are special-cased to be 32-bit */
       assert(glsl_type_is_boolean(deref->type));
       assert(deref_size == num_components * 4);
       load->dest.ssa.bit_size = 32;
       return nir_b2b1(b, &load->dest.ssa);
    } else {
       assert(deref_size == num_components * bit_size / 8);
       return &load->dest.ssa;
    }
 }

 static void
 handle_constant_store(void *mem_ctx, struct var_info *info,
                       nir_deref_instr *deref, nir_const_value *val,
                       unsigned writemask,
                       glsl_type_size_align_func size_align)
 {
    assert(!nir_deref_instr_has_indirect(deref));
    const unsigned bit_size = glsl_get_bit_size(deref->type);
    const unsigned num_components = glsl_get_vector_elements(deref->type);

    if (info->constant_data_size == 0) {
       unsigned var_size, var_align;
       size_align(info->var->type, &var_size, &var_align);
       info->constant_data_size = var_size;
       info->constant_data = rzalloc_size(mem_ctx, var_size);
    }

    const unsigned offset = nir_deref_instr_get_const_offset(deref, size_align);
    if (offset >= info->constant_data_size)
       return;

    char *dst = (char *)info->constant_data + offset;

    for (unsigned i = 0; i < num_components; i++) {
       if (!(writemask & (1 << i)))
          continue;

       switch (bit_size) {
       case 1:
          /* Booleans are special-cased to be 32-bit */
          ((int32_t *)dst)[i] = -(int)val[i].b;
          break;

       case 8:
          ((uint8_t *)dst)[i] = val[i].u8;
          break;

       case 16:
          ((uint16_t *)dst)[i] = val[i].u16;
          break;

       case 32:
          ((uint32_t *)dst)[i] = val[i].u32;
          break;

       case 64:
          ((uint64_t *)dst)[i] = val[i].u64;
          break;

       default:
          unreachable("Invalid bit size");
       }
    }
 }

 /** Lower large constant variables to shader constant data
  *
  * This pass looks for large (type_size(var->type) > threshold) variables
  * which are statically constant and moves them into shader constant data.
  * This is especially useful when large tables are baked into the shader
  * source code because they can be moved into a UBO by the driver to reduce
  * register pressure and make indirect access cheaper.
  */
 bool
 nir_opt_large_constants(nir_shader *shader,
                         glsl_type_size_align_func size_align,
                         unsigned threshold)
 {
    /* Default to a natural alignment if none is provided */
    if (size_align == NULL)
       size_align = glsl_get_natural_size_align_bytes;

    /* This only works with a single entrypoint */
    nir_function_impl *impl = nir_shader_get_entrypoint(shader);

    unsigned num_locals = nir_function_impl_index_vars(impl);

    if (num_locals == 0) {
       nir_shader_preserve_all_metadata(shader);
       return false;
    }

    struct var_info *var_infos = ralloc_array(NULL, struct var_info, num_locals);
    nir_foreach_function_temp_variable(var, impl) {
       var_infos[var->index] = (struct var_info) {
          .var = var,
          .is_constant = true,
          .found_read = false,
       };
    }

    nir_metadata_require(impl, nir_metadata_dominance);

    /* First, walk through the shader and figure out what variables we can
     * lower to the constant blob.
     */
    nir_foreach_block(block, impl) {
       nir_foreach_instr(instr, block) {
          if (instr->type == nir_instr_type_deref) {
             /* If we ever see a complex use of a deref_var, we have to assume
              * that variable is non-constant because we can't guarantee we
              * will find all of the writers of that variable.
              */
             nir_deref_instr *deref = nir_instr_as_deref(instr);
             if (deref->deref_type == nir_deref_type_var &&
                 deref->mode == nir_var_function_temp &&
                 nir_deref_instr_has_complex_use(deref))
                var_infos[deref->var->index].is_constant = false;
             continue;
          }

          if (instr->type != nir_instr_type_intrinsic)
             continue;

          nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);

          bool src_is_const = false;
          nir_deref_instr *src_deref = NULL, *dst_deref = NULL;
          unsigned writemask = 0;
          switch (intrin->intrinsic) {
          case nir_intrinsic_store_deref:
             dst_deref = nir_src_as_deref(intrin->src[0]);
             src_is_const = nir_src_is_const(intrin->src[1]);
             writemask = nir_intrinsic_write_mask(intrin);
             break;

