Currently we generate a jump to an OOL path and generate an (unused) inline double path. I'll try to add an inline integer path for this and measure perf impact for micro-benchmarks and SS/V8/kraken. I'd also like to test compiling -x as x * -1. JSOP_NEG with integer arg seems quite common, so we should make it as fast as possible.

This patch adds an inline integer path for known integers. It also optimizes the is-0 and is-MIN_INT checks to one test instruction (both have 31 lower bits zero). This passes jit-tests and jstests with -m -n -a. For this micro-benchmark: -- function f() { var a = 0; var t0 = new Date; for(var i=1; i<10000000; i++) { a = -i; } print(new Date - t0); print(a); } f(); -- ...these numbers: d8: 52 ms JM: 62 ms TM: 27 ms JM+TI (old): 39 ms JM+TI (new): 17 ms I don't think this helps SS/V8/Kraken much but I think it's worth the small amount of extra code, -int seems like a common thing to do. The code is also pretty straight-forward.

Comment on attachment 520020 [details] [diff] [review] Patch Nice!