Some integer/float binary operations of 386 can take a direct memory
operand, which is more efficient than loading to a register.

These CL does this optimization by copying the similar solution
of amd64. And the go1 benchmark shows some inprovements, especially
the test case Template. (excluding noise)

name                     old time/op    new time/op    delta
BinaryTree17-4              3.42s ± 2%     3.40s ± 2%    ~     (p=0.069 n=38+39)
Fannkuch11-4                3.48s ± 1%     3.53s ± 1%  +1.59%  (p=0.000 n=40+40)
FmtFprintfEmpty-4          46.7ns ± 4%    46.3ns ± 3%  -1.03%  (p=0.001 n=40+40)
FmtFprintfString-4         80.1ns ± 3%    80.6ns ± 3%  +0.56%  (p=0.029 n=40+40)
FmtFprintfInt-4            92.4ns ± 2%    92.3ns ± 3%    ~     (p=0.847 n=40+40)
FmtFprintfIntInt-4          147ns ± 3%     144ns ± 3%  -1.87%  (p=0.000 n=40+40)
FmtFprintfPrefixedInt-4     182ns ± 2%     184ns ± 3%  +0.99%  (p=0.002 n=40+40)
FmtFprintfFloat-4           387ns ± 3%     384ns ± 3%    ~     (p=0.069 n=40+40)
FmtManyArgs-4               619ns ± 3%     616ns ± 3%    ~     (p=0.320 n=40+40)
GobDecode-4                7.28ms ± 6%    7.27ms ± 5%    ~     (p=0.897 n=40+40)
GobEncode-4                7.33ms ± 6%    7.21ms ± 6%  -1.56%  (p=0.022 n=38+40)
Gzip-4                      357ms ± 4%     357ms ± 4%    ~     (p=0.071 n=40+40)
Gunzip-4                   45.3ms ± 3%    45.4ms ± 3%    ~     (p=0.452 n=40+40)
HTTPClientServer-4         63.0µs ± 2%    62.9µs ± 3%    ~     (p=0.760 n=38+39)
JSONEncode-4               22.0ms ± 4%    21.7ms ± 4%  -1.49%  (p=0.000 n=40+40)
JSONDecode-4               67.7ms ± 4%    68.3ms ± 3%  +0.86%  (p=0.039 n=40+40)
Mandelbrot200-4            5.16ms ± 3%    5.17ms ± 3%    ~     (p=0.418 n=40+40)
GoParse-4                  3.30ms ± 2%    3.32ms ± 3%  +0.55%  (p=0.017 n=40+40)
RegexpMatchEasy0_32-4       104ns ± 3%     104ns ± 4%    ~     (p=0.992 n=40+40)
RegexpMatchEasy0_1K-4       852ns ± 3%     851ns ± 2%    ~     (p=0.344 n=40+40)
RegexpMatchEasy1_32-4       113ns ± 4%     113ns ± 5%    ~     (p=0.937 n=40+40)
RegexpMatchEasy1_1K-4      1.03µs ± 5%    1.04µs ± 4%    ~     (p=0.430 n=40+40)
RegexpMatchMedium_32-4      132ns ± 4%     131ns ± 3%  -1.06%  (p=0.027 n=40+40)
RegexpMatchMedium_1K-4     43.0µs ± 3%    43.2µs ± 3%    ~     (p=0.122 n=40+40)
RegexpMatchHard_32-4       2.21µs ± 4%    2.20µs ± 4%    ~     (p=0.146 n=40+40)
RegexpMatchHard_1K-4       67.1µs ± 4%    67.2µs ± 3%    ~     (p=0.859 n=40+40)
Revcomp-4                   1.85s ± 2%     1.85s ± 3%    ~     (p=0.184 n=40+40)
Template-4                 70.1ms ± 4%    67.5ms ± 3%  -3.65%  (p=0.000 n=40+40)
TimeParse-4                 457ns ±16%     439ns ± 4%    ~     (p=0.683 n=40+34)
TimeFormat-4                413ns ± 3%     414ns ± 3%    ~     (p=0.850 n=40+40)
[Geo mean]                 67.5µs         67.3µs       -0.38%

name                     old speed      new speed      delta
GobDecode-4               105MB/s ± 6%   106MB/s ± 5%    ~     (p=0.893 n=40+40)
GobEncode-4               105MB/s ± 6%   107MB/s ± 7%  +1.60%  (p=0.023 n=38+40)
Gzip-4                   54.4MB/s ± 4%  54.5MB/s ± 4%    ~     (p=0.073 n=40+40)
Gunzip-4                  429MB/s ± 3%   428MB/s ± 3%    ~     (p=0.453 n=40+40)
JSONEncode-4             88.3MB/s ± 5%  89.6MB/s ± 4%  +1.51%  (p=0.000 n=40+40)
JSONDecode-4             28.7MB/s ± 4%  28.4MB/s ± 3%  -0.87%  (p=0.039 n=40+40)
GoParse-4                17.6MB/s ± 3%  17.5MB/s ± 3%  -0.55%  (p=0.020 n=40+40)
RegexpMatchEasy0_32-4     308MB/s ± 4%   308MB/s ± 5%    ~     (p=0.988 n=40+40)
RegexpMatchEasy0_1K-4    1.20GB/s ± 3%  1.20GB/s ± 2%    ~     (p=0.329 n=40+40)
RegexpMatchEasy1_32-4     283MB/s ± 4%   283MB/s ± 4%    ~     (p=0.507 n=40+40)
RegexpMatchEasy1_1K-4     991MB/s ± 5%   987MB/s ± 4%    ~     (p=0.446 n=40+40)
RegexpMatchMedium_32-4   7.54MB/s ± 4%  7.63MB/s ± 3%  +1.26%  (p=0.004 n=40+40)
RegexpMatchMedium_1K-4   23.8MB/s ± 3%  23.7MB/s ± 4%    ~     (p=0.121 n=40+40)
RegexpMatchHard_32-4     14.5MB/s ± 4%  14.6MB/s ± 4%    ~     (p=0.145 n=40+40)
RegexpMatchHard_1K-4     15.3MB/s ± 4%  15.2MB/s ± 3%    ~     (p=0.874 n=40+40)
Revcomp-4                 137MB/s ± 2%   137MB/s ± 3%    ~     (p=0.179 n=40+40)
Template-4               27.7MB/s ± 4%  28.7MB/s ± 3%  +3.78%  (p=0.000 n=40+40)
[Geo mean]               78.9MB/s       79.2MB/s       +0.38%

Change-Id: I3ba688c253b665485c1ebdf5a75f4ce82cc3def3
Reviewed-on: https://go-review.googlesource.com/102036
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Keith Randall <khr@golang.org>