fmt: optimize struct layout and intbuf size

fmt: optimize struct layout and intbuf size

Move boolean fields to the end of the pp struct for better packing.

Increase the fmt.intbuf size to leave no padding space unused
at the end of the fmt struct on 32 bit architectures.

The size of the pp struct on amd64 is decreased from 192 byte
to 184 byte and on 386 from 132 byte to 128 byte.

Simplify buffer size calculation in fmt_integer.

Consolidate test cases for intbuf overflow checks.

amd64 Haswell:

name                     old time/op  new time/op  delta
SprintfPadding-2          227ns ± 2%   227ns ± 1%    ~     (p=0.941 n=25+25)
SprintfEmpty-2           38.4ns ± 6%  35.8ns ±23%  -6.71%  (p=0.030 n=24+25)
SprintfString-2           100ns ± 0%   101ns ± 0%  +1.00%  (p=0.000 n=19+18)
SprintfTruncateString-2   142ns ± 1%   142ns ± 1%  +0.37%  (p=0.028 n=25+25)
SprintfQuoteString-2      397ns ± 0%   393ns ± 0%  -0.82%  (p=0.000 n=21+24)
SprintfInt-2              101ns ± 2%   102ns ± 4%    ~     (p=0.159 n=21+24)
SprintfIntInt-2           155ns ± 3%   155ns ± 3%    ~     (p=0.934 n=25+25)
SprintfPrefixedInt-2      252ns ± 2%   251ns ± 2%    ~     (p=0.198 n=25+25)
SprintfFloat-2            184ns ± 3%   179ns ± 2%  -3.07%  (p=0.000 n=24+25)
SprintfComplex-2          532ns ± 2%   535ns ± 2%  +0.64%  (p=0.046 n=25+24)
SprintfBoolean-2         90.5ns ± 3%  91.6ns ± 2%  +1.17%  (p=0.000 n=22+22)
SprintfHexString-2        164ns ± 2%   165ns ± 3%    ~     (p=0.066 n=25+25)
SprintfHexBytes-2         171ns ± 3%   170ns ± 3%    ~     (p=0.941 n=25+24)
SprintfBytes-2            320ns ± 1%   313ns ± 1%  -2.31%  (p=0.000 n=24+21)
SprintfStringer-2         347ns ± 2%   348ns ± 2%    ~     (p=0.426 n=24+24)
SprintfStructure-2        753ns ± 1%   742ns ± 1%  -1.49%  (p=0.000 n=24+25)
FprintInt-2               145ns ± 0%   144ns ± 0%  -0.69%  (p=0.000 n=24+23)
FprintfBytes-2            163ns ± 0%   163ns ± 0%  -0.27%  (p=0.000 n=25+25)
FprintIntNoAlloc-2        108ns ± 0%   105ns ± 0%  -2.78%  (p=0.000 n=25+2

386 Haswell:

name                     old time/op  new time/op  delta
SprintfPadding-2          426ns ± 2%   422ns ± 1%  -0.89%  (p=0.000 n=25+24)
SprintfEmpty-2           24.6ns ± 1%  24.5ns ± 0%  -0.39%  (p=0.000 n=22+15)
SprintfString-2          99.1ns ± 3%  95.6ns ± 0%  -3.52%  (p=0.000 n=25+24)
SprintfTruncateString-2   156ns ± 4%   153ns ± 1%  -1.65%  (p=0.000 n=24+23)
SprintfQuoteString-2      500ns ± 2%   493ns ± 1%  -1.49%  (p=0.000 n=25+24)
SprintfInt-2             92.6ns ± 9%  88.3ns ± 1%  -4.72%  (p=0.000 n=25+25)
SprintfIntInt-2           143ns ± 7%   137ns ± 2%  -4.01%  (p=0.000 n=23+25)
SprintfPrefixedInt-2      268ns ±19%   264ns ±16%    ~     (p=0.826 n=24+24)
SprintfFloat-2            242ns ± 4%   246ns ± 2%  +1.60%  (p=0.000 n=25+25)
SprintfComplex-2         1.04µs ± 3%  1.03µs ± 1%  -0.89%  (p=0.026 n=25+25)
SprintfBoolean-2         82.2ns ± 9%  80.7ns ± 2%    ~     (p=0.163 n=24+24)
SprintfHexString-2        240ns ± 5%   224ns ± 2%  -6.94%  (p=0.000 n=25+25)
SprintfHexBytes-2         245ns ± 3%   234ns ± 2%  -4.55%  (p=0.000 n=25+25)
SprintfBytes-2            432ns ±13%   419ns ± 2%    ~     (p=0.081 n=23+25)
SprintfStringer-2         356ns ± 4%   356ns ± 4%    ~     (p=0.988 n=25+25)
SprintfStructure-2        968ns ± 5%   948ns ± 2%  -2.11%  (p=0.000 n=25+25)
FprintInt-2               206ns ± 0%   201ns ± 0%  -2.43%  (p=0.000 n=25+21)
FprintfBytes-2            187ns ± 1%   187ns ± 1%    ~     (p=0.420 n=25+25)
FprintIntNoAlloc-2        173ns ± 0%   168ns ± 0%  -2.89%  (p=0.000 n=25+2

