[Mesa-dev] [PATCH] glsl: handle a switch where default is in the middle of cases

[Tapani Pälli]

This fixes following tests in es3conform:

   shaders.switch.default_not_last_dynamic_vertex
   shaders.switch.default_not_last_dynamic_fragment

and makes following tests in Piglit pass:

   glsl-1.30/execution/switch/fs-default-notlast-fallthrough
   glsl-1.30/execution/switch/fs-default_notlast

No Piglit regressions.

Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
---
 src/glsl/ast_to_hir.cpp       | 88 +++++++++++++++++++++++++++++++++++++++++--
 src/glsl/glsl_parser_extras.h |  3 ++
 2 files changed, 88 insertions(+), 3 deletions(-)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 132a955..0073768 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -4503,6 +4503,12 @@ ast_switch_statement::hir(exec_list *instructions,
    instructions->push_tail(new(ctx) ir_assignment(deref_is_break_var,
                                                   is_break_val));
 
+   state->switch_state.run_default =
+      new(ctx) ir_variable(glsl_type::bool_type,
+                             "run_default_tmp",
+                             ir_var_temporary);
+   instructions->push_tail(state->switch_state.run_default);
+
    /* Cache test expression.
     */
    test_to_hir(instructions, state);
@@ -4557,8 +4563,76 @@ ir_rvalue *
 ast_case_statement_list::hir(exec_list *instructions,
                              struct _mesa_glsl_parse_state *state)
 {
-   foreach_list_typed (ast_case_statement, case_stmt, link, & this->cases)
-      case_stmt->hir(instructions, state);
+   exec_list default_case, after_default, tmp;
+
+   foreach_list_typed (ast_case_statement, case_stmt, link, & this->cases) {
+      case_stmt->hir(&tmp, state);
+
+      /* Default case. */
+      if (state->switch_state.previous_default && default_case.is_empty()) {
+         default_case.append_list(&tmp);
+         continue;
+      }
+
+      /* If default case found, append 'after_default' list. */
+      if (!default_case.is_empty())
+         after_default.append_list(&tmp);
+      else
+         instructions->append_list(&tmp);
+   }
+
+   /* Handle the default case. This is done here because default might not be
+    * the last case. We need to add checks against following cases first to see
+    * if default should be chosen or not.
+    */
+   if (!default_case.is_empty()) {
+
+      /* Default case was the last one, no checks required. */
+      if (after_default.is_empty()) {
+         instructions->append_list(&default_case);
+         return NULL;
+      }
+
+      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 initially, following conditions might
+       * change this
+       */
+      ir_assignment *const init_var =
+         new(state) ir_assignment(deref_run_default_var, true_val);
+      instructions->push_tail(init_var);
+
+      foreach_list(n, &after_default) {
+         ir_instruction *ir = (ir_instruction *) n;
+         ir_assignment *assign = ir->as_assignment();
+
+         if (!assign)
+            continue;
+
+         /* Clone the check between case label and init expression. */
+         ir_expression *exp = (ir_expression*) assign->condition;
+         ir_expression *clone = exp->clone(state, NULL);
+
+         /* If condition is true we should not run default case. */
+         ir_if *const default_if = new(state) ir_if(clone);
+         instructions->push_tail(default_if);
+
+         ir_dereference_variable *deref_var =
+            new(state) ir_dereference_variable(state->switch_state.run_default);
+         ir_rvalue *const false_val = new (state) ir_constant(false);
+
+         ir_assignment *const set_false =
+            new(state) ir_assignment(deref_var, false_val);
+
+         default_if->then_instructions.push_tail(set_false);
+      }
+
+      /* Append default case and all cases after it. */
+      instructions->append_list(&default_case);
+      instructions->append_list(&after_default);
+   }
 
    /* Case statements do not have r-values. */
    return NULL;
@@ -4718,9 +4792,17 @@ ast_case_label::hir(exec_list *instructions,
       }
       state->switch_state.previous_default = this;
 
+      /* Set fallthru condition on 'run_default' bool. */
+      ir_dereference_variable *deref_run_default =
+         new(ctx) ir_dereference_variable(state->switch_state.run_default);
+      ir_rvalue *const cond_true = new(ctx) ir_constant(true);
+      ir_expression *test_cond = new(ctx) ir_expression(ir_binop_all_equal,
+                                                        cond_true,
+                                                        deref_run_default);
+
       /* Set falltrhu state. */
       ir_assignment *set_fallthru =
-         new(ctx) ir_assignment(deref_fallthru_var, true_val);
+         new(ctx) ir_assignment(deref_fallthru_var, true_val, test_cond);
 
       instructions->push_tail(set_fallthru);
    }
diff --git a/src/glsl/glsl_parser_extras.h b/src/glsl/glsl_parser_extras.h
index a59090f..de23d33 100644
--- a/src/glsl/glsl_parser_extras.h
+++ b/src/glsl/glsl_parser_extras.h
@@ -43,6 +43,9 @@ struct glsl_switch_state {
    ir_variable *is_break_var;
    class ast_switch_statement *switch_nesting_ast;
 
+   /** Used to set condition if 'default' label should be chosen. */
+   ir_variable *run_default;
+
    /** Table of constant values already used in case labels */
    struct hash_table *labels_ht;
    class ast_case_label *previous_default;
-- 
1.8.3.1