[Mesa-dev] [PATCH 4/5] glsl: Fix conversions in array constructors

[Chad Versace]

Array constructors obey narrower conversion rules than other constructors
[1] --- they use the implicit conversion rules [2] instead of the scalar
constructor conversions [3].  But process_array_constructor() was
incorrectly applying the broader rules.

[1] GLSL 1.50 spec, Section 5.4.4 Array Constructors, page 52 (58 of pdf)
[2] GLSL 1.50 spec, Section 4.1.10 Implicit Conversions, page 25 (31 of pdf)
[3] GLSL 1.50 spec, Section 5.4.1 Conversion, page 48 (54 of pdf)

To fix this, first check (with glsl_type::can_be_implicitly_converted_to)
if an implicit conversion is legal before performing the conversion.

Fixes:
piglit:spec/glsl-1.20/compiler/structure-and-array-operations/array-ctor-implicit-conversion-bool-float.vert
piglit:spec/glsl-1.20/compiler/structure-and-array-operations/array-ctor-implicit-conversion-bvec*-vec*.vert

v2:
    - Fix error in comment, identified by Ken.

Note: This is a candidate for the 7.10 and 7.11 branches.
CC: Ian Romanick <ian.d.romanick at intel.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Signed-off-by: Chad Versace <chad at chad-versace.us>
---
 src/glsl/ast_function.cpp |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/glsl/ast_function.cpp b/src/glsl/ast_function.cpp
index bdb73f4..8bcf48d 100644
--- a/src/glsl/ast_function.cpp
+++ b/src/glsl/ast_function.cpp
@@ -442,13 +442,21 @@ process_array_constructor(exec_list *instructions,
       ir_rvalue *ir = (ir_rvalue *) n;
       ir_rvalue *result = ir;
 
-      /* Apply implicit conversions (not the scalar constructor rules!) */
+      /* Apply implicit conversions (not the scalar constructor rules!). See
+       * the spec quote above. */
       if (constructor_type->element_type()->is_float()) {
 	 const glsl_type *desired_type =
 	    glsl_type::get_instance(GLSL_TYPE_FLOAT,
 				    ir->type->vector_elements,
 				    ir->type->matrix_columns);
-	 result = convert_component(ir, desired_type);
+	 if (result->type->can_implicitly_convert_to(desired_type)) {
+	    /* Even though convert_component() implements the constructor
+	     * conversion rules (not the implicit conversion rules), its safe
+	     * to use it here because we already checked that the implicit
+	     * conversion is legal.
+	     */
+	    result = convert_component(ir, desired_type);
+	 }
       }
 
       if (result->type != constructor_type->element_type()) {
-- 
1.7.6