[PATCH] Select elimination pass

[Gerolf Hoflehner]

Hi echristo,

In special cases select instructions can be eliminated by
replacing them with a cheaper bitwise operation. The instance implemented
by this pass is %x=icmp.eq; %y=select %x,%r, null; %z=icmp.eq %y, null;
br %z,true, false ==> %x=icmp.ne; %y=icmp.eq %r,null; %z=or %x,%y; br
%z,true,false. The optimization is global and performed only when all uses
of the select result can be replaced by the select true value. For this
dominator information is used.

http://reviews.llvm.org/D5156

Files:
  bindings/ocaml/transforms/scalar/scalar_opts_ocaml.c
  include/llvm-c/Transforms/Scalar.h
  include/llvm/InitializePasses.h
  include/llvm/LinkAllPasses.h
  include/llvm/Transforms/Scalar.h
  lib/LTO/LTOCodeGenerator.cpp
  lib/Transforms/IPO/PassManagerBuilder.cpp
  lib/Transforms/Scalar/CMakeLists.txt
  lib/Transforms/Scalar/Scalar.cpp
  lib/Transforms/Scalar/SelectElimination.cpp
  test/Transforms/SelectElim/
  test/Transforms/SelectElim/select-elim-or.ll
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