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

 /*
  * Copyright © 2015 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.
  */

 /*
  * Implements a pass that lowers output and/or input variables to a
  * temporary plus an output variable with a single copy at each exit
  * point of the shader and/or an input variable with a single copy
  * at the entrance point of the shader.  This way the output variable
  * is only ever written once and/or input is only read once, and there
  * are no indirect outut/input accesses.
  */

 #include "nir.h"
 #include "nir_builder.h"
 #include "nir_deref.h"

 struct lower_io_state {
    nir_shader *shader;
    nir_function_impl *entrypoint;
    struct exec_list old_outputs;
    struct exec_list old_inputs;
    struct exec_list new_outputs;
    struct exec_list new_inputs;

    /* map from temporary to new input */
    struct hash_table *input_map;
 };

 static void
 emit_copies(nir_builder *b, struct exec_list *dest_vars,
             struct exec_list *src_vars)
 {
    assert(exec_list_length(dest_vars) == exec_list_length(src_vars));

    foreach_two_lists(dest_node, dest_vars, src_node, src_vars) {
       nir_variable *dest = exec_node_data(nir_variable, dest_node, node);
       nir_variable *src = exec_node_data(nir_variable, src_node, node);

       /* No need to copy the contents of a non-fb_fetch_output output variable
        * to the temporary allocated for it, since its initial value is
        * undefined.
        */
       if (src->data.mode == nir_var_shader_out &&
           !src->data.fb_fetch_output)
          continue;

       /* Can't copy the contents of the temporary back to a read-only
        * interface variable.  The value of the temporary won't have been
        * modified by the shader anyway.
        */
       if (dest->data.read_only)
          continue;

       nir_copy_var(b, dest, src);
    }
 }

 static void
 emit_output_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
 {
    nir_builder b;
    nir_builder_init(&b, impl);

    if (state->shader->info.stage == MESA_SHADER_GEOMETRY) {
       /* For geometry shaders, we have to emit the output copies right
        * before each EmitVertex call.
        */
       nir_foreach_block(block, impl) {
          nir_foreach_instr(instr, block) {
             if (instr->type != nir_instr_type_intrinsic)
                continue;

             nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
             if (intrin->intrinsic == nir_intrinsic_emit_vertex ||
                 intrin->intrinsic == nir_intrinsic_emit_vertex_with_counter) {
                b.cursor = nir_before_instr(&intrin->instr);
                emit_copies(&b, &state->new_outputs, &state->old_outputs);
             }
          }
       }
    } else if (impl == state->entrypoint) {
       b.cursor = nir_before_block(nir_start_block(impl));
       emit_copies(&b, &state->old_outputs, &state->new_outputs);

       /* For all other shader types, we need to do the copies right before
        * the jumps to the end block.
        */
       set_foreach(impl->end_block->predecessors, block_entry) {
          struct nir_block *block = (void *)block_entry->key;
          b.cursor = nir_after_block_before_jump(block);
          emit_copies(&b, &state->new_outputs, &state->old_outputs);
       }
    }
 }

 /* For fragment shader inputs, when we lower to temporaries we'll invalidate
  * interpolateAt*() because now they'll be pointing to the temporary instead
  * of the actual variable. Since the caller presumably doesn't support
  * indirect indexing of inputs, we'll need to lower something like:
  *
  * in vec4 foo[3];
  *
  * ... = interpolateAtCentroid(foo[i]);
  *
  * to a sequence of interpolations that store to our temporary, then a
  * load at the end:
  *
  * in vec4 foo[3];
  * vec4 foo_tmp[3];
  *
  * foo_tmp[0] = interpolateAtCentroid(foo[0]);
  * foo_tmp[1] = interpolateAtCentroid(foo[1]);
  * ... = foo_tmp[i];
  */

