i965: Keep track of whether LRI is allowed in the context struct.

This stores the result of can_do_pipelined_register_writes() in the
context struct so we can find out later whether LRI can be used to
program the L3 configuration.

v2:
 * Split change of gen check in can_do_pipelined_register_writes (jljusten)

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kristian Høgsberg  <krh@bitplanet.net>

src/mesa/drivers/dri/i965/brw_context.h

@@ -865,6 +865,11 @@ struct brw_context
    bool use_rep_send;
    bool use_resource_streamer;
 
+   /**
+    * Whether LRI can be used to write register values from the batch buffer.
+    */
+   bool can_do_pipelined_register_writes;
+
    /**
     * Some versions of Gen hardware don't do centroid interpolation correctly
     * on unlit pixels, causing incorrect values for derivatives near triangle

src/mesa/drivers/dri/i965/intel_extensions.c

@@ -320,6 +320,8 @@ intelInitExtensions(struct gl_context *ctx)
    }
 
    brw->predicate.supported = false;
+   brw->can_do_pipelined_register_writes =
+      can_do_pipelined_register_writes(brw);
 
    if (brw->gen >= 7) {
       ctx->Extensions.ARB_conservative_depth = true;
@@ -336,7 +338,7 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Extensions.ARB_shader_storage_buffer_object = true;
       ctx->Extensions.EXT_shader_samples_identical = true;
 
-      if (can_do_pipelined_register_writes(brw)) {
+      if (brw->can_do_pipelined_register_writes) {
          ctx->Extensions.ARB_draw_indirect = true;
          ctx->Extensions.ARB_transform_feedback2 = true;
          ctx->Extensions.ARB_transform_feedback3 = true;