strconv: remove arch-specific decision in formatBase10

There is only one architecture-specific code segment left in formatBase10.
Remove it for simplicity.

The only affected system is ppc64le, which does add 10-20% to the
runtime, but that's a ppc64le problem, not a strconv problem.
Changing the "uint32" to "uint" makes ppc64le not slower anymore,
meaning that somehow uint32 divide-by-constant is slower than
uint divide-by-constant on ppc64le. If this minor slowdown matters,
it should be addressed by improving the generated code for
ppc64le division, not by complicating strconv.
Even though some percentages look big, the geomean is +6% and
the worst case slowdown is only about 6ns/call.

benchmark \ host                    local       s7  s7:GOARCH=386  linux-amd64  linux-386  linux-ppc64le
                                  vs base  vs base        vs base      vs base    vs base        vs base
AppendFloat/Decimal                     ~        ~         -0.75%            ~          ~              ~
AppendFloat/Float                       ~        ~              ~            ~          ~              ~
AppendFloat/Exp                         ~        ~              ~            ~          ~              ~
AppendFloat/NegExp                      ~        ~              ~            ~          ~              ~
AppendFloat/LongExp                     ~        ~              ~            ~          ~              ~
AppendFloat/Big                         ~        ~              ~            ~          ~              ~
AppendFloat/BinaryExp                   ~        ~              ~            ~     -2.92%        +10.31%
AppendFloat/32Integer                   ~        ~              ~            ~          ~              ~
AppendFloat/32ExactFraction             ~        ~         -0.43%            ~          ~              ~
AppendFloat/32Point                     ~        ~              ~            ~          ~              ~
AppendFloat/32Exp                       ~        ~              ~            ~          ~              ~
AppendFloat/32NegExp                    ~        ~              ~            ~          ~              ~
AppendFloat/32Shortest                  ~        ~              ~            ~          ~              ~
AppendFloat/32Fixed8Hard                ~        ~         -1.12%            ~     -4.19%         +5.39%
AppendFloat/32Fixed9Hard                ~        ~              ~            ~          ~        +12.09%
AppendFloat/64Fixed1                    ~        ~              ~            ~     -0.78%              ~
AppendFloat/64Fixed2                    ~        ~         +0.53%            ~     -0.74%              ~
AppendFloat/64Fixed3                    ~        ~              ~            ~     -0.82%              ~
AppendFloat/64Fixed4                    ~        ~              ~            ~     -0.63%         +2.55%
AppendFloat/64Fixed12                   ~        ~         +0.63%       -1.83%     -1.01%         +5.68%
AppendFloat/64Fixed16                   ~        ~         +0.63%            ~     -1.33%              ~
AppendFloat/64Fixed12Hard               ~        ~         +1.31%            ~     -0.34%         +4.43%
AppendFloat/64Fixed17Hard               ~        ~              ~            ~     -1.66%         +4.63%
AppendFloat/64Fixed18Hard               ~        ~              ~            ~          ~              ~
AppendFloat/Slowpath64                  ~        ~              ~            ~          ~              ~
AppendFloat/SlowpathDenormal64          ~        ~              ~            ~          ~              ~
AppendInt                               ~        ~              ~            ~     -0.77%        +11.06%
AppendUint                              ~        ~         +0.42%            ~     -1.35%         +7.27%
AppendIntSmall                          ~        ~              ~            ~          ~              ~
AppendUintVarlen/digits=1               ~        ~              ~            ~          ~              ~
AppendUintVarlen/digits=2               ~        ~              ~            ~          ~         +4.80%
AppendUintVarlen/digits=3               ~        ~         -1.61%            ~     -4.49%        +10.04%
AppendUintVarlen/digits=4               ~        ~         -2.09%            ~     -2.88%         +9.99%