 /*
  * Recursively emit the interpolation instructions. Here old_interp_deref
  * refers to foo[i], temp_deref is foo_tmp[0/1], and new_interp_deref is
  * foo[0/1].
  */

 static void
 emit_interp(nir_builder *b, nir_deref_instr **old_interp_deref,
             nir_deref_instr *temp_deref, nir_deref_instr *new_interp_deref,
             nir_intrinsic_instr *interp)
 {
    while (*old_interp_deref) {
       switch ((*old_interp_deref)->deref_type) {
       case nir_deref_type_struct:
          temp_deref =
             nir_build_deref_struct(b, temp_deref,
                                    (*old_interp_deref)->strct.index);
          new_interp_deref =
             nir_build_deref_struct(b, new_interp_deref,
                                    (*old_interp_deref)->strct.index);
          break;
       case nir_deref_type_array:
          if (nir_src_is_const((*old_interp_deref)->arr.index)) {
             temp_deref =
                nir_build_deref_array(b, temp_deref,
                                      (*old_interp_deref)->arr.index.ssa);
             new_interp_deref =
                nir_build_deref_array(b, new_interp_deref,
                                      (*old_interp_deref)->arr.index.ssa);
             break;
          } else {
             /* We have an indirect deref, so we have to emit interpolations
              * for every index. Recurse in case we have an array of arrays.
              */
             unsigned length = glsl_get_length(temp_deref->type);
             for (unsigned i = 0; i < length; i++) {
                nir_deref_instr *new_temp =
                   nir_build_deref_array_imm(b, temp_deref, i);
                nir_deref_instr *new_interp =
                   nir_build_deref_array_imm(b, new_interp_deref, i);

                emit_interp(b, old_interp_deref + 1, new_temp, new_interp,
                            interp);
             }

             return;
          }

       case nir_deref_type_var:
       case nir_deref_type_array_wildcard:
       case nir_deref_type_ptr_as_array:
       case nir_deref_type_cast:
          unreachable("bad deref type");
       }

       old_interp_deref++;
    }

    /* Now that we've constructed a fully-qualified deref with all the indirect
     * derefs replaced with direct ones, it's time to actually emit the new
     * interpolation instruction.
     */

    nir_intrinsic_instr *new_interp =
       nir_intrinsic_instr_create(b->shader, interp->intrinsic);

    new_interp->src[0] = nir_src_for_ssa(&new_interp_deref->dest.ssa);
    if (interp->intrinsic == nir_intrinsic_interp_deref_at_sample ||
        interp->intrinsic == nir_intrinsic_interp_deref_at_offset ||
        interp->intrinsic == nir_intrinsic_interp_deref_at_vertex) {
       new_interp->src[1] = interp->src[1];
    }

    new_interp->num_components = interp->num_components;
    nir_ssa_dest_init(&new_interp->instr, &new_interp->dest,
                      interp->dest.ssa.num_components,
                      interp->dest.ssa.bit_size, NULL);

    nir_builder_instr_insert(b, &new_interp->instr);
    nir_store_deref(b, temp_deref, &new_interp->dest.ssa,
                    (1 << interp->dest.ssa.num_components) - 1);
 }

 static void
 fixup_interpolation_instr(struct lower_io_state *state,
                           nir_intrinsic_instr *interp, nir_builder *b)
 {
    nir_deref_path interp_path;
    nir_deref_path_init(&interp_path, nir_src_as_deref(interp->src[0]), NULL);

    b->cursor = nir_before_instr(&interp->instr);

    /* The original interpolation instruction should contain a deref path
     * starting with the original variable, which is now the temporary.
     */
    nir_deref_instr *temp_root = interp_path.path[0];

    /* Fish out the newly-created input variable. */
    assert(temp_root->deref_type == nir_deref_type_var);
    struct hash_entry *entry = _mesa_hash_table_search(state->input_map,
                                                       temp_root->var);
    assert(entry);
    nir_variable *input = entry->data;
    nir_deref_instr *input_root = nir_build_deref_var(b, input);

    /* Emit the interpolation instructions. */
    emit_interp(b, interp_path.path + 1, temp_root, input_root, interp);

    /* Now the temporary contains the interpolation results, and we can just
     * load from it. We can reuse the original deref, since it points to the
     * correct part of the temporary.
     */
    nir_ssa_def *load = nir_load_deref(b, nir_src_as_deref(interp->src[0]));
    nir_ssa_def_rewrite_uses(&interp->dest.ssa, nir_src_for_ssa(load));
    nir_instr_remove(&interp->instr);

    nir_deref_path_finish(&interp_path);
 }

 static void
 fixup_interpolation(struct lower_io_state *state, nir_function_impl *impl,
                     nir_builder *b)
 {
    nir_foreach_block(block, impl) {
       nir_foreach_instr_safe(instr, block) {
          if (instr->type != nir_instr_type_intrinsic)
             continue;

