[llvm-commits] [PATCH] Add the transformation ~(~X >>s Y) --> (X >>s Y)

[Edmund Grimley Evans]

Add this transformation in InstCombineAndOrXor.cpp:

~(~X >>s Y) --> (X >>s Y)

It seems unlikely it could do any harm and it does have at least one
use: together with other standard transformations it enables the
following way of expressing an arithmetic shift right in portable C to
be simplified into a single ASR operation:

int asr(int a, int b)
{
  return a < 0 ? -(-a - 1 >> b) - 1 : a >> b;
}

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