AppendUintVarlen/digits=5               ~        ~         -3.97%            ~     -8.92%         +7.19%
AppendUintVarlen/digits=6               ~        ~         -3.88%            ~     -7.84%         +5.25%
AppendUintVarlen/digits=7               ~        ~         -2.93%            ~    -11.08%              ~
AppendUintVarlen/digits=8               ~        ~         -2.88%            ~    -10.09%        +10.74%
AppendUintVarlen/digits=9               ~        ~         -3.69%            ~    -10.98%        +11.56%
AppendUintVarlen/digits=10              ~        ~         +0.90%            ~     -1.09%        +34.49%
AppendUintVarlen/digits=11              ~        ~         +2.11%            ~     +0.72%        +20.63%
AppendUintVarlen/digits=12              ~        ~         +1.21%            ~     -2.26%        +27.38%
AppendUintVarlen/digits=13              ~        ~         +2.07%            ~     -2.13%        +15.37%
AppendUintVarlen/digits=14              ~        ~              ~            ~     -3.27%        +19.32%
AppendUintVarlen/digits=15              ~        ~         +0.56%            ~     -3.18%         +8.55%
AppendUintVarlen/digits=16              ~        ~              ~            ~     -4.31%        +15.69%
AppendUintVarlen/digits=17              ~        ~              ~            ~     -4.50%         +7.61%
AppendUintVarlen/digits=18              ~        ~              ~            ~     -5.54%        +12.74%
AppendUintVarlen/digits=19              ~        ~         +0.87%            ~     +0.41%        +13.82%
AppendUintVarlen/digits=20              ~        ~         +1.40%            ~     +0.82%        +15.80%

host: local
                                  │ e8ffcf3095c │            3c5742b667a             │
                                  │   sec/op    │   sec/op     vs base               │
AppendFloat/Decimal-12              21.04n ± 2%   21.10n ± 0%       ~ (p=0.542 n=20)
AppendFloat/Float-12                32.77n ± 1%   32.56n ± 0%       ~ (p=0.213 n=20)
AppendFloat/Exp-12                  32.42n ± 1%   32.42n ± 0%       ~ (p=0.995 n=20)
AppendFloat/NegExp-12               31.78n ± 2%   31.79n ± 2%       ~ (p=0.542 n=20)
AppendFloat/LongExp-12              31.54n ± 1%   31.45n ± 1%       ~ (p=0.507 n=20)
AppendFloat/Big-12                  33.75n ± 1%   33.59n ± 1%       ~ (p=0.597 n=20)
AppendFloat/BinaryExp-12            19.16n ± 1%   19.14n ± 1%       ~ (p=0.635 n=20)
AppendFloat/32Integer-12            21.59n ± 1%   21.63n ± 1%       ~ (p=0.569 n=20)
AppendFloat/32ExactFraction-12      31.12n ± 1%   31.17n ± 1%       ~ (p=0.337 n=20)
AppendFloat/32Point-12              31.11n ± 1%   31.13n ± 0%       ~ (p=0.899 n=20)
AppendFloat/32Exp-12                32.27n ± 0%   32.24n ± 1%       ~ (p=0.794 n=20)
AppendFloat/32NegExp-12             30.56n ± 1%   30.64n ± 1%       ~ (p=0.899 n=20)
AppendFloat/32Shortest-12           26.88n ± 0%   27.11n ± 1%       ~ (p=0.001 n=20)
AppendFloat/32Fixed8Hard-12         20.63n ± 1%   20.63n ± 0%       ~ (p=0.596 n=20)
AppendFloat/32Fixed9Hard-12         22.69n ± 1%   22.81n ± 1%       ~ (p=0.763 n=20)
AppendFloat/64Fixed1-12             18.65n ± 0%   18.73n ± 1%       ~ (p=0.112 n=20)
AppendFloat/64Fixed2-12             18.91n ± 1%   18.88n ± 0%       ~ (p=0.569 n=20)
AppendFloat/64Fixed3-12             18.73n ± 1%   18.60n ± 0%       ~ (p=0.003 n=20)
AppendFloat/64Fixed4-12             17.87n ± 3%   17.84n ± 1%       ~ (p=0.569 n=20)
AppendFloat/64Fixed12-12            28.18n ± 0%   28.30n ± 0%       ~ (p=0.010 n=20)
AppendFloat/64Fixed16-12            24.38n ± 1%   24.34n ± 1%       ~ (p=0.683 n=20)
AppendFloat/64Fixed12Hard-12        21.61n ± 0%   21.63n ± 1%       ~ (p=0.542 n=20)
AppendFloat/64Fixed17Hard-12        27.02n ± 1%   26.94n ± 0%       ~ (p=0.077 n=20)
AppendFloat/64Fixed18Hard-12        2.179µ ± 1%   2.189µ ± 1%       ~ (p=0.337 n=20)
AppendFloat/Slowpath64-12           29.93n ± 1%   30.01n ± 1%       ~ (p=0.402 n=20)
AppendFloat/SlowpathDenormal64-12   28.29n ± 1%   28.35n ± 0%       ~ (p=0.952 n=20)
AppendInt-12                        400.7n ± 1%   401.8n ± 1%       ~ (p=0.176 n=20)
AppendUint-12                       95.87n ± 1%   96.06n ± 1%       ~ (p=0.208 n=20)
AppendIntSmall-12                   3.450n ± 0%   3.455n ± 1%       ~ (p=0.203 n=20)
AppendUintVarlen/digits=1-12        3.150n ± 1%   3.175n ± 1%       ~ (p=0.147 n=20)
