mirror of
https://github.com/golang/go
synced 2024-07-21 01:55:06 +00:00
cmd/compile: initialize sparse slice literals dynamically
When a slice composite literal is sparse, initialize it dynamically instead of statically. s := []int{5:5, 20:20} To initialize the backing store for s, use 2 constant writes instead of copying from a static array with 21 entries. This CL also fixes pathologies in the compiler when the slice is *very* sparse. Fixes #23780 Change-Id: Iae95c6e6f6a0e2994675cbc750d7a4dd6436b13b Reviewed-on: https://go-review.googlesource.com/c/151319 Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
parent
1602e49701
commit
6fff980cf1
|
@ -612,6 +612,15 @@ func getdyn(n *Node, top bool) initGenType {
|
|||
if !top {
|
||||
return initDynamic
|
||||
}
|
||||
if n.Right.Int64()/4 > int64(n.List.Len()) {
|
||||
// <25% of entries have explicit values.
|
||||
// Very rough estimation, it takes 4 bytes of instructions
|
||||
// to initialize 1 byte of result. So don't use a static
|
||||
// initializer if the dynamic initialization code would be
|
||||
// smaller than the static value.
|
||||
// See issue 23780.
|
||||
return initDynamic
|
||||
}
|
||||
|
||||
case OARRAYLIT, OSTRUCTLIT:
|
||||
}
|
||||
|
@ -902,7 +911,7 @@ func slicelit(ctxt initContext, n *Node, var_ *Node, init *Nodes) {
|
|||
continue
|
||||
}
|
||||
|
||||
if isLiteral(value) {
|
||||
if vstat != nil && isLiteral(value) { // already set by copy from static value
|
||||
continue
|
||||
}
|
||||
|
||||
|
|
|
@ -622,7 +622,7 @@ const (
|
|||
OMAPLIT // Type{List} (composite literal, Type is map)
|
||||
OSTRUCTLIT // Type{List} (composite literal, Type is struct)
|
||||
OARRAYLIT // Type{List} (composite literal, Type is array)
|
||||
OSLICELIT // Type{List} (composite literal, Type is slice)
|
||||
OSLICELIT // Type{List} (composite literal, Type is slice) Right.Int64() = slice length.
|
||||
OPTRLIT // &Left (left is composite literal)
|
||||
OCONV // Type(Left) (type conversion)
|
||||
OCONVIFACE // Type(Left) (type conversion, to interface)
|
||||
|
|
17
test/fixedbugs/issue23780.go
Normal file
17
test/fixedbugs/issue23780.go
Normal file
|
@ -0,0 +1,17 @@
|
|||
// compile
|
||||
|
||||
// Copyright 2018 The Go Authors. All rights reserved.
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
package p
|
||||
|
||||
func f() {
|
||||
_ = []byte{1 << 30: 1}
|
||||
}
|
||||
|
||||
func g() {
|
||||
sink = []byte{1 << 30: 1}
|
||||
}
|
||||
|
||||
var sink []byte
|
Loading…
Reference in a new issue