V8 JavaScript Engine with AOTC

This is a modified version of V8 JavaScript Engine. AOTC means "Ahead-Of-Time Compilation" and in this project it allows to save machine-dependent optimized Lithium IR of Crankshaft JIT compiler into a file. Saving is available through command line "d8" interface. Based on V8 version 3.31.

Building

V8 build instructions. Building process is the same, our implementation is only for x64 platform, basically build is done using "make x64.release" command.

New command line options for d8

option	description
--save-code <file>	Save Lithium IR into file
--load-code <file>	Load Lithium IR from file
--saveload-edge	Set other d8 options which may break something when using saved Lithium IR. For example, concurrent JIT and concurrent on-stack-replacement must be disabled.

This implementation supports only a single JavaScript source file.

Example

One of arewefastyet.com asm.js benchmarks

$ wget -q https://raw.githubusercontent.com/h4writer/arewefastyet/master/benchmarks/asmjs-apps/box2d.js
$ #three standard runs with different size
$ /usr/bin/time -f %U ./d8 --saveload-edge box2d.js -- 1
frame averages: 17.725 +- 42.323, range: 3.000 to 264.000 
0.68
$ /usr/bin/time -f %U ./d8 --saveload-edge box2d.js -- 2
frame averages: 6.347 +- 14.352, range: 3.000 to 178.000 
1.24
$ /usr/bin/time -f %U ./d8 --saveload-edge box2d.js -- 3
frame averages: 4.892 +- 10.184, range: 3.000 to 179.000 
1.98

Gaining up to ~0.2 second speedup using saved Lithium

$ #saving
$ /usr/bin/time -f %U ./d8 --saveload-edge --save-code box2d.lithium box2d.js -- 1
frame averages: 16.425 +- 32.401, range: 4.000 to 191.000 
0.69
$ #three runs with loading
$ /usr/bin/time -f %U ./d8 --saveload-edge --load-code box2d.lithium box2d.js -- 1
frame averages: 10.400 +- 13.926, range: 3.000 to 69.000 
0.43
$ /usr/bin/time -f %U ./d8 --saveload-edge --load-code box2d.lithium box2d.js -- 2
frame averages: 5.601 +- 7.078, range: 3.000 to 70.000 
1.08
$ /usr/bin/time -f %U ./d8 --saveload-edge --load-code box2d.lithium box2d.js -- 3
frame averages: 4.632 +- 5.095, range: 2.000 to 68.000 
1.82

Resources

• Augmenting JavaScript JIT with Ahead-of-Time Compilation. Compiler, Architecture and Tools Conference 2015, Haifa, Israel. (slides)
• Ahead-of-Time Compilation of JavaScript Programs. Programming and Computer Software, 2017, Vol. 43, No. 1, pp. 51–59, ISSN 0361-7688
• Ahead of Time Optimization for JavaScript Programs. Trudy ISP RAN/Proc. ISP RAS, vol. 27, issue 6, 2015, pp. 67-86 (in Russian)