AppendUintVarlen/digits=2-12        2.654n ± 0%   2.667n ± 1%       ~ (p=0.003 n=20)
AppendUintVarlen/digits=3-12        5.044n ± 0%   5.069n ± 0%       ~ (p=0.026 n=20)
AppendUintVarlen/digits=4-12        5.046n ± 0%   5.047n ± 1%       ~ (p=0.408 n=20)
AppendUintVarlen/digits=5-12        5.851n ± 0%   5.860n ± 1%       ~ (p=0.132 n=20)
AppendUintVarlen/digits=6-12        6.118n ± 0%   6.120n ± 0%       ~ (p=0.888 n=20)
AppendUintVarlen/digits=7-12        7.333n ± 0%   7.334n ± 0%       ~ (p=0.588 n=20)
AppendUintVarlen/digits=8-12        7.312n ± 1%   7.322n ± 0%       ~ (p=0.805 n=20)
AppendUintVarlen/digits=9-12        7.832n ± 1%   7.838n ± 1%       ~ (p=0.465 n=20)
AppendUintVarlen/digits=10-12       8.606n ± 1%   8.602n ± 1%       ~ (p=0.974 n=20)
AppendUintVarlen/digits=11-12       8.908n ± 0%   8.899n ± 1%       ~ (p=0.931 n=20)
AppendUintVarlen/digits=12-12       9.178n ± 0%   9.118n ± 0%       ~ (p=0.007 n=20)
AppendUintVarlen/digits=13-12       9.398n ± 1%   9.405n ± 1%       ~ (p=0.888 n=20)
AppendUintVarlen/digits=14-12       10.24n ± 0%   10.22n ± 0%       ~ (p=0.154 n=20)
AppendUintVarlen/digits=15-12       10.50n ± 0%   10.48n ± 0%       ~ (p=0.692 n=20)
AppendUintVarlen/digits=16-12       11.66n ± 0%   11.75n ± 2%       ~ (p=0.087 n=20)
AppendUintVarlen/digits=17-12       11.65n ± 0%   11.72n ± 1%       ~ (p=0.079 n=20)
AppendUintVarlen/digits=18-12       12.38n ± 1%   12.42n ± 2%       ~ (p=0.035 n=20)
AppendUintVarlen/digits=19-12       13.59n ± 1%   13.60n ± 0%       ~ (p=0.673 n=20)
AppendUintVarlen/digits=20-12       13.85n ± 1%   13.84n ± 0%       ~ (p=0.634 n=20)
geomean                             17.99n        18.01n       +0.09%

host: s7
                                  │ e8ffcf3095c │            3c5742b667a             │
                                  │   sec/op    │   sec/op     vs base               │
AppendFloat/Decimal-32              22.24n ± 0%   22.20n ± 0%       ~ (p=0.143 n=20)
AppendFloat/Float-32                34.70n ± 0%   34.59n ± 0%       ~ (p=0.057 n=20)
AppendFloat/Exp-32                  34.85n ± 0%   34.77n ± 0%       ~ (p=0.051 n=20)
AppendFloat/NegExp-32               35.19n ± 0%   35.17n ± 0%       ~ (p=0.533 n=20)
AppendFloat/LongExp-32              36.80n ± 0%   36.78n ± 0%       ~ (p=0.941 n=20)
AppendFloat/Big-32                  38.63n ± 0%   38.71n ± 0%       ~ (p=0.143 n=20)
AppendFloat/BinaryExp-32            17.39n ± 0%   17.36n ± 0%       ~ (p=0.049 n=20)
AppendFloat/32Integer-32            22.29n ± 0%   22.23n ± 0%       ~ (p=0.068 n=20)
AppendFloat/32ExactFraction-32      33.52n ± 0%   33.44n ± 0%       ~ (p=0.058 n=20)
AppendFloat/32Point-32              32.96n ± 0%   32.93n ± 0%       ~ (p=0.256 n=20)
AppendFloat/32Exp-32                35.31n ± 0%   35.24n ± 0%       ~ (p=0.014 n=20)
AppendFloat/32NegExp-32             33.56n ± 0%   33.50n ± 0%       ~ (p=0.032 n=20)
AppendFloat/32Shortest-32           30.03n ± 0%   29.97n ± 0%       ~ (p=0.351 n=20)
AppendFloat/32Fixed8Hard-32         22.93n ± 0%   22.94n ± 0%       ~ (p=0.920 n=20)
AppendFloat/32Fixed9Hard-32         26.27n ± 0%   26.22n ± 0%       ~ (p=0.693 n=20)
AppendFloat/64Fixed1-32             21.15n ± 0%   21.09n ± 0%       ~ (p=0.006 n=20)
AppendFloat/64Fixed2-32             20.75n ± 0%   20.75n ± 0%       ~ (p=0.898 n=20)
AppendFloat/64Fixed3-32             21.29n ± 0%   21.28n ± 0%       ~ (p=0.524 n=20)
AppendFloat/64Fixed4-32             20.59n ± 0%   20.63n ± 0%       ~ (p=0.350 n=20)
AppendFloat/64Fixed12-32            32.53n ± 0%   32.51n ± 0%       ~ (p=0.804 n=20)
AppendFloat/64Fixed16-32            28.43n ± 0%   28.34n ± 0%       ~ (p=0.060 n=20)
AppendFloat/64Fixed12Hard-32        27.27n ± 0%   27.22n ± 0%       ~ (p=0.056 n=20)
AppendFloat/64Fixed17Hard-32        30.76n ± 0%   30.70n ± 0%       ~ (p=0.304 n=20)
AppendFloat/64Fixed18Hard-32        1.812µ ± 0%   1.806µ ± 1%       ~ (p=0.216 n=20)
AppendFloat/Slowpath64-32           35.48n ± 0%   35.43n ± 0%       ~ (p=0.129 n=20)
AppendFloat/SlowpathDenormal64-32   35.62n ± 0%   35.60n ± 0%       ~ (p=0.273 n=20)
AppendInt-32                        387.5n ± 0%   387.9n ± 0%       ~ (p=0.417 n=20)
AppendUint-32                       104.9n ± 0%   104.9n ± 0%       ~ (p=0.641 n=20)
AppendIntSmall-32                   3.329n ± 5%   3.489n ± 5%       ~ (p=0.723 n=20)
AppendUintVarlen/digits=1-32        2.396n ± 7%   2.398n ± 8%       ~ (p=0.409 n=20)
