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5c8aa950fe
source addition. Apparently the buildbots were wrong about failures. --- Add some switches helpful for debugging: -print-before=<Pass Name> Dump IR before running pass <Pass Name>. -print-before-all Dump IR before running each pass. -print-after-all Dump IR after running each pass. These are helpful when tracking down a miscompilation. It is easy to get IR dumps and do diffs on them, etc. To make this work well, add a new getPrinterPass API to Pass so that each kind of pass (ModulePass, FunctionPass, etc.) can create a Pass suitable for dumping out the kind of object the Pass works on. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100249 91177308-0d34-0410-b5e6-96231b3b80d8
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.
//===---------------------------------------------------------------------===//