          case nir_intrinsic_load_deref:
             src_deref = nir_src_as_deref(intrin->src[0]);
             break;

          case nir_intrinsic_copy_deref:
             assert(!"Lowering of copy_deref with large constants is prohibited");
             break;

          default:
             continue;
          }

          if (dst_deref && dst_deref->mode == nir_var_function_temp) {
             nir_variable *var = nir_deref_instr_get_variable(dst_deref);
             if (var == NULL)
                continue;

             assert(var->data.mode == nir_var_function_temp);

             struct var_info *info = &var_infos[var->index];
             if (!info->is_constant)
                continue;

             if (!info->block)
                info->block = block;

             /* We only consider variables constant if they only have constant
              * stores, all the stores come before any reads, and all stores
              * come from the same block.  We also can't handle indirect stores.
              */
             if (!src_is_const || info->found_read || block != info->block ||
                 nir_deref_instr_has_indirect(dst_deref)) {
                info->is_constant = false;
             } else {
                nir_const_value *val = nir_src_as_const_value(intrin->src[1]);
                handle_constant_store(var_infos, info, dst_deref, val, writemask,
                                      size_align);
             }
          }

          if (src_deref && src_deref->mode == nir_var_function_temp) {
             nir_variable *var = nir_deref_instr_get_variable(src_deref);
             if (var == NULL)
                continue;

             assert(var->data.mode == nir_var_function_temp);

             /* We only consider variables constant if all the reads are
              * dominated by the block that writes to it.
              */
             struct var_info *info = &var_infos[var->index];
             if (!info->is_constant)
                continue;

             if (!info->block || !nir_block_dominates(info->block, block))
                info->is_constant = false;

             info->found_read = true;
          }
       }
    }

    /* Allocate constant data space for each variable that just has constant
     * data.  We sort them by size and content so we can easily find
     * duplicates.
     */
    const unsigned old_constant_data_size = shader->constant_data_size;
    qsort(var_infos, num_locals, sizeof(struct var_info), var_info_cmp);
    for (int i = 0; i < num_locals; i++) {
       struct var_info *info = &var_infos[i];

       /* Fix up indices after we sorted. */
       info->var->index = i;

       if (!info->is_constant)
          continue;

       unsigned var_size, var_align;
       size_align(info->var->type, &var_size, &var_align);
       if (var_size <= threshold || !info->found_read) {
          /* Don't bother lowering small stuff or data that's never read */
          info->is_constant = false;
          continue;
       }

       if (i > 0 && var_info_cmp(info, &var_infos[i - 1]) == 0) {
          info->var->data.location = var_infos[i - 1].var->data.location;
          info->duplicate = true;
       } else {
          info->var->data.location = ALIGN_POT(shader->constant_data_size, var_align);
          shader->constant_data_size = info->var->data.location + var_size;
       }
    }

    if (shader->constant_data_size == old_constant_data_size) {
       nir_shader_preserve_all_metadata(shader);
       ralloc_free(var_infos);
       return false;
    }

    assert(shader->constant_data_size > old_constant_data_size);
    shader->constant_data = rerzalloc_size(shader, shader->constant_data,
                                           old_constant_data_size,
                                           shader->constant_data_size);
    for (int i = 0; i < num_locals; i++) {
       struct var_info *info = &var_infos[i];
       if (!info->duplicate && info->is_constant) {
          memcpy((char *)shader->constant_data + info->var->data.location,
                 info->constant_data, info->constant_data_size);
       }
    }

    nir_builder b;
    nir_builder_init(&b, impl);

    nir_foreach_block(block, impl) {
       nir_foreach_instr_safe(instr, block) {
          if (instr->type != nir_instr_type_intrinsic)
             continue;

          nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);

          switch (intrin->intrinsic) {
          case nir_intrinsic_load_deref: {
             nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
             if (deref->mode != nir_var_function_temp)
                continue;

             nir_variable *var = nir_deref_instr_get_variable(deref);
             if (var == NULL)
                continue;

             struct var_info *info = &var_infos[var->index];
             if (info->is_constant) {
                b.cursor = nir_after_instr(&intrin->instr);
                nir_ssa_def *val = build_constant_load(&b, deref, size_align);
                nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
                                         nir_src_for_ssa(val));
                nir_instr_remove(&intrin->instr);
                nir_deref_instr_remove_if_unused(deref);
             }
             break;
          }

