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Right now we generate hash functions for all types, just in case they are used as map keys. That's a lot of wasted effort and binary size for types which will never be used as a map key. Instead, generate hash functions only for types that we know are map keys. Just doing that is a bit too simple, since maps with an interface type as a key might have to hash any concrete key type that implements that interface. So for that case, implement hashing of such types at runtime (instead of with generated code). It will be slower, but only for maps with interface types as keys, and maybe only a bit slower as the aeshash time probably dominates the dispatch time. Reorg where we keep the equals and hash functions. Move the hash function from the key type to the map type, saving a field in every non-map type. That leaves only one function in the alg structure, so get rid of that and just keep the equal function in the type descriptor itself. cmd/go now has 10 generated hash functions, instead of 504. Makes cmd/go 1.0% smaller. Update #6853. Speed on non-interface keys is unchanged. Speed on interface keys is ~20% slower: name old time/op new time/op delta MapInterfaceString-8 23.0ns ±21% 27.6ns ±14% +20.01% (p=0.002 n=10+10) MapInterfacePtr-8 19.4ns ±16% 23.7ns ± 7% +22.48% (p=0.000 n=10+8) Change-Id: I7c2e42292a46b5d4e288aaec4029bdbb01089263 Reviewed-on: https://go-review.googlesource.com/c/go/+/191198 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Vendoring in std and cmd
========================
The Go command maintains copies of external packages needed by the
standard library in the src/vendor and src/cmd/vendor directories.
In GOPATH mode, imports of vendored packages are resolved to these
directories following normal vendor directory logic
(see golang.org/s/go15vendor).
In module mode, std and cmd are modules (defined in src/go.mod and
src/cmd/go.mod). When a package outside std or cmd is imported
by a package inside std or cmd, the import path is interpreted
as if it had a "vendor/" prefix. For example, within "crypto/tls",
an import of "golang.org/x/crypto/cryptobyte" resolves to
"vendor/golang.org/x/crypto/cryptobyte". When a package with the
same path is imported from a package outside std or cmd, it will
be resolved normally. Consequently, a binary may be built with two
copies of a package at different versions if the package is
imported normally and vendored by the standard library.
Vendored packages are internally renamed with a "vendor/" prefix
to preserve the invariant that all packages have distinct paths.
This is necessary to avoid compiler and linker conflicts. Adding
a "vendor/" prefix also maintains the invariant that standard
library packages begin with a dotless path element.
The module requirements of std and cmd do not influence version
selection in other modules. They are only considered when running
module commands like 'go get' and 'go mod vendor' from a directory
in GOROOT/src.
Maintaining vendor directories
==============================
Before updating vendor directories, ensure that module mode is enabled.
Make sure GO111MODULE=off is not set ('on' or 'auto' should work).
Requirements may be added, updated, and removed with 'go get'.
The vendor directory may be updated with 'go mod vendor'.
A typical sequence might be:
cd src
go get -d golang.org/x/net@latest
go mod tidy
go mod vendor
Use caution when passing '-u' to 'go get'. The '-u' flag updates
modules providing all transitively imported packages, not only
the module providing the target package.
Note that 'go mod vendor' only copies packages that are transitively
imported by packages in the current module. If a new package is needed,
it should be imported before running 'go mod vendor'.