Comment # 1 on bug 91985 from Ilia Mirkin

Seems more likely that the culprit is

>From f9caabe8f1bff86d19b53d9ecba5c72b238d9e23 Mon Sep 17 00:00:00 2001
From: Dave Airlie <airlied@redhat.com>
Date: Fri, 11 Sep 2015 04:43:53 +0100
Subject: r600g: lower number of driver const buffers

I'm going to want a driver constant buffer for tess to coordinate
LDS storage, so before I go tackling that I decided to merge the
clip/samplepos and texture info buffers into one. So I can steal
the spare one.

This creates a single constant buffer between the two, with
clip/samplepos taking up a reserved 128 bytes at the start.

Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Glenn Kennard <glenn.kennard@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

than a commit from 2013...