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07c2241e45
resisted this for too long. Just with the basic testing here I was able to exercise the analysis in more detail and sift out both type signature bugs in the API and a bug in the DFS numbering. All of these are fixed here as well. The unittests will be much more important for the mutation support where it is necessary to craft minimal mutations and then inspect the state of the graph. There is just no way to do that with a standard FileCheck test. However, unittesting these kinds of analyses is really quite easy, especially as they're designed with the new pass manager where there is essentially no infrastructure required to rig up the core logic and exercise it at an API level. As a minor aside about the DFS numbering bug, the DFS numbering used in LCG is a bit unusual. Rather than numbering from 0, we number from 1, and use 0 as the sentinel "unvisited" state. Other implementations often use '-1' for this, but I find it easier to deal with 0 and it shouldn't make any real difference provided someone doesn't write silly bugs like forgetting to actually initialize the DFS numbering. Oops. ;] git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206954 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.
//===---------------------------------------------------------------------===//
In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,
ScalarEvolution is forming this expression:
((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))
This could be folded to
(-1 * (trunc i64 undef to i32))
//===---------------------------------------------------------------------===//