linker: Only over-ride built-ins when a prototype has been seen

The GLSL spec says:

    "If a built-in function is redeclared in a shader (i.e., a
    prototype is visible) before a call to it, then the linker will
    only attempt to resolve that call within the set of shaders that
    are linked with it."

This patch enforces this behavior.  When a function call is processed
a flag is set in the ir_call to indicate whether the previously seen
prototype is the built-in or not.  At link time a call will only bind
to an instance of a function that matches the "want built-in" setting
in the ir_call.

This has the odd side effect that first call to abs() in the shader
below will call the built-in and the second will not:

float foo(float x) { return abs(x); }
float abs(float x) { return -x; }
float bar(float x) { return abs(x); }

This seems insane, but it matches what the spec says.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31744

1 files changed, 4 insertions, 0 deletions

diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 42a3936976a..80ad3dd295e 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -991,6 +991,7 @@ public:
       assert(callee->return_type != NULL);
       type = callee->return_type;
       actual_parameters->move_nodes_to(& this->actual_parameters);
+      this->use_builtin = callee->is_builtin;
    }
 
    virtual ir_call *clone(void *mem_ctx, struct hash_table *ht) const;
@@ -1054,6 +1055,9 @@ public:
    /* List of ir_rvalue of paramaters passed in this call. */
    exec_list actual_parameters;
 
+   /** Should this call only bind to a built-in function? */
+   bool use_builtin;
+
 private:
    ir_call()
       : callee(NULL)