          case nir_intrinsic_store_deref: {
             nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
             if (deref->mode != nir_var_function_temp)
                continue;

             nir_variable *var = nir_deref_instr_get_variable(deref);
             if (var == NULL)
                continue;

             struct var_info *info = &var_infos[var->index];
             if (info->is_constant) {
                nir_instr_remove(&intrin->instr);
                nir_deref_instr_remove_if_unused(deref);
             }
             break;
          }
          case nir_intrinsic_copy_deref:
          default:
             continue;
          }
       }
    }

    /* Clean up the now unused variables */
    for (int i = 0; i < num_locals; i++) {
       struct var_info *info = &var_infos[i];
       if (info->is_constant)
          exec_node_remove(&info->var->node);
    }

    ralloc_free(var_infos);

    nir_metadata_preserve(impl, nir_metadata_block_index |
                                nir_metadata_dominance);
    return true;
 }
	/*
	* Copyright © 2018 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 "nir_deref.h"

	struct var_info {
	nir_variable *var;

	bool is_constant;
	bool found_read;
	bool duplicate;

	/* Block that has all the variable stores. All the blocks with reads
	* should be dominated by this block.
	*/
	nir_block *block;

	/* If is_constant, hold the collected constant data for this var. */
	uint32_t constant_data_size;
	void *constant_data;
	};

	static int
	var_info_cmp(const void _a, const void _b)
	{
	const struct var_info *a = _a;
	const struct var_info *b = _b;
	uint32_t a_size = a->constant_data_size;
	uint32_t b_size = b->constant_data_size;

	if (a_size < b_size) {
	return -1;
	} else if (a_size > b_size) {
	return 1;
	} else if (a_size == 0) {
	/* Don't call memcmp with invalid pointers. */
	return 0;
	} else {
	return memcmp(a->constant_data, b->constant_data, a_size);
	}
	}

	static nir_ssa_def *
	build_constant_load(nir_builder b, nir_deref_instr deref,
	glsl_type_size_align_func size_align)
	{
	nir_variable *var = nir_deref_instr_get_variable(deref);

	const unsigned bit_size = glsl_get_bit_size(deref->type);
	const unsigned num_components = glsl_get_vector_elements(deref->type);

	UNUSED unsigned var_size, var_align;
	size_align(var->type, &var_size, &var_align);
	assert(var->data.location % var_align == 0);

	UNUSED unsigned deref_size, deref_align;
	size_align(deref->type, &deref_size, &deref_align);

	nir_intrinsic_instr *load =
	nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_constant);
	load->num_components = num_components;
	nir_intrinsic_set_base(load, var->data.location);
	nir_intrinsic_set_range(load, var_size);
	nir_intrinsic_set_align(load, deref_align, 0);
	load->src[0] = nir_src_for_ssa(nir_build_deref_offset(b, deref, size_align));
	nir_ssa_dest_init(&load->instr, &load->dest,
	num_components, bit_size, NULL);
	nir_builder_instr_insert(b, &load->instr);

	if (load->dest.ssa.bit_size < 8) {
	/* Booleans are special-cased to be 32-bit */
	assert(glsl_type_is_boolean(deref->type));
	assert(deref_size == num_components * 4);
	load->dest.ssa.bit_size = 32;
	return nir_b2b1(b, &load->dest.ssa);
	} else {
	assert(deref_size == num_components * bit_size / 8);
	return &load->dest.ssa;
	}
	}

	static void
	handle_constant_store(void mem_ctx, struct var_info info,
	nir_deref_instr deref, nir_const_value val,
	unsigned writemask,
	glsl_type_size_align_func size_align)
	{
	assert(!nir_deref_instr_has_indirect(deref));
	const unsigned bit_size = glsl_get_bit_size(deref->type);
	const unsigned num_components = glsl_get_vector_elements(deref->type);

	if (info->constant_data_size == 0) {
	unsigned var_size, var_align;
	size_align(info->var->type, &var_size, &var_align);
	info->constant_data_size = var_size;
	info->constant_data = rzalloc_size(mem_ctx, var_size);
	}

