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

 /*
  * Copyright © 2014 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.
  *
  * Authors:
  *    Jason Ekstrand (jason@jlekstrand.net)
  *
  */

 #include "nir.h"
 #include "nir_builder.h"
 #include "nir_constant_expressions.h"
 #include "nir_deref.h"
 #include <math.h>

 /*
  * Implements SSA-based constant folding.
  */

 struct constant_fold_state {
    bool has_load_constant;
    bool has_indirect_load_const;
 };

 static bool
 try_fold_alu(nir_builder *b, nir_alu_instr *instr)
 {
    nir_const_value src[NIR_MAX_VEC_COMPONENTS][NIR_MAX_VEC_COMPONENTS];

    if (!instr->dest.dest.is_ssa)
       return false;

    /* In the case that any outputs/inputs have unsized types, then we need to
     * guess the bit-size. In this case, the validator ensures that all
     * bit-sizes match so we can just take the bit-size from first
     * output/input with an unsized type. If all the outputs/inputs are sized
     * then we don't need to guess the bit-size at all because the code we
     * generate for constant opcodes in this case already knows the sizes of
     * the types involved and does not need the provided bit-size for anything
     * (although it still requires to receive a valid bit-size).
     */
    unsigned bit_size = 0;
    if (!nir_alu_type_get_type_size(nir_op_infos[instr->op].output_type))
       bit_size = instr->dest.dest.ssa.bit_size;

    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
       if (!instr->src[i].src.is_ssa)
          return false;

       if (bit_size == 0 &&
           !nir_alu_type_get_type_size(nir_op_infos[instr->op].input_types[i]))
          bit_size = instr->src[i].src.ssa->bit_size;

       nir_instr *src_instr = instr->src[i].src.ssa->parent_instr;

       if (src_instr->type != nir_instr_type_load_const)
          return false;
       nir_load_const_instr* load_const = nir_instr_as_load_const(src_instr);

       for (unsigned j = 0; j < nir_ssa_alu_instr_src_components(instr, i);
            j++) {
          src[i][j] = load_const->value[instr->src[i].swizzle[j]];
       }

       /* We shouldn't have any source modifiers in the optimization loop. */
       assert(!instr->src[i].abs && !instr->src[i].negate);
    }

    if (bit_size == 0)
       bit_size = 32;

    /* We shouldn't have any saturate modifiers in the optimization loop. */
    assert(!instr->dest.saturate);

    nir_const_value dest[NIR_MAX_VEC_COMPONENTS];
    nir_const_value *srcs[NIR_MAX_VEC_COMPONENTS];
    memset(dest, 0, sizeof(dest));
    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; ++i)
       srcs[i] = src[i];
    nir_eval_const_opcode(instr->op, dest, instr->dest.dest.ssa.num_components,
                          bit_size, srcs,
                          b->shader->info.float_controls_execution_mode);

    b->cursor = nir_before_instr(&instr->instr);
    nir_ssa_def *imm = nir_build_imm(b, instr->dest.dest.ssa.num_components,
                                        instr->dest.dest.ssa.bit_size,
                                        dest);
    nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, nir_src_for_ssa(imm));
    nir_instr_remove(&instr->instr);

    ralloc_free(instr);

    return true;
 }

 static nir_const_value *
 const_value_for_deref(nir_deref_instr *deref)
 {
    if (deref->mode != nir_var_mem_constant)
       return NULL;

    nir_deref_path path;
    nir_deref_path_init(&path, deref, NULL);
    if (path.path[0]->deref_type != nir_deref_type_var)
       goto fail;

    nir_variable *var = path.path[0]->var;
    assert(var->data.mode == nir_var_mem_constant);
    if (var->constant_initializer == NULL)
       goto fail;

    nir_constant *c = var->constant_initializer;
    nir_const_value *v = NULL; /* Vector value for array-deref-of-vec */

    for (unsigned i = 1; path.path[i] != NULL; i++) {
       nir_deref_instr *p = path.path[i];
       switch (p->deref_type) {
       case nir_deref_type_var:
          unreachable("Deref paths can only start with a var deref");

       case nir_deref_type_array: {
          assert(v == NULL);
          if (!nir_src_is_const(p->arr.index))
             goto fail;

          uint64_t idx = nir_src_as_uint(p->arr.index);
          if (c->num_elements > 0) {
             assert(glsl_type_is_array(path.path[i-1]->type));
             if (idx >= c->num_elements)
                goto fail;
             c = c->elements[idx];
          } else {
             assert(glsl_type_is_vector(path.path[i-1]->type));
             assert(glsl_type_is_scalar(p->type));
             if (idx >= NIR_MAX_VEC_COMPONENTS)
                goto fail;
             v = &c->values[idx];
          }
          break;
       }

