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8700c2d093
not attched to a basic block or function. There are conservatively correct answers in these cases, and this makes the analysis more useful in contexts where we have a partially formed bit of IR. I don't have any way to test this directly... suggestions welcome here, but I'm not seeing anything sadly. I only found this using a subsequent patch to the inliner which runs instsimplify on partially inlined instructions, and even then only on a quite large program. I never got a reasonable testcase out of it, and anything I do get is likely to be quite fragile due to requiring an interaction of two different passes, and the only result being a segfault if it goes wrong. llvm-svn: 153176
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))
//===---------------------------------------------------------------------===//