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glsl: Stop tree grafting if a variable is overwritten as an 'out' param.

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While reviewing some compiler cleanups I'd sent out, Paul noticed that
tree grafting wasn't taking "out" parameters into account.

Further investigation revealed that it isn't strictly necessary: ir_call
ends basic blocks, and tree grafting currently only operates on basic
blocks.  So calls already kill grafts.

However, just to be safe, this patch makes "out" parameters explicitly
kill grafts.  Paul and I both prefer this.  It's a bit clearer.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
This commit is contained in:
Kenneth Graunke 2011-09-22 15:04:56 -07:00
parent f8377b411d
commit 3c22e35165
1 changed files with 29 additions and 12 deletions
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41
src/glsl/opt_tree_grafting.cpp
View file

@ -76,6 +76,8 @@ public:
virtual ir_visitor_status visit_enter(class ir_swizzle *);
virtual ir_visitor_status visit_enter(class ir_texture *);
ir_visitor_status check_graft(ir_instruction *ir, ir_variable *var);
bool do_graft(ir_rvalue **rvalue);
bool progress;
@ -148,6 +150,28 @@ ir_tree_grafting_visitor::visit_enter(ir_loop *ir)
return visit_stop;
}
/**
* Check if we can continue grafting after writing to a variable. If the
* expression we're trying to graft references the variable, we must stop.
*
* \param ir An instruction that writes to a variable.
* \param var The variable being updated.
*/
ir_visitor_status
ir_tree_grafting_visitor::check_graft(ir_instruction *ir, ir_variable *var)
{
if (dereferences_variable(this->graft_assign->rhs, var)) {
if (debug) {
printf("graft killed by: ");
ir->print();
printf("\n");
}
return visit_stop;
}
return visit_continue;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_leave(ir_assignment *ir)
{
@ -158,17 +182,7 @@ ir_tree_grafting_visitor::visit_leave(ir_assignment *ir)
/* If this assignment updates a variable used in the assignment
* we're trying to graft, then we're done.
*/
if (dereferences_variable(this->graft_assign->rhs,
ir->lhs->variable_referenced())) {
if (debug) {
printf("graft killed by: ");
ir->print();
printf("\n");
}
return visit_stop;
}
return visit_continue;
return check_graft(ir, ir->lhs->variable_referenced());
}
ir_visitor_status
@ -195,8 +209,11 @@ ir_tree_grafting_visitor::visit_enter(ir_call *ir)
ir_rvalue *ir = (ir_rvalue *)iter.get();
ir_rvalue *new_ir = ir;
if (sig_param->mode != ir_var_in && sig_param->mode != ir_var_const_in)
if (sig_param->mode != ir_var_in && sig_param->mode != ir_var_const_in) {
if (check_graft(ir, sig_param) == visit_stop)
return visit_stop;
continue;
}
if (do_graft(&new_ir)) {
ir->replace_with(new_ir);