cmd/compile: share dominator tree among many passes
These passes do not modify the dominator tree too much.
% benchstat old.txt new.txt
name old time/op new time/op delta
Template 335ms ± 3% 325ms ± 8% ~ (p=0.074 n=8+9)
GoTypes 1.05s ± 1% 1.05s ± 3% ~ (p=0.095 n=9+10)
Compiler 5.37s ± 4% 5.29s ± 1% -1.42% (p=0.022 n=9+10)
MakeBash 34.9s ± 3% 34.4s ± 2% ~ (p=0.095 n=9+10)
name old alloc/op new alloc/op delta
Template 55.4MB ± 0% 54.9MB ± 0% -0.81% (p=0.000 n=10+10)
GoTypes 179MB ± 0% 178MB ± 0% -0.89% (p=0.000 n=10+10)
Compiler 807MB ± 0% 798MB ± 0% -1.10% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
Template 498k ± 0% 496k ± 0% -0.29% (p=0.000 n=9+9)
GoTypes 1.42M ± 0% 1.41M ± 0% -0.24% (p=0.000 n=10+10)
Compiler 5.61M ± 0% 5.60M ± 0% -0.12% (p=0.000 n=10+10)
Change-Id: I4cd20cfba3f132ebf371e16046ab14d7e42799ec
Reviewed-on: https://go-review.googlesource.com/21806
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>