glsl: Store a predicate for whether a built-in signature is available.

For the upcoming built-in function rewrite, we'll need to be able to
answer "Is this built-in function signature available?".

This is actually a somewhat complex question, since it depends on the
language version, GLSL vs. GLSL ES, enabled extensions, and the current
shader stage.

Storing such a set of constraints in a structure would be painful, so
instead we store a function pointer.  When creating a signature, we
simply point to a predicate that inspects _mesa_glsl_parse_state and
answers whether the signature is available in the current shader.

Unfortunately, IR reader doesn't actually know when built-in functions
are available, so this patch makes it lie and say that they're always
present.  This allows us to hook up the new functionality; it just won't
be useful until real data is populated.  In the meantime, the existing
profile mechanism ensures built-ins are available in the right places.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/glsl/ir.cpp

@@ -1579,11 +1579,13 @@ ir_variable::determine_interpolation_mode(bool flat_shade)
 }
 
 
-ir_function_signature::ir_function_signature(const glsl_type *return_type)
-   : return_type(return_type), is_defined(false), _function(NULL)
+ir_function_signature::ir_function_signature(const glsl_type *return_type,
+                                             builtin_available_predicate b)
+   : return_type(return_type), is_defined(false), builtin_info(b),
+     _function(NULL)
 {
    this->ir_type = ir_type_function_signature;
-   this->is_builtin = false;
+   this->is_builtin = builtin_info != NULL;
    this->origin = NULL;
 }
 

src/glsl/ir.h

@@ -591,6 +591,11 @@ public:
    const glsl_type *interface_type;
 };
 
+/**
+ * A function that returns whether a built-in function is available in the
+ * current shading language (based on version, ES or desktop, and extensions).
+ */
+typedef bool (*builtin_available_predicate)(const _mesa_glsl_parse_state *);
 
 /*@{*/
 /**
@@ -602,7 +607,8 @@ class ir_function_signature : public ir_instruction {
     * an ir_function.
     */
 public:
-   ir_function_signature(const glsl_type *return_type);
+   ir_function_signature(const glsl_type *return_type,
+                         builtin_available_predicate builtin_info = NULL);
 
    virtual ir_function_signature *clone(void *mem_ctx,
 					struct hash_table *ht) const;
@@ -684,6 +690,12 @@ public:
    struct exec_list body;
 
 private:
+   /**
+    * A function pointer to a predicate that answers whether a built-in
+    * function is available in the current shader.  NULL if not a built-in.
+    */
+   builtin_available_predicate builtin_info;
+
    /** Function of which this signature is one overload. */
    class ir_function *_function;
 

src/glsl/ir_clone.cpp

@@ -330,6 +330,7 @@ ir_function_signature::clone_prototype(void *mem_ctx, struct hash_table *ht) con
 
    copy->is_defined = false;
    copy->is_builtin = this->is_builtin;
+   copy->builtin_info = this->builtin_info;
    copy->origin = this;
 
    /* Clone the parameter list, but NOT the body.

src/glsl/ir_reader.cpp

@@ -211,6 +211,12 @@ ir_reader::read_function(s_expression *expr, bool skip_body)
    return added ? f : NULL;
 }
 
+static bool
+always_available(const _mesa_glsl_parse_state *)
+{
+   return true;
+}
+
 void
 ir_reader::read_function_sig(ir_function *f, s_expression *expr, bool skip_body)
 {
@@ -251,8 +257,11 @@ ir_reader::read_function_sig(ir_function *f, s_expression *expr, bool skip_body)
    ir_function_signature *sig = f->exact_matching_signature(&hir_parameters);
    if (sig == NULL && skip_body) {
       /* If scanning for prototypes, generate a new signature. */
-      sig = new(mem_ctx) ir_function_signature(return_type);
-      sig->is_builtin = true;
+      /* ir_reader doesn't know what languages support a given built-in, so
+       * just say that they're always available.  For now, other mechanisms
+       * guarantee the right built-ins are available.
+       */
+      sig = new(mem_ctx) ir_function_signature(return_type, always_available);
       f->add_signature(sig);
    } else if (sig != NULL) {
       const char *badvar = sig->qualifiers_match(&hir_parameters);