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cmd/compile: pass stack allocated bucket to makemap inside hmap

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name         old time/op    new time/op    delta
NewEmptyMap    53.2ns ± 7%    48.0ns ± 5%  -9.77%  (p=0.000 n=20+20)
NewSmallMap     111ns ± 1%     106ns ± 2%  -3.78%  (p=0.000 n=20+19)

Change-Id: I979d21ab16eae9f6893873becca517db57e054b5
Reviewed-on: https://go-review.googlesource.com/56290
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This commit is contained in:
Martin Möhrmann 2017-08-16 23:36:58 +02:00
parent 1a2ac46edd
commit 06a78b5737
4 changed files with 57 additions and 43 deletions
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47
src/runtime/hashmap.go
View file

@ -259,8 +259,8 @@ func (h *hmap) createOverflow() {
// If the compiler has determined that the map or the first bucket
// can be created on the stack, h and/or bucket may be non-nil.
// If h != nil, the map can be created directly in h.
// If bucket != nil, bucket can be used as the first bucket.
func makemap(t *maptype, hint int64, h *hmap, bucket unsafe.Pointer) *hmap {
// If h.buckets != nil, bucket pointed to can be used as the first bucket.
func makemap(t *maptype, hint int64, h *hmap) *hmap {
if sz := unsafe.Sizeof(hmap{}); sz > 48 || sz != t.hmap.size {
println("runtime: sizeof(hmap) =", sz, ", t.hmap.size =", t.hmap.size)
throw("bad hmap size")
@ -312,33 +312,30 @@ func makemap(t *maptype, hint int64, h *hmap, bucket unsafe.Pointer) *hmap {
throw("bad evacuatedN")
}
// find size parameter which will hold the requested # of elements
B := uint8(0)
for ; overLoadFactor(hint, B); B++ {
}
// allocate initial hash table
// if B == 0, the buckets field is allocated lazily later (in mapassign)
// If hint is large zeroing this memory could take a while.
buckets := bucket
var extra *mapextra
if B != 0 {
var nextOverflow *bmap
buckets, nextOverflow = makeBucketArray(t, B)
if nextOverflow != nil {
extra = new(mapextra)
extra.nextOverflow = nextOverflow
}
}
// initialize Hmap
if h == nil {
h = (*hmap)(newobject(t.hmap))
}
h.B = B
h.extra = extra
h.hash0 = fastrand()
h.buckets = buckets
// find size parameter which will hold the requested # of elements
B := uint8(0)
for overLoadFactor(hint, B) {
B++
}
h.B = B
// allocate initial hash table
// if B == 0, the buckets field is allocated lazily later (in mapassign)
// If hint is large zeroing this memory could take a while.
if h.B != 0 {
var nextOverflow *bmap
h.buckets, nextOverflow = makeBucketArray(t, h.B)
if nextOverflow != nil {
h.extra = new(mapextra)
h.extra.nextOverflow = nextOverflow
}
}
return h
}
@ -1171,7 +1168,7 @@ func ismapkey(t *_type) bool {
//go:linkname reflect_makemap reflect.makemap
func reflect_makemap(t *maptype, cap int) *hmap {
return makemap(t, int64(cap), nil, nil)
return makemap(t, int64(cap), nil)
}
//go:linkname reflect_mapaccess reflect.mapaccess