[Mesa-dev] [PATCH 2/2] glsl: Ensure that sampler declarations are always uniform or "in" parameters.

[Paul Berry]

This brings us into compliance with page 17 (page 22 of the PDF) of
the GLSL 1.20 spec:

    "[Sampler types] can only be declared as function parameters or
    uniform variables (see Section 4.3.5 "Uniform"). ... [Samplers]
    cannot be used as out or inout function parameters."

The spec isn't explicit about whether this rule applies to
structs/arrays containing shaders, but the intent seems to be to
ensure that it can always be determined at compile time which sampler
is being used in each texture lookup.  So to avoid creating a
loophole, the rule needs to apply to structs/arrays containing shaders
as well.

Fixes piglit tests spec/glsl-1.10/compiler/samplers/*.frag, and fixes
bug 38987.
---
 src/glsl/ast_to_hir.cpp |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 2e54e8c..2312c29 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -2704,6 +2704,17 @@ ast_declarator_list::hir(exec_list *instructions,
 						       : "and integer");
       }
 
+      /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
+       *
+       *    "[Sampler types] can only be declared as function
+       *    parameters or uniform variables (see Section 4.3.5
+       *    "Uniform")".
+       */
+      if (var_type->contains_sampler() &&
+          !this->type->qualifier.flags.q.uniform) {
+         _mesa_glsl_error(&loc, state, "samplers must be declared uniform");
+      }
+
       /* Process the initializer and add its instructions to a temporary
        * list.  This list will be added to the instruction stream (below) after
        * the declaration is added.  This is done because in some cases (such as
@@ -2864,6 +2875,18 @@ ast_parameter_declarator::hir(exec_list *instructions,
     */
    apply_type_qualifier_to_variable(& this->type->qualifier, var, state, & loc);
 
+   /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
+    *
+    *    "Samplers cannot be treated as l-values; hence cannot be used
+    *    as out or inout function parameters, nor can they be assigned
+    *    into."
+    */
+   if ((var->mode == ir_var_inout || var->mode == ir_var_out)
+       && type->contains_sampler()) {
+      _mesa_glsl_error(&loc, state, "out and inout parameters cannot contain samplers");
+      type = glsl_type::error_type;
+   }
+
    instructions->push_tail(var);
 
    /* Parameter declarations do not have r-values.
@@ -2992,6 +3015,18 @@ ast_function::hir(exec_list *instructions,
 		       "function `%s' return type has qualifiers", name);
    }
 
+   /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
+    *
+    *    "[Sampler types] can only be declared as function parameters
+    *    or uniform variables (see Section 4.3.5 "Uniform")".
+    */
+   if (return_type->contains_sampler()) {
+      YYLTYPE loc = this->get_location();
+      _mesa_glsl_error(&loc, state,
+                       "function `%s' return type can't contain a sampler",
+                       name);
+   }
+
    /* Verify that this function's signature either doesn't match a previously
     * seen signature for a function with the same name, or, if a match is found,
     * that the previously seen signature does not have an associated definition.
-- 
1.7.6