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cmd/compile: decrease inlining call cost from 60 to 57

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A Go user made a well-documented request for a slightly
lower threshold.  I tested against a selection of other
people's benchmarks, and saw a tiny benefit (possibly noise)
at equally tiny cost, and no unpleasant surprises observed
in benchmarking.

I.e., might help, doesn't hurt, low risk, request was
delivered on a silver platter.

It did, however, change the behavior of one test because
now bytes.Buffer.Grow is eligible for inlining.

Updates #19348.

Change-Id: I85e3088a4911290872b8c6bda9601b5354c48695
Reviewed-on: https://go-review.googlesource.com/c/151977
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
David Chase 2018-11-30 08:36:00 -05:00
parent f70bd91435
commit 624e197c71
2 changed files with 16 additions and 16 deletions
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2
src/cmd/compile/internal/gc/inl.go
View File

@ -39,7 +39,7 @@ const (
inlineMaxBudget = 80
inlineExtraAppendCost = 0
// default is to inline if there's at most one call. -l=4 overrides this by using 1 instead.
inlineExtraCallCost = inlineMaxBudget * 3 / 4
inlineExtraCallCost = 57 // 57 was benchmarked to provided most benefit with no bad surprises; see https://github.com/golang/go/issues/19348#issuecomment-439370742
inlineExtraPanicCost = 1 // do not penalize inlining panics.
inlineExtraThrowCost = inlineMaxBudget // with current (2018-05/1.11) code, inlining runtime.throw does not help.

30
test/fixedbugs/issue7921.go
View File

@ -17,41 +17,41 @@ func bufferNotEscape() string {
// copied during String() call, but object "handle" itself
// can be stack-allocated.
var b bytes.Buffer
b.WriteString("123") // ERROR "b does not escape"
b.Write([]byte{'4'}) // ERROR "b does not escape" "\[\]byte literal does not escape"
return b.String() // ERROR "b does not escape" "inlining call" "string\(bytes\.b\.buf\[bytes.b.off:\]\) escapes to heap"
b.WriteString("123") // ERROR "bufferNotEscape b does not escape$"
b.Write([]byte{'4'}) // ERROR "bufferNotEscape \[\]byte literal does not escape$" "bufferNotEscape b does not escape$"
return b.String() // ERROR "bufferNotEscape b does not escape$" "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
}
func bufferNoEscape2(xs []string) int { // ERROR "xs does not escape"
b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "inlining call" "make\(\[\]byte, 0, 64\) does not escape" "&bytes.Buffer literal does not escape"
func bufferNoEscape2(xs []string) int { // ERROR "bufferNoEscape2 xs does not escape$"
b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "bufferNoEscape2 &bytes.Buffer literal does not escape$" "bufferNoEscape2 make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
for _, x := range xs {
b.WriteString(x)
}
return b.Len() // ERROR "inlining call"
return b.Len() // ERROR "inlining call to bytes.\(\*Buffer\).Len$"
}
func bufferNoEscape3(xs []string) string { // ERROR "xs does not escape"
b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "inlining call" "make\(\[\]byte, 0, 64\) does not escape" "&bytes.Buffer literal does not escape"
func bufferNoEscape3(xs []string) string { // ERROR "bufferNoEscape3 xs does not escape$"
b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "bufferNoEscape3 &bytes.Buffer literal does not escape$" "bufferNoEscape3 make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
for _, x := range xs {
b.WriteString(x)
b.WriteByte(',')
}
return b.String() // ERROR "inlining call" "string\(bytes.b.buf\[bytes\.b\.off:\]\) escapes to heap"
return b.String() // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
}
func bufferNoEscape4() []byte {
var b bytes.Buffer
b.Grow(64) // ERROR "b does not escape"
useBuffer(&b) // ERROR "&b does not escape"
return b.Bytes() // ERROR "inlining call" "b does not escape"
b.Grow(64) // ERROR "bufferNoEscape4 b does not escape$" "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m·3\]$" "inlining call to bytes.\(\*Buffer\).Grow$"
useBuffer(&b) // ERROR "bufferNoEscape4 &b does not escape$"
return b.Bytes() // ERROR "bufferNoEscape4 b does not escape$" "inlining call to bytes.\(\*Buffer\).Bytes$"
}
func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5"
b := bytes.NewBuffer(make([]byte, 0, 128)) // ERROR "inlining call" "make\(\[\]byte, 0, 128\) does not escape" "&bytes.Buffer literal does not escape"
func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5$"
b := bytes.NewBuffer(make([]byte, 0, 128)) // ERROR "bufferNoEscape5 &bytes.Buffer literal does not escape$" "bufferNoEscape5 make\(\[\]byte, 0, 128\) does not escape$" "inlining call to bytes.NewBuffer$"
useBuffer(b)
}
//go:noinline
func useBuffer(b *bytes.Buffer) { // ERROR "b does not escape"
func useBuffer(b *bytes.Buffer) { // ERROR "useBuffer b does not escape$"
b.WriteString("1234")
}