AppendUintVarlen/digits=2-32        2.399n ± 7%   2.315n ± 4%       ~ (p=0.386 n=20)
AppendUintVarlen/digits=3-32        5.516n ± 0%   5.506n ± 0%       ~ (p=0.026 n=20)
AppendUintVarlen/digits=4-32        5.515n ± 0%   5.510n ± 0%       ~ (p=0.291 n=20)
AppendUintVarlen/digits=5-32        5.748n ± 1%   5.731n ± 0%       ~ (p=0.014 n=20)
AppendUintVarlen/digits=6-32        5.873n ± 0%   5.853n ± 0%       ~ (p=0.011 n=20)
AppendUintVarlen/digits=7-32        6.460n ± 0%   6.444n ± 0%       ~ (p=0.041 n=20)
AppendUintVarlen/digits=8-32        6.457n ± 0%   6.446n ± 0%       ~ (p=0.047 n=20)
AppendUintVarlen/digits=9-32        7.377n ± 0%   7.373n ± 0%       ~ (p=0.569 n=20)
AppendUintVarlen/digits=10-32       8.496n ± 0%   8.492n ± 0%       ~ (p=0.525 n=20)
AppendUintVarlen/digits=11-32       8.674n ± 0%   8.653n ± 0%       ~ (p=0.060 n=20)
AppendUintVarlen/digits=12-32       9.416n ± 0%   9.386n ± 0%       ~ (p=0.035 n=20)
AppendUintVarlen/digits=13-32       9.621n ± 0%   9.594n ± 0%       ~ (p=0.069 n=20)
AppendUintVarlen/digits=14-32       10.34n ± 0%   10.35n ± 0%       ~ (p=0.332 n=20)
AppendUintVarlen/digits=15-32       10.48n ± 0%   10.52n ± 0%       ~ (p=0.196 n=20)
AppendUintVarlen/digits=16-32       11.27n ± 0%   11.27n ± 0%       ~ (p=0.445 n=20)
AppendUintVarlen/digits=17-32       11.50n ± 0%   11.48n ± 0%       ~ (p=0.283 n=20)
AppendUintVarlen/digits=18-32       12.15n ± 0%   12.18n ± 0%       ~ (p=0.414 n=20)
AppendUintVarlen/digits=19-32       13.42n ± 0%   13.42n ± 0%       ~ (p=0.782 n=20)
AppendUintVarlen/digits=20-32       13.70n ± 0%   13.71n ± 0%       ~ (p=0.540 n=20)
geomean                             18.71n        18.70n       -0.08%

host: s7:GOARCH=386
                                  │ e8ffcf3095c  │            3c5742b667a             │
                                  │    sec/op    │   sec/op     vs base               │
AppendFloat/Decimal-32               42.03n ± 0%   41.71n ± 1%  -0.75% (p=0.000 n=20)
AppendFloat/Float-32                 69.99n ± 0%   69.85n ± 0%       ~ (p=0.062 n=20)
AppendFloat/Exp-32                   73.07n ± 0%   73.13n ± 0%       ~ (p=0.240 n=20)
AppendFloat/NegExp-32                72.75n ± 0%   72.72n ± 0%       ~ (p=0.298 n=20)
AppendFloat/LongExp-32               74.20n ± 0%   74.13n ± 0%       ~ (p=0.952 n=20)
AppendFloat/Big-32                   82.88n ± 0%   82.91n ± 0%       ~ (p=0.909 n=20)
AppendFloat/BinaryExp-32             32.12n ± 0%   32.23n ± 0%       ~ (p=0.014 n=20)
AppendFloat/32Integer-32             41.18n ± 0%   41.15n ± 0%       ~ (p=0.212 n=20)
AppendFloat/32ExactFraction-32       62.65n ± 0%   62.38n ± 0%  -0.43% (p=0.000 n=20)
AppendFloat/32Point-32               59.98n ± 0%   59.82n ± 0%       ~ (p=0.109 n=20)
AppendFloat/32Exp-32                 72.62n ± 0%   72.69n ± 0%       ~ (p=0.417 n=20)
AppendFloat/32NegExp-32              62.36n ± 0%   62.49n ± 0%       ~ (p=0.578 n=20)
AppendFloat/32Shortest-32            58.03n ± 0%   57.95n ± 0%       ~ (p=0.615 n=20)
AppendFloat/32Fixed8Hard-32          36.75n ± 0%   36.34n ± 0%  -1.12% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-32          53.83n ± 0%   53.96n ± 0%       ~ (p=0.126 n=20)
AppendFloat/64Fixed1-32              48.52n ± 0%   48.72n ± 0%       ~ (p=0.075 n=20)
AppendFloat/64Fixed2-32              46.50n ± 0%   46.74n ± 0%  +0.53% (p=0.000 n=20)
AppendFloat/64Fixed3-32              46.43n ± 0%   46.24n ± 1%       ~ (p=0.147 n=20)
AppendFloat/64Fixed4-32              42.52n ± 0%   42.69n ± 0%       ~ (p=0.038 n=20)
AppendFloat/64Fixed12-32             54.51n ± 1%   54.85n ± 0%  +0.63% (p=0.000 n=20)
AppendFloat/64Fixed16-32             52.61n ± 0%   52.94n ± 0%  +0.63% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-32         50.78n ± 0%   51.45n ± 0%  +1.31% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-32         59.91n ± 0%   59.91n ± 0%       ~ (p=0.713 n=20)
AppendFloat/64Fixed18Hard-32         3.984µ ± 1%   4.000µ ± 1%       ~ (p=0.569 n=20)
AppendFloat/Slowpath64-32            73.42n ± 0%   73.37n ± 0%       ~ (p=0.425 n=20)
AppendFloat/SlowpathDenormal64-32    73.27n ± 0%   73.36n ± 0%       ~ (p=0.298 n=20)
AppendInt-32                         1.036µ ± 1%   1.041µ ± 1%       ~ (p=0.024 n=20)
AppendUint-32                        261.1n ± 0%   262.1n ± 1%  +0.42% (p=0.000 n=20)
AppendIntSmall-32                    5.515n ± 0%   5.506n ± 0%       ~ (p=0.394 n=20)
