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authormarha <marha@users.sourceforge.net>2010-11-29 22:05:53 +0000
committermarha <marha@users.sourceforge.net>2010-11-29 22:05:53 +0000
commitfed109d6a33c0871291d1bb2f3f6b7a3d1a3e9d7 (patch)
treefa1ba494685a71e28a096990a8707680c7cb378b /mesalib/src/glsl/ir_constant_propagation.cpp
parentae340911c1ba1f98b418bd8f1a487fa4d79491b0 (diff)
parent6fda93be42ace9eeab0e82ceebb6798961c9105c (diff)
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svn merge ^/branches/released .
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diff --git a/mesalib/src/glsl/ir_constant_propagation.cpp b/mesalib/src/glsl/ir_constant_propagation.cpp
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+/*
+ * 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 ir_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 "glsl_types.h"
+
+class acp_entry : public exec_node
+{
+public:
+ 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;
+ }
+
+ ir_variable *var;
+ ir_constant *constant;
+ unsigned write_mask;
+};
+
+
+class kill_entry : public exec_node
+{
+public:
+ kill_entry(ir_variable *var, unsigned write_mask)
+ {
+ assert(var);
+ this->var = var;
+ this->write_mask = write_mask;
+ }
+
+ ir_variable *var;
+ unsigned write_mask;
+};
+
+class ir_constant_propagation_visitor : public ir_rvalue_visitor {
+public:
+ ir_constant_propagation_visitor()
+ {
+ progress = false;
+ mem_ctx = talloc_new(0);
+ this->acp = new(mem_ctx) exec_list;
+ this->kills = new(mem_ctx) exec_list;
+ }
+ ~ir_constant_propagation_visitor()
+ {
+ talloc_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 kill(ir_variable *ir, unsigned write_mask);
+ void handle_if_block(exec_list *instructions);
+ void handle_rvalue(ir_rvalue **rvalue);
+
+ /** List of acp_entry: The available constants to propagate */
+ exec_list *acp;
+
+ /**
+ * List of kill_entry: The masks of variables whose values were
+ * killed in this block.
+ */
+ exec_list *kills;
+
+ bool progress;
+
+ bool killed_all;
+
+ void *mem_ctx;
+};
+
+
+void
+ir_constant_propagation_visitor::handle_rvalue(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_iter(exec_list_iterator, iter, *this->acp) {
+ acp_entry *entry = (acp_entry *)iter.get();
+ 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->write_mask & (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_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_BOOL:
+ data.b[i] = found->constant->value.b[rhs_channel];
+ break;
+ default:
+ assert(!"not reached");
+ break;
+ }
+ }
+
+ *rvalue = new(talloc_parent(deref)) ir_constant(type, &data);
+ this->progress = true;
+}
+
+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;
+ exec_list *orig_kills = this->kills;
+ bool orig_killed_all = this->killed_all;
+
+ this->acp = new(mem_ctx) exec_list;
+ this->kills = new(mem_ctx) exec_list;
+ 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)
+{
+ if (this->in_assignee)
+ return visit_continue;
+
+ kill(ir->lhs->variable_referenced(), ir->write_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 */
+ exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator();
+ foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
+ ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
+ ir_rvalue *param = (ir_rvalue *)iter.get();
+ if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
+ ir_rvalue *new_param = param;
+ handle_rvalue(&new_param);
+ if (new_param != param)
+ param->replace_with(new_param);
+ else
+ param->accept(this);
+ }
+ sig_param_iter.next();
+ }
+
+ /* 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)
+{
+ exec_list *orig_acp = this->acp;
+ exec_list *orig_kills = this->kills;
+ bool orig_killed_all = this->killed_all;
+
+ this->acp = new(mem_ctx) exec_list;
+ this->kills = new(mem_ctx) exec_list;
+ this->killed_all = false;
+
+ /* Populate the initial acp with a constant of the original */
+ foreach_iter(exec_list_iterator, iter, *orig_acp) {
+ acp_entry *a = (acp_entry *)iter.get();
+ this->acp->push_tail(new(this->mem_ctx) acp_entry(a->var, a->write_mask,
+ a->constant));
+ }
+
+ visit_list_elements(this, instructions);
+
+ if (this->killed_all) {
+ orig_acp->make_empty();
+ }
+
+ exec_list *new_kills = this->kills;
+ this->kills = orig_kills;
+ this->acp = orig_acp;
+ this->killed_all = this->killed_all || orig_killed_all;
+
+ foreach_iter(exec_list_iterator, iter, *new_kills) {
+ kill_entry *k = (kill_entry *)iter.get();
+ kill(k->var, k->write_mask);
+ }
+}
+
+ir_visitor_status
+ir_constant_propagation_visitor::visit_enter(ir_if *ir)
+{
+ ir->condition->accept(this);
+ handle_rvalue(&ir->condition);
+
+ handle_if_block(&ir->then_instructions);
+ handle_if_block(&ir->else_instructions);
+
+ /* handle_if_block() already descended into the children. */
+ return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_constant_propagation_visitor::visit_enter(ir_loop *ir)
+{
+ exec_list *orig_acp = this->acp;
+ exec_list *orig_kills = this->kills;
+ bool orig_killed_all = this->killed_all;
+
+ /* FINISHME: For now, the initial acp for loops is totally empty.
+ * We could go through once, then go through again with the acp
+ * cloned minus the killed entries after the first run through.
+ */
+ this->acp = new(mem_ctx) exec_list;
+ this->kills = new(mem_ctx) exec_list;
+ this->killed_all = false;
+
+ visit_list_elements(this, &ir->body_instructions);
+
+ if (this->killed_all) {
+ orig_acp->make_empty();
+ }
+
+ exec_list *new_kills = this->kills;
+ this->kills = orig_kills;
+ this->acp = orig_acp;
+ this->killed_all = this->killed_all || orig_killed_all;
+
+ foreach_iter(exec_list_iterator, iter, *new_kills) {
+ kill_entry *k = (kill_entry *)iter.get();
+ kill(k->var, k->write_mask);
+ }
+
+ /* 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_iter(exec_list_iterator, iter, *this->acp) {
+ acp_entry *entry = (acp_entry *)iter.get();
+
+ if (entry->var == var) {
+ entry->write_mask &= ~write_mask;
+ if (entry->write_mask == 0)
+ entry->remove();
+ }
+ }
+
+ /* Add this writemask of the variable to the list of killed
+ * variables in this block.
+ */
+ foreach_iter(exec_list_iterator, iter, *this->kills) {
+ kill_entry *entry = (kill_entry *)iter.get();
+
+ if (entry->var == var) {
+ entry->write_mask |= write_mask;
+ return;
+ }
+ }
+ /* Not already in the list. Make new entry. */
+ this->kills->push_tail(new(this->mem_ctx) kill_entry(var, 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) {
+ ir_constant *condition = ir->condition->as_constant();
+ if (!condition || !condition->value.b[0])
+ 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;
+
+ entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant);
+ this->acp->push_tail(entry);
+}
+
+/**
+ * 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;
+}