+++ /dev/null
-/*
- * Copyright © 2010 Intel Corporation
- *
- * Permission is hereby granted, free of charge, to any person obtaining a
- * constant of this software and associated documentation files (the "Software"),
- * to deal in the Software without restriction, including without limitation
- * the rights to use, constant, 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 constantright 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 CONSTANTRIGHT 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.
- */
-
-/**
- * \file opt_constant_propagation.cpp
- *
- * Tracks assignments of constants to channels of variables, and
- * usage of those constant channels with direct usage of the constants.
- *
- * This can lead to constant folding and algebraic optimizations in
- * those later expressions, while causing no increase in instruction
- * count (due to constants being generally free to load from a
- * constant push buffer or as instruction immediate values) and
- * possibly reducing register pressure.
- */
-
-#include "ir.h"
-#include "ir_visitor.h"
-#include "ir_rvalue_visitor.h"
-#include "ir_basic_block.h"
-#include "ir_optimization.h"
-#include "compiler/glsl_types.h"
-#include "util/hash_table.h"
-
-namespace {
-
-class acp_entry : public exec_node
-{
-public:
- /* override operator new from exec_node */
- DECLARE_LINEAR_ZALLOC_CXX_OPERATORS(acp_entry)
-
- acp_entry(ir_variable *var, unsigned write_mask, ir_constant *constant)
- {
- assert(var);
- assert(constant);
- this->var = var;
- this->write_mask = write_mask;
- this->constant = constant;
- this->initial_values = write_mask;
- }
-
- acp_entry(const acp_entry *src)
- {
- this->var = src->var;
- this->write_mask = src->write_mask;
- this->constant = src->constant;
- this->initial_values = src->initial_values;
- }
-
- ir_variable *var;
- ir_constant *constant;
- unsigned write_mask;
-
- /** Mask of values initially available in the constant. */
- unsigned initial_values;
-};
-
-
-class ir_constant_propagation_visitor : public ir_rvalue_visitor {
-public:
- ir_constant_propagation_visitor()
- {
- progress = false;
- killed_all = false;
- mem_ctx = ralloc_context(0);
- this->lin_ctx = linear_alloc_parent(this->mem_ctx, 0);
- this->acp = new(mem_ctx) exec_list;
- this->kills = _mesa_pointer_hash_table_create(mem_ctx);
- }
- ~ir_constant_propagation_visitor()
- {
- ralloc_free(mem_ctx);
- }
-
- virtual ir_visitor_status visit_enter(class ir_loop *);
- virtual ir_visitor_status visit_enter(class ir_function_signature *);
- virtual ir_visitor_status visit_enter(class ir_function *);
- virtual ir_visitor_status visit_leave(class ir_assignment *);
- virtual ir_visitor_status visit_enter(class ir_call *);
- virtual ir_visitor_status visit_enter(class ir_if *);
-
- void add_constant(ir_assignment *ir);
- void constant_folding(ir_rvalue **rvalue);
- void constant_propagation(ir_rvalue **rvalue);
- void kill(ir_variable *ir, unsigned write_mask);
- void handle_if_block(exec_list *instructions, hash_table *kills, bool *killed_all);
- void handle_loop(class ir_loop *, bool keep_acp);
- void handle_rvalue(ir_rvalue **rvalue);
-
- /** List of acp_entry: The available constants to propagate */
- exec_list *acp;
-
- /**
- * Hash table of killed entries: maps variables to the mask of killed channels.