       case nir_deref_type_struct:
          assert(glsl_type_is_struct(path.path[i-1]->type));
          assert(v == NULL && c->num_elements > 0);
          if (p->strct.index >= c->num_elements)
             goto fail;
          c = c->elements[p->strct.index];
          break;

       default:
          goto fail;
       }
    }

    /* We have to have ended at a vector */
    assert(c->num_elements == 0);
    return v ? v : c->values;

 fail:
    nir_deref_path_finish(&path);
    return NULL;
 }

 static bool
 try_fold_intrinsic(nir_builder *b, nir_intrinsic_instr *instr,
                    struct constant_fold_state *state)
 {
    bool progress = false;

    if ((instr->intrinsic == nir_intrinsic_demote_if ||
         instr->intrinsic == nir_intrinsic_discard_if ||
         instr->intrinsic == nir_intrinsic_terminate_if) &&
        nir_src_is_const(instr->src[0])) {
       if (nir_src_as_bool(instr->src[0])) {
          b->cursor = nir_before_instr(&instr->instr);
          nir_intrinsic_op op;
          switch (instr->intrinsic) {
          case nir_intrinsic_discard_if:
             op = nir_intrinsic_discard;
             break;
          case nir_intrinsic_demote_if:
             op = nir_intrinsic_demote;
             break;
          case nir_intrinsic_terminate_if:
             op = nir_intrinsic_terminate;
             break;
          default:
             unreachable("invalid intrinsic");
          }
          nir_intrinsic_instr *new_instr =
             nir_intrinsic_instr_create(b->shader, op);
          nir_builder_instr_insert(b, &new_instr->instr);
       }
       nir_instr_remove(&instr->instr);
       progress = true;
    } else if (instr->intrinsic == nir_intrinsic_load_deref) {
       nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
       nir_const_value *v = const_value_for_deref(deref);
       if (v) {
          b->cursor = nir_before_instr(&instr->instr);
          nir_ssa_def *val = nir_build_imm(b, instr->dest.ssa.num_components,
                                              instr->dest.ssa.bit_size, v);
          nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(val));
          nir_instr_remove(&instr->instr);
          progress = true;
       }
    } else if (instr->intrinsic == nir_intrinsic_load_constant) {
       state->has_load_constant = true;

       if (!nir_src_is_const(instr->src[0])) {
          state->has_indirect_load_const = true;
          return progress;
       }

       unsigned offset = nir_src_as_uint(instr->src[0]);
       unsigned base = nir_intrinsic_base(instr);
       unsigned range = nir_intrinsic_range(instr);
       assert(base + range <= b->shader->constant_data_size);

       b->cursor = nir_before_instr(&instr->instr);
       nir_ssa_def *val;
       if (offset >= range) {
          val = nir_ssa_undef(b, instr->dest.ssa.num_components,
                                 instr->dest.ssa.bit_size);
       } else {
          nir_const_value imm[NIR_MAX_VEC_COMPONENTS];
          memset(imm, 0, sizeof(imm));
          uint8_t *data = (uint8_t*)b->shader->constant_data + base;
          for (unsigned i = 0; i < instr->num_components; i++) {
             unsigned bytes = instr->dest.ssa.bit_size / 8;
             bytes = MIN2(bytes, range - offset);

             memcpy(&imm[i].u64, data + offset, bytes);
             offset += bytes;
          }
          val = nir_build_imm(b, instr->dest.ssa.num_components,
                                 instr->dest.ssa.bit_size, imm);
       }
       nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(val));
       nir_instr_remove(&instr->instr);
       progress = true;
    }

    return progress;
 }

 static bool
 try_fold_instr(nir_builder *b, nir_instr *instr, void *_state)
 {
    switch (instr->type) {
    case nir_instr_type_alu:
       return try_fold_alu(b, nir_instr_as_alu(instr));
    case nir_instr_type_intrinsic:
       return try_fold_intrinsic(b, nir_instr_as_intrinsic(instr), _state);
    default:
       /* Don't know how to constant fold */
       return false;
    }
 }

 bool
 nir_opt_constant_folding(nir_shader *shader)
 {
    struct constant_fold_state state;
    state.has_load_constant = false;
    state.has_indirect_load_const = false;

    bool progress = nir_shader_instructions_pass(shader, try_fold_instr,
                                                 nir_metadata_block_index |
                                                 nir_metadata_dominance,
                                                 &state);

    /* This doesn't free the constant data if there are no constant loads because
     * the data might still be used but the loads have been lowered to load_ubo
     */
    if (state.has_load_constant && !state.has_indirect_load_const &&
        shader->constant_data_size) {
       ralloc_free(shader->constant_data);
       shader->constant_data = NULL;
       shader->constant_data_size = 0;
    }

    return progress;
 }
	/*
	* Copyright © 2014 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.
	*
	* Authors:
	* Jason Ekstrand (jason@jlekstrand.net)
	*
	*/

