aboutsummaryrefslogtreecommitdiff
path: root/src
diff options
context:
space:
mode:
Diffstat (limited to 'src')
-rw-r--r--src/cmd/compile/internal/gc/builtin.go164
-rw-r--r--src/cmd/compile/internal/gc/builtin/runtime.go1
-rw-r--r--src/cmd/compile/internal/gc/order.go14
-rw-r--r--src/cmd/compile/internal/gc/range.go71
-rw-r--r--src/runtime/map.go122
-rw-r--r--src/runtime/map_benchmark_test.go29
6 files changed, 291 insertions, 110 deletions
diff --git a/src/cmd/compile/internal/gc/builtin.go b/src/cmd/compile/internal/gc/builtin.go
index 3ca1adc1f7..6b416c8a5c 100644
--- a/src/cmd/compile/internal/gc/builtin.go
+++ b/src/cmd/compile/internal/gc/builtin.go
@@ -100,59 +100,60 @@ var runtimeDecls = [...]struct {
{"mapdelete_fast64", funcTag, 73},
{"mapdelete_faststr", funcTag, 73},
{"mapiternext", funcTag, 74},
- {"makechan64", funcTag, 76},
- {"makechan", funcTag, 77},
- {"chanrecv1", funcTag, 79},
- {"chanrecv2", funcTag, 80},
- {"chansend1", funcTag, 82},
+ {"mapclear", funcTag, 75},
+ {"makechan64", funcTag, 77},
+ {"makechan", funcTag, 78},
+ {"chanrecv1", funcTag, 80},
+ {"chanrecv2", funcTag, 81},
+ {"chansend1", funcTag, 83},
{"closechan", funcTag, 23},
- {"writeBarrier", varTag, 84},
- {"typedmemmove", funcTag, 85},
- {"typedmemclr", funcTag, 86},
- {"typedslicecopy", funcTag, 87},
- {"selectnbsend", funcTag, 88},
- {"selectnbrecv", funcTag, 89},
- {"selectnbrecv2", funcTag, 91},
+ {"writeBarrier", varTag, 85},
+ {"typedmemmove", funcTag, 86},
+ {"typedmemclr", funcTag, 87},
+ {"typedslicecopy", funcTag, 88},
+ {"selectnbsend", funcTag, 89},
+ {"selectnbrecv", funcTag, 90},
+ {"selectnbrecv2", funcTag, 92},
{"selectsetpc", funcTag, 56},
- {"selectgo", funcTag, 92},
+ {"selectgo", funcTag, 93},
{"block", funcTag, 5},
- {"makeslice", funcTag, 94},
- {"makeslice64", funcTag, 95},
- {"growslice", funcTag, 96},
- {"memmove", funcTag, 97},
- {"memclrNoHeapPointers", funcTag, 98},
- {"memclrHasPointers", funcTag, 98},
- {"memequal", funcTag, 99},
- {"memequal8", funcTag, 100},
- {"memequal16", funcTag, 100},
- {"memequal32", funcTag, 100},
- {"memequal64", funcTag, 100},
- {"memequal128", funcTag, 100},
- {"int64div", funcTag, 101},
- {"uint64div", funcTag, 102},
- {"int64mod", funcTag, 101},
- {"uint64mod", funcTag, 102},
- {"float64toint64", funcTag, 103},
- {"float64touint64", funcTag, 104},
- {"float64touint32", funcTag, 105},
- {"int64tofloat64", funcTag, 106},
- {"uint64tofloat64", funcTag, 107},
- {"uint32tofloat64", funcTag, 108},
- {"complex128div", funcTag, 109},
- {"racefuncenter", funcTag, 110},
+ {"makeslice", funcTag, 95},
+ {"makeslice64", funcTag, 96},
+ {"growslice", funcTag, 97},
+ {"memmove", funcTag, 98},
+ {"memclrNoHeapPointers", funcTag, 99},
+ {"memclrHasPointers", funcTag, 99},
+ {"memequal", funcTag, 100},
+ {"memequal8", funcTag, 101},
+ {"memequal16", funcTag, 101},
+ {"memequal32", funcTag, 101},
+ {"memequal64", funcTag, 101},
+ {"memequal128", funcTag, 101},
+ {"int64div", funcTag, 102},
+ {"uint64div", funcTag, 103},
+ {"int64mod", funcTag, 102},
+ {"uint64mod", funcTag, 103},
+ {"float64toint64", funcTag, 104},
+ {"float64touint64", funcTag, 105},
+ {"float64touint32", funcTag, 106},
+ {"int64tofloat64", funcTag, 107},
+ {"uint64tofloat64", funcTag, 108},
+ {"uint32tofloat64", funcTag, 109},
+ {"complex128div", funcTag, 110},
+ {"racefuncenter", funcTag, 111},
{"racefuncexit", funcTag, 5},
- {"raceread", funcTag, 110},
- {"racewrite", funcTag, 110},
- {"racereadrange", funcTag, 111},
- {"racewriterange", funcTag, 111},
