llvm/lib/Analysis
Dan Gohman 2166f62290 Add a function to Passes.h to allow clients to create instances
of the ScalarEvolution pass without needing to #include ScalarEvolution.h.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85716 91177308-0d34-0410-b5e6-96231b3b80d8
2009-11-01 15:28:36 +00:00
..
2009-10-26 23:43:48 +00:00
2009-10-29 04:41:24 +00:00

Analysis Opportunities:

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

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.

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