runtime: use multiply instead of divide in heapBitsForObject
These benchmarks show the effect of the combination of this change
and Rick's pending CL 6665. Code with interior pointers is helped
much more than code without, but even code without doesn't suffer
too badly.
benchmark old ns/op new ns/op delta
BenchmarkBinaryTree17
6989407768 6851728175 -1.97%
BenchmarkFannkuch11
4416250775 4405762558 -0.24%
BenchmarkFmtFprintfEmpty 134 130 -2.99%
BenchmarkFmtFprintfString 491 402 -18.13%
BenchmarkFmtFprintfInt 430 420 -2.33%
BenchmarkFmtFprintfIntInt 748 663 -11.36%
BenchmarkFmtFprintfPrefixedInt 602 534 -11.30%
BenchmarkFmtFprintfFloat 728 699 -3.98%
BenchmarkFmtManyArgs 2528 2507 -0.83%
BenchmarkGobDecode
17448191 17749756 +1.73%
BenchmarkGobEncode
14579824 14370183 -1.44%
BenchmarkGzip
656489990 652669348 -0.58%
BenchmarkGunzip
141254147 141099278 -0.11%
BenchmarkHTTPClientServer 94111 93738 -0.40%
BenchmarkJSONEncode
36305013 36696440 +1.08%
BenchmarkJSONDecode
124652000 128176454 +2.83%
BenchmarkMandelbrot200
6009333 5997093 -0.20%
BenchmarkGoParse
7651583 7623494 -0.37%
BenchmarkRegexpMatchEasy0_32 213 213 +0.00%
BenchmarkRegexpMatchEasy0_1K 511 494 -3.33%
BenchmarkRegexpMatchEasy1_32 186 187 +0.54%
BenchmarkRegexpMatchEasy1_1K 1834 1827 -0.38%
BenchmarkRegexpMatchMedium_32 427 412 -3.51%
BenchmarkRegexpMatchMedium_1K 154841 153086 -1.13%
BenchmarkRegexpMatchHard_32 7473 7478 +0.07%
BenchmarkRegexpMatchHard_1K 233587 232272 -0.56%
BenchmarkRevcomp
918797689 944528032 +2.80%
BenchmarkTemplate
167665081 167773121 +0.06%
BenchmarkTimeParse 631 636 +0.79%
BenchmarkTimeFormat 672 666 -0.89%
Change-Id: Ia923de3cdb3993b640fe0a02cbe2c7babc16f32c
Reviewed-on: https://go-review.googlesource.com/6782
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Austin Clements <austin@google.com>