- {"msanread", funcTag, 111},
- {"msanwrite", funcTag, 111},
+ {"raceread", funcTag, 111},
+ {"racewrite", funcTag, 111},
+ {"racereadrange", funcTag, 112},
+ {"racewriterange", funcTag, 112},
+ {"msanread", funcTag, 112},
+ {"msanwrite", funcTag, 112},
{"support_popcnt", varTag, 11},
{"support_sse41", varTag, 11},
}
func runtimeTypes() []*types.Type {
- var typs [112]*types.Type
+ var typs [113]*types.Type
typs[0] = types.Bytetype
typs[1] = types.NewPtr(typs[0])
typs[2] = types.Types[TANY]
@@ -228,42 +229,43 @@ func runtimeTypes() []*types.Type {
typs[72] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[62]), anonfield(typs[3])}, nil)
typs[73] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[62]), anonfield(typs[2])}, nil)
typs[74] = functype(nil, []*Node{anonfield(typs[3])}, nil)
- typs[75] = types.NewChan(typs[2], types.Cboth)
- typs[76] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15])}, []*Node{anonfield(typs[75])})
- typs[77] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32])}, []*Node{anonfield(typs[75])})
- typs[78] = types.NewChan(typs[2], types.Crecv)
- typs[79] = functype(nil, []*Node{anonfield(typs[78]), anonfield(typs[3])}, nil)
- typs[80] = functype(nil, []*Node{anonfield(typs[78]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
- typs[81] = types.NewChan(typs[2], types.Csend)
- typs[82] = functype(nil, []*Node{anonfield(typs[81]), anonfield(typs[3])}, nil)
- typs[83] = types.NewArray(typs[0], 3)
- typs[84] = tostruct([]*Node{namedfield("enabled", typs[11]), namedfield("pad", typs[83]), namedfield("needed", typs[11]), namedfield("cgo", typs[11]), namedfield("alignme", typs[17])})
- typs[85] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[3])}, nil)
- typs[86] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3])}, nil)
- typs[87] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[2]), anonfield(typs[2])}, []*Node{anonfield(typs[32])})
- typs[88] = functype(nil, []*Node{anonfield(typs[81]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
- typs[89] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[78])}, []*Node{anonfield(typs[11])})
- typs[90] = types.NewPtr(typs[11])
- typs[91] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[90]), anonfield(typs[78])}, []*Node{anonfield(typs[11])})
- typs[92] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[1]), anonfield(typs[32])}, []*Node{anonfield(typs[32]), anonfield(typs[11])})
- typs[93] = types.NewSlice(typs[2])
- typs[94] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[93])})
- typs[95] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[93])})
- typs[96] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[93]), anonfield(typs[32])}, []*Node{anonfield(typs[93])})
- typs[97] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, nil)
- typs[98] = functype(nil, []*Node{anonfield(typs[58]), anonfield(typs[47])}, nil)
- typs[99] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, []*Node{anonfield(typs[11])})
- typs[100] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
- typs[101] = functype(nil, []*Node{anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[15])})
- typs[102] = functype(nil, []*Node{anonfield(typs[17]), anonfield(typs[17])}, []*Node{anonfield(typs[17])})
- typs[103] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[15])})
- typs[104] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[17])})
- typs[105] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[60])})
- typs[106] = functype(nil, []*Node{anonfield(typs[15])}, []*Node{anonfield(typs[13])})
