cmd/compile: incrementally compact liveness maps
The per-Value slice of liveness maps is currently one of the largest
sources of allocation in the compiler. On cmd/compile/internal/ssa,
it's 5% of overall allocation, or 75MB in total. Enabling liveness
maps everywhere significantly increased this allocation footprint,
which in turn slowed down the compiler.
Improve this by compacting the liveness maps after every block is
processed. There are typically very few distinct liveness maps, so
compacting the maps after every block, rather than at the end of the
function, can significantly reduce these allocations.
Passes toolstash -cmp.
name old time/op new time/op delta
Template 198ms ± 2% 196ms ± 1% -1.11% (p=0.008 n=9+10)
Unicode 100ms ± 1% 99ms ± 1% -0.94% (p=0.015 n=8+9)
GoTypes 703ms ± 2% 695ms ± 1% -1.15% (p=0.000 n=10+10)
Compiler 3.38s ± 3% 3.33s ± 0% -1.66% (p=0.000 n=10+9)
SSA 7.96s ± 1% 7.93s ± 1% ~ (p=0.113 n=9+10)
Flate 134ms ± 1% 132ms ± 1% -1.30% (p=0.000 n=8+10)
GoParser 165ms ± 2% 163ms ± 1% -1.32% (p=0.013 n=9+10)
Reflect 462ms ± 2% 459ms ± 0% -0.65% (p=0.036 n=9+8)
Tar 188ms ± 2% 186ms ± 1% ~ (p=0.173 n=8+10)
XML 243ms ± 7% 239ms ± 1% ~ (p=0.684 n=10+10)
[Geo mean] 421ms 416ms -1.10%
name old alloc/op new alloc/op delta
Template 38.0MB ± 0% 36.5MB ± 0% -3.98% (p=0.000 n=10+10)
Unicode 30.3MB ± 0% 29.6MB ± 0% -2.21% (p=0.000 n=10+10)
GoTypes 125MB ± 0% 120MB ± 0% -4.51% (p=0.000 n=10+9)
Compiler 575MB ± 0% 546MB ± 0% -5.06% (p=0.000 n=10+10)
SSA 1.64GB ± 0% 1.55GB ± 0% -4.97% (p=0.000 n=10+10)
Flate 25.9MB ± 0% 25.0MB ± 0% -3.41% (p=0.000 n=10+10)
GoParser 30.7MB ± 0% 29.5MB ± 0% -3.97% (p=0.000 n=10+10)
Reflect 84.1MB ± 0% 81.9MB ± 0% -2.64% (p=0.000 n=10+10)
Tar 37.0MB ± 0% 35.8MB ± 0% -3.27% (p=0.000 n=10+9)
XML 47.2MB ± 0% 45.0MB ± 0% -4.57% (p=0.000 n=10+10)
[Geo mean] 83.2MB 79.9MB -3.86%
name old allocs/op new allocs/op delta
Template 337k ± 0% 337k ± 0% -0.06% (p=0.000 n=10+10)
Unicode 340k ± 0% 340k ± 0% -0.01% (p=0.014 n=10+10)
GoTypes 1.18M ± 0% 1.18M ± 0% -0.04% (p=0.000 n=10+10)
Compiler 4.97M ± 0% 4.97M ± 0% -0.03% (p=0.000 n=10+10)
SSA 12.3M ± 0% 12.3M ± 0% -0.01% (p=0.000 n=10+10)
Flate 226k ± 0% 225k ± 0% -0.09% (p=0.000 n=10+10)
GoParser 283k ± 0% 283k ± 0% -0.06% (p=0.000 n=10+9)
Reflect 972k ± 0% 971k ± 0% -0.04% (p=0.000 n=10+8)
Tar 333k ± 0% 332k ± 0% -0.05% (p=0.000 n=10+9)
XML 395k ± 0% 395k ± 0% -0.04% (p=0.000 n=10+10)
[Geo mean] 764k 764k -0.04%
Updates #24543.
Change-Id: I6fdc46e4ddb6a8eea95d38242345205eb8397f0b
Reviewed-on: https://go-review.googlesource.com/110177
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>