	const unsigned offset = nir_deref_instr_get_const_offset(deref, size_align);
	if (offset >= info->constant_data_size)
	return;

	char dst = (char )info->constant_data + offset;

	for (unsigned i = 0; i < num_components; i++) {
	if (!(writemask & (1 << i)))
	continue;

	switch (bit_size) {
	case 1:
	/* Booleans are special-cased to be 32-bit */
	((int32_t *)dst)[i] = -(int)val[i].b;
	break;

	case 8:
	((uint8_t *)dst)[i] = val[i].u8;
	break;

	case 16:
	((uint16_t *)dst)[i] = val[i].u16;
	break;

	case 32:
	((uint32_t *)dst)[i] = val[i].u32;
	break;

	case 64:
	((uint64_t *)dst)[i] = val[i].u64;
	break;

	default:
	unreachable("Invalid bit size");
	}
	}
	}

	/** Lower large constant variables to shader constant data
	*
	* This pass looks for large (type_size(var->type) > threshold) variables
	* which are statically constant and moves them into shader constant data.
	* This is especially useful when large tables are baked into the shader
	* source code because they can be moved into a UBO by the driver to reduce
	* register pressure and make indirect access cheaper.
	*/
	bool
	nir_opt_large_constants(nir_shader *shader,
	glsl_type_size_align_func size_align,
	unsigned threshold)
	{
	/* Default to a natural alignment if none is provided */
	if (size_align == NULL)
	size_align = glsl_get_natural_size_align_bytes;

	/* This only works with a single entrypoint */
	nir_function_impl *impl = nir_shader_get_entrypoint(shader);

	unsigned num_locals = nir_function_impl_index_vars(impl);

	if (num_locals == 0) {
	nir_shader_preserve_all_metadata(shader);
	return false;
	}

	struct var_info *var_infos = ralloc_array(NULL, struct var_info, num_locals);
	nir_foreach_function_temp_variable(var, impl) {
	var_infos[var->index] = (struct var_info) {
	.var = var,
	.is_constant = true,
	.found_read = false,
	};
	}

	nir_metadata_require(impl, nir_metadata_dominance);

	/* First, walk through the shader and figure out what variables we can
	* lower to the constant blob.
	*/
	nir_foreach_block(block, impl) {
	nir_foreach_instr(instr, block) {
	if (instr->type == nir_instr_type_deref) {
	/* If we ever see a complex use of a deref_var, we have to assume
	* that variable is non-constant because we can't guarantee we
	* will find all of the writers of that variable.
	*/
	nir_deref_instr *deref = nir_instr_as_deref(instr);
	if (deref->deref_type == nir_deref_type_var &&
	deref->mode == nir_var_function_temp &&
	nir_deref_instr_has_complex_use(deref))
	var_infos[deref->var->index].is_constant = false;
	continue;
	}

	if (instr->type != nir_instr_type_intrinsic)
	continue;

	nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);

	bool src_is_const = false;
	nir_deref_instr src_deref = NULL, dst_deref = NULL;
	unsigned writemask = 0;
	switch (intrin->intrinsic) {
	case nir_intrinsic_store_deref:
	dst_deref = nir_src_as_deref(intrin->src[0]);
	src_is_const = nir_src_is_const(intrin->src[1]);
	writemask = nir_intrinsic_write_mask(intrin);
	break;

	case nir_intrinsic_load_deref:
	src_deref = nir_src_as_deref(intrin->src[0]);
	break;

	case nir_intrinsic_copy_deref:
	assert(!"Lowering of copy_deref with large constants is prohibited");
	break;

	default:
	continue;
	}

	if (dst_deref && dst_deref->mode == nir_var_function_temp) {
	nir_variable *var = nir_deref_instr_get_variable(dst_deref);
	if (var == NULL)
	continue;

	assert(var->data.mode == nir_var_function_temp);

	struct var_info *info = &var_infos[var->index];
	if (!info->is_constant)
	continue;

	if (!info->block)
	info->block = block;

