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295307ae78
With this change, code like
h := sha1.New()
h.Write(buf)
sum := h.Sum()
gets compiled into static calls rather than
interface calls, because the compiler is able
to prove that 'h' is really a *sha1.digest.
The InterCall re-write rule hits a few dozen times
during make.bash, and hundreds of times during all.bash.
The most common pattern identified by the compiler
is a constructor like
func New() Interface { return &impl{...} }
where the constructor gets inlined into the caller,
and the result is used immediately. Examples include
{sha1,md5,crc32,crc64,...}.New, base64.NewEncoder,
base64.NewDecoder, errors.New, net.Pipe, and so on.
Some existing benchmarks that change on darwin/amd64:
Crc64/ISO4KB-8 2.67µs ± 1% 2.66µs ± 0% -0.36% (p=0.015 n=10+10)
Crc64/ISO1KB-8 694ns ± 0% 690ns ± 1% -0.59% (p=0.001 n=10+10)
Adler32KB-8 473ns ± 1% 471ns ± 0% -0.39% (p=0.010 n=10+9)
On architectures like amd64, the reduction in code size
appears to contribute more to benchmark improvements than just
removing the indirect call, since that branch gets predicted
accurately when called in a loop.
Updates #19361
Change-Id: I57d4dc21ef40a05ec0fbd55a9bb0eb74cdc67a3d
Reviewed-on: https://go-review.googlesource.com/38139
Run-TryBot: Philip Hofer <phofer@umich.edu>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
40 lines
599 B
Go
40 lines
599 B
Go
// errorcheck -0 -d=ssa/opt/debug=3
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package main
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// Trivial interface call devirtualization test.
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type real struct {
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value int
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}
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func (r *real) Value() int { return r.value }
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type Valuer interface {
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Value() int
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}
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type indirectiface struct {
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a, b, c int
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}
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func (i indirectiface) Value() int {
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return i.a + i.b + i.c
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}
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func main() {
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var r Valuer
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rptr := &real{value: 3}
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r = rptr
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if r.Value() != 3 { // ERROR "de-virtualizing call$"
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panic("not 3")
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}
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// Can't do types that aren't "direct" interfaces (yet).
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r = indirectiface{3, 4, 5}
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if r.Value() != 12 {
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panic("not 12")
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}
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}
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