Mesa (glsl2): glsl2: Teach copy propagation about "if" and "loop" instructions.
Eric Anholt
anholt at kemper.freedesktop.org
Tue Aug 10 00:17:04 UTC 2010
Module: Mesa
Branch: glsl2
Commit: 2dd3ae0d4ae681cd7b6b28caf35ca45965621c79
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=2dd3ae0d4ae681cd7b6b28caf35ca45965621c79
Author: Eric Anholt <eric at anholt.net>
Date: Sun Aug 8 17:56:34 2010 -0700
glsl2: Teach copy propagation about "if" and "loop" instructions.
This lets us track copies across basic block boundaries. The loop
doesn't get a filled out list of available copies into it yet, though.
glsl-fs-raytrace drops from 585 to 535 Mesa IR instructions out of the
compiler, and it appears that Yo Frankie's largest shaders decrease in
Mesa IR count by about 10% as well.
---
src/glsl/ir_copy_propagation.cpp | 248 ++++++++++++++++++++++++--------------
1 files changed, 158 insertions(+), 90 deletions(-)
diff --git a/src/glsl/ir_copy_propagation.cpp b/src/glsl/ir_copy_propagation.cpp
index 90a49d5..6c211f0 100644
--- a/src/glsl/ir_copy_propagation.cpp
+++ b/src/glsl/ir_copy_propagation.cpp
@@ -25,7 +25,7 @@
* \file ir_copy_propagation.cpp
*
* Moves usage of recently-copied variables to the previous copy of
- * the variable within basic blocks.
+ * the variable.
*
* This should reduce the number of MOV instructions in the generated
* programs unless copy propagation is also done on the LIR, and may
@@ -53,13 +53,31 @@ public:
ir_variable *rhs;
};
+
+class kill_entry : public exec_node
+{
+public:
+ kill_entry(ir_variable *var)
+ {
+ assert(var);
+ this->var = var;
+ }
+
+ ir_variable *var;
+};
+
class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
public:
- ir_copy_propagation_visitor(exec_list *acp)
+ ir_copy_propagation_visitor()
{
progress = false;
- in_lhs = false;
- this->acp = acp;
+ mem_ctx = talloc_new(0);
+ this->acp = new(mem_ctx) exec_list;
+ this->kills = new(mem_ctx) exec_list;
+ }
+ ~ir_copy_propagation_visitor()
+ {
+ talloc_free(mem_ctx);
}
virtual ir_visitor_status visit(class ir_dereference_variable *);
@@ -70,26 +88,46 @@ public:
virtual ir_visitor_status visit_enter(class ir_call *);
virtual ir_visitor_status visit_enter(class ir_if *);
- /** List of acp_entry */
+ void add_copy(ir_assignment *ir);
+ void kill(ir_variable *ir);
+ void handle_if_block(exec_list *instructions);
+
+ /** List of acp_entry: The available copies to propagate */
exec_list *acp;
- bool progress;
+ /**
+ * List of kill_entry: The variables whose values were killed in this
+ * block.
+ */
+ exec_list *kills;
- /** Currently in the LHS of an assignment? */
- bool in_lhs;
-};
+ bool progress;
+ bool killed_all;
-ir_visitor_status
-ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
-{
- (void)ir;
- return visit_continue_with_parent;
-}
+ void *mem_ctx;
+};
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)
{
- (void)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;
}
@@ -98,34 +136,33 @@ ir_copy_propagation_visitor::visit_enter(ir_assignment *ir)
{
ir_visitor_status s;
- /* Inline the rest of ir_assignment::accept(ir_hv *v), wrapping the
- * LHS part with setting in_lhs so that we can avoid copy
- * propagating into the LHS.
+ /* ir_assignment::accept(ir_hv *v), skipping the LHS so that we can
+ * avoid copy propagating into the LHS.
*
* Note that this means we won't copy propagate into the derefs of
* an array index. Oh well.
*/
- this->in_lhs = true;
- s = ir->lhs->accept(this);
- this->in_lhs = false;
- if (s != visit_continue)
- return (s == visit_continue_with_parent) ? visit_continue : s;
s = ir->rhs->accept(this);
- if (s != visit_continue)
- return (s == visit_continue_with_parent) ? visit_continue : s;
+ assert(s == visit_continue);
- if (ir->condition)
+ if (ir->condition) {
s = ir->condition->accept(this);
+ assert(s == visit_continue);
+ }
+
+ kill(ir->lhs->variable_referenced());
- return (s == visit_stop) ? s : visit_continue_with_parent;
+ add_copy(ir);
+
+ return visit_continue_with_parent;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function *ir)
{
(void) ir;
- return visit_continue_with_parent;
+ return visit_continue;
}
/**
@@ -138,14 +175,7 @@ ir_copy_propagation_visitor::visit_enter(ir_function *ir)
ir_visitor_status
ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
{
- /* Ignores the LHS. Don't want to rewrite the LHS to point at some
- * other storage!