AppendUintVarlen/digits=1-32         3.679n ± 0%   3.685n ± 0%       ~ (p=0.815 n=20)
AppendUintVarlen/digits=2-32         3.683n ± 0%   3.687n ± 0%       ~ (p=0.899 n=20)
AppendUintVarlen/digits=3-32         8.988n ± 2%   8.843n ± 1%  -1.61% (p=0.000 n=20)
AppendUintVarlen/digits=4-32         9.300n ± 1%   9.106n ± 1%  -2.09% (p=0.000 n=20)
AppendUintVarlen/digits=5-32        10.235n ± 1%   9.829n ± 1%  -3.97% (p=0.000 n=20)
AppendUintVarlen/digits=6-32         10.44n ± 1%   10.03n ± 0%  -3.88% (p=0.000 n=20)
AppendUintVarlen/digits=7-32         11.27n ± 1%   10.94n ± 1%  -2.93% (p=0.000 n=20)
AppendUintVarlen/digits=8-32         11.46n ± 1%   11.13n ± 1%  -2.88% (p=0.000 n=20)
AppendUintVarlen/digits=9-32         12.74n ± 0%   12.27n ± 1%  -3.69% (p=0.000 n=20)
AppendUintVarlen/digits=10-32        15.57n ± 0%   15.71n ± 1%  +0.90% (p=0.000 n=20)
AppendUintVarlen/digits=11-32        15.65n ± 1%   15.98n ± 0%  +2.11% (p=0.000 n=20)
AppendUintVarlen/digits=12-32        16.54n ± 0%   16.73n ± 0%  +1.21% (p=0.000 n=20)
AppendUintVarlen/digits=13-32        16.69n ± 0%   17.04n ± 0%  +2.07% (p=0.000 n=20)
AppendUintVarlen/digits=14-32        17.52n ± 1%   17.62n ± 0%       ~ (p=0.005 n=20)
AppendUintVarlen/digits=15-32        17.76n ± 0%   17.86n ± 0%  +0.56% (p=0.001 n=20)
AppendUintVarlen/digits=16-32        18.68n ± 1%   18.59n ± 0%       ~ (p=0.006 n=20)
AppendUintVarlen/digits=17-32        18.78n ± 1%   18.74n ± 0%       ~ (p=0.040 n=20)
AppendUintVarlen/digits=18-32        19.63n ± 1%   19.54n ± 0%       ~ (p=0.202 n=20)
AppendUintVarlen/digits=19-32        24.02n ± 1%   24.23n ± 1%  +0.87% (p=0.000 n=20)
AppendUintVarlen/digits=20-32        23.87n ± 1%   24.20n ± 1%  +1.40% (p=0.000 n=20)
geomean                              35.08n        35.00n       -0.21%

host: linux-amd64
                                  │ e8ffcf3095c │            3c5742b667a             │
                                  │   sec/op    │   sec/op     vs base               │
AppendFloat/Decimal-16              62.16n ± 1%   61.81n ± 0%       ~ (p=0.060 n=20)
AppendFloat/Float-16                91.66n ± 1%   91.22n ± 1%       ~ (p=0.606 n=20)
AppendFloat/Exp-16                  95.42n ± 2%   95.22n ± 1%       ~ (p=0.417 n=20)
AppendFloat/NegExp-16               96.88n ± 1%   95.89n ± 1%       ~ (p=0.185 n=20)
AppendFloat/LongExp-16              102.0n ± 1%   101.6n ± 1%       ~ (p=0.794 n=20)
AppendFloat/Big-16                  110.8n ± 1%   110.8n ± 1%       ~ (p=0.984 n=20)
AppendFloat/BinaryExp-16            46.33n ± 1%   46.19n ± 1%       ~ (p=0.723 n=20)
AppendFloat/32Integer-16            62.62n ± 2%   61.88n ± 1%       ~ (p=0.286 n=20)
AppendFloat/32ExactFraction-16      89.09n ± 3%   88.25n ± 2%       ~ (p=0.101 n=20)
AppendFloat/32Point-16              86.17n ± 1%   86.90n ± 1%       ~ (p=0.251 n=20)
AppendFloat/32Exp-16                101.7n ± 1%   101.2n ± 1%       ~ (p=0.379 n=20)
AppendFloat/32NegExp-16             92.17n ± 1%   92.81n ± 1%       ~ (p=0.165 n=20)
AppendFloat/32Shortest-16           82.38n ± 1%   82.89n ± 1%       ~ (p=0.185 n=20)
AppendFloat/32Fixed8Hard-16         60.32n ± 1%   60.41n ± 1%       ~ (p=0.337 n=20)
AppendFloat/32Fixed9Hard-16         69.58n ± 1%   69.22n ± 1%       ~ (p=0.794 n=20)
AppendFloat/64Fixed1-16             57.56n ± 1%   57.65n ± 1%       ~ (p=0.597 n=20)
AppendFloat/64Fixed2-16             55.84n ± 1%   55.54n ± 1%       ~ (p=0.059 n=20)
AppendFloat/64Fixed3-16             57.12n ± 2%   56.55n ± 1%       ~ (p=0.449 n=20)
AppendFloat/64Fixed4-16             55.38n ± 2%   54.50n ± 2%       ~ (p=0.010 n=20)
AppendFloat/64Fixed12-16            88.28n ± 1%   86.67n ± 1%  -1.83% (p=0.000 n=20)
AppendFloat/64Fixed16-16            73.41n ± 1%   73.56n ± 2%       ~ (p=0.794 n=20)
AppendFloat/64Fixed12Hard-16        72.08n ± 1%   71.71n ± 1%       ~ (p=0.116 n=20)
AppendFloat/64Fixed17Hard-16        79.78n ± 1%   79.78n ± 1%       ~ (p=0.224 n=20)
AppendFloat/64Fixed18Hard-16        4.720µ ± 1%   4.746µ ± 1%       ~ (p=0.877 n=20)
AppendFloat/Slowpath64-16           98.71n ± 1%   98.79n ± 1%       ~ (p=0.678 n=20)
AppendFloat/SlowpathDenormal64-16   97.58n ± 2%   98.16n ± 2%       ~ (p=0.862 n=20)
AppendInt-16                        1.185µ ± 1%   1.194µ ± 1%       ~ (p=0.457 n=20)
AppendUint-16                       292.6n ± 1%   293.9n ± 1%       ~ (p=0.351 n=20)
AppendIntSmall-16                   7.197n ± 1%   7.203n ± 1%       ~ (p=0.952 n=20)
