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586f69a118
cannot be folded into target cmp instruction. - Avoid a phase ordering issue where early cmp optimization would prevent the later count-to-zero optimization. - Add missing checks which could cause LSR to reuse stride that does not have users. - Fix a bug in count-to-zero optimization code which failed to find the pre-inc iv's phi node. - Remove, tighten, loosen some incorrect checks disable valid transformations. - Quite a bit of code clean up. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86969 91177308-0d34-0410-b5e6-96231b3b80d8
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.
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