- */
- if (this->in_lhs) {
- return visit_continue;
- }
-
- ir_variable *var = ir->variable_referenced();
+ ir_variable *var = ir->var;
foreach_iter(exec_list_iterator, iter, *this->acp) {
acp_entry *entry = (acp_entry *)iter.get();
@@ -169,43 +199,108 @@ ir_copy_propagation_visitor::visit_enter(ir_call *ir)
foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
ir_instruction *ir = (ir_instruction *)iter.get();
- if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout &&
- sig_param->mode != ir_var_uniform) {
+ if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
ir->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_copy_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 copy 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->lhs, a->rhs));
+ }
+
+ 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);
+ }
+}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_if *ir)
{
ir->condition->accept(this);
- /* Do not traverse into the body of the if-statement since that is a
- * different basic block.
- */
+ 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;
}
-static bool
-propagate_copies(ir_instruction *ir, exec_list *acp)
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
{
- ir_copy_propagation_visitor v(acp);
+ exec_list *orig_acp = this->acp;
+ exec_list *orig_kills = this->kills;
+ bool orig_killed_all = this->killed_all;
- ir->accept(&v);
+ /* 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;
- return v.progress;
+ 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);
+ }
+
+ /* already descended into the children. */
+ return visit_continue_with_parent;
}
-static void
-kill_invalidated_copies(ir_assignment *ir, exec_list *acp)
+void
+ir_copy_propagation_visitor::kill(ir_variable *var)
{
- ir_variable *var = ir->lhs->variable_referenced();
assert(var != NULL);
+ /* Remove any entries currently in the ACP for this kill. */
foreach_iter(exec_list_iterator, iter, *acp) {
acp_entry *entry = (acp_entry *)iter.get();
@@ -213,21 +308,25 @@ kill_invalidated_copies(ir_assignment *ir, exec_list *acp)
entry->remove();
}
}
+
+ /* Add the LHS variable to the list of killed variables in this block.
+ */
+ this->kills->push_tail(new(this->mem_ctx) kill_entry(var));
}
/**
* Adds an entry to the available copy list if it's a plain assignment
* of a variable to a variable.
*/
-static bool
-add_copy(void *ctx, ir_assignment *ir, exec_list *acp)
+void
+ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
{
acp_entry *entry;
if (ir->condition) {
ir_constant *condition = ir->condition->as_constant();
if (!condition || !condition->value.b[0])
- return false;
+ return;
}
ir_variable *lhs_var = ir->whole_variable_written();
@@ -241,43 +340,12 @@ add_copy(void *ctx, ir_assignment *ir, exec_list *acp)
* will clean up the mess.
*/
ir->condition = new(talloc_parent(ir)) ir_constant(false);
- return true;
+ this->progress = true;
} else {
- entry = new(ctx) acp_entry(lhs_var, rhs_var);
- acp->push_tail(entry);
+ entry = new(this->mem_ctx) acp_entry(lhs_var, rhs_var);
+ this->acp->push_tail(entry);
}
}
-
- return false;
-}
-
-static void
-copy_propagation_basic_block(ir_instruction *first,
- ir_instruction *last,
- void *data)
-{
- ir_instruction *ir;
- /* List of avaialble_copy */
- exec_list acp;
- bool *out_progress = (bool *)data;
- bool progress = false;
-
- void *ctx = talloc_new(NULL);
- for (ir = first;; ir = (ir_instruction *)ir->next) {
- ir_assignment *ir_assign = ir->as_assignment();
-
- progress = propagate_copies(ir, &acp) || progress;
-
- if (ir_assign) {
- kill_invalidated_copies(ir_assign, &acp);
-
- progress = add_copy(ctx, ir_assign, &acp) || progress;
- }
- if (ir == last)
- break;
- }
- *out_progress = progress;
- talloc_free(ctx);
}
/**
@@ -286,9 +354,9 @@ copy_propagation_basic_block(ir_instruction *first,
bool
do_copy_propagation(exec_list *instructions)
{
- bool progress = false;
+ ir_copy_propagation_visitor v;
- call_for_basic_blocks(instructions, copy_propagation_basic_block, &progress);
+ visit_list_elements(&v, instructions);
- return progress;
+ return v.progress;
}
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