          nir_intrinsic_instr *interp = nir_instr_as_intrinsic(instr);

          if (interp->intrinsic == nir_intrinsic_interp_deref_at_centroid ||
              interp->intrinsic == nir_intrinsic_interp_deref_at_sample ||
              interp->intrinsic == nir_intrinsic_interp_deref_at_offset ||
              interp->intrinsic == nir_intrinsic_interp_deref_at_vertex) {
             fixup_interpolation_instr(state, interp, b);
          }
       }
    }
 }

 static void
 emit_input_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
 {
    if (impl == state->entrypoint) {
       nir_builder b;
       nir_builder_init(&b, impl);
       b.cursor = nir_before_block(nir_start_block(impl));
       emit_copies(&b, &state->old_inputs, &state->new_inputs);
       if (state->shader->info.stage == MESA_SHADER_FRAGMENT)
          fixup_interpolation(state, impl, &b);
    }
 }

 static nir_variable *
 create_shadow_temp(struct lower_io_state *state, nir_variable *var)
 {
    nir_variable *nvar = ralloc(state->shader, nir_variable);
    memcpy(nvar, var, sizeof *nvar);
    nvar->data.cannot_coalesce = true;

    /* The original is now the temporary */
    nir_variable *temp = var;

    /* Reparent the name to the new variable */
    ralloc_steal(nvar, nvar->name);

    assert(nvar->constant_initializer == NULL && nvar->pointer_initializer == NULL);

    /* Give the original a new name with @<mode>-temp appended */
    const char *mode = (temp->data.mode == nir_var_shader_in) ? "in" : "out";
    temp->name = ralloc_asprintf(var, "%s@%s-temp", mode, nvar->name);
    temp->data.mode = nir_var_shader_temp;
    temp->data.read_only = false;
    temp->data.fb_fetch_output = false;
    temp->data.compact = false;

    return nvar;
 }

 static void
 move_variables_to_list(nir_shader *shader, nir_variable_mode mode,
                        struct exec_list *dst_list)
 {
    nir_foreach_variable_with_modes_safe(var, shader, mode) {
       exec_node_remove(&var->node);
       exec_list_push_tail(dst_list, &var->node);
    }
 }

 void
 nir_lower_io_to_temporaries(nir_shader *shader, nir_function_impl *entrypoint,
                             bool outputs, bool inputs)
 {
    struct lower_io_state state;

    if (shader->info.stage == MESA_SHADER_TESS_CTRL)
       return;

    state.shader = shader;
    state.entrypoint = entrypoint;
    state.input_map = _mesa_pointer_hash_table_create(NULL);

    exec_list_make_empty(&state.old_inputs);
    if (inputs)
       move_variables_to_list(shader, nir_var_shader_in, &state.old_inputs);

    exec_list_make_empty(&state.old_outputs);
    if (outputs)
       move_variables_to_list(shader, nir_var_shader_out, &state.old_outputs);

    exec_list_make_empty(&state.new_inputs);
    exec_list_make_empty(&state.new_outputs);

    /* Walk over all of the outputs turn each output into a temporary and
     * make a new variable for the actual output.
     */
    nir_foreach_variable_in_list(var, &state.old_outputs) {
       nir_variable *output = create_shadow_temp(&state, var);
       exec_list_push_tail(&state.new_outputs, &output->node);
    }

    /* and same for inputs: */
    nir_foreach_variable_in_list(var, &state.old_inputs) {
       nir_variable *input = create_shadow_temp(&state, var);
       exec_list_push_tail(&state.new_inputs, &input->node);
       _mesa_hash_table_insert(state.input_map, var, input);
    }

    nir_foreach_function(function, shader) {
       if (function->impl == NULL)
          continue;

       if (inputs)
          emit_input_copies_impl(&state, function->impl);

       if (outputs)
          emit_output_copies_impl(&state, function->impl);

       nir_metadata_preserve(function->impl, nir_metadata_block_index |
                                             nir_metadata_dominance);
    }

    exec_list_append(&shader->variables, &state.old_inputs);
    exec_list_append(&shader->variables, &state.old_outputs);
    exec_list_append(&shader->variables, &state.new_inputs);
    exec_list_append(&shader->variables, &state.new_outputs);

    nir_fixup_deref_modes(shader);

    _mesa_hash_table_destroy(state.input_map, NULL);
 }
	/*
	* Copyright © 2015 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.
	*/

