Teach LSR about loop-variant expressions, such as loops like this:
Teach LSR about loop-variant expressions, such as loops like this:

  for (i = 0; i < N; ++i)
    A[i][foo()] = 0;

here we still want to strength reduce the A[i] part, even though foo() is
l-v.

This also simplifies some of the 'CanReduce' logic.

This implements Transforms/LoopStrengthReduce/ops_after_indvar.ll


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@22652 91177308-0d34-0410-b5e6-96231b3b80d8

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