	#include "nir.h"
	#include "nir_builder.h"
	#include "nir_constant_expressions.h"
	#include "nir_deref.h"
	#include <math.h>

	/*
	* Implements SSA-based constant folding.
	*/

	struct constant_fold_state {
	bool has_load_constant;
	bool has_indirect_load_const;
	};

	static bool
	try_fold_alu(nir_builder b, nir_alu_instr instr)
	{
	nir_const_value src[NIR_MAX_VEC_COMPONENTS][NIR_MAX_VEC_COMPONENTS];

	if (!instr->dest.dest.is_ssa)
	return false;

	/* In the case that any outputs/inputs have unsized types, then we need to
	* guess the bit-size. In this case, the validator ensures that all
	* bit-sizes match so we can just take the bit-size from first
	* output/input with an unsized type. If all the outputs/inputs are sized
	* then we don't need to guess the bit-size at all because the code we
	* generate for constant opcodes in this case already knows the sizes of
	* the types involved and does not need the provided bit-size for anything
	* (although it still requires to receive a valid bit-size).
	*/
	unsigned bit_size = 0;
	if (!nir_alu_type_get_type_size(nir_op_infos[instr->op].output_type))
	bit_size = instr->dest.dest.ssa.bit_size;

	for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
	if (!instr->src[i].src.is_ssa)
	return false;

	if (bit_size == 0 &&
	!nir_alu_type_get_type_size(nir_op_infos[instr->op].input_types[i]))
	bit_size = instr->src[i].src.ssa->bit_size;

	nir_instr *src_instr = instr->src[i].src.ssa->parent_instr;

	if (src_instr->type != nir_instr_type_load_const)
	return false;
	nir_load_const_instr* load_const = nir_instr_as_load_const(src_instr);

	for (unsigned j = 0; j < nir_ssa_alu_instr_src_components(instr, i);
	j++) {
	src[i][j] = load_const->value[instr->src[i].swizzle[j]];
	}

	/* We shouldn't have any source modifiers in the optimization loop. */
	assert(!instr->src[i].abs && !instr->src[i].negate);
	}

	if (bit_size == 0)
	bit_size = 32;

	/* We shouldn't have any saturate modifiers in the optimization loop. */
	assert(!instr->dest.saturate);

	nir_const_value dest[NIR_MAX_VEC_COMPONENTS];
	nir_const_value *srcs[NIR_MAX_VEC_COMPONENTS];
	memset(dest, 0, sizeof(dest));
	for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; ++i)
	srcs[i] = src[i];
	nir_eval_const_opcode(instr->op, dest, instr->dest.dest.ssa.num_components,
	bit_size, srcs,
	b->shader->info.float_controls_execution_mode);

	b->cursor = nir_before_instr(&instr->instr);
	nir_ssa_def *imm = nir_build_imm(b, instr->dest.dest.ssa.num_components,
	instr->dest.dest.ssa.bit_size,
	dest);
	nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, nir_src_for_ssa(imm));
	nir_instr_remove(&instr->instr);

	ralloc_free(instr);

	return true;
	}

	static nir_const_value *
	const_value_for_deref(nir_deref_instr *deref)
	{
	if (deref->mode != nir_var_mem_constant)
	return NULL;

	nir_deref_path path;
	nir_deref_path_init(&path, deref, NULL);
	if (path.path[0]->deref_type != nir_deref_type_var)
	goto fail;

	nir_variable *var = path.path[0]->var;
	assert(var->data.mode == nir_var_mem_constant);
	if (var->constant_initializer == NULL)
	goto fail;

	nir_constant *c = var->constant_initializer;
	nir_const_value v = NULL; / Vector value for array-deref-of-vec */

	for (unsigned i = 1; path.path[i] != NULL; i++) {
	nir_deref_instr *p = path.path[i];
	switch (p->deref_type) {
	case nir_deref_type_var:
	unreachable("Deref paths can only start with a var deref");

	case nir_deref_type_array: {
	assert(v == NULL);
	if (!nir_src_is_const(p->arr.index))
	goto fail;

	uint64_t idx = nir_src_as_uint(p->arr.index);
	if (c->num_elements > 0) {
	assert(glsl_type_is_array(path.path[i-1]->type));
	if (idx >= c->num_elements)
	goto fail;
	c = c->elements[idx];
	} else {
	assert(glsl_type_is_vector(path.path[i-1]->type));
	assert(glsl_type_is_scalar(p->type));
	if (idx >= NIR_MAX_VEC_COMPONENTS)
	goto fail;
	v = &c->values[idx];
	}
	break;
	}

