Comment 16 for bug 1173787

I just upgraded from llvm 2.8.1 to llvm 2.9

I do not have crash anymore, BUT once the multiresolution modifier has 7+ subdivision, Blender is extremely slow.
Well not all Blender, at least the selection process is.
It goes like this :
- when doing nothing blender use <5% cpu
- right click in the scene => cpu goes to 100% for 10 seconds
- then cpu usage goes back to normal

Using gdb, I paused randomly Blender execution when cpu was high, and it always gave me this stacktrace :
[...]
#4 0x00007fffe921ee6e in tgsi_exec_machine_run (mach=0x1f10fa0) at tgsi/tgsi_exec.c:4036
#5 0x00007fffe9209128 in vs_exec_run_linear (shader=0x2d1c3e0, input=0x3478634, output=0x34c0fc4, constants=0x1f07248, const_size=0x1f07348, count=2728, input_stride=84, output_stride=84) at draw/draw_vs_ex
ec.c:149
#6 0x00007fffe9200abb in draw_vertex_shader_run (vshader=0x2d1c3e0, constants=0x1f07248, const_size=0x1f07348, input_verts=0x7ffffffd5d00, output_verts=0x7ffffffd5ce0) at draw/draw_pt_fetch_shade_pipeline.c
:189
#7 0x00007fffe9200c25 in fetch_pipeline_generic (middle=0x1f10d70, fetch_info=0x0, prim_info=0x7ffffffd5dc0) at draw/draw_pt_fetch_shade_pipeline.c:238
#8 0x00007fffe9200e6a in fetch_pipeline_linear_run (middle=0x1f10d70, start=0, count=2728, prim_flags=0) at draw/draw_pt_fetch_shade_pipeline.c:345
#9 0x00007fffe9205e77 in vsplit_segment_simple_linear (vsplit=0x1f0e150, flags=0, istart=0, icount=2728) at draw/draw_pt_vsplit_tmp.h:237
#10 0x00007fffe920617c in vsplit_run_linear (frontend=0x1f0e150, start=0, count=2728) at draw/draw_split_tmp.h:61
#11 0x00007fffe91fe34e in draw_pt_arrays (draw=0x1f06c40, prim=7, start=0, count=2728) at draw/draw_pt.c:113
#12 0x00007fffe91fef39 in draw_vbo