Chris Lattner 8ef27511e3 remove LoopVR pass. According to Nick:
"LoopVR's logic was copied into ScalarEvolution::getUnsignedRange and 
::getSignedRange. Please delete LoopVR."



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83531 91177308-0d34-0410-b5e6-96231b3b80d8
2009-10-08 06:42:44 +00:00
..
2009-08-11 16:02:12 +00:00
2009-07-26 08:34:35 +00:00
2009-09-11 08:43:15 +00:00

Analysis Opportunities:

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In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:

  {1,+,3,+,2}<loop>

Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as

  (-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))

In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.

//===---------------------------------------------------------------------===//