backend: add global immediate optimization

there are some global immediates in global var list of LLVM.
these imm can be integrated in instructions. for compiler_global_immediate_optimized test
in utest, there are two global immediates:
  L0:
  MOV(1)              %42<0>:UD       :       0x0:UD
  MOV(1)              %43<0>:UD       :       0x30:UD

  used by:
  ADD(16)             %49<1>:D        :       %42<0,1,0>:D    %48<8,8,1>:D
  ADD(16)             %54<1>:D        :       %43<0,1,0>:D    %53<8,8,1>:D

  it can be
  ADD(16)             %49<1>:D    :       %48<8,8,1>:D   0x0:UD
  ADD(16)             %54<1>:D    :       %53<8,8,1>:D   0x30:UD

Then the MOV can be removed. And after this optimization, ADD 0 can be change
to MOV, then local copy propagation can be done.

V2: (1) add environment variable to enable/disable the optimization
    (2) refine the architecture of imm optimization, inherit from global
        optimizer not local block optimizer

V3: merge with latest master driver

V4: (1)refine some type errors
    (2)remove UD/D check for no need
    (3)refine imm calculate for UD/D

Signed-off-by: rander.wang <rander.wang@intel.com>
Reviewed-by: Ruiling Song <ruiling.song@intel.com>

0 files changed, 0 insertions, 0 deletions