all: wire up swisstable maps

Use the new SwissTable-based map in internal/runtime/maps as the basis
for the runtime map when GOEXPERIMENT=swissmap.

Integration is complete enough to pass all.bash. Notable missing
features:

* Race integration / concurrent write detection
* Stack-allocated maps
* Specialized "fast" map variants
* Indirect key / elem

For #54766.

Cq-Include-Trybots: luci.golang.try:gotip-linux-ppc64_power10,gotip-linux-amd64-longtest-swissmap
Change-Id: Ie97b656b6d8e05c0403311ae08fef9f51756a639
Reviewed-on: https://go-review.googlesource.com/c/go/+/594596
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

11 files changed, 268 insertions, 1724 deletions

diff --git a/src/runtime/export_map_noswiss_test.go b/src/runtime/export_map_noswiss_test.go
index 9e6d81a77c..4638afa6b8 100644
--- a/src/runtime/export_map_noswiss_test.go
+++ b/src/runtime/export_map_noswiss_test.go
@@ -11,6 +11,12 @@ import (
 	"unsafe"
 )
 
+const RuntimeHmapSize = unsafe.Sizeof(hmap{})
+
+func OverLoadFactor(count int, B uint8) bool {
+	return overLoadFactor(count, B)
+}
+
 func MapBucketsCount(m map[int]int) int {
 	h := *(**hmap)(unsafe.Pointer(&m))
 	return 1 << h.B
diff --git a/src/runtime/export_map_swiss_test.go b/src/runtime/export_map_swiss_test.go
index ac0308fce0..55a7d6ff04 100644
--- a/src/runtime/export_map_swiss_test.go
+++ b/src/runtime/export_map_swiss_test.go
@@ -6,53 +6,6 @@
 
 package runtime
 
-import (
-	"internal/abi"
-	"unsafe"
-)
-
-func MapBucketsCount(m map[int]int) int {
-	h := *(**hmap)(unsafe.Pointer(&m))
-	return 1 << h.B
-}
-
-func MapBucketsPointerIsNil(m map[int]int) bool {
-	h := *(**hmap)(unsafe.Pointer(&m))
-	return h.buckets == nil
-}
-
 func MapTombstoneCheck(m map[int]int) {
-	// Make sure emptyOne and emptyRest are distributed correctly.
-	// We should have a series of filled and emptyOne cells, followed by
-	// a series of emptyRest cells.
-	h := *(**hmap)(unsafe.Pointer(&m))
-	i := any(m)
-	t := *(**maptype)(unsafe.Pointer(&i))
-
-	for x := 0; x < 1<<h.B; x++ {
-		b0 := (*bmap)(add(h.buckets, uintptr(x)*uintptr(t.BucketSize)))
-		n := 0
-		for b := b0; b != nil; b = b.overflow(t) {
-			for i := 0; i < abi.SwissMapBucketCount; i++ {
-				if b.tophash[i] != emptyRest {
-					n++
-				}
-			}
-		}
-		k := 0
-		for b := b0; b != nil; b = b.overflow(t) {
-			for i := 0; i < abi.SwissMapBucketCount; i++ {
-				if k < n && b.tophash[i] == emptyRest {
-					panic("early emptyRest")
-				}
-				if k >= n && b.tophash[i] != emptyRest {
-					panic("late non-emptyRest")
-				}
-				if k == n-1 && b.tophash[i] == emptyOne {
-					panic("last non-emptyRest entry is emptyOne")
-				}
-				k++
-			}
-		}
-	}
+	// TODO
 }
diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 3bde1aea29..5c8d2b18c6 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -481,12 +481,6 @@ func (rw *RWMutex) Unlock() {
 	rw.rw.unlock()
 }
 