- */
- hash_table *kills;
-
- bool progress;
-
- bool killed_all;
-
- void *mem_ctx;
- void *lin_ctx;
-};
-
-
-void
-ir_constant_propagation_visitor::constant_folding(ir_rvalue **rvalue)
-{
- if (this->in_assignee || *rvalue == NULL)
- return;
-
- if (ir_constant_fold(rvalue))
- this->progress = true;
-
- ir_dereference_variable *var_ref = (*rvalue)->as_dereference_variable();
- if (var_ref && !var_ref->type->is_array()) {
- ir_constant *constant =
- var_ref->constant_expression_value(ralloc_parent(var_ref));
- if (constant) {
- *rvalue = constant;
- this->progress = true;
- }
- }
-}
-
-void
-ir_constant_propagation_visitor::constant_propagation(ir_rvalue **rvalue) {
-
- if (this->in_assignee || !*rvalue)
- return;
-
- const glsl_type *type = (*rvalue)->type;
- if (!type->is_scalar() && !type->is_vector())
- return;
-
- ir_swizzle *swiz = NULL;
- ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();
- if (!deref) {
- swiz = (*rvalue)->as_swizzle();
- if (!swiz)
- return;
-
- deref = swiz->val->as_dereference_variable();
- if (!deref)
- return;
- }
-
- ir_constant_data data;
- memset(&data, 0, sizeof(data));
-
- for (unsigned int i = 0; i < type->components(); i++) {
- int channel;
- acp_entry *found = NULL;
-
- if (swiz) {
- switch (i) {
- case 0: channel = swiz->mask.x; break;
- case 1: channel = swiz->mask.y; break;
- case 2: channel = swiz->mask.z; break;
- case 3: channel = swiz->mask.w; break;
- default: assert(!"shouldn't be reached"); channel = 0; break;
- }
- } else {
- channel = i;
- }
-
- foreach_in_list(acp_entry, entry, this->acp) {
- if (entry->var == deref->var && entry->write_mask & (1 << channel)) {
- found = entry;
- break;
- }
- }
-
- if (!found)
- return;
-
- int rhs_channel = 0;
- for (int j = 0; j < 4; j++) {
- if (j == channel)
- break;
- if (found->initial_values & (1 << j))
- rhs_channel++;
- }
-
- switch (type->base_type) {
- case GLSL_TYPE_FLOAT:
- data.f[i] = found->constant->value.f[rhs_channel];
- break;
- case GLSL_TYPE_FLOAT16:
- data.f16[i] = found->constant->value.f16[rhs_channel];
- break;
- case GLSL_TYPE_DOUBLE:
- data.d[i] = found->constant->value.d[rhs_channel];
- break;
- case GLSL_TYPE_INT:
- data.i[i] = found->constant->value.i[rhs_channel];
- break;
- case GLSL_TYPE_UINT:
- data.u[i] = found->constant->value.u[rhs_channel];
- break;
- case GLSL_TYPE_INT16:
- data.i16[i] = found->constant->value.i16[rhs_channel];
- break;
- case GLSL_TYPE_UINT16:
- data.u16[i] = found->constant->value.u16[rhs_channel];
- break;
- case GLSL_TYPE_BOOL:
- data.b[i] = found->constant->value.b[rhs_channel];
- break;
- case GLSL_TYPE_UINT64:
- data.u64[i] = found->constant->value.u64[rhs_channel];
- break;
- case GLSL_TYPE_INT64:
- data.i64[i] = found->constant->value.i64[rhs_channel];
- break;
- default:
- assert(!"not reached");
- break;
- }
- }
-
- *rvalue = new(ralloc_parent(deref)) ir_constant(type, &data);
- this->progress = true;
-}
-
-void
-ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue)
-{
- constant_propagation(rvalue);
- constant_folding(rvalue);
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_enter(ir_function_signature *ir)
-{
- /* Treat entry into a function signature as a completely separate
- * block. Any instructions at global scope will be shuffled into
- * main() at link time, so they're irrelevant to us.
