linker: Check that initializers for global variables match

This requires tracking a couple extra fields in ir_variable:

 * A flag to indicate that a variable had an initializer.

 * For non-const variables, a field to track the constant value of the
   variable's initializer.

For variables non-constant initalizers, ir_variable::has_initializer
will be true, but ir_variable::constant_initializer will be NULL.  The
linker can use the values of these fields to check adherence to the
GLSL 4.20 rules for shared global variables:

    "If a shared global has multiple initializers, the initializers
    must all be constant expressions, and they must all have the same
    value. Otherwise, a link error will result. (A shared global
    having only one initializer does not require that initializer to
    be a constant expression.)"

Previous to 4.20 the GLSL spec simply said that initializers must have
the same value.  In this case of non-constant initializers, this was
impossible to determine.  As a result, no vendor actually implemented
that behavior.  The 4.20 behavior matches the behavior of NVIDIA's
shipping implementations.

NOTE: This is candidate for the 7.11 branch.  This patch also needs
the preceding patch "glsl: Refactor generate_ARB_draw_buffers_variables
to use add_builtin_constant"

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=34687
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/glsl/ir_clone.cpp b/src/glsl/ir_clone.cpp
index 9adf47050d1..e8ac9fbe456 100644
--- a/src/glsl/ir_clone.cpp
+++ b/src/glsl/ir_clone.cpp
@@ -50,6 +50,7 @@ ir_variable::clone(void *mem_ctx, struct hash_table *ht) const
    var->origin_upper_left = this->origin_upper_left;
    var->pixel_center_integer = this->pixel_center_integer;
    var->explicit_location = this->explicit_location;
+   var->has_initializer = this->has_initializer;
 
    var->num_state_slots = this->num_state_slots;
    if (this->state_slots) {
@@ -68,6 +69,10 @@ ir_variable::clone(void *mem_ctx, struct hash_table *ht) const
    if (this->constant_value)
       var->constant_value = this->constant_value->clone(mem_ctx, ht);
 
+   if (this->constant_initializer)
+      var->constant_initializer =
+	 this->constant_initializer->clone(mem_ctx, ht);
+
    if (ht) {
       hash_table_insert(ht, var, (void *)const_cast<ir_variable *>(this));
    }