[Mesa-dev] [RFC PATCH V3 01/10] allow builtin functions to require parameters to be shader inputs

[Chris Forbes]

The new interpolateAt* builtins have strange restrictions on the
<interpolant> parameter.

- It must be a shader input, or an element of a shader input array.
- It must not include a swizzle.

V2: Don't abuse ir_var_mode_shader_in for this; make a new flag.

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
---
 src/glsl/ast_function.cpp | 18 ++++++++++++++++++
 src/glsl/ir.h             |  6 ++++++
 src/glsl/ir_clone.cpp     |  1 +
 3 files changed, 25 insertions(+)

diff --git a/src/glsl/ast_function.cpp b/src/glsl/ast_function.cpp
index 2707522..8730e71 100644
--- a/src/glsl/ast_function.cpp
+++ b/src/glsl/ast_function.cpp
@@ -131,6 +131,24 @@ verify_parameter_modes(_mesa_glsl_parse_state *state,
 	 return false;
       }
 
+      /* Verify that shader_in parameters are shader inputs */
+      if (formal->must_be_shader_input) {
+         ir_variable *var = actual->variable_referenced();
+         if (var && var->mode != ir_var_shader_in) {
+            _mesa_glsl_error(&loc, state,
+                             "parameter `%s` must be a shader input",
+                             formal->name);
+            return false;
+         }
+
+         if (actual->ir_type == ir_type_swizzle) {
+            _mesa_glsl_error(&loc, state,
+                             "parameter `%s` must not be swizzled",
+                             formal->name);
+            return false;
+         }
+      }
+
       /* Verify that 'out' and 'inout' actual parameters are lvalues. */
       if (formal->mode == ir_var_function_out
           || formal->mode == ir_var_function_inout) {
diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 4f775da..61dd520 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -646,6 +646,12 @@ public:
    unsigned from_named_ifc_block_array:1;
 
    /**
+    * Non-zero if the variable must be a shader input. This is useful for
+    * constraints on function parameters.
+    */
+   unsigned must_be_shader_input:1;
+
+   /**
     * \brief Layout qualifier for gl_FragDepth.
     *
     * This is not equal to \c ir_depth_layout_none if and only if this
diff --git a/src/glsl/ir_clone.cpp b/src/glsl/ir_clone.cpp
index 40ed33a..edf578b 100644
--- a/src/glsl/ir_clone.cpp
+++ b/src/glsl/ir_clone.cpp
@@ -70,6 +70,7 @@ ir_variable::clone(void *mem_ctx, struct hash_table *ht) const
    var->assigned = this->assigned;
    var->how_declared = this->how_declared;
    var->used = this->used;
+   var->must_be_shader_input = this->must_be_shader_input;
 
    var->num_state_slots = this->num_state_slots;
    if (this->state_slots) {
-- 
1.8.4.2