glsl: handle implicit sized arrays in ssbo

The current code disallows unsized arrays except at the end of
an SSBO but it is a bit overzealous in doing so.

struct a {
	int b[];
	int f[4];
};

is valid as long as b is implicitly sized within the shader,
i.e. it is accessed only by integer indices.

I've submitted some piglit tests to test for this.

This also has no regressions on piglit on my Haswell.
This fixes:
GL45-CTS.shader_storage_buffer_object.basic-syntax
GL45-CTS.shader_storage_buffer_object.basic-syntaxSSO

This patch moves a chunk of the linker code down, so
that we don't link the uniform blocks until after we've
merged all the variables. The logic went something like:

Removing the checks for last ssbo member unsized from
the compiler and into the linker, meant doing the check
in the link_uniform_blocks code. However to do that the
array sizing had to happen first, so we knew that the
only unsized arrays were in the last block. But array
sizing required the variable to be merged, otherwise
you'd get two different array sizes in different
version of two variables, and one would get lost
when merged. So the solution was to move array sizing
up, after variable merging, but before uniform block
visiting.

Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/src/compiler/glsl/link_uniform_blocks.cpp b/src/compiler/glsl/link_uniform_blocks.cpp
index ac415b5..3c2d13c 100644
--- a/src/compiler/glsl/link_uniform_blocks.cpp
+++ b/src/compiler/glsl/link_uniform_blocks.cpp
@@ -34,9 +34,10 @@ namespace {
 class ubo_visitor : public program_resource_visitor {
 public:
    ubo_visitor(void *mem_ctx, gl_uniform_buffer_variable *variables,
-               unsigned num_variables)
+               unsigned num_variables, struct gl_shader_program *prog)
       : index(0), offset(0), buffer_size(0), variables(variables),
-        num_variables(num_variables), mem_ctx(mem_ctx), is_array_instance(false)
+        num_variables(num_variables), mem_ctx(mem_ctx), is_array_instance(false),
+        prog(prog)
    {
       /* empty */
    }
@@ -56,6 +57,7 @@ public:
    unsigned num_variables;
    void *mem_ctx;
    bool is_array_instance;
+   struct gl_shader_program *prog;
 
 private:
    virtual void visit_field(const glsl_type *type, const char *name,
@@ -148,7 +150,13 @@ private:
        */
       const glsl_type *type_for_size = type;
       if (type->is_unsized_array()) {
-         assert(last_field);
+         if (!last_field) {
+            linker_error(prog, "unsized array `%s' definition: "
+                         "only last member of a shader storage block "
+                         "can be defined as unsized array",
+                         name);
+         }
+
          type_for_size = type->without_array();
       }
 
@@ -314,7 +322,7 @@ create_buffer_blocks(void *mem_ctx, struct gl_context *ctx,
    /* Add each variable from each uniform block to the API tracking
     * structures.
     */
-   ubo_visitor parcel(blocks, variables, num_variables);
+   ubo_visitor parcel(blocks, variables, num_variables, prog);
 
    STATIC_ASSERT(unsigned(GLSL_INTERFACE_PACKING_STD140)
                  == unsigned(ubo_packing_std140));