I noticed multiple ubo piglit regressions on 10.3-devel / r600g / BARTS
since this commit:

commit 01bf8bb87565ed3677e43c6b6deeb90378d88647
Author: Brian Paul <brianp@vmware.com>
Date:   Tue Jul 1 07:57:43 2014 -0600

    st/mesa: don't use address register for constant-indexed ir_binop_ubo_load
    
    Before, we were always using the address register and indirect addressing
    to index into a UBO constant buffer.  With this change we only do that
    when necessary.
    
    Using the piglit bin/arb_uniform_buffer_object-rendering test as an
    example:
    
    Shader code:
      uniform ub_rot {float rotation; };
      ...
      m[1][1] = cos(rotation);
    
    Before:
      IMM[1] INT32 {0, 1, 0, 0}
      1: UARL ADDR[0].x, IMM[1].xxxx
      2: MOV TEMP[0].x, CONST[3][ADDR[0].x].xxxx
      3: COS TEMP[1].x, TEMP[0].xxxx
    
    After:
      0: COS TEMP[0].x, CONST[3][0].xxxx
    
    Reviewed-by: Roland Scheidegger <sroland@vmware.com>

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index d660a6b..69d67e1 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -1971,9 +1971,17 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
       assert(ir->type->is_vector() || ir->type->is_scalar());
 
       if (const_offset_ir) {
-         index_reg = st_src_reg_for_int(const_offset / 16);
-      } else {
-         emit(ir, TGSI_OPCODE_USHR, st_dst_reg(index_reg), op[1], st_src_reg_for_int(4));
+         /* Constant index into constant buffer */
+         cbuf.reladdr = NULL;
+         cbuf.index = const_offset / 16;
+         cbuf.has_index2 = true;
+      }
+      else {
+         /* Relative/variable index into constant buffer */
+         emit(ir, TGSI_OPCODE_USHR, st_dst_reg(index_reg), op[1],
+              st_src_reg_for_int(4));
+         cbuf.reladdr = ralloc(mem_ctx, st_src_reg);
+         memcpy(cbuf.reladdr, &index_reg, sizeof(index_reg));
       }
 
       cbuf.swizzle = swizzle_for_size(ir->type->vector_elements);
@@ -1982,9 +1990,6 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
                                     const_offset % 16 / 4,
                                     const_offset % 16 / 4);
 
-      cbuf.reladdr = ralloc(mem_ctx, st_src_reg);
-      memcpy(cbuf.reladdr, &index_reg, sizeof(index_reg));
-
       if (ir->type->base_type == GLSL_TYPE_BOOL) {
          emit(ir, TGSI_OPCODE_USNE, result_dst, cbuf, st_src_reg_for_int(0));
       } else {


I guess it unhides a driver bug, since softpipe and llvmpipe are not affected.

Regressed tests:

spec/ARB_uniform_buffer_object/bufferstorage
spec/ARB_uniform_buffer_object/maxblocks
spec/ARB_uniform_buffer_object/rendering

spec/glsl-1.40/uniform_buffer/fs-mat4
spec/glsl-1.40/uniform_buffer/fs-two-members
spec/glsl-1.40/uniform_buffer/vs-mat4
spec/glsl-1.40/uniform_buffer/vs-two-members

spec/glsl-1.50/uniform_buffer/gs-mat4
spec/glsl-1.50/uniform_buffer/gs-two-members


Thanks,
Andreas.