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glsl: Fix loop analysis of nested loops.

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Previously, when visiting a variable dereference, loop analysis would
only consider its effect on the innermost enclosing loop.  As a
result, when encountering a loop like this:

    for (int i = 0; i < 3; i++) {
      for (int j = 0; j < 3; j++) {
        ...
        i = 2;
      }
    }

it would incorrectly conclude that the outer loop ran three times.

Fixes piglit test "vs-inner-loop-modifies-outer-loop-var.shader_test".

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Paul Berry
2013-11-28 10:48:37 -08:00
parent 2e060551bd
commit 877db5a792
2 changed files with 29 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
src/glsl/loop_analysis.cpp
View File

@@ -38,20 +38,22 @@ static ir_rvalue *get_basic_induction_increment(ir_assignment *, hash_table *);
*
* \arg in_assignee is true if the reference was on the LHS of an assignment.
*
* \arg in_conditional_code is true if the reference occurred inside an if
* statement.
* \arg in_conditional_code_or_nested_loop is true if the reference occurred
* inside an if statement or a nested loop.
*
* \arg current_assignment is the ir_assignment node that the loop variable is
* on the LHS of, if any (ignored if \c in_assignee is false).
*/
void
loop_variable::record_reference(bool in_assignee, bool in_conditional_code,
loop_variable::record_reference(bool in_assignee,
bool in_conditional_code_or_nested_loop,
ir_assignment *current_assignment)
{
if (in_assignee) {
assert(current_assignment != NULL);
this->conditional_assignment = in_conditional_code
this->conditional_or_nested_assignment =
in_conditional_code_or_nested_loop
|| current_assignment->condition != NULL;
if (this->first_assignment == NULL) {
@@ -241,14 +243,19 @@ loop_analysis::visit(ir_dereference_variable *ir)
if (this->state.is_empty())
return visit_continue;
loop_variable_state *const ls =
(loop_variable_state *) this->state.get_head();
bool nested = false;
foreach_list(node, &this->state) {
loop_variable_state *const ls = (loop_variable_state *) node;
ir_variable *var = ir->variable_referenced();
loop_variable *lv = ls->get_or_insert(var, this->in_assignee);
lv->record_reference(this->in_assignee, this->if_statement_depth > 0,
lv->record_reference(this->in_assignee,
nested || this->if_statement_depth > 0,
this->current_assignment);
nested = true;
}
return visit_continue;
}
@@ -328,7 +335,7 @@ loop_analysis::visit_leave(ir_loop *ir)
foreach_list_safe(node, &ls->variables) {
loop_variable *lv = (loop_variable *) node;
if (lv->conditional_assignment || (lv->num_assignments > 1))
if (lv->conditional_or_nested_assignment || (lv->num_assignments > 1))
continue;
/* Process the RHS of the assignment. If all of the variables
@@ -368,9 +375,10 @@ loop_analysis::visit_leave(ir_loop *ir)
assert(lv->num_assignments == 1);
assert(lv->first_assignment != NULL);
/* The assignmnet to the variable in the loop must be unconditional.
/* The assignment to the variable in the loop must be unconditional and
* not inside a nested loop.
*/
if (lv->conditional_assignment)
if (lv->conditional_or_nested_assignment)
continue;
/* Basic loop induction variables have a single assignment in the loop

12
src/glsl/loop_analysis.h
View File

@@ -167,8 +167,11 @@ public:
/** Are all variables in the RHS of the assignment loop constants? */
bool rhs_clean;
/** Is there an assignment to the variable that is conditional? */
bool conditional_assignment;
/**
* Is there an assignment to the variable that is conditional, or inside a
* nested loop?
*/
bool conditional_or_nested_assignment;
/** Reference to the first assignment to the variable in the loop body. */
ir_assignment *first_assignment;
@@ -197,7 +200,7 @@ public:
{
const bool is_const = (this->num_assignments == 0)
|| ((this->num_assignments == 1)
&& !this->conditional_assignment
&& !this->conditional_or_nested_assignment
&& !this->read_before_write
&& this->rhs_clean);
@@ -214,7 +217,8 @@ public:
return is_const;
}
void record_reference(bool in_assignee, bool in_conditional_code,
void record_reference(bool in_assignee,
bool in_conditional_code_or_nested_loop,
ir_assignment *current_assignment);
};