- typs[107] = functype(nil, []*Node{anonfield(typs[17])}, []*Node{anonfield(typs[13])})
- typs[108] = functype(nil, []*Node{anonfield(typs[60])}, []*Node{anonfield(typs[13])})
- typs[109] = functype(nil, []*Node{anonfield(typs[19]), anonfield(typs[19])}, []*Node{anonfield(typs[19])})
- typs[110] = functype(nil, []*Node{anonfield(typs[47])}, nil)
- typs[111] = functype(nil, []*Node{anonfield(typs[47]), anonfield(typs[47])}, nil)
+ typs[75] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[62])}, nil)
+ typs[76] = types.NewChan(typs[2], types.Cboth)
+ typs[77] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15])}, []*Node{anonfield(typs[76])})
+ typs[78] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32])}, []*Node{anonfield(typs[76])})
+ typs[79] = types.NewChan(typs[2], types.Crecv)
+ typs[80] = functype(nil, []*Node{anonfield(typs[79]), anonfield(typs[3])}, nil)
+ typs[81] = functype(nil, []*Node{anonfield(typs[79]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+ typs[82] = types.NewChan(typs[2], types.Csend)
+ typs[83] = functype(nil, []*Node{anonfield(typs[82]), anonfield(typs[3])}, nil)
+ typs[84] = types.NewArray(typs[0], 3)
+ typs[85] = tostruct([]*Node{namedfield("enabled", typs[11]), namedfield("pad", typs[84]), namedfield("needed", typs[11]), namedfield("cgo", typs[11]), namedfield("alignme", typs[17])})
+ typs[86] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[3])}, nil)
+ typs[87] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3])}, nil)
+ typs[88] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[2]), anonfield(typs[2])}, []*Node{anonfield(typs[32])})
+ typs[89] = functype(nil, []*Node{anonfield(typs[82]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+ typs[90] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[79])}, []*Node{anonfield(typs[11])})
+ typs[91] = types.NewPtr(typs[11])
+ typs[92] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[91]), anonfield(typs[79])}, []*Node{anonfield(typs[11])})
+ typs[93] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[1]), anonfield(typs[32])}, []*Node{anonfield(typs[32]), anonfield(typs[11])})
+ typs[94] = types.NewSlice(typs[2])
+ typs[95] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[94])})
+ typs[96] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[94])})
+ typs[97] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[94]), anonfield(typs[32])}, []*Node{anonfield(typs[94])})
+ typs[98] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, nil)
+ typs[99] = functype(nil, []*Node{anonfield(typs[58]), anonfield(typs[47])}, nil)
+ typs[100] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, []*Node{anonfield(typs[11])})
+ typs[101] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+ typs[102] = functype(nil, []*Node{anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[15])})
+ typs[103] = functype(nil, []*Node{anonfield(typs[17]), anonfield(typs[17])}, []*Node{anonfield(typs[17])})
+ typs[104] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[15])})
+ typs[105] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[17])})
+ typs[106] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[60])})
+ typs[107] = functype(nil, []*Node{anonfield(typs[15])}, []*Node{anonfield(typs[13])})
+ typs[108] = functype(nil, []*Node{anonfield(typs[17])}, []*Node{anonfield(typs[13])})
+ typs[109] = functype(nil, []*Node{anonfield(typs[60])}, []*Node{anonfield(typs[13])})
+ typs[110] = functype(nil, []*Node{anonfield(typs[19]), anonfield(typs[19])}, []*Node{anonfield(typs[19])})