	/*
	* Implements a pass that lowers output and/or input variables to a
	* temporary plus an output variable with a single copy at each exit
	* point of the shader and/or an input variable with a single copy
	* at the entrance point of the shader. This way the output variable
	* is only ever written once and/or input is only read once, and there
	* are no indirect outut/input accesses.
	*/

	#include "nir.h"
	#include "nir_builder.h"
	#include "nir_deref.h"

	struct lower_io_state {
	nir_shader *shader;
	nir_function_impl *entrypoint;
	struct exec_list old_outputs;
	struct exec_list old_inputs;
	struct exec_list new_outputs;
	struct exec_list new_inputs;

	/* map from temporary to new input */
	struct hash_table *input_map;
	};

	static void
	emit_copies(nir_builder b, struct exec_list dest_vars,
	struct exec_list *src_vars)
	{
	assert(exec_list_length(dest_vars) == exec_list_length(src_vars));

	foreach_two_lists(dest_node, dest_vars, src_node, src_vars) {
	nir_variable *dest = exec_node_data(nir_variable, dest_node, node);
	nir_variable *src = exec_node_data(nir_variable, src_node, node);

	/* No need to copy the contents of a non-fb_fetch_output output variable
	* to the temporary allocated for it, since its initial value is
	* undefined.
	*/
	if (src->data.mode == nir_var_shader_out &&
	!src->data.fb_fetch_output)
	continue;

	/* Can't copy the contents of the temporary back to a read-only
	* interface variable. The value of the temporary won't have been
	* modified by the shader anyway.
	*/
	if (dest->data.read_only)
	continue;

	nir_copy_var(b, dest, src);
	}
	}

	static void
	emit_output_copies_impl(struct lower_io_state state, nir_function_impl impl)
	{
	nir_builder b;
	nir_builder_init(&b, impl);

	if (state->shader->info.stage == MESA_SHADER_GEOMETRY) {
	/* For geometry shaders, we have to emit the output copies right
	* before each EmitVertex call.
	*/
	nir_foreach_block(block, impl) {
	nir_foreach_instr(instr, block) {
	if (instr->type != nir_instr_type_intrinsic)
	continue;

	nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
	if (intrin->intrinsic == nir_intrinsic_emit_vertex \|\|
	intrin->intrinsic == nir_intrinsic_emit_vertex_with_counter) {
	b.cursor = nir_before_instr(&intrin->instr);
	emit_copies(&b, &state->new_outputs, &state->old_outputs);
	}
	}
	}
	} else if (impl == state->entrypoint) {
	b.cursor = nir_before_block(nir_start_block(impl));
	emit_copies(&b, &state->old_outputs, &state->new_outputs);

	/* For all other shader types, we need to do the copies right before
	* the jumps to the end block.
	*/
	set_foreach(impl->end_block->predecessors, block_entry) {
	struct nir_block block = (void )block_entry->key;
	b.cursor = nir_after_block_before_jump(block);
	emit_copies(&b, &state->new_outputs, &state->old_outputs);
	}
	}
	}

	/* For fragment shader inputs, when we lower to temporaries we'll invalidate
	* interpolateAt*() because now they'll be pointing to the temporary instead
	* of the actual variable. Since the caller presumably doesn't support
	* indirect indexing of inputs, we'll need to lower something like:
	*
	* in vec4 foo[3];
	*
	* ... = interpolateAtCentroid(foo[i]);
	*
	* to a sequence of interpolations that store to our temporary, then a
	* load at the end:
	*
	* in vec4 foo[3];
	* vec4 foo_tmp[3];
	*
	* foo_tmp[0] = interpolateAtCentroid(foo[0]);
	* foo_tmp[1] = interpolateAtCentroid(foo[1]);
	* ... = foo_tmp[i];
	*/