amd64 Ivy Bridge:

name                     old time/op  new time/op  delta
SprintfPadding-4          203ns ± 4%   210ns ± 8%  +3.27%  (p=0.000 n=23+25)
SprintfEmpty-4           24.4ns ± 2%  24.4ns ± 3%    ~     (p=0.487 n=24+25)
SprintfString-4          92.4ns ± 2%  93.1ns ± 3%    ~     (p=0.087 n=22+25)
SprintfTruncateString-4   137ns ± 3%   136ns ± 2%  -1.02%  (p=0.002 n=25+25)
SprintfQuoteString-4      378ns ± 1%   373ns ± 1%  -1.32%  (p=0.000 n=24+22)
SprintfInt-4             89.9ns ± 3%  90.3ns ± 4%    ~     (p=0.444 n=25+25)
SprintfIntInt-4           137ns ± 4%   138ns ± 3%    ~     (p=0.112 n=25+23)
SprintfPrefixedInt-4      155ns ±14%   154ns ±14%    ~     (p=0.791 n=25+25)
SprintfFloat-4            154ns ± 2%   154ns ± 3%    ~     (p=0.789 n=25+25)
SprintfComplex-4          396ns ± 2%   402ns ± 3%  +1.53%  (p=0.001 n=23+25)
SprintfBoolean-4         71.0ns ± 3%  71.2ns ± 2%    ~     (p=0.515 n=25+24)
SprintfHexString-4        156ns ± 3%   150ns ± 5%  -3.69%  (p=0.000 n=24+25)
SprintfHexBytes-4         154ns ± 3%   157ns ± 5%  +1.72%  (p=0.003 n=24+25)
SprintfBytes-4            297ns ± 4%   291ns ± 3%  -1.86%  (p=0.000 n=25+25)
SprintfStringer-4         275ns ± 3%   265ns ± 3%  -3.51%  (p=0.000 n=25+25)
SprintfStructure-4        878ns ± 2%   823ns ± 2%  -6.21%  (p=0.000 n=25+22)
FprintInt-4               145ns ± 1%   147ns ± 2%  +0.94%  (p=0.001 n=23+25)
FprintfBytes-4            166ns ± 1%   168ns ± 2%  +0.81%  (p=0.000 n=24+25)
FprintIntNoAlloc-4        113ns ± 2%   109ns ± 2%  -3.79%  (p=0.000 n=24+25)

386 Ivy Bridge:

name                     old time/op  new time/op  delta
SprintfPadding-4          353ns ± 4%   354ns ± 4%    ~     (p=0.769 n=25+24)
SprintfEmpty-4           21.9ns ± 6%  21.1ns ± 3%  -3.45%  (p=0.000 n=24+25)
SprintfString-4          94.7ns ± 1%  93.0ns ± 3%  -1.77%  (p=0.000 n=24+23)
SprintfTruncateString-4   150ns ± 2%   147ns ± 0%  -1.71%  (p=0.000 n=25+21)
SprintfQuoteString-4      472ns ± 1%   479ns ± 1%  +1.48%  (p=0.000 n=25+23)
SprintfInt-4             87.0ns ± 2%  85.3ns ± 2%  -1.95%  (p=0.000 n=25+25)
SprintfIntInt-4           137ns ± 2%   134ns ± 2%  -1.97%  (p=0.000 n=24+23)
SprintfPrefixedInt-4      166ns ± 8%   161ns ± 8%  -3.07%  (p=0.023 n=24+24)
SprintfFloat-4            226ns ± 1%   219ns ± 1%  -2.97%  (p=0.000 n=24+25)
SprintfComplex-4          867ns ± 1%   784ns ± 1%  -9.47%  (p=0.000 n=24+23)
SprintfBoolean-4         77.2ns ± 2%  76.0ns ± 2%  -1.63%  (p=0.000 n=25+25)
SprintfHexString-4        212ns ± 2%   214ns ± 2%  +0.96%  (p=0.000 n=25+25)
SprintfHexBytes-4         221ns ± 2%   218ns ± 1%  -1.42%  (p=0.000 n=25+24)
SprintfBytes-4            423ns ± 3%   417ns ± 1%  -1.49%  (p=0.000 n=25+24)
SprintfStringer-4         306ns ± 3%   298ns ± 3%  -2.57%  (p=0.000 n=24+25)
SprintfStructure-4       1.00µs ± 2%  0.98µs ± 2%  -1.34%  (p=0.000 n=24+24)
FprintInt-4               202ns ± 3%   197ns ± 2%  -2.04%  (p=0.000 n=25+25)
FprintfBytes-4            186ns ± 2%   184ns ± 2%  -0.88%  (p=0.000 n=24+25)
FprintIntNoAlloc-4        170ns ± 2%   166ns ± 2%  -2.26%  (p=0.000 n=24+25)

Change-Id: I46e62bf8b6afa90a24f75b40f1d354b2084b910b
Reviewed-on: https://go-review.googlesource.com/20984
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>