+ typs[111] = functype(nil, []*Node{anonfield(typs[47])}, nil)
+ typs[112] = functype(nil, []*Node{anonfield(typs[47]), anonfield(typs[47])}, nil)
return typs[:]
}
diff --git a/src/cmd/compile/internal/gc/builtin/runtime.go b/src/cmd/compile/internal/gc/builtin/runtime.go
index 1d3f17c0d1..d459c07cbe 100644
--- a/src/cmd/compile/internal/gc/builtin/runtime.go
+++ b/src/cmd/compile/internal/gc/builtin/runtime.go
@@ -122,6 +122,7 @@ func mapdelete_fast32(mapType *byte, hmap map[any]any, key any)
func mapdelete_fast64(mapType *byte, hmap map[any]any, key any)
func mapdelete_faststr(mapType *byte, hmap map[any]any, key any)
func mapiternext(hiter *any)
+func mapclear(mapType *byte, hmap map[any]any)
// *byte is really *runtime.Type
func makechan64(chanType *byte, size int64) (hchan chan any)
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index 45a3b5cc42..dce68a6c17 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -695,6 +695,8 @@ func (o *Order) stmt(n *Node) {
t := o.markTemp()
n.Right = o.expr(n.Right, nil)
+
+ orderBody := true
switch n.Type.Etype {
default:
Fatalf("orderstmt range %v", n.Type)
@@ -721,6 +723,14 @@ func (o *Order) stmt(n *Node) {
n.Right = o.copyExpr(r, r.Type, false)
case TMAP:
+ if isMapClear(n) {
+ // Preserve the body of the map clear pattern so it can
+ // be detected during walk. The loop body will not be used
+ // when optimizing away the range loop to a runtime call.
+ orderBody = false
+ break
+ }
+
// copy the map value in case it is a map literal.
// TODO(rsc): Make tmp = literal expressions reuse tmp.
// For maps tmp is just one word so it hardly matters.
@@ -732,7 +742,9 @@ func (o *Order) stmt(n *Node) {
prealloc[n] = o.newTemp(hiter(n.Type), true)
}
o.exprListInPlace(n.List)
- orderBlock(&n.Nbody)
+ if orderBody {
+ orderBlock(&n.Nbody)
+ }
o.out = append(o.out, n)
o.cleanTemp(t)
diff --git a/src/cmd/compile/internal/gc/range.go b/src/cmd/compile/internal/gc/range.go
index 5c3c5ca088..af818f6f4c 100644
--- a/src/cmd/compile/internal/gc/range.go
+++ b/src/cmd/compile/internal/gc/range.go
@@ -154,6 +154,14 @@ func cheapComputableIndex(width int64) bool {
// Node n may also be modified in place, and may also be
// the returned node.
func walkrange(n *Node) *Node {
+ if isMapClear(n) {
+ m := n.Right
+ lno := setlineno(m)
+ n = mapClear(m)
+ lineno = lno
+ return n
+ }
+
// variable name conventions:
// ohv1, hv1, hv2: hidden (old) val 1, 2
// ha, hit: hidden aggregate, iterator
@@ -449,6 +457,69 @@ func walkrange(n *Node) *Node {
return n
}
+// isMapClear checks if n is of the form:
+//
+// for k := range m {
+// delete(m, k)
+// }
+//
+// where == for keys of map m is reflexive.
+func isMapClear(n *Node) bool {
+ if Debug['N'] != 0 || instrumenting {
+ return false
+ }
+
+ if n.Op != ORANGE || n.Type.Etype != TMAP || n.List.Len() != 1 {
+ return false
+ }
+
+ k := n.List.First()
+ if k == nil || k.isBlank() {
+ return false
+ }
+
+ // Require k to be a new variable name.
+ if k.Name == nil || k.Name.Defn != n {
+ return false
+ }
+
+ if n.Nbody.Len() != 1 {
+ return false
+ }
+
+ stmt := n.Nbody.First() // only stmt in body
+ if stmt == nil || stmt.Op != ODELETE {
+ return false
+ }
+
+ m := n.Right
+ if !samesafeexpr(stmt.List.First(), m) || !samesafeexpr(stmt.List.Second(), k) {
+ return false
+ }
+
+ // Keys where equality is not reflexive can not be deleted from maps.
+ if !isreflexive(m.Type.Key()) {
+ return false
+ }
+
+ return true
+}
+
+// mapClear constructs a call to runtime.mapclear for the map m.
