Mesa (main): glsl: evaluate switch expression once

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Module: Mesa
Branch: main
Commit: bdae3c366e1b8bda26702fdbdf9e6d8fab446cb2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=bdae3c366e1b8bda26702fdbdf9e6d8fab446cb2

Author: Marcin Ślusarz <marcin.slusarz at intel.com>
Date:   Fri Aug  6 10:49:29 2021 +0200

glsl: evaluate switch expression once

v2: intialize test_val in constructor

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5185

Signed-off-by: Marcin Ślusarz <marcin.slusarz at intel.com>
Cc: mesa-stable
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12234>

---

 src/compiler/glsl/ast.h                  |  3 +++
 src/compiler/glsl/ast_to_hir.cpp         | 16 +++++++++++-----
 src/compiler/glsl/glsl_parser_extras.cpp |  1 +
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/compiler/glsl/ast.h b/src/compiler/glsl/ast.h
index 3a960c2ff32..c6b578cb894 100644
--- a/src/compiler/glsl/ast.h
+++ b/src/compiler/glsl/ast.h
@@ -1170,6 +1170,9 @@ public:
 
 protected:
    void test_to_hir(exec_list *, struct _mesa_glsl_parse_state *);
+   void eval_test_expression(exec_list *instructions,
+                             struct _mesa_glsl_parse_state *state);
+   ir_rvalue *test_val;
 };
 
 class ast_iteration_statement : public ast_node {
diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index 2ab21f2ffaa..370f6934bd4 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -6678,6 +6678,13 @@ key_contents(const void *key)
    return ((struct case_label *) key)->value;
 }
 
+void
+ast_switch_statement::eval_test_expression(exec_list *instructions,
+                                           struct _mesa_glsl_parse_state *state)
+{
+   if (test_val == NULL)
+      test_val = this->test_expression->hir(instructions, state);
+}
 
 ir_rvalue *
 ast_switch_statement::hir(exec_list *instructions,
@@ -6685,16 +6692,15 @@ ast_switch_statement::hir(exec_list *instructions,
 {
    void *ctx = state;
 
-   ir_rvalue *const test_expression =
-      this->test_expression->hir(instructions, state);
+   this->eval_test_expression(instructions, state);
 
    /* From page 66 (page 55 of the PDF) of the GLSL 1.50 spec:
     *
     *    "The type of init-expression in a switch statement must be a
     *     scalar integer."
     */
-   if (!test_expression->type->is_scalar() ||
-       !test_expression->type->is_integer_32()) {
+   if (!test_val->type->is_scalar() ||
+       !test_val->type->is_integer_32()) {
       YYLTYPE loc = this->test_expression->get_location();
 
       _mesa_glsl_error(& loc,
@@ -6807,7 +6813,7 @@ ast_switch_statement::test_to_hir(exec_list *instructions,
     */
    test_expression->set_is_lhs(true);
    /* Cache value of test expression. */
-   ir_rvalue *const test_val = test_expression->hir(instructions, state);
+   this->eval_test_expression(instructions, state);
 
    state->switch_state.test_var = new(ctx) ir_variable(test_val->type,
                                                        "switch_test_tmp",
diff --git a/src/compiler/glsl/glsl_parser_extras.cpp b/src/compiler/glsl/glsl_parser_extras.cpp
index 44c041633d2..35dd433bc89 100644
--- a/src/compiler/glsl/glsl_parser_extras.cpp
+++ b/src/compiler/glsl/glsl_parser_extras.cpp
@@ -1595,6 +1595,7 @@ ast_switch_statement::ast_switch_statement(ast_expression *test_expression,
 {
    this->test_expression = test_expression;
    this->body = body;
+   this->test_val = NULL;
 }