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c320ed14d2
Now the analysis won't "fail" if the memchecks exceed the threshold. It is the transform pass' responsibility to perform the check. This allows the transform pass to further analyze/eliminate the memchecks. E.g. in Loop distribution we only need to check pointers that end up in different partitions. Note that there is a slight change of functionality here. The logic in analyzeLoop is that if dependence checking fails due to non-constant distance between the pointers, another attempt is made to prove safety of the dependences purely using run-time checks. Before this patch we could fail the loop due to exceeding the memcheck threshold after the first step, now we only check the threshold in the client after the full analysis. There is no measurable compile-time effect but I wanted to record this here. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231817 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))
//===---------------------------------------------------------------------===//