+func mapClear(m *Node) *Node {
+ t := m.Type
+
+ // instantiate mapclear(typ *type, hmap map[any]any)
+ fn := syslook("mapclear")
+ fn = substArgTypes(fn, t.Key(), t.Elem())
+ n := mkcall1(fn, nil, nil, typename(t), m)
+
+ n = typecheck(n, Etop)
+ n = walkstmt(n)
+
+ return n
+}
+
// Lower n into runtime·memclr if possible, for
// fast zeroing of slices and arrays (issue 5373).
// Look for instances of
diff --git a/src/runtime/map.go b/src/runtime/map.go
index 1926123458..cc1358a977 100644
--- a/src/runtime/map.go
+++ b/src/runtime/map.go
@@ -318,7 +318,7 @@ func makemap(t *maptype, hint int, h *hmap) *hmap {
// 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)
+ h.buckets, nextOverflow = makeBucketArray(t, h.B, nil)
if nextOverflow != nil {
h.extra = new(mapextra)
h.extra.nextOverflow = nextOverflow
@@ -328,6 +328,57 @@ func makemap(t *maptype, hint int, h *hmap) *hmap {
return h
}
+// makeBucketArray initializes a backing array for map buckets.
+// 1<<b is the minimum number of buckets to allocate.
+// dirtyalloc should either be nil or a bucket array previously
+// allocated by makeBucketArray with the same t and b parameters.
+// If dirtyalloc is nil a new backing array will be alloced and
+// otherwise dirtyalloc will be cleared and reused as backing array.
+func makeBucketArray(t *maptype, b uint8, dirtyalloc unsafe.Pointer) (buckets unsafe.Pointer, nextOverflow *bmap) {
+ base := bucketShift(b)
+ nbuckets := base
+ // For small b, overflow buckets are unlikely.
+ // Avoid the overhead of the calculation.
+ if b >= 4 {
+ // Add on the estimated number of overflow buckets
+ // required to insert the median number of elements
+ // used with this value of b.
+ nbuckets += bucketShift(b - 4)
+ sz := t.bucket.size * nbuckets
+ up := roundupsize(sz)
+ if up != sz {
+ nbuckets = up / t.bucket.size
+ }
+ }
+
+ if dirtyalloc == nil {
+ buckets = newarray(t.bucket, int(nbuckets))
+ } else {
+ // dirtyalloc was previously generated by
+ // the above newarray(t.bucket, int(nbuckets))
+ // but may not be empty.
+ buckets = dirtyalloc
+ size := t.bucket.size * nbuckets
+ if t.bucket.kind&kindNoPointers == 0 {
+ memclrHasPointers(buckets, size)
+ } else {
+ memclrNoHeapPointers(buckets, size)
+ }
+ }
+
+ if base != nbuckets {
+ // We preallocated some overflow buckets.
+ // To keep the overhead of tracking these overflow buckets to a minimum,
+ // we use the convention that if a preallocated overflow bucket's overflow
+ // pointer is nil, then there are more available by bumping the pointer.
+ // We need a safe non-nil pointer for the last overflow bucket; just use buckets.
+ nextOverflow = (*bmap)(add(buckets, base*uintptr(t.bucketsize)))
+ last := (*bmap)(add(buckets, (nbuckets-1)*uintptr(t.bucketsize)))
+ last.setoverflow(t, (*bmap)(buckets))
+ }
+ return buckets, nextOverflow
+}
+
// mapaccess1 returns a pointer to h[key]. Never returns nil, instead
// it will return a reference to the zero object for the value type if
// the key is not in the map.
@@ -855,34 +906,49 @@ next:
goto next
}
-func makeBucketArray(t *maptype, b uint8) (buckets unsafe.Pointer, nextOverflow *bmap) {
- base := bucketShift(b)
- nbuckets := base
- // For small b, overflow buckets are unlikely.
- // Avoid the overhead of the calculation.
- if b >= 4 {
- // Add on the estimated number of overflow buckets
- // required to insert the median number of elements
- // used with this value of b.
- nbuckets += bucketShift(b - 4)
- sz := t.bucket.size * nbuckets
- up := roundupsize(sz)
- if up != sz {
- nbuckets = up / t.bucket.size
- }
+// mapclear deletes all keys from a map.
