[LazyValueInfo] Avoid unnecessary copies of ConstantRanges
Summary:
ConstantRange contains two APInts which can allocate memory if their width is larger than 64-bits. So we shouldn't copy it when we can avoid it.
This changes LVILatticeVal::getConstantRange() to return its internal ConstantRange by reference. This allows many places that just need a ConstantRange reference to avoid making a copy.
Several places now capture the return value of getConstantRange() by reference so they can call methods on it that don't need a new object.
Lastly it adds std::move in one place to capture to move a local ConstantRange into an LVILatticeVal.
Reviewers: reames, dberlin, sanjoy, anna
Reviewed By: reames
Subscribers: grandinj, llvm-commits
Differential Revision: https://reviews.llvm.org/D32884
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302331
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