[Mesa-dev] [PATCH 9/9] glsl: Track existence of default float precision in GLSL ES fragment shaders

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

This is required by the spec, and it's a bit tricky because the default
precision is scoped.  As a result, I'm slightly abusing the symbol
table.

Fixes piglit no-default-float-precision.frag tests and the piglit
default-precision-nested-scope-0[1234].frag tests that are currently on
the piglit mailing list for review.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Cc: "9.2" <mesa-stable at lists.freedesktop.org>
---
 src/glsl/ast.h          |  4 +++
 src/glsl/ast_to_hir.cpp | 68 ++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/src/glsl/ast.h b/src/glsl/ast.h
index 9b194db..335374d 100644
--- a/src/glsl/ast.h
+++ b/src/glsl/ast.h
@@ -610,6 +610,10 @@ public:
    virtual void print(void) const;
    bool has_qualifiers() const;
 
+   const struct glsl_type *glsl_type(const char **name,
+				     struct _mesa_glsl_parse_state *state)
+      const;
+
    ast_type_qualifier qualifier;
    ast_type_specifier *specifier;
 };
diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 091e0e6..8b69da4 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -1797,6 +1797,28 @@ ast_type_specifier::glsl_type(const char **name,
    return type;
 }
 
+const glsl_type *
+ast_fully_specified_type::glsl_type(const char **name,
+                                    struct _mesa_glsl_parse_state *state) const
+{
+   const struct glsl_type *type = this->specifier->glsl_type(name, state);
+
+   if (type == NULL)
+      return NULL;
+
+   if (type->base_type == GLSL_TYPE_FLOAT
+       && state->es_shader
+       && state->target == fragment_shader
+       && this->qualifier.precision == ast_precision_none
+       && state->symbols->get_variable("#default precision") == NULL) {
+      YYLTYPE loc = this->get_location();
+      _mesa_glsl_error(&loc, state,
+                       "no precision specified this scope for type `%s'",
+                       type->name);
+   }
+
+   return type;
+}
 
 /**
  * Determine whether a toplevel variable declaration declares a varying.  This
@@ -2685,7 +2707,7 @@ ast_declarator_list::hir(exec_list *instructions,
     */
    (void) this->type->specifier->hir(instructions, state);
 
-   decl_type = this->type->specifier->glsl_type(& type_name, state);
+   decl_type = this->type->glsl_type(& type_name, state);
    if (this->declarations.is_empty()) {
       /* If there is no structure involved in the program text, there are two
        * possible scenarios:
@@ -3252,7 +3274,7 @@ ast_parameter_declarator::hir(exec_list *instructions,
    const char *name = NULL;
    YYLTYPE loc = this->get_location();
 
-   type = this->type->specifier->glsl_type(& name, state);
+   type = this->type->glsl_type(& name, state);
 
    if (type == NULL) {
       if (name != NULL) {
@@ -3459,7 +3481,7 @@ ast_function::hir(exec_list *instructions,
 
    const char *return_type_name;
    const glsl_type *return_type =
-      this->return_type->specifier->glsl_type(& return_type_name, state);
+      this->return_type->glsl_type(& return_type_name, state);
 
    if (!return_type) {
       YYLTYPE loc = this->get_location();
@@ -4263,6 +4285,44 @@ ast_type_specifier::hir(exec_list *instructions,
          return NULL;
       }
 
+      if (type->base_type == GLSL_TYPE_FLOAT
+          && state->es_shader
+          && state->target == fragment_shader) {
+         /* Section 4.5.3 (Default Precision Qualifiers) of the GLSL ES 1.00
+          * spec says:
+          *
+          *     "The fragment language has no default precision qualifier for
+          *     floating point types."
+          *
+          * As a result, we have to track whether or not default precision has
+          * been specified for float in GLSL ES fragment shaders.
+          *
+          * Earlier in that same section, the spec says:
+          *
+          *     "Non-precision qualified declarations will use the precision
+          *     qualifier specified in the most recent precision statement
+          *     that is still in scope. The precision statement has the same
+          *     scoping rules as variable declarations. If it is declared
+          *     inside a compound statement, its effect stops at the end of
+          *     the innermost statement it was declared in. Precision
+          *     statements in nested scopes override precision statements in
+          *     outer scopes. Multiple precision statements for the same basic
+          *     type can appear inside the same scope, with later statements
+          *     overriding earlier statements within that scope."
+          *
+          * Default precision specifications follow the same scope rules as
+          * variables.  So, we can track the state of the default float
+          * precision in the symbol table, and the rules will just work.  This
+          * is a slight abuse of the symbol table, but it has the semantics
+          * that we want.
+          */
+         ir_variable *const junk =
+            new(state) ir_variable(type, "#default precision",
+                                   ir_var_temporary);
+
+         state->symbols->add_variable(junk);
+      }
+
       /* FINISHME: Translate precision statements into IR. */
       return NULL;
    }
@@ -4343,7 +4403,7 @@ ast_process_structure_or_interface_block(exec_list *instructions,
       }
 
       const glsl_type *decl_type =
-	 decl_list->type->specifier->glsl_type(& type_name, state);
+         decl_list->type->glsl_type(& type_name, state);
 
       foreach_list_typed (ast_declaration, decl, link,
 			  &decl_list->declarations) {
-- 
1.8.1.4