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glsl: Improve the local dead code optimization to eliminate unused channels.

Browse source 
Total instructions: 261582 -> 261316
135/2147 programs affected (6.3%)
36752 -> 36486 instructions in affected programs (0.7% reduction)

This excludes a tropics shader that now gets 16-wide mode and throws
off the numbers.  5 shaders are hurt: two extra MOVs in 4 tropics
shaders it looks like because we don't split register names according
to independent webs, and one gstreamer shader where it looks like
try_rewrite_rhs_to_dst() is falling on its face.

This should also help avoid a regression in VSes from idr's ARB
programs to GLSL work.
This commit is contained in:
Eric Anholt 2012-02-23 11:51:04 -08:00
parent f220f73b9c
commit 05c200bac0
1 changed files with 126 additions and 23 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

149
src/glsl/opt_dead_code_local.cpp
View file

@ -43,16 +43,20 @@ static bool debug = false;
class assignment_entry : public exec_node
{
public:
assignment_entry(ir_variable *lhs, ir_instruction *ir)
assignment_entry(ir_variable *lhs, ir_assignment *ir)
{
assert(lhs);
assert(ir);
this->lhs = lhs;
this->ir = ir;
this->available = ir->write_mask;
}
ir_variable *lhs;
ir_instruction *ir;
ir_assignment *ir;
/* bitmask of xyzw channels written that haven't been used so far. */
int available;
};
class kill_for_derefs_visitor : public ir_hierarchical_visitor {
@ -62,23 +66,52 @@ public:
this->assignments = assignments;
}
virtual ir_visitor_status visit(ir_dereference_variable *ir)
void kill_channels(ir_variable *const var, int used)
{
ir_variable *const var = ir->variable_referenced();
foreach_iter(exec_list_iterator, iter, *this->assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (entry->lhs == var) {
if (debug)
printf("kill %s\n", entry->lhs->name);
entry->remove();
if (var->type->is_scalar() || var->type->is_vector()) {
if (debug)
printf("kill %s (0x%01x - 0x%01x)\n", entry->lhs->name,
entry->available, used);
entry->available &= ~used;
if (!entry->available)
entry->remove();
} else {
if (debug)
printf("kill %s\n", entry->lhs->name);
entry->remove();
}
}
}
}
virtual ir_visitor_status visit(ir_dereference_variable *ir)
{
kill_channels(ir->var, ~0);
return visit_continue;
}
virtual ir_visitor_status visit(ir_swizzle *ir)
{
ir_dereference_variable *deref = ir->val->as_dereference_variable();
if (!deref)
return visit_continue;
int used = 0;
used |= 1 << ir->mask.x;
used |= 1 << ir->mask.y;
used |= 1 << ir->mask.z;
used |= 1 << ir->mask.w;
kill_channels(deref->var, used);
return visit_continue_with_parent;
}
private:
exec_list *assignments;
};
@ -130,21 +163,91 @@ process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
assert(var);
/* Now, check if we did a whole-variable assignment. */
if (!ir->condition && (ir->whole_variable_written() != NULL)) {
/* We did a whole-variable assignment. So, any instruction in
* the assignment list with the same LHS is dead.
*/
if (debug)
printf("looking for %s to remove\n", var->name);
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (!ir->condition) {
ir_dereference_variable *deref_var = ir->lhs->as_dereference_variable();
if (entry->lhs == var) {
if (debug)
printf("removing %s\n", var->name);
entry->ir->remove();
entry->remove();
progress = true;
/* If it's a vector type, we can do per-channel elimination of
* use of the RHS.
*/
if (deref_var && (deref_var->var->type->is_scalar() ||
deref_var->var->type->is_vector())) {
if (debug)
printf("looking for %s.0x%01x to remove\n", var->name,
ir->write_mask);
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (entry->lhs != var)
continue;
int remove = entry->available & ir->write_mask;
if (debug) {
printf("%s 0x%01x - 0x%01x = 0x%01x\n",
var->name,
entry->ir->write_mask,
remove, entry->ir->write_mask & ~remove);
}
if (remove) {
progress = true;
if (debug) {
printf("rewriting:\n ");
entry->ir->print();
printf("\n");
}
entry->ir->write_mask &= ~remove;
entry->available &= ~remove;
if (entry->ir->write_mask == 0) {
/* Delete the dead assignment. */
entry->ir->remove();
entry->remove();
} else {
void *mem_ctx = ralloc_parent(entry->ir);
/* Reswizzle the RHS arguments according to the new
* write_mask.
*/
unsigned components[4];
unsigned channels = 0;
unsigned next = 0;
for (int i = 0; i < 4; i++) {
if ((entry->ir->write_mask | remove) & (1 << i)) {
if (!(remove & (1 << i)))
components[channels++] = next;
next++;
}
}
entry->ir->rhs = new(mem_ctx) ir_swizzle(entry->ir->rhs,
components,
channels);
if (debug) {
printf("to:\n ");
entry->ir->print();
printf("\n");
}
}
}
}
} else if (ir->whole_variable_written() != NULL) {
/* We did a whole-variable assignment. So, any instruction in
* the assignment list with the same LHS is dead.
*/
if (debug)
printf("looking for %s to remove\n", var->name);
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (entry->lhs == var) {
if (debug)
printf("removing %s\n", var->name);
entry->ir->remove();
entry->remove();
progress = true;
}
}
}
}
@ -160,7 +263,7 @@ process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
printf(" %s\n", entry->lhs->name);
printf(" %s (0x%01x)\n", entry->lhs->name, entry->available);
}
}