| /* |
| * 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->condition) |
| return; |
| |
| 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; |
| } |