AppendUintVarlen/digits=1-16        5.905n ± 1%   5.897n ± 2%       ~ (p=0.474 n=20)
AppendUintVarlen/digits=2-16        5.770n ± 1%   5.733n ± 1%       ~ (p=0.180 n=20)
AppendUintVarlen/digits=3-16        14.00n ± 2%   14.00n ± 1%       ~ (p=0.909 n=20)
AppendUintVarlen/digits=4-16        13.99n ± 1%   14.03n ± 1%       ~ (p=0.578 n=20)
AppendUintVarlen/digits=5-16        15.88n ± 2%   15.83n ± 1%       ~ (p=0.542 n=20)
AppendUintVarlen/digits=6-16        16.25n ± 1%   16.30n ± 1%       ~ (p=0.899 n=20)
AppendUintVarlen/digits=7-16        17.66n ± 1%   17.70n ± 1%       ~ (p=0.440 n=20)
AppendUintVarlen/digits=8-16        18.54n ± 1%   18.58n ± 2%       ~ (p=0.262 n=20)
AppendUintVarlen/digits=9-16        20.25n ± 2%   20.43n ± 1%       ~ (p=0.007 n=20)
AppendUintVarlen/digits=10-16       23.88n ± 1%   24.00n ± 1%       ~ (p=0.473 n=20)
AppendUintVarlen/digits=11-16       24.42n ± 1%   24.57n ± 2%       ~ (p=0.743 n=20)
AppendUintVarlen/digits=12-16       25.54n ± 2%   25.88n ± 1%       ~ (p=0.499 n=20)
AppendUintVarlen/digits=13-16       26.55n ± 1%   26.60n ± 1%       ~ (p=0.774 n=20)
AppendUintVarlen/digits=14-16       28.18n ± 1%   28.16n ± 1%       ~ (p=0.606 n=20)
AppendUintVarlen/digits=15-16       28.66n ± 1%   28.85n ± 0%       ~ (p=0.031 n=20)
AppendUintVarlen/digits=16-16       29.84n ± 1%   30.00n ± 1%       ~ (p=0.151 n=20)
AppendUintVarlen/digits=17-16       30.54n ± 1%   30.60n ± 1%       ~ (p=0.952 n=20)
AppendUintVarlen/digits=18-16       32.01n ± 1%   32.26n ± 2%       ~ (p=0.239 n=20)
AppendUintVarlen/digits=19-16       35.50n ± 1%   35.56n ± 1%       ~ (p=0.256 n=20)
AppendUintVarlen/digits=20-16       35.94n ± 1%   35.96n ± 1%       ~ (p=0.867 n=20)
geomean                             50.35n        50.35n       -0.01%

host: linux-386
                                  │ e8ffcf3095c │             3c5742b667a             │
                                  │   sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-16              122.9n ± 0%   122.9n ± 0%        ~ (p=0.351 n=20)
AppendFloat/Float-16                226.7n ± 0%   227.1n ± 0%        ~ (p=0.003 n=20)
AppendFloat/Exp-16                  238.3n ± 0%   238.3n ± 0%        ~ (p=0.301 n=20)
AppendFloat/NegExp-16               239.2n ± 0%   239.5n ± 0%        ~ (p=0.015 n=20)
AppendFloat/LongExp-16              237.6n ± 0%   237.8n ± 0%        ~ (p=0.357 n=20)
AppendFloat/Big-16                  275.6n ± 0%   275.7n ± 0%        ~ (p=0.576 n=20)
AppendFloat/BinaryExp-16            90.33n ± 0%   87.69n ± 0%   -2.92% (p=0.000 n=20)
AppendFloat/32Integer-16            121.7n ± 0%   121.8n ± 0%        ~ (p=0.340 n=20)
AppendFloat/32ExactFraction-16      209.4n ± 0%   209.4n ± 0%        ~ (p=0.566 n=20)
AppendFloat/32Point-16              196.1n ± 0%   196.5n ± 0%        ~ (p=0.036 n=20)
AppendFloat/32Exp-16                246.3n ± 0%   246.4n ± 0%        ~ (p=0.407 n=20)
AppendFloat/32NegExp-16             205.4n ± 0%   205.4n ± 0%        ~ (p=0.221 n=20)
AppendFloat/32Shortest-16           187.8n ± 0%   187.8n ± 0%        ~ (p=0.671 n=20)
AppendFloat/32Fixed8Hard-16         112.3n ± 0%   107.6n ± 0%   -4.19% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-16         182.3n ± 0%   182.1n ± 0%        ~ (p=0.098 n=20)
AppendFloat/64Fixed1-16             167.0n ± 0%   165.7n ± 0%   -0.78% (p=0.000 n=20)
AppendFloat/64Fixed2-16             161.9n ± 0%   160.7n ± 0%   -0.74% (p=0.000 n=20)
AppendFloat/64Fixed3-16             157.7n ± 0%   156.4n ± 0%   -0.82% (p=0.000 n=20)
AppendFloat/64Fixed4-16             134.4n ± 0%   133.5n ± 0%   -0.63% (p=0.000 n=20)
AppendFloat/64Fixed12-16            178.2n ± 0%   176.4n ± 0%   -1.01% (p=0.000 n=20)
AppendFloat/64Fixed16-16            168.7n ± 0%   166.4n ± 0%   -1.33% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-16        162.8n ± 0%   162.2n ± 0%   -0.34% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-16        201.9n ± 0%   198.6n ± 0%   -1.66% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-16        14.45µ ± 0%   14.46µ ± 0%        ~ (p=0.189 n=20)
AppendFloat/Slowpath64-16           232.8n ± 0%   232.8n ± 0%        ~ (p=0.995 n=20)
AppendFloat/SlowpathDenormal64-16   229.0n ± 0%   228.9n ± 0%        ~ (p=0.605 n=20)
AppendInt-16                        3.123µ ± 0%   3.099µ ± 0%   -0.77% (p=0.000 n=20)
AppendUint-16                       832.0n ± 0%   820.8n ± 0%   -1.35% (p=0.000 n=20)
