From 4fa050024fbdfff9eb43c930c5b1f73b1a16fafa Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Thu, 28 Apr 2016 16:52:47 -0700 Subject: cmd/compile: enable constant-time CFG editing Provide indexes along with block pointers for Preds and Succs arrays. This allows us to splice edges in and out of those arrays in constant time. Fixes worst-case O(n^2) behavior in deadcode and fuse. benchmark old ns/op new ns/op delta BenchmarkFuse1-8 2065 2057 -0.39% BenchmarkFuse10-8 9408 9073 -3.56% BenchmarkFuse100-8 105238 76277 -27.52% BenchmarkFuse1000-8 3982562 1026750 -74.22% BenchmarkFuse10000-8 301220329 12824005 -95.74% BenchmarkDeadCode1-8 1588 1566 -1.39% BenchmarkDeadCode10-8 4333 4250 -1.92% BenchmarkDeadCode100-8 32031 32574 +1.70% BenchmarkDeadCode1000-8 590407 468275 -20.69% BenchmarkDeadCode10000-8 17822890 5000818 -71.94% BenchmarkDeadCode100000-8 1388706640 78021127 -94.38% BenchmarkDeadCode200000-8 5372518479 168598762 -96.86% Change-Id: Iccabdbb9343fd1c921ba07bbf673330a1c36ee17 Reviewed-on: https://go-review.googlesource.com/22589 Reviewed-by: Josh Bleecher Snyder Run-TryBot: Keith Randall TryBot-Result: Gobot Gobot --- src/cmd/compile/internal/ssa/stackalloc.go | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'src/cmd/compile/internal/ssa/stackalloc.go') diff --git a/src/cmd/compile/internal/ssa/stackalloc.go b/src/cmd/compile/internal/ssa/stackalloc.go index 44f4096cb2..c08ed79cd6 100644 --- a/src/cmd/compile/internal/ssa/stackalloc.go +++ b/src/cmd/compile/internal/ssa/stackalloc.go @@ -304,7 +304,8 @@ func (s *stackAllocState) computeLive(spillLive [][]ID) { // for each predecessor of b, expand its list of live-at-end values // invariant: s contains the values live at the start of b (excluding phi inputs) - for i, p := range b.Preds { + for i, e := range b.Preds { + p := e.b t.clear() t.addAll(s.live[p.ID]) t.addAll(live.contents()) -- cgit v1.3