	/*
	* Recursively emit the interpolation instructions. Here old_interp_deref
	* refers to foo[i], temp_deref is foo_tmp[0/1], and new_interp_deref is
	* foo[0/1].
	*/

	static void
	emit_interp(nir_builder b, nir_deref_instr *old_interp_deref,
	nir_deref_instr temp_deref, nir_deref_instr new_interp_deref,
	nir_intrinsic_instr *interp)
	{
	while (*old_interp_deref) {
	switch ((*old_interp_deref)->deref_type) {
	case nir_deref_type_struct:
	temp_deref =
	nir_build_deref_struct(b, temp_deref,
	(*old_interp_deref)->strct.index);
	new_interp_deref =
	nir_build_deref_struct(b, new_interp_deref,
	(*old_interp_deref)->strct.index);
	break;
	case nir_deref_type_array:
	if (nir_src_is_const((*old_interp_deref)->arr.index)) {
	temp_deref =
	nir_build_deref_array(b, temp_deref,
	(*old_interp_deref)->arr.index.ssa);
	new_interp_deref =
	nir_build_deref_array(b, new_interp_deref,
	(*old_interp_deref)->arr.index.ssa);
	break;
	} else {
	/* We have an indirect deref, so we have to emit interpolations
	* for every index. Recurse in case we have an array of arrays.
	*/
	unsigned length = glsl_get_length(temp_deref->type);
	for (unsigned i = 0; i < length; i++) {
	nir_deref_instr *new_temp =
	nir_build_deref_array_imm(b, temp_deref, i);
	nir_deref_instr *new_interp =
	nir_build_deref_array_imm(b, new_interp_deref, i);

	emit_interp(b, old_interp_deref + 1, new_temp, new_interp,
	interp);
	}

	return;
	}

	case nir_deref_type_var:
	case nir_deref_type_array_wildcard:
	case nir_deref_type_ptr_as_array:
	case nir_deref_type_cast:
	unreachable("bad deref type");
	}

	old_interp_deref++;
	}

	/* Now that we've constructed a fully-qualified deref with all the indirect
	* derefs replaced with direct ones, it's time to actually emit the new
	* interpolation instruction.
	*/

	nir_intrinsic_instr *new_interp =
	nir_intrinsic_instr_create(b->shader, interp->intrinsic);

	new_interp->src[0] = nir_src_for_ssa(&new_interp_deref->dest.ssa);
	if (interp->intrinsic == nir_intrinsic_interp_deref_at_sample \|\|
	interp->intrinsic == nir_intrinsic_interp_deref_at_offset \|\|
	interp->intrinsic == nir_intrinsic_interp_deref_at_vertex) {
	new_interp->src[1] = interp->src[1];
	}

	new_interp->num_components = interp->num_components;
	nir_ssa_dest_init(&new_interp->instr, &new_interp->dest,
	interp->dest.ssa.num_components,
	interp->dest.ssa.bit_size, NULL);

	nir_builder_instr_insert(b, &new_interp->instr);
	nir_store_deref(b, temp_deref, &new_interp->dest.ssa,
	(1 << interp->dest.ssa.num_components) - 1);
	}

	static void
	fixup_interpolation_instr(struct lower_io_state *state,
	nir_intrinsic_instr interp, nir_builder b)
	{
	nir_deref_path interp_path;
	nir_deref_path_init(&interp_path, nir_src_as_deref(interp->src[0]), NULL);

	b->cursor = nir_before_instr(&interp->instr);

	/* The original interpolation instruction should contain a deref path
	* starting with the original variable, which is now the temporary.
	*/
	nir_deref_instr *temp_root = interp_path.path[0];

	/* Fish out the newly-created input variable. */
	assert(temp_root->deref_type == nir_deref_type_var);
	struct hash_entry *entry = _mesa_hash_table_search(state->input_map,
	temp_root->var);
	assert(entry);
	nir_variable *input = entry->data;
	nir_deref_instr *input_root = nir_build_deref_var(b, input);

	/* Emit the interpolation instructions. */
	emit_interp(b, interp_path.path + 1, temp_root, input_root, interp);

	/* Now the temporary contains the interpolation results, and we can just
	* load from it. We can reuse the original deref, since it points to the
	* correct part of the temporary.
	*/
	nir_ssa_def *load = nir_load_deref(b, nir_src_as_deref(interp->src[0]));
	nir_ssa_def_rewrite_uses(&interp->dest.ssa, nir_src_for_ssa(load));
	nir_instr_remove(&interp->instr);

	nir_deref_path_finish(&interp_path);
	}

	static void
	fixup_interpolation(struct lower_io_state state, nir_function_impl impl,
	nir_builder *b)
	{
	nir_foreach_block(block, impl) {
	nir_foreach_instr_safe(instr, block) {
	if (instr->type != nir_instr_type_intrinsic)
	continue;

	nir_intrinsic_instr *interp = nir_instr_as_intrinsic(instr);

