cmd/internal/gc: statically initialize function pointers
Previously, gc would compile code like
func foo() { ... }
var bar = foo
by emitting a static closure to wrap "foo", but then emitting runtime
initialization code to assign the closure to "bar". This CL changes
gc to instead statically initialize "bar".
Notably, this change shrinks the "go" tool's text segment by ~7.4kB on
linux/amd64 while only increasing the data segment by ~100B:
text data bss dec hex filename
7237819 122412 215616
7575847 739927 go.before
7230398 122540 215232
7568170 737b2a go.after
Fixes issue #10081.
Change-Id: If5e26cf46b323393ba6f2199a82a06e9e4baf411
Reviewed-on: https://go-review.googlesource.com/6880
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>