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glsl/ast: Generate a more compact expression to disable execution of default case

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Instead of generating a sequence like:

    run_default = true;
    if (i == 3) // some label that appears after default
        run_default = false;
    if (i == 4) // some label that appears after default
        run_default = false;
    ...
    if (run_default) {
        ...
    }

generate something like:

    run_default = !((i == 3) || (i == 4) || ...);
    if (run_default) {
        ...
    }

This eliminates one use of conditional assignment, and it enables the
elimination of another.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
This commit is contained in:
Ian Romanick
2017-09-19 15:59:00 -05:00
parent 3e5cd2aba9
commit d5361d9f01
1 changed files with 10 additions and 21 deletions
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31
src/compiler/glsl/ast_to_hir.cpp
View File

@@ -6579,27 +6579,11 @@ ast_case_statement_list::hir(exec_list *instructions,
* if default should be chosen or not.
*/
if (!default_case.is_empty()) {
ir_rvalue *const true_val = new (state) ir_constant(true);
ir_dereference_variable *deref_run_default_var =
new(state) ir_dereference_variable(state->switch_state.run_default);
/* Choose to run default case initially, following conditional
* assignments might change this.
*/
ir_assignment *const init_var =
new(state) ir_assignment(deref_run_default_var, true_val);
instructions->push_tail(init_var);
/* Default case was the last one, no checks required. */
if (after_default.is_empty()) {
instructions->append_list(&default_case);
return NULL;
}
struct hash_entry *entry;
ir_factory body(instructions, state);
ir_expression *cmp = NULL;
hash_table_foreach(state->switch_state.labels_ht, entry) {
const struct case_label *const l = (struct case_label *) entry->data;
@@ -6613,12 +6597,17 @@ ast_case_statement_list::hir(exec_list *instructions,
? body.constant(unsigned(l->value))
: body.constant(int(l->value));
body.emit(assign(state->switch_state.run_default,
body.constant(false),
equal(cnst, state->switch_state.test_var)));
cmp = cmp == NULL
? equal(cnst, state->switch_state.test_var)
: logic_or(cmp, equal(cnst, state->switch_state.test_var));
}
}
if (cmp != NULL)
body.emit(assign(state->switch_state.run_default, logic_not(cmp)));
else
body.emit(assign(state->switch_state.run_default, body.constant(true)));
/* Append default case and all cases after it. */
instructions->append_list(&default_case);
instructions->append_list(&after_default);