- */
- exec_list *orig_acp = this->acp;
- hash_table *orig_kills = this->kills;
- bool orig_killed_all = this->killed_all;
-
- this->acp = new(mem_ctx) exec_list;
- this->kills = _mesa_pointer_hash_table_create(mem_ctx);
- this->killed_all = false;
-
- visit_list_elements(this, &ir->body);
-
- this->kills = orig_kills;
- this->acp = orig_acp;
- this->killed_all = orig_killed_all;
-
- return visit_continue_with_parent;
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_leave(ir_assignment *ir)
-{
- constant_folding(&ir->rhs);
-
- if (this->in_assignee)
- return visit_continue;
-
- unsigned kill_mask = ir->write_mask;
- if (ir->lhs->as_dereference_array()) {
- /* The LHS of the assignment uses an array indexing operator (e.g. v[i]
- * = ...;). Since we only try to constant propagate vectors and
- * scalars, this means that either (a) array indexing is being used to
- * select a vector component, or (b) the variable in question is neither
- * a scalar or a vector, so we don't care about it. In the former case,
- * we want to kill the whole vector, since in general we can't predict
- * which vector component will be selected by array indexing. In the
- * latter case, it doesn't matter what we do, so go ahead and kill the
- * whole variable anyway.
- *
- * Note that if the array index is constant (e.g. v[2] = ...;), we could
- * in principle be smarter, but we don't need to, because a future
- * optimization pass will convert it to a simple assignment with the
- * correct mask.
- */
- kill_mask = ~0;
- }
- kill(ir->lhs->variable_referenced(), kill_mask);
-
- add_constant(ir);
-
- return visit_continue;
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_enter(ir_function *ir)
-{
- (void) ir;
- return visit_continue;
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_enter(ir_call *ir)
-{
- /* Do constant propagation on call parameters, but skip any out params */
- foreach_two_lists(formal_node, &ir->callee->parameters,
- actual_node, &ir->actual_parameters) {
- ir_variable *sig_param = (ir_variable *) formal_node;
- ir_rvalue *param = (ir_rvalue *) actual_node;
- if (sig_param->data.mode != ir_var_function_out
- && sig_param->data.mode != ir_var_function_inout) {
- ir_rvalue *new_param = param;
- handle_rvalue(&new_param);
- if (new_param != param)
- param->replace_with(new_param);
- else
- param->accept(this);
- }
- }
-
- /* Since we're unlinked, we don't (necssarily) know the side effects of
- * this call. So kill all copies.
- */
- acp->make_empty();
- this->killed_all = true;
-
- return visit_continue_with_parent;
-}
-
-void
-ir_constant_propagation_visitor::handle_if_block(exec_list *instructions, hash_table *kills, bool *killed_all)
-{
- exec_list *orig_acp = this->acp;
- hash_table *orig_kills = this->kills;
- bool orig_killed_all = this->killed_all;
-
- this->acp = new(mem_ctx) exec_list;
- this->kills = kills;
- this->killed_all = false;
-
- /* Populate the initial acp with a constant of the original */
- foreach_in_list(acp_entry, a, orig_acp) {
- this->acp->push_tail(new(this->lin_ctx) acp_entry(a));
- }
-
- visit_list_elements(this, instructions);
-
- *killed_all = this->killed_all;
- this->kills = orig_kills;
- this->acp = orig_acp;
- this->killed_all = orig_killed_all;
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_enter(ir_if *ir)
-{
- ir->condition->accept(this);
- handle_rvalue(&ir->condition);
-
- hash_table *new_kills = _mesa_pointer_hash_table_create(mem_ctx);
- bool then_killed_all = false;
- bool else_killed_all = false;
-
- handle_if_block(&ir->then_instructions, new_kills, &then_killed_all);
- handle_if_block(&ir->else_instructions, new_kills, &else_killed_all);
-
- if (then_killed_all || else_killed_all) {
- acp->make_empty();
- killed_all = true;
- } else {
- hash_table_foreach(new_kills, htk)
- kill((ir_variable *) htk->key, (uintptr_t) htk->data);
- }
-
- _mesa_hash_table_destroy(new_kills, NULL);
-
- /* handle_if_block() already descended into the children. */
- return visit_continue_with_parent;
-}
-
-void
-ir_constant_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
-{
- exec_list *orig_acp = this->acp;
- hash_table *orig_kills = this->kills;
- bool orig_killed_all = this->killed_all;
-
- this->acp = new(mem_ctx) exec_list;
- this->kills = _mesa_pointer_hash_table_create(mem_ctx);
- this->killed_all = false;
-
- if (keep_acp) {
- foreach_in_list(acp_entry, a, orig_acp) {
- this->acp->push_tail(new(this->lin_ctx) acp_entry(a));
- }
- }
-
- visit_list_elements(this, &ir->body_instructions);
-
- if (this->killed_all) {
- orig_acp->make_empty();
- }
-
- hash_table *new_kills = this->kills;
- this->kills = orig_kills;
- this->acp = orig_acp;
- this->killed_all = this->killed_all || orig_killed_all;
-
- hash_table_foreach(new_kills, htk) {
- kill((ir_variable *) htk->key, (uintptr_t) htk->data);
- }
-}
-
-ir_visitor_status
-ir_constant_propagation_visitor::visit_enter(ir_loop *ir)
-{
- /* Make a conservative first pass over the loop with an empty ACP set.