	case nir_deref_type_struct:
	assert(glsl_type_is_struct(path.path[i-1]->type));
	assert(v == NULL && c->num_elements > 0);
	if (p->strct.index >= c->num_elements)
	goto fail;
	c = c->elements[p->strct.index];
	break;

	default:
	goto fail;
	}
	}

	/* We have to have ended at a vector */
	assert(c->num_elements == 0);
	return v ? v : c->values;

	fail:
	nir_deref_path_finish(&path);
	return NULL;
	}

	static bool
	try_fold_intrinsic(nir_builder b, nir_intrinsic_instr instr,
	struct constant_fold_state *state)
	{
	bool progress = false;

	if ((instr->intrinsic == nir_intrinsic_demote_if \|\|
	instr->intrinsic == nir_intrinsic_discard_if \|\|
	instr->intrinsic == nir_intrinsic_terminate_if) &&
	nir_src_is_const(instr->src[0])) {
	if (nir_src_as_bool(instr->src[0])) {
	b->cursor = nir_before_instr(&instr->instr);
	nir_intrinsic_op op;
	switch (instr->intrinsic) {
	case nir_intrinsic_discard_if:
	op = nir_intrinsic_discard;
	break;
	case nir_intrinsic_demote_if:
	op = nir_intrinsic_demote;
	break;
	case nir_intrinsic_terminate_if:
	op = nir_intrinsic_terminate;
	break;
	default:
	unreachable("invalid intrinsic");
	}
	nir_intrinsic_instr *new_instr =
	nir_intrinsic_instr_create(b->shader, op);
	nir_builder_instr_insert(b, &new_instr->instr);
	}
	nir_instr_remove(&instr->instr);
	progress = true;
	} else if (instr->intrinsic == nir_intrinsic_load_deref) {
	nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
	nir_const_value *v = const_value_for_deref(deref);
	if (v) {
	b->cursor = nir_before_instr(&instr->instr);
	nir_ssa_def *val = nir_build_imm(b, instr->dest.ssa.num_components,
	instr->dest.ssa.bit_size, v);
	nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(val));
	nir_instr_remove(&instr->instr);
	progress = true;
	}
	} else if (instr->intrinsic == nir_intrinsic_load_constant) {
	state->has_load_constant = true;

	if (!nir_src_is_const(instr->src[0])) {
	state->has_indirect_load_const = true;
	return progress;
	}

	unsigned offset = nir_src_as_uint(instr->src[0]);
	unsigned base = nir_intrinsic_base(instr);
	unsigned range = nir_intrinsic_range(instr);
	assert(base + range <= b->shader->constant_data_size);

	b->cursor = nir_before_instr(&instr->instr);
	nir_ssa_def *val;
	if (offset >= range) {
	val = nir_ssa_undef(b, instr->dest.ssa.num_components,
	instr->dest.ssa.bit_size);
	} else {
	nir_const_value imm[NIR_MAX_VEC_COMPONENTS];
	memset(imm, 0, sizeof(imm));
	uint8_t data = (uint8_t)b->shader->constant_data + base;
	for (unsigned i = 0; i < instr->num_components; i++) {
	unsigned bytes = instr->dest.ssa.bit_size / 8;
	bytes = MIN2(bytes, range - offset);

	memcpy(&imm[i].u64, data + offset, bytes);
	offset += bytes;
	}
	val = nir_build_imm(b, instr->dest.ssa.num_components,
	instr->dest.ssa.bit_size, imm);
	}
	nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(val));
	nir_instr_remove(&instr->instr);
	progress = true;
	}

	return progress;
	}

	static bool
	try_fold_instr(nir_builder b, nir_instr instr, void *_state)
	{
	switch (instr->type) {
	case nir_instr_type_alu:
	return try_fold_alu(b, nir_instr_as_alu(instr));
	case nir_instr_type_intrinsic:
	return try_fold_intrinsic(b, nir_instr_as_intrinsic(instr), _state);
	default:
	/* Don't know how to constant fold */
	return false;
	}
	}

	bool
	nir_opt_constant_folding(nir_shader *shader)
	{
	struct constant_fold_state state;
	state.has_load_constant = false;
	state.has_indirect_load_const = false;

	bool progress = nir_shader_instructions_pass(shader, try_fold_instr,
	nir_metadata_block_index \|
	nir_metadata_dominance,
	&state);

	/* This doesn't free the constant data if there are no constant loads because
	* the data might still be used but the loads have been lowered to load_ubo
	*/
	if (state.has_load_constant && !state.has_indirect_load_const &&
	shader->constant_data_size) {
	ralloc_free(shader->constant_data);
	shader->constant_data = NULL;
	shader->constant_data_size = 0;
	}

	return progress;
	}