[PATCH] [Polly] Data flow reduction detection

[Johannes Doerfert]

Hi grosser, simbuerg, sebpop,

  This implements a data flow reduction detection on basic block level.
  We propagate the used loads and the number of uses, as well as the kind of
  binary operation performed until we reach a store. Using this we lift the
  "one binary operator" restriction, thus we can detect the following reductions
  withouth normalizing the source code:
    sum += A[i];                  // Worked already before
    sum = sum + A[i];             // Worked already before
    sum = A[i] + sum;             // Worked already before
    sum += A[i] + B[i];           // Works now
    sum = A[i] + sum + B[i];      // Works now
    sum = (A[i] + (sum + B[i]));  // Works now

  The analysis information is also interesting to recognize additional idioms
  later.

  + 7 Test cases to show the potential and limits of this detection.

http://reviews.llvm.org/D5190

Files:
  include/polly/ScopInfo.h
  lib/Analysis/ScopInfo.cpp
  test/Dependences/reduction_indirect_access.ll
  test/ScopInfo/reduction_escaping_intermediate_3.ll
  test/ScopInfo/reduction_indirect_access.ll
  test/ScopInfo/reduction_indirect_access_2.ll
  test/ScopInfo/reduction_long_reduction_chain.ll
  test/ScopInfo/reduction_long_reduction_chain_double_use.ll
  test/ScopInfo/reduction_multiple_different_operators.ll
  test/ScopInfo/reduction_only_reduction_like_access.ll
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