[dev.ssa] cmd/compile/ssa: dominator tests and benchmarks
This change has some tests verifying functionality and an assortment of
benchmarks of various block lists. It modifies NewBlock to allocate in
contiguous blocks improving the performance of intersect() for extremely
large graphs by 30-40%.
benchmark old ns/op new ns/op delta
BenchmarkDominatorsLinear-8
1185619 901154 -23.99%
BenchmarkDominatorsFwdBack-8
1302138 863537 -33.68%
BenchmarkDominatorsManyPred-8
404670521 247450911 -38.85%
BenchmarkDominatorsMaxPred-8
455809002 471675119 +3.48%
BenchmarkDominatorsMaxPredVal-8
819315864 468257300 -42.85%
BenchmarkNilCheckDeep1-8 766 706 -7.83%
BenchmarkNilCheckDeep10-8 2553 2209 -13.47%
BenchmarkNilCheckDeep100-8 58606 57545 -1.81%
BenchmarkNilCheckDeep1000-8
7753012 8025750 +3.52%
BenchmarkNilCheckDeep10000-8
1224165946 789995184 -35.47%
Change-Id: Id3d6bc9cb1138e8177934441073ac7873ddf7ade
Reviewed-on: https://go-review.googlesource.com/11716
Reviewed-by: Keith Randall <khr@golang.org>