Patch by Benjamin Kramer!
Use the BlockFrequency class instead of floats in the Hopfield network
computations. This rescales the node Bias field from a [-2;2] float
range to two block frequencies BiasN and BiasP pulling in opposite
directions. This construct has a more predictable behavior when block
frequencies saturate.
The per-node scaling factors are no longer necessary, assuming the block
frequencies around a bundle are consistent.
This patch can cause the register allocator to make different spilling
decisions. The differences should be small.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185393 91177308-0d34-0410-b5e6-96231b3b80d8
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
This is a band-aid to fix the most severe regressions we're seeing from basing
spill decisions on block frequencies, until we have a better solution.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184835 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