	/* We only consider variables constant if they only have constant
	* stores, all the stores come before any reads, and all stores
	* come from the same block. We also can't handle indirect stores.
	*/
	if (!src_is_const \|\| info->found_read \|\| block != info->block \|\|
	nir_deref_instr_has_indirect(dst_deref)) {
	info->is_constant = false;
	} else {
	nir_const_value *val = nir_src_as_const_value(intrin->src[1]);
	handle_constant_store(var_infos, info, dst_deref, val, writemask,
	size_align);
	}
	}

	if (src_deref && src_deref->mode == nir_var_function_temp) {
	nir_variable *var = nir_deref_instr_get_variable(src_deref);
	if (var == NULL)
	continue;

	assert(var->data.mode == nir_var_function_temp);

	/* We only consider variables constant if all the reads are
	* dominated by the block that writes to it.
	*/
	struct var_info *info = &var_infos[var->index];
	if (!info->is_constant)
	continue;

	if (!info->block \|\| !nir_block_dominates(info->block, block))
	info->is_constant = false;

	info->found_read = true;
	}
	}
	}

	/* Allocate constant data space for each variable that just has constant
	* data. We sort them by size and content so we can easily find
	* duplicates.
	*/
	const unsigned old_constant_data_size = shader->constant_data_size;
	qsort(var_infos, num_locals, sizeof(struct var_info), var_info_cmp);
	for (int i = 0; i < num_locals; i++) {
	struct var_info *info = &var_infos[i];

	/* Fix up indices after we sorted. */
	info->var->index = i;

	if (!info->is_constant)
	continue;

	unsigned var_size, var_align;
	size_align(info->var->type, &var_size, &var_align);
	if (var_size <= threshold \|\| !info->found_read) {
	/* Don't bother lowering small stuff or data that's never read */
	info->is_constant = false;
	continue;
	}

	if (i > 0 && var_info_cmp(info, &var_infos[i - 1]) == 0) {
	info->var->data.location = var_infos[i - 1].var->data.location;
	info->duplicate = true;
	} else {
	info->var->data.location = ALIGN_POT(shader->constant_data_size, var_align);
	shader->constant_data_size = info->var->data.location + var_size;
	}
	}

	if (shader->constant_data_size == old_constant_data_size) {
	nir_shader_preserve_all_metadata(shader);
	ralloc_free(var_infos);
	return false;
	}

	assert(shader->constant_data_size > old_constant_data_size);
	shader->constant_data = rerzalloc_size(shader, shader->constant_data,
	old_constant_data_size,
	shader->constant_data_size);
	for (int i = 0; i < num_locals; i++) {
	struct var_info *info = &var_infos[i];
	if (!info->duplicate && info->is_constant) {
	memcpy((char *)shader->constant_data + info->var->data.location,
	info->constant_data, info->constant_data_size);
	}
	}

	nir_builder b;
	nir_builder_init(&b, impl);

	nir_foreach_block(block, impl) {
	nir_foreach_instr_safe(instr, block) {
	if (instr->type != nir_instr_type_intrinsic)
	continue;

	nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);

	switch (intrin->intrinsic) {
	case nir_intrinsic_load_deref: {
	nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
	if (deref->mode != nir_var_function_temp)
	continue;

	nir_variable *var = nir_deref_instr_get_variable(deref);
	if (var == NULL)
	continue;

	struct var_info *info = &var_infos[var->index];
	if (info->is_constant) {
	b.cursor = nir_after_instr(&intrin->instr);
	nir_ssa_def *val = build_constant_load(&b, deref, size_align);
	nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
	nir_src_for_ssa(val));
	nir_instr_remove(&intrin->instr);
	nir_deref_instr_remove_if_unused(deref);
	}
	break;
	}

	case nir_intrinsic_store_deref: {
	nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
	if (deref->mode != nir_var_function_temp)
	continue;

	nir_variable *var = nir_deref_instr_get_variable(deref);
	if (var == NULL)
	continue;

	struct var_info *info = &var_infos[var->index];
	if (info->is_constant) {
	nir_instr_remove(&intrin->instr);
	nir_deref_instr_remove_if_unused(deref);
	}
	break;
	}
	case nir_intrinsic_copy_deref:
	default:
	continue;
	}
	}
	}

	/* Clean up the now unused variables */
	for (int i = 0; i < num_locals; i++) {
	struct var_info *info = &var_infos[i];
	if (info->is_constant)
	exec_node_remove(&info->var->node);
	}

	ralloc_free(var_infos);

	nir_metadata_preserve(impl, nir_metadata_block_index \|
	nir_metadata_dominance);
	return true;
	}