[Mesa-dev] [PATCH] i965: Write at least some data in SIMD8 URB write messages.

[Kenneth Graunke]

According to the "URB SIMD8 Write > Write Data Payload" documentation,
"The write data payload can be between 1 and 8 message phases long."

Apparently, the simulator considers it an error if you issue an URB
SIMD8 message with only a header and no actual data to write.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 9a4bad6..7074b5c 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -1800,14 +1800,13 @@ fs_visitor::emit_urb_writes(gl_clip_plane *clip_planes)
    /* If we don't have any valid slots to write, just do a minimal urb write
     * send to terminate the shader. */
    if (vue_map->slots_valid == 0) {
-
-      fs_reg payload = fs_reg(GRF, alloc.allocate(1), BRW_REGISTER_TYPE_UD);
+      fs_reg payload = fs_reg(GRF, alloc.allocate(2), BRW_REGISTER_TYPE_UD);
       bld.exec_all().MOV(payload, fs_reg(retype(brw_vec8_grf(1, 0),
                                                 BRW_REGISTER_TYPE_UD)));
 
       fs_inst *inst = bld.emit(SHADER_OPCODE_URB_WRITE_SIMD8, reg_undef, payload);
       inst->eot = true;
-      inst->mlen = 1;
+      inst->mlen = 2;
       inst->offset = 1;
       return;
    }
-- 
1.7.10.4