AppendIntSmall-16                   13.27n ± 0%   13.28n ± 0%        ~ (p=0.127 n=20)
AppendUintVarlen/digits=1-16        10.19n ± 0%   10.20n ± 0%        ~ (p=0.414 n=20)
AppendUintVarlen/digits=2-16        10.19n ± 0%   10.19n ± 0%        ~ (p=0.700 n=20)
AppendUintVarlen/digits=3-16        21.47n ± 0%   20.51n ± 0%   -4.49% (p=0.000 n=20)
AppendUintVarlen/digits=4-16        21.68n ± 0%   21.05n ± 0%   -2.88% (p=0.000 n=20)
AppendUintVarlen/digits=5-16        26.28n ± 0%   23.94n ± 0%   -8.92% (p=0.000 n=20)
AppendUintVarlen/digits=6-16        26.77n ± 0%   24.67n ± 0%   -7.84% (p=0.000 n=20)
AppendUintVarlen/digits=7-16        30.65n ± 0%   27.25n ± 0%  -11.08% (p=0.000 n=20)
AppendUintVarlen/digits=8-16        31.27n ± 0%   28.11n ± 0%  -10.09% (p=0.000 n=20)
AppendUintVarlen/digits=9-16        36.55n ± 0%   32.53n ± 0%  -10.98% (p=0.000 n=20)
AppendUintVarlen/digits=10-16       42.53n ± 0%   42.06n ± 0%   -1.09% (p=0.000 n=20)
AppendUintVarlen/digits=11-16       42.21n ± 0%   42.51n ± 0%   +0.72% (p=0.000 n=20)
AppendUintVarlen/digits=12-16       45.44n ± 0%   44.41n ± 0%   -2.26% (p=0.000 n=20)
AppendUintVarlen/digits=13-16       46.04n ± 0%   45.06n ± 0%   -2.13% (p=0.000 n=20)
AppendUintVarlen/digits=14-16       49.35n ± 0%   47.73n ± 0%   -3.27% (p=0.000 n=20)
AppendUintVarlen/digits=15-16       50.04n ± 0%   48.45n ± 0%   -3.18% (p=0.000 n=20)
AppendUintVarlen/digits=16-16       53.51n ± 0%   51.21n ± 0%   -4.31% (p=0.000 n=20)
AppendUintVarlen/digits=17-16       53.60n ± 0%   51.19n ± 0%   -4.50% (p=0.000 n=20)
AppendUintVarlen/digits=18-16       57.21n ± 0%   54.03n ± 0%   -5.54% (p=0.000 n=20)
AppendUintVarlen/digits=19-16       64.41n ± 0%   64.68n ± 0%   +0.41% (p=0.000 n=20)
AppendUintVarlen/digits=20-16       64.51n ± 0%   65.04n ± 0%   +0.82% (p=0.000 n=20)
geomean                             104.9n        102.8n        -2.02%

host: linux-ppc64le
                                 │ e8ffcf3095c │             3c5742b667a             │
                                 │   sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-5              53.78n ± 1%   53.62n ± 1%        ~ (p=0.588 n=20)
AppendFloat/Float-5                76.29n ± 2%   75.77n ± 2%        ~ (p=0.402 n=20)
AppendFloat/Exp-5                  83.73n ± 0%   82.25n ± 2%        ~ (p=0.009 n=20)
AppendFloat/NegExp-5               84.22n ± 1%   83.15n ± 1%        ~ (p=0.031 n=20)
AppendFloat/LongExp-5              88.66n ± 1%   88.34n ± 1%        ~ (p=0.213 n=20)
AppendFloat/Big-5                  93.25n ± 0%   92.73n ± 1%        ~ (p=0.007 n=20)
AppendFloat/BinaryExp-5            40.69n ± 0%   44.88n ± 1%  +10.31% (p=0.000 n=20)
AppendFloat/32Integer-5            54.17n ± 0%   54.39n ± 1%        ~ (p=0.245 n=20)
AppendFloat/32ExactFraction-5      79.89n ± 1%   79.41n ± 1%        ~ (p=0.457 n=20)
AppendFloat/32Point-5              74.81n ± 1%   74.89n ± 0%        ~ (p=0.625 n=20)
AppendFloat/32Exp-5                85.59n ± 1%   85.42n ± 1%        ~ (p=0.331 n=20)
AppendFloat/32NegExp-5             82.74n ± 1%   82.22n ± 1%        ~ (p=0.025 n=20)
AppendFloat/32Shortest-5           69.72n ± 0%   69.79n ± 1%        ~ (p=0.625 n=20)
AppendFloat/32Fixed8Hard-5         54.60n ± 0%   57.54n ± 0%   +5.39% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-5         58.49n ± 1%   65.56n ± 0%  +12.09% (p=0.000 n=20)
AppendFloat/64Fixed1-5             47.07n ± 1%   47.81n ± 1%        ~ (p=0.002 n=20)
AppendFloat/64Fixed2-5             47.88n ± 1%   48.52n ± 1%        ~ (p=0.007 n=20)
AppendFloat/64Fixed3-5             47.47n ± 1%   48.32n ± 1%        ~ (p=0.007 n=20)
AppendFloat/64Fixed4-5             45.12n ± 1%   46.26n ± 1%   +2.55% (p=0.000 n=20)
AppendFloat/64Fixed12-5            79.27n ± 0%   83.78n ± 1%   +5.68% (p=0.000 n=20)
AppendFloat/64Fixed16-5            69.28n ± 1%   70.69n ± 0%        ~ (p=0.001 n=20)
AppendFloat/64Fixed12Hard-5        65.42n ± 0%   68.31n ± 1%   +4.43% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-5        73.89n ± 0%   77.30n ± 1%   +4.63% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-5        5.163µ ± 1%   5.169µ ± 0%        ~ (p=0.733 n=20)
AppendFloat/Slowpath64-5           86.31n ± 1%   86.70n ± 2%        ~ (p=0.578 n=20)
AppendFloat/SlowpathDenormal64-5   83.10n ± 1%   82.97n ± 1%        ~ (p=0.218 n=20)
AppendInt-5                        1.013µ ± 1%   1.125µ ± 0%  +11.06% (p=0.000 n=20)
