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Updated CompilerOptimizations (markdown)

Josh Bleecher Snyder 2015-02-04 09:50:03 -08:00
parent 5871177867
commit 5afa467228
1 changed files with 23 additions and 6 deletions
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29
CompilerOptimizations.md

@ -2,31 +2,48 @@
This page lists optimizations done by the compilers. Note that these are not guaranteed by the language specification.
## Zero-width types in interface values
## Interface values
### Zero-width types in interface values
Putting a zero-width type in an interface value doesn't allocate.
* **gc:** 1.0+
* **gccgo:** ?
## Word-sized value in an interface value
### Word-sized value in an interface value
Putting a word-sized-or-less non-pointer type in an interface value doesn't allocate.
* **gc:** 1.0-1.3, but *not* in 1.4+
* **gccgo:** never
## Map lookup by []byte
## string and []byte
### Map lookup by []byte
For a map m of type map[string]T and []byte b, m[string(b)] doesn't allocate. (the temporary string copy of the byte slice isn't made)
* **gc:** 1.4+
* **gccgo:** ?
## Escape analysis: foo
## Escape analysis
TODO
## Escape analysis: bar
## Idioms
TODO
### Optimized memclr
For a slice or array s, loops of the form
```go
for i := range s {
a[i] = <zero value for element of s>
}
```
are converted into efficient runtime memclr calls. [Issue](golang.org/issue/5373) and [commit](https://golang.org/change/f03c9202c43e0abb130669852082117ca50aa9b1).
* **gc:** 1.5+
* **gccgo:** ?