+func mapclear(t *maptype, h *hmap) {
+ if raceenabled && h != nil {
+ callerpc := getcallerpc()
+ pc := funcPC(mapclear)
+ racewritepc(unsafe.Pointer(h), callerpc, pc)
}
- buckets = newarray(t.bucket, int(nbuckets))
- if base != nbuckets {
- // We preallocated some overflow buckets.
- // To keep the overhead of tracking these overflow buckets to a minimum,
- // we use the convention that if a preallocated overflow bucket's overflow
- // pointer is nil, then there are more available by bumping the pointer.
- // We need a safe non-nil pointer for the last overflow bucket; just use buckets.
- nextOverflow = (*bmap)(add(buckets, base*uintptr(t.bucketsize)))
- last := (*bmap)(add(buckets, (nbuckets-1)*uintptr(t.bucketsize)))
- last.setoverflow(t, (*bmap)(buckets))
+
+ if h == nil || h.count == 0 {
+ return
}
- return buckets, nextOverflow
+
+ if h.flags&hashWriting != 0 {
+ throw("concurrent map writes")
+ }
+
+ h.flags |= hashWriting
+
+ h.flags &^= sameSizeGrow
+ h.oldbuckets = nil
+ h.nevacuate = 0
+ h.noverflow = 0
+ h.count = 0
+
+ // Keep the mapextra allocation but clear any extra information.
+ if h.extra != nil {
+ *h.extra = mapextra{}
+ }
+
+ // makeBucketArray clears the memory pointed to by h.buckets
+ // and recovers any overflow buckets by generating them
+ // as if h.buckets was newly alloced.
+ _, nextOverflow := makeBucketArray(t, h.B, h.buckets)
+ if nextOverflow != nil {
+ // If overflow buckets are created then h.extra
+ // will have been allocated during initial bucket creation.
+ h.extra.nextOverflow = nextOverflow
+ }
+
+ if h.flags&hashWriting == 0 {
+ throw("concurrent map writes")
+ }
+ h.flags &^= hashWriting
}
func hashGrow(t *maptype, h *hmap) {
@@ -895,7 +961,7 @@ func hashGrow(t *maptype, h *hmap) {
h.flags |= sameSizeGrow
}
oldbuckets := h.buckets
- newbuckets, nextOverflow := makeBucketArray(t, h.B+bigger)
+ newbuckets, nextOverflow := makeBucketArray(t, h.B+bigger, nil)
flags := h.flags &^ (iterator | oldIterator)
if h.flags&iterator != 0 {
diff --git a/src/runtime/map_benchmark_test.go b/src/runtime/map_benchmark_test.go
index aec0c51f3f..025c0398d3 100644
--- a/src/runtime/map_benchmark_test.go
+++ b/src/runtime/map_benchmark_test.go
@@ -341,3 +341,32 @@ func BenchmarkComplexAlgMap(b *testing.B) {
_ = m[k]
}
}
+
+func BenchmarkGoMapClear(b *testing.B) {
+ b.Run("Reflexive", func(b *testing.B) {
+ for size := 1; size < 100000; size *= 10 {
+ b.Run(strconv.Itoa(size), func(b *testing.B) {
+ m := make(map[int]int, size)
+ for i := 0; i < b.N; i++ {
+ m[0] = size // Add one element so len(m) != 0 avoiding fast paths.
+ for k := range m {
+ delete(m, k)
+ }
+ }
+ })
+ }
+ })
+ b.Run("NonReflexive", func(b *testing.B) {
+ for size := 1; size < 100000; size *= 10 {
+ b.Run(strconv.Itoa(size), func(b *testing.B) {
+ m := make(map[float64]int, size)
+ for i := 0; i < b.N; i++ {
+ m[1.0] = size // Add one element so len(m) != 0 avoiding fast paths.
+ for k := range m {
+ delete(m, k)
+ }
+ }
+ })
+ }
+ })
+}
generated by cgit v1.3-5-g9baa (git 2.53.0) at 2026-04-17 07:09:38 +0000