glsl: Simplify aggregate type inference to prepare for ARB_arrays_of_arrays.

Most of the time it is not necessary to perform type inference to
compile GLSL; the type of every expression can be inferred from the
contents of the expression itself (and previous type declarations).
The exception is aggregate initializers: their type is determined by
the LHS of the variable being assigned to.  For example, in the
statement:

   mat2 foo = { { 1, 2 }, { 3, 4 } };

the type of { 1, 2 } is only known to be vec2 (as opposed to, say,
ivec2, uvec2, int[2], or a struct) because of the fact that the result
is being assigned to a mat2.

Previous to this patch, we handled this situation by doing some type
inference during parsing: when parsing a declaration like the one
above, we would call _mesa_set_aggregate_type(), which would infer the
type of each aggregate initializer and store it in the corresponding
ast_aggregate_initializer::constructor_type field.  Since this
happened at parse time, we couldn't do the type inference using
glsl_type objects; we had to use ast_type_specifiers, which are much
more awkward to work with.  Things are about to get more complicated
when we add support for ARB_arrays_of_arrays.

This patch simplifies things by postponing the call to
_mesa_set_aggregate_type() until ast-to-hir time, when we have access
to glsl_type objects.  As a side benefit, we only need to have one
call to _mesa_set_aggregate_type() now, instead of six.

Reviewed-by: Matt Turner <mattst88@gmail.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/src/glsl/ast.h b/src/glsl/ast.h
index 76911f056d3..b24052bfd04 100644
--- a/src/glsl/ast.h
+++ b/src/glsl/ast.h
@@ -296,7 +296,16 @@ public:
       /* empty */
    }
 
-   ast_type_specifier *constructor_type;
+   /**
+    * glsl_type of the aggregate, which is inferred from the LHS of whatever
+    * the aggregate is being used to initialize.  This can't be inferred at
+    * parse time (since the parser deals with ast_type_specifiers, not
+    * glsl_types), so the parser leaves it NULL.  However, the ast-to-hir
+    * conversion code makes sure to fill it in with the appropriate type
+    * before hir() is called.
+    */
+   const glsl_type *constructor_type;
+
    virtual ir_rvalue *hir(exec_list *instructions,
                           struct _mesa_glsl_parse_state *state);
 };
@@ -978,9 +987,8 @@ _mesa_ast_array_index_to_hir(void *mem_ctx,
 			     YYLTYPE &loc, YYLTYPE &idx_loc);
 
 extern void
-_mesa_ast_set_aggregate_type(const ast_type_specifier *type,
-                             ast_expression *expr,
-                             _mesa_glsl_parse_state *state);
+_mesa_ast_set_aggregate_type(const glsl_type *type,
+                             ast_expression *expr);
 
 void
 emit_function(_mesa_glsl_parse_state *state, ir_function *f);