use -O1 for code in Plots.jl

[JeffBezanson]

On julia master this reduces the time to first plot for me by about 5 seconds. So far I have not detected any measurable slowdowns e.g. for plotting many points (the drawing itself inside gksterm is by far the limiting factor).

[codecov]

Codecov Report

Merging #2544 into master will decrease coverage by 0.42%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2544      +/-   ##
==========================================
- Coverage   66.15%   65.72%   -0.43%     
==========================================
  Files          25       25              
  Lines        7395     7393       -2     
==========================================
- Hits         4892     4859      -33     
- Misses       2503     2534      +31

Impacted Files	Coverage Δ
src/Plots.jl	32.25% <ø> (ø)	⬆️
src/examples.jl	49.09% <0%> (-3.64%)	⬇️
src/args.jl	70.94% <0%> (-2.32%)	⬇️
src/types.jl	53.84% <0%> (-1.93%)	⬇️
src/axes.jl	70.2% <0%> (-0.94%)	⬇️
src/backends/pgfplotsx.jl	64.43% <0%> (-0.93%)	⬇️
src/pipeline.jl	91.13% <0%> (-0.5%)	⬇️
src/recipes.jl	39.85% <0%> (-0.31%)	⬇️
src/series.jl	47.6% <0%> (-0.3%)	⬇️
src/components.jl	34.65% <0%> (-0.29%)	⬇️
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ae396ef...6807f53. Read the comment docs.

[daschw]

Nice, thanks a lot!

[ChrisRackauckas]

Why not -O0? Does 1 offer some optimizations that helps Plots?

[mkborregaard]

Another question: will this behaviour change if called by packagecompiler to form a system image?

[JeffBezanson]

-O0 would be fine too. I made some changes to -O1 that make it very close to -O0 compiler performance while generating significantly better code, so I feel -O1 is overall a good default. It often pays for itself.

This option currently only affects the JIT; building a system image will only use whatever -O option is passed on the command line.

[mkborregaard]

Perfect <3