Allow a BlockFrequency to be divided by a non-zero BranchProbability
with saturating arithmetic. This will be used to compute the frequency
of a loop header given the probability of leaving the loop.
Our long division algorithm already saturates on overflow, so that was a
freebie.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185184 91177308-0d34-0410-b5e6-96231b3b80d8
Zero is used by BlockFrequencyInfo as a special "don't know" value. It also
causes a sink for frequencies as you can't ever get off a zero frequency with
more multiplies.
This recovers a 10% regression on MultiSource/Benchmarks/7zip. A zero frequency
was propagated into an inner loop causing excessive spilling.
PR16402.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184584 91177308-0d34-0410-b5e6-96231b3b80d8
Add a test case for the edge case that triggers this. Thanks to Chandler for bringing this to my attention.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142794 91177308-0d34-0410-b5e6-96231b3b80d8
