LibJS: Get this from execution context for non-arrow functions

[kalenikaliaksandr]

Allows to skip function environment allocation for non-arrow functions if the only reason it is needed is to hold this binding.

The parser is changed to do following:

• If a function is an arrow function and uses this then all functions in a scope chain are marked to allocate function environment for this binding.
• If a function uses new.target then all functions in a scope chain are marked to allocate function environment.

ordinary_call_bind_this() is changed to put this value in execution context when function environment allocation is skipped.

35% improvement in Octane/typescript.js
50% improvement in Octane/deltablue.js
19% improvement in Octane/raytrace.js

Suite       Test                                   Speedup  Old (Mean ± Range)        New (Mean ± Range)
----------  -----------------------------------  ---------  ------------------------  ------------------------
Kraken      ai-astar.js                              0.957  1.875 ± 1.870 … 1.880     1.960 ± 1.950 … 1.970
Kraken      audio-beat-detection.js                  0.986  1.410 ± 1.410 … 1.410     1.430 ± 1.430 … 1.430
Kraken      audio-dft.js                             1.017  1.205 ± 1.190 … 1.220     1.185 ± 1.170 … 1.200
Kraken      audio-fft.js                             1.004  1.320 ± 1.310 … 1.330     1.315 ± 1.310 … 1.320
Kraken      audio-oscillator.js                      0.993  1.445 ± 1.440 … 1.450     1.455 ± 1.450 … 1.460
Kraken      imaging-darkroom.js                      0.966  2.430 ± 2.400 … 2.460     2.515 ± 2.510 … 2.520
Kraken      imaging-desaturate.js                    0.985  2.010 ± 2.010 … 2.010     2.040 ± 2.040 … 2.040
Kraken      imaging-gaussian-blur.js                 0.991  7.515 ± 7.490 … 7.540     7.585 ± 7.560 … 7.610
Kraken      json-parse-financial.js                  0.778  0.140 ± 0.140 … 0.140     0.180 ± 0.160 … 0.200
Kraken      json-stringify-tinderbox.js              0.906  0.240 ± 0.240 … 0.240     0.265 ± 0.260 … 0.270
Kraken      stanford-crypto-aes.js                   1.045  0.690 ± 0.690 … 0.690     0.660 ± 0.650 … 0.670
Kraken      stanford-crypto-ccm.js                   1.072  0.595 ± 0.590 … 0.600     0.555 ± 0.550 … 0.560
Kraken      stanford-crypto-pbkdf2.js                1.059  1.175 ± 1.170 … 1.180     1.110 ± 1.100 … 1.120
Kraken      stanford-crypto-sha256-iterative.js      1.043  0.485 ± 0.480 … 0.490     0.465 ± 0.460 … 0.470
Octane      box2d.js                                 1.203  2.545 ± 2.540 … 2.550     2.115 ± 2.110 … 2.120
Octane      code-load.js                             0.993  2.070 ± 2.060 … 2.080     2.085 ± 2.080 … 2.090
Octane      crypto.js                                1.151  7.130 ± 7.110 … 7.150     6.195 ± 6.110 … 6.280
Octane      deltablue.js                             1.51   3.050 ± 3.050 … 3.050     2.020 ± 2.010 … 2.030
Octane      earley-boyer.js                          1.109  19.405 ± 19.280 … 19.530  17.490 ± 17.480 … 17.500
Octane      gbemu.js                                 1.06   3.175 ± 3.150 … 3.200     2.995 ± 2.980 … 3.010
Octane      mandreel.js                              1      13.955 ± 13.880 … 14.030  13.960 ± 13.830 … 14.090
Octane      navier-stokes.js                         1.005  3.185 ± 3.140 … 3.230     3.170 ± 3.160 … 3.180
Octane      pdfjs.js                                 1.062  3.085 ± 3.070 … 3.100     2.905 ± 2.900 … 2.910
Octane      raytrace.js                              1.188  6.625 ± 6.550 … 6.700     5.575 ± 5.570 … 5.580
Octane      regexp.js                                1.005  22.905 ± 22.760 … 23.050  22.795 ± 22.770 … 22.820
Octane      richards.js                              1.002  2.020 ± 2.020 … 2.020     2.015 ± 2.010 … 2.020
Octane      splay.js                                 1.026  2.715 ± 2.710 … 2.720     2.645 ± 2.620 … 2.670
Octane      typescript.js                            1.395  36.855 ± 36.360 … 37.350  26.415 ± 26.310 … 26.520
Octane      zlib.js                                  1.005  72.960 ± 72.530 … 73.390  72.565 ± 72.130 … 73.000
Kraken      Total                                    0.992  22.535                    22.720
Octane      Total                                    1.09   201.680                   184.945
All Suites  Total                                    1.08   224.215                   207.665