- * This also removes any killed entries from the original ACP set.
- */
- handle_loop(ir, false);
-
- /* Then, run it again with the real ACP set, minus any killed entries.
- * This takes care of propagating values from before the loop into it.
- */
- handle_loop(ir, true);
-
- /* already descended into the children. */
- return visit_continue_with_parent;
-}
-
-void
-ir_constant_propagation_visitor::kill(ir_variable *var, unsigned write_mask)
-{
- assert(var != NULL);
-
- /* We don't track non-vectors. */
- if (!var->type->is_vector() && !var->type->is_scalar())
- return;
-
- /* Remove any entries currently in the ACP for this kill. */
- foreach_in_list_safe(acp_entry, entry, this->acp) {
- if (entry->var == var) {
- entry->write_mask &= ~write_mask;
- if (entry->write_mask == 0)
- entry->remove();
- }
- }
-
- /* Add this writemask of the variable to the hash table of killed
- * variables in this block.
- */
- hash_entry *kill_hash_entry = _mesa_hash_table_search(this->kills, var);
- if (kill_hash_entry) {
- uintptr_t new_write_mask = ((uintptr_t) kill_hash_entry->data) | write_mask;
- kill_hash_entry->data = (void *) new_write_mask;
- return;
- }
- /* Not already in the hash table. Make new entry. */
- _mesa_hash_table_insert(this->kills, var, (void *) uintptr_t(write_mask));
-}
-
-/**
- * Adds an entry to the available constant list if it's a plain assignment
- * of a variable to a variable.
- */
-void
-ir_constant_propagation_visitor::add_constant(ir_assignment *ir)
-{
- acp_entry *entry;
-
- if (!ir->write_mask)
- return;
-
- ir_dereference_variable *deref = ir->lhs->as_dereference_variable();
- ir_constant *constant = ir->rhs->as_constant();
-
- if (!deref || !constant)
- return;
-
- /* Only do constant propagation on vectors. Constant matrices,
- * arrays, or structures would require more work elsewhere.
- */
- if (!deref->var->type->is_vector() && !deref->var->type->is_scalar())
- return;
-
- /* We can't do copy propagation on buffer variables, since the underlying
- * memory storage is shared across multiple threads we can't be sure that
- * the variable value isn't modified between this assignment and the next
- * instruction where its value is read.
- */
- if (deref->var->data.mode == ir_var_shader_storage ||
- deref->var->data.mode == ir_var_shader_shared)
- return;
-
- entry = new(this->lin_ctx) acp_entry(deref->var, ir->write_mask, constant);
- this->acp->push_tail(entry);
-}
-
-} /* unnamed namespace */
-
-/**
- * Does a constant propagation pass on the code present in the instruction stream.
- */
-bool
-do_constant_propagation(exec_list *instructions)
-{
- ir_constant_propagation_visitor v;
-
- visit_list_elements(&v, instructions);
-
- return v.progress;
-}
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