diff options
Diffstat (limited to 'src/glsl/linker.cpp')
| -rw-r--r-- | src/glsl/linker.cpp | 87 |
1 files changed, 72 insertions, 15 deletions
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp index c2f7f486391..a2e43073e53 100644 --- a/src/glsl/linker.cpp +++ b/src/glsl/linker.cpp @@ -1798,10 +1798,12 @@ assign_attribute_or_color_locations(gl_shader_program *prog, * active attribute array, both of which require multiple * contiguous generic attributes." * - * Previous versions of the spec contain similar language but omit - * the bit about attribute arrays. + * I think above text prohibits the aliasing of explicit and + * automatic assignments. But, aliasing is allowed in manual + * assignments of attribute locations. See below comments for + * the details. * - * Page 61 of the OpenGL 4.0 spec also says: + * From OpenGL 4.0 spec, page 61: * * "It is possible for an application to bind more than one * attribute name to the same location. This is referred to as @@ -1814,29 +1816,84 @@ assign_attribute_or_color_locations(gl_shader_program *prog, * but implementations are not required to generate an error * in this case." * - * These two paragraphs are either somewhat contradictory, or I - * don't fully understand one or both of them. - */ - /* FINISHME: The code as currently written does not support - * FINISHME: attribute location aliasing (see comment above). + * From GLSL 4.30 spec, page 54: + * + * "A program will fail to link if any two non-vertex shader + * input variables are assigned to the same location. For + * vertex shaders, multiple input variables may be assigned + * to the same location using either layout qualifiers or via + * the OpenGL API. However, such aliasing is intended only to + * support vertex shaders where each execution path accesses + * at most one input per each location. Implementations are + * permitted, but not required, to generate link-time errors + * if they detect that every path through the vertex shader + * executable accesses multiple inputs assigned to any single + * location. For all shader types, a program will fail to link + * if explicit location assignments leave the linker unable + * to find space for other variables without explicit + * assignments." + * + * From OpenGL ES 3.0 spec, page 56: + * + * "Binding more than one attribute name to the same location + * is referred to as aliasing, and is not permitted in OpenGL + * ES Shading Language 3.00 vertex shaders. LinkProgram will + * fail when this condition exists. However, aliasing is + * possible in OpenGL ES Shading Language 1.00 vertex shaders. + * This will only work if only one of the aliased attributes + * is active in the executable program, or if no path through + * the shader consumes more than one attribute of a set of + * attributes aliased to the same location. A link error can + * occur if the linker determines that every path through the + * shader consumes multiple aliased attributes, but implemen- + * tations are not required to generate an error in this case." + * + * After looking at above references from OpenGL, OpenGL ES and + * GLSL specifications, we allow aliasing of vertex input variables + * in: OpenGL 2.0 (and above) and OpenGL ES 2.0. + * + * NOTE: This is not required by the spec but its worth mentioning + * here that we're not doing anything to make sure that no path + * through the vertex shader executable accesses multiple inputs + * assigned to any single location. */ + /* Mask representing the contiguous slots that will be used by * this attribute. */ const unsigned attr = var->data.location - generic_base; const unsigned use_mask = (1 << slots) - 1; + const char *const string = (target_index == MESA_SHADER_VERTEX) + ? "vertex shader input" : "fragment shader output"; + + /* Generate a link error if the requested locations for this + * attribute exceed the maximum allowed attribute location. + */ + if (attr + slots > max_index) { + linker_error(prog, + "insufficient contiguous locations " + "available for %s `%s' %d %d %d", string, + var->name, used_locations, use_mask, attr); + return false; + } /* Generate a link error if the set of bits requested for this * attribute overlaps any previously allocated bits. */ if ((~(use_mask << attr) & used_locations) != used_locations) { - const char *const string = (target_index == MESA_SHADER_VERTEX) - ? "vertex shader input" : "fragment shader output"; - linker_error(prog, - "insufficient contiguous locations " - "available for %s `%s' %d %d %d", string, - var->name, used_locations, use_mask, attr); - return false; + if (target_index == MESA_SHADER_FRAGMENT || + (prog->IsES && prog->Version >= 300)) { + linker_error(prog, + "overlapping location is assigned " + "to %s `%s' %d %d %d\n", string, + var->name, used_locations, use_mask, attr); + return false; + } else { + linker_warning(prog, + "overlapping location is assigned " + "to %s `%s' %d %d %d\n", string, + var->name, used_locations, use_mask, attr); + } } used_locations |= (use_mask << attr); |