Files
llvm/lib/Analysis
Craig Topper 038bc52dc9 [SCEV] Use move semantics in ScalarEvolution::setRange
Summary: This makes setRange take ConstantRange by rvalue reference since most callers were passing an unnamed temporary ConstantRange. We can then move that ConstantRange into the DenseMap caches. For the callers that weren't passing a temporary, I've added std::move to to the local variable being passed.

Reviewers: sanjoy, mzolotukhin, efriedma

Reviewed By: sanjoy

Subscribers: takuto.ikuta, llvm-commits

Differential Revision: https://reviews.llvm.org/D32943

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302371 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-07 16:28:17 +00:00
..
2016-08-25 01:29:55 +00:00
2017-01-28 02:02:38 +00:00
2016-04-18 09:17:29 +00:00
2017-02-14 17:21:12 +00:00

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))

//===---------------------------------------------------------------------===//