AppendUint-5                       268.2n ± 0%   287.7n ± 1%   +7.27% (p=0.000 n=20)
AppendIntSmall-5                   6.644n ± 3%   6.936n ± 2%        ~ (p=0.023 n=20)
AppendUintVarlen/digits=1-5        5.556n ± 4%   5.381n ± 3%        ~ (p=0.108 n=20)
AppendUintVarlen/digits=2-5        5.165n ± 1%   5.413n ± 1%   +4.80% (p=0.000 n=20)
AppendUintVarlen/digits=3-5        10.26n ± 1%   11.29n ± 2%  +10.04% (p=0.000 n=20)
AppendUintVarlen/digits=4-5        10.11n ± 1%   11.12n ± 1%   +9.99% (p=0.000 n=20)
AppendUintVarlen/digits=5-5        12.37n ± 2%   13.26n ± 1%   +7.19% (p=0.000 n=20)
AppendUintVarlen/digits=6-5        12.85n ± 3%   13.52n ± 1%   +5.25% (p=0.000 n=20)
AppendUintVarlen/digits=7-5        15.46n ± 7%   16.52n ± 1%        ~ (p=0.005 n=20)
AppendUintVarlen/digits=8-5        14.99n ± 1%   16.60n ± 1%  +10.74% (p=0.000 n=20)
AppendUintVarlen/digits=9-5        18.13n ± 1%   20.23n ± 1%  +11.56% (p=0.000 n=20)
AppendUintVarlen/digits=10-5       19.05n ± 3%   25.62n ± 1%  +34.49% (p=0.000 n=20)
AppendUintVarlen/digits=11-5       21.64n ± 2%   26.11n ± 1%  +20.63% (p=0.000 n=20)
AppendUintVarlen/digits=12-5       21.91n ± 1%   27.91n ± 0%  +27.38% (p=0.000 n=20)
AppendUintVarlen/digits=13-5       24.60n ± 1%   28.38n ± 1%  +15.37% (p=0.000 n=20)
AppendUintVarlen/digits=14-5       25.80n ± 1%   30.79n ± 0%  +19.32% (p=0.000 n=20)
AppendUintVarlen/digits=15-5       28.90n ± 1%   31.38n ± 3%   +8.55% (p=0.000 n=20)
AppendUintVarlen/digits=16-5       28.13n ± 2%   32.54n ± 0%  +15.69% (p=0.000 n=20)
AppendUintVarlen/digits=17-5       30.82n ± 1%   33.16n ± 1%   +7.61% (p=0.000 n=20)
AppendUintVarlen/digits=18-5       32.03n ± 0%   36.12n ± 1%  +12.74% (p=0.000 n=20)
AppendUintVarlen/digits=19-5       35.99n ± 3%   40.97n ± 1%  +13.82% (p=0.000 n=20)
AppendUintVarlen/digits=20-5       35.15n ± 1%   40.71n ± 0%  +15.80% (p=0.000 n=20)
geomean                            44.34n        47.15n        +6.34%

Change-Id: Ia6a3971a76f39d6187b10d6944071ee1c1b47316
Reviewed-on: https://go-review.googlesource.com/c/go/+/716462
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
This commit is contained in:
Russ Cox 2025-10-29 12:09:18 -04:00 committed by Gopher Robot
parent 6aca04a73a
commit cbbd385cb8

View file

@ -4,10 +4,7 @@
package strconv package strconv
import ( import "math/bits"
"internal/goarch"
"math/bits"
)
// FormatUint returns the string representation of i in the given base, // FormatUint returns the string representation of i in the given base,
// for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z' // for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z'
@ -184,41 +181,13 @@ func small(i int) string {
// //
// the decimal representation is in a[i:]. // the decimal representation is in a[i:].
func formatBase10(a []byte, u uint64) int { func formatBase10(a []byte, u uint64) int {
// Decide implementation strategy based on architecture. // Split into 9-digit chunks that fit in uint32s
const ( // and convert each chunk using uint32 math instead of uint64 math.
// 64-bit systems can work in 64-bit math the whole time // The obvious way to write the outer loop is "for u >= 1e9", but most numbers are small,
// or can split the uint64 into uint32-sized chunks. // so the setup for the comparison u >= 1e9 is usually pure overhead.
// On most systems, the uint32 math is faster, but not all. // Instead, we approximate it by u>>29 != 0, which is usually faster and good enough.
// The decision here is based on benchmarking.
itoaPure64 = host64bit && goarch.GOARCH != "amd64" && goarch.GOARCH != "arm64" && goarch.GOARCH != "s390x"
)
if itoaPure64 {
// Convert 2 digits at a time, using 64-bit math.
i := len(a)
u := uint(u)
for u >= 100 {
var dd uint
u, dd = u/100, (u%100)*2
i -= 2
a[i+0], a[i+1] = smalls[dd+0], smalls[dd+1]
}
dd := u * 2
i--
a[i] = smalls[dd+1]
if u >= 10 {
i--
a[i] = smalls[dd]
}
return i
}
// Split into 9-digit chunks that fit in uint32s and convert each chunk using 32-bit math.
// Most numbers are small, so the comparison u >= 1e9 is usually pure overhead,
// so we approximate it by u>>29 != 0, which is usually faster and good enough.
i := len(a) i := len(a)
for (host64bit && u>>29 != 0) || (!host64bit && (u>>32 != 0 || uint32(u)>>29 != 0)) { for (host64bit && u>>29 != 0) || (!host64bit && uint32(u)>>29|uint32(u>>32) != 0) {
var lo uint32 var lo uint32
u, lo = u/1e9, uint32(u%1e9) u, lo = u/1e9, uint32(u%1e9)