[Mesa-dev] [PATCH 1/5] glsl: Add method glsl_type::can_implicitly_convert_to()

[Chad Versace]

This method checks if a source type is identical to or can be implicitly
converted to a target type according to the GLSL 1.20 spec, Section 4.1.10
Implicit Conversions.

The following commits use the method for a bugfix:
    glsl: Fix implicit conversions in non-constructor function calls
    glsl: Fix implicit conversions in array constructors

Note: This is a candidate for the 7.10 and 7.11 branches.
CC: Ian Romanick <ian.d.romanick at intel.com>
CC: Kenneth Graunke <kenneth at whitecape.org>
Signed-off-by: Chad Versace <chad at chad-versace.us>
---
 src/glsl/glsl_types.cpp |   30 ++++++++++++++++++++++++++++++
 src/glsl/glsl_types.h   |   40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 0 deletions(-)

diff --git a/src/glsl/glsl_types.cpp b/src/glsl/glsl_types.cpp
index a5e21bb..9cfdcab 100644
--- a/src/glsl/glsl_types.cpp
+++ b/src/glsl/glsl_types.cpp
@@ -523,3 +523,33 @@ glsl_type::component_slots() const
       return 0;
    }
 }
+
+bool
+glsl_type::can_implicitly_convert_to(const glsl_type *desired) const
+{
+   if (this == desired)
+      return true;
+
+   /* There is no conversion among matrix types. */
+   if (this->matrix_columns != 1 || desired->matrix_columns != 1)
+      return false;
+
+   switch (desired->base_type) {
+   case GLSL_TYPE_UINT:
+   case GLSL_TYPE_INT:
+   case GLSL_TYPE_BOOL:
+   case GLSL_TYPE_SAMPLER:
+   case GLSL_TYPE_STRUCT:
+   case GLSL_TYPE_VOID:
+   case GLSL_TYPE_ERROR:
+      return false;
+
+   case GLSL_TYPE_FLOAT:
+      return this->is_integer()
+	     && this->vector_elements == desired->vector_elements;
+
+   default:
+      assert(0);
+      return false;
+   }
+}
diff --git a/src/glsl/glsl_types.h b/src/glsl/glsl_types.h
index 87f57e7..6add33e 100644
--- a/src/glsl/glsl_types.h
+++ b/src/glsl/glsl_types.h
@@ -224,6 +224,46 @@ struct glsl_type {
     */
    unsigned component_slots() const;
 
+   /**
+    * \brief Can this type be implicitly converted to another?
+    *
+    * \return True if the types are identical or if this type can be converted
+    *         to \c desired according to Section 4.1.10 of the GLSL spec.
+    *
+    * \verbatim
+    * From page 25 (31 of the pdf) of the GLSL 1.50 spec, Section 4.1.10
+    * Implicit Conversions:
+    *
+    *     In some situations, an expression and its type will be implicitly
+    *     converted to a different type. The following table shows all allowed
+    *     implicit conversions:
+    *
+    *     Type of expression | Can be implicitly converted to
+    *     --------------------------------------------------
+    *     int                  float
+    *     uint
+    *
+    *     ivec2                vec2
+    *     uvec2
+    *
+    *     ivec3                vec3
+    *     uvec3
+    *
+    *     ivec4                vec4
+    *     uvec4
+    *
+    *     There are no implicit array or structure conversions. For example,
+    *     an array of int cannot be implicitly converted to an array of float.
+    *     There are no implicit conversions between signed and unsigned
+    *     integers.  When an implicit conversion is done, it is not a
+    *     re-interpretation of the expression's bit pattern, but a conversion
+    *     of its value to an equivalent value in the new type. For example,
+    *     the integer value -5 will be converted to the floating-point value
+    *     -5.0. Integer values having more bits of precision than a floating
+    *     point mantissa will lose precision when converted to float.
+    * \endverbatim
+    */
+   bool can_implicitly_convert_to(const glsl_type *desired) const;
 
    /**
     * Query whether or not a type is a scalar (non-vector and non-matrix).
-- 
1.7.6