runtime: make span map sparse

This splits the span map into separate chunks for every 64MB of the
heap. The span map chunks now live in the same indirect structure as
the bitmap.

Updates #10460.

This causes a slight improvement in compilebench and the x/benchmarks
garbage benchmark. I'm not sure why it improves performance.

name       old time/op     new time/op     delta
Template       185ms ± 1%      184ms ± 1%    ~            (p=0.315 n=9+10)
Unicode       86.9ms ± 1%     86.9ms ± 3%    ~            (p=0.356 n=9+10)
GoTypes        602ms ± 1%      599ms ± 0%  -0.59%         (p=0.002 n=9+10)
Compiler       2.89s ± 0%      2.87s ± 1%  -0.50%          (p=0.003 n=9+9)
SSA            7.25s ± 0%      7.29s ± 1%    ~            (p=0.400 n=9+10)
Flate          118ms ± 1%      118ms ± 2%    ~            (p=0.065 n=10+9)
GoParser       147ms ± 2%      147ms ± 1%    ~            (p=0.549 n=10+9)
Reflect        403ms ± 1%      401ms ± 1%  -0.47%         (p=0.035 n=9+10)
Tar            176ms ± 1%      175ms ± 1%  -0.59%         (p=0.013 n=10+9)
XML            211ms ± 1%      209ms ± 1%  -0.83%        (p=0.011 n=10+10)

(https://perf.golang.org/search?q=upload:20171231.1)

name                       old time/op  new time/op  delta
Garbage/benchmem-MB=64-12  2.24ms ± 1%  2.23ms ± 1%  -0.36%  (p=0.001 n=20+19)

(https://perf.golang.org/search?q=upload:20171231.2)

Change-Id: I2563f8704ab9812434947faf293c5327f9b0d07a
Reviewed-on: https://go-review.googlesource.com/85885
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

0 files changed, 0 insertions, 0 deletions