Josh Bleecher Snyder
dffe5ac9f2
cmd/compile: eliminate dead code in if statements after typechecking
...
This is a more thorough and cleaner fix
than doing dead code elimination separately
during inlining, escape analysis, and export.
Unfortunately, it does add another full walk of the AST.
The performance impact is very small, but not non-zero.
If a label or goto is present in the dead code, it is not eliminated.
This restriction can be removed once label/goto checking occurs
much earlier in the compiler. In practice, it probably doesn't
matter much.
Updates #19699
Fixes #19705
name old alloc/op new alloc/op delta
Template 39.2MB ± 0% 39.3MB ± 0% +0.28% (p=0.008 n=5+5)
Unicode 29.8MB ± 0% 29.8MB ± 0% ~ (p=1.000 n=5+5)
GoTypes 113MB ± 0% 113MB ± 0% -0.55% (p=0.008 n=5+5)
SSA 1.25GB ± 0% 1.25GB ± 0% +0.02% (p=0.008 n=5+5)
Flate 25.3MB ± 0% 25.3MB ± 0% -0.24% (p=0.032 n=5+5)
GoParser 31.7MB ± 0% 31.8MB ± 0% +0.31% (p=0.008 n=5+5)
Reflect 78.2MB ± 0% 78.3MB ± 0% ~ (p=0.421 n=5+5)
Tar 26.6MB ± 0% 26.7MB ± 0% +0.21% (p=0.008 n=5+5)
XML 42.2MB ± 0% 42.2MB ± 0% ~ (p=0.056 n=5+5)
name old allocs/op new allocs/op delta
Template 385k ± 0% 387k ± 0% +0.51% (p=0.016 n=5+5)
Unicode 321k ± 0% 321k ± 0% ~ (p=1.000 n=5+5)
GoTypes 1.14M ± 0% 1.14M ± 0% ~ (p=1.000 n=5+5)
SSA 9.71M ± 0% 9.72M ± 0% +0.10% (p=0.008 n=5+5)
Flate 234k ± 1% 234k ± 1% ~ (p=0.690 n=5+5)
GoParser 315k ± 0% 317k ± 0% +0.71% (p=0.008 n=5+5)
Reflect 980k ± 0% 983k ± 0% +0.30% (p=0.032 n=5+5)
Tar 251k ± 0% 252k ± 0% +0.55% (p=0.016 n=5+5)
XML 392k ± 0% 393k ± 0% +0.30% (p=0.008 n=5+5)
Change-Id: Ia10ff4bbf5c6eae782582cc9cbc9785494d4fb83
Reviewed-on: https://go-review.googlesource.com/38773
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2017-04-18 17:13:30 +00:00