	if (interp->intrinsic == nir_intrinsic_interp_deref_at_centroid \|\|
	interp->intrinsic == nir_intrinsic_interp_deref_at_sample \|\|
	interp->intrinsic == nir_intrinsic_interp_deref_at_offset \|\|
	interp->intrinsic == nir_intrinsic_interp_deref_at_vertex) {
	fixup_interpolation_instr(state, interp, b);
	}
	}
	}
	}

	static void
	emit_input_copies_impl(struct lower_io_state state, nir_function_impl impl)
	{
	if (impl == state->entrypoint) {
	nir_builder b;
	nir_builder_init(&b, impl);
	b.cursor = nir_before_block(nir_start_block(impl));
	emit_copies(&b, &state->old_inputs, &state->new_inputs);
	if (state->shader->info.stage == MESA_SHADER_FRAGMENT)
	fixup_interpolation(state, impl, &b);
	}
	}

	static nir_variable *
	create_shadow_temp(struct lower_io_state state, nir_variable var)
	{
	nir_variable *nvar = ralloc(state->shader, nir_variable);
	memcpy(nvar, var, sizeof *nvar);
	nvar->data.cannot_coalesce = true;

	/* The original is now the temporary */
	nir_variable *temp = var;

	/* Reparent the name to the new variable */
	ralloc_steal(nvar, nvar->name);

	assert(nvar->constant_initializer == NULL && nvar->pointer_initializer == NULL);

	/* Give the original a new name with @<mode>-temp appended */
	const char *mode = (temp->data.mode == nir_var_shader_in) ? "in" : "out";
	temp->name = ralloc_asprintf(var, "%s@%s-temp", mode, nvar->name);
	temp->data.mode = nir_var_shader_temp;
	temp->data.read_only = false;
	temp->data.fb_fetch_output = false;
	temp->data.compact = false;

	return nvar;
	}

	static void
	move_variables_to_list(nir_shader *shader, nir_variable_mode mode,
	struct exec_list *dst_list)
	{
	nir_foreach_variable_with_modes_safe(var, shader, mode) {
	exec_node_remove(&var->node);
	exec_list_push_tail(dst_list, &var->node);
	}
	}

	void
	nir_lower_io_to_temporaries(nir_shader shader, nir_function_impl entrypoint,
	bool outputs, bool inputs)
	{
	struct lower_io_state state;

	if (shader->info.stage == MESA_SHADER_TESS_CTRL)
	return;

	state.shader = shader;
	state.entrypoint = entrypoint;
	state.input_map = _mesa_pointer_hash_table_create(NULL);

	exec_list_make_empty(&state.old_inputs);
	if (inputs)
	move_variables_to_list(shader, nir_var_shader_in, &state.old_inputs);

	exec_list_make_empty(&state.old_outputs);
	if (outputs)
	move_variables_to_list(shader, nir_var_shader_out, &state.old_outputs);

	exec_list_make_empty(&state.new_inputs);
	exec_list_make_empty(&state.new_outputs);

	/* Walk over all of the outputs turn each output into a temporary and
	* make a new variable for the actual output.
	*/
	nir_foreach_variable_in_list(var, &state.old_outputs) {
	nir_variable *output = create_shadow_temp(&state, var);
	exec_list_push_tail(&state.new_outputs, &output->node);
	}

	/* and same for inputs: */
	nir_foreach_variable_in_list(var, &state.old_inputs) {
	nir_variable *input = create_shadow_temp(&state, var);
	exec_list_push_tail(&state.new_inputs, &input->node);
	_mesa_hash_table_insert(state.input_map, var, input);
	}

	nir_foreach_function(function, shader) {
	if (function->impl == NULL)
	continue;

	if (inputs)
	emit_input_copies_impl(&state, function->impl);

	if (outputs)
	emit_output_copies_impl(&state, function->impl);

	nir_metadata_preserve(function->impl, nir_metadata_block_index \|
	nir_metadata_dominance);
	}

	exec_list_append(&shader->variables, &state.old_inputs);
	exec_list_append(&shader->variables, &state.old_outputs);
	exec_list_append(&shader->variables, &state.new_inputs);
	exec_list_append(&shader->variables, &state.new_outputs);

	nir_fixup_deref_modes(shader);

	_mesa_hash_table_destroy(state.input_map, NULL);
	}