[Mesa-dev] [PATCH] glsl: look for frag data bindings with [0] tacked onto the end for arrays

[Ilia Mirkin]

The GL spec is very unclear on this point. Apparently this is discussed
without resolution in the closed Khronos bugtracker at
https://cvs.khronos.org/bugzilla/show_bug.cgi?id=7829 . The
recommendation is to allow dropping the [0] for looking up the bindings.

The approach taken in this patch is to instead tack on [0]'s for each
arrayness level of the output's type, and doing the lookup again. That
way, for

out vec4 foo[2][2][2]

we will end up looking for bindings for foo, foo[0], foo[0][0], and
foo[0][0][0], in that order of preference.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96765
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/compiler/glsl/linker.cpp | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index d963f54..9d54c2f 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2566,6 +2566,7 @@ find_available_slots(unsigned used_mask, unsigned needed_count)
 /**
  * Assign locations for either VS inputs or FS outputs
  *
+ * \param mem_ctx       Temporary ralloc context used for linking
  * \param prog          Shader program whose variables need locations assigned
  * \param constants     Driver specific constant values for the program.
  * \param target_index  Selector for the program target to receive location
@@ -2577,7 +2578,8 @@ find_available_slots(unsigned used_mask, unsigned needed_count)
  * error is emitted to the shader link log and false is returned.
  */
 bool
-assign_attribute_or_color_locations(gl_shader_program *prog,
+assign_attribute_or_color_locations(void *mem_ctx,
+                                    gl_shader_program *prog,
                                     struct gl_constants *constants,
                                     unsigned target_index)
 {
@@ -2680,16 +2682,31 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
       } else if (target_index == MESA_SHADER_FRAGMENT) {
 	 unsigned binding;
 	 unsigned index;
+         const char *name = var->name;
+         const glsl_type *type = var->type;
+
+         while (type) {
+            /* Check if there's a binding for the variable name */
+            if (prog->FragDataBindings->get(binding, name)) {
+               assert(binding >= FRAG_RESULT_DATA0);
+               var->data.location = binding;
+               var->data.is_unmatched_generic_inout = 0;
+
+               if (prog->FragDataIndexBindings->get(index, name)) {
+                  var->data.index = index;
+               }
+               break;
+            }
 
-	 if (prog->FragDataBindings->get(binding, var->name)) {
-	    assert(binding >= FRAG_RESULT_DATA0);
-	    var->data.location = binding;
-            var->data.is_unmatched_generic_inout = 0;
+            /* If not, but it's an array type, look for name[0] */
+            if (type->is_array()) {
+               name = ralloc_asprintf(mem_ctx, "%s[0]", name);
+               type = type->fields.array;
+               continue;
+            }
 
-	    if (prog->FragDataIndexBindings->get(index, var->name)) {
-	       var->data.index = index;
-	    }
-	 }
+            break;
+         }
       }
 
       /* From GL4.5 core spec, section 15.2 (Shader Execution):
@@ -4816,12 +4833,12 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       prev = i;
    }
 
-   if (!assign_attribute_or_color_locations(prog, &ctx->Const,
+   if (!assign_attribute_or_color_locations(mem_ctx, prog, &ctx->Const,
                                             MESA_SHADER_VERTEX)) {
       goto done;
    }
 
-   if (!assign_attribute_or_color_locations(prog, &ctx->Const,
+   if (!assign_attribute_or_color_locations(mem_ctx, prog, &ctx->Const,
                                             MESA_SHADER_FRAGMENT)) {
       goto done;
    }
-- 
2.7.3