RFC: optimize for size?

[domenpk]

I was looking at led-roulette disassembly and something looked a bit off. A loop going through 8 LEDs was unrolled.

In my experience, it's normally size that developers care about and compare, so we might not want to look bad in that respect.

Changing opt-level to s or z, reduces the sizes of binaries by about 1kB:

As is:

   4762	   1816	      4	   6582	   19b6	hello-world
   4750	   1152	      4	   5906	   1712	registers
   4510	   1152	      4	   5666	   1622	leds-again
   4774	   1152	      4	   5930	   172a	clocks-and-timers
   4682	   1152	      4	   5838	   16ce	usart
   5910	   1472	      4	   7386	   1cda	i2c
   6704	   1312	      4	   8020	   1f54	led-compass
  30766	  10032	      4	  40802	   9f62	punch-o-meter

opt-level = "s":

   3682	   1816	      4	   5502	   157e	hello-world
   3900	   1152	      4	   5056	   13c0	registers
   3686	   1152	      4	   4842	   12ea	leds-again
   3904	   1152	      4	   5060	   13c4	clocks-and-timers
   3866	   1152	      4	   5022	   139e	usart
   4960	   1476	      4	   6440	   1928	i2c
   5724	   1312	      4	   7040	   1b80	led-compass
  28230	  10032	      4	  38266	   957a	punch-o-meter

opt-level = "z":

   3642	   1816	      4	   5462	   1556	hello-world
   3858	   1152	      4	   5014	   1396	registers
   3642	   1152	      4	   4798	   12be	leds-again
   3902	   1248	      4	   5154	   1422	clocks-and-timers
   3822	   1152	      4	   4978	   1372	usart
   4910	   1476	      4	   6390	   18f6	i2c
   5604	   1312	      4	   6920	   1b08	led-compass
  28134	  10032	      4	  38170	   951a	punch-o-meter

Output created by:
for i in [0-9]*; do cd $i; bin=$(grep name Cargo.toml | cut -f2 -d'"'); cargo size --target $target --bin $bin --release | tail -1 >> ../size_z.txt ;cd ..; done

I'd create a pull request, but thought I'd first ask what are your views on this.

[bahrozjaved]

you think that in my repo there is a memory mamnagement issues