-const RuntimeHmapSize = unsafe.Sizeof(hmap{})
-
-func OverLoadFactor(count int, B uint8) bool {
-	return overLoadFactor(count, B)
-}
-
 func LockOSCounts() (external, internal uint32) {
 	gp := getg()
 	if gp.m.lockedExt+gp.m.lockedInt == 0 {
diff --git a/src/runtime/map_fast32_swiss.go b/src/runtime/map_fast32_swiss.go
index f2482393dd..5cc2376982 100644
--- a/src/runtime/map_fast32_swiss.go
+++ b/src/runtime/map_fast32_swiss.go
@@ -7,29 +7,31 @@
 package runtime
 
 import (
+	"internal/abi"
+	"internal/runtime/maps"
 	"unsafe"
 )
 
-func mapaccess1_fast32(t *maptype, h *hmap, key uint32) unsafe.Pointer {
+func mapaccess1_fast32(t *abi.SwissMapType, m *maps.Map, key uint32) unsafe.Pointer {
 	throw("mapaccess1_fast32 unimplemented")
 	panic("unreachable")
 }
 
-func mapaccess2_fast32(t *maptype, h *hmap, key uint32) (unsafe.Pointer, bool) {
+func mapaccess2_fast32(t *abi.SwissMapType, m *maps.Map, key uint32) (unsafe.Pointer, bool) {
 	throw("mapaccess2_fast32 unimplemented")
 	panic("unreachable")
 }
 
-func mapassign_fast32(t *maptype, h *hmap, key uint32) unsafe.Pointer {
+func mapassign_fast32(t *abi.SwissMapType, m *maps.Map, key uint32) unsafe.Pointer {
 	throw("mapassign_fast32 unimplemented")
 	panic("unreachable")
 }
 
-func mapassign_fast32ptr(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
+func mapassign_fast32ptr(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) unsafe.Pointer {
 	throw("mapassign_fast32ptr unimplemented")
 	panic("unreachable")
 }
 
-func mapdelete_fast32(t *maptype, h *hmap, key uint32) {
+func mapdelete_fast32(t *abi.SwissMapType, m *maps.Map, key uint32) {
 	throw("mapdelete_fast32 unimplemented")
 }
diff --git a/src/runtime/map_fast64_swiss.go b/src/runtime/map_fast64_swiss.go
index 07ed9934c3..bf892fe83f 100644
--- a/src/runtime/map_fast64_swiss.go
+++ b/src/runtime/map_fast64_swiss.go
@@ -7,29 +7,31 @@
 package runtime
 
 import (
+	"internal/abi"
+	"internal/runtime/maps"
 	"unsafe"
 )
 
-func mapaccess1_fast64(t *maptype, h *hmap, key uint64) unsafe.Pointer {
+func mapaccess1_fast64(t *abi.SwissMapType, m *maps.Map, key uint64) unsafe.Pointer {
 	throw("mapaccess1_fast64 unimplemented")
 	panic("unreachable")
 }
 
-func mapaccess2_fast64(t *maptype, h *hmap, key uint64) (unsafe.Pointer, bool) {
+func mapaccess2_fast64(t *abi.SwissMapType, m *maps.Map, key uint64) (unsafe.Pointer, bool) {
 	throw("mapaccess2_fast64 unimplemented")
 	panic("unreachable")
 }
 
-func mapassign_fast64(t *maptype, h *hmap, key uint64) unsafe.Pointer {
+func mapassign_fast64(t *abi.SwissMapType, m *maps.Map, key uint64) unsafe.Pointer {
 	throw("mapassign_fast64 unimplemented")
 	panic("unreachable")
 }
 
-func mapassign_fast64ptr(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
+func mapassign_fast64ptr(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) unsafe.Pointer {
 	throw("mapassign_fast64ptr unimplemented")
 	panic("unreachable")
 }
 
-func mapdelete_fast64(t *maptype, h *hmap, key uint64) {
+func mapdelete_fast64(t *abi.SwissMapType, m *maps.Map, key uint64) {
 	throw("mapdelete_fast64 unimplemented")
 }
diff --git a/src/runtime/map_faststr_swiss.go b/src/runtime/map_faststr_swiss.go
index 41090d7381..b0fb54315a 100644
--- a/src/runtime/map_faststr_swiss.go
+++ b/src/runtime/map_faststr_swiss.go
@@ -7,24 +7,26 @@
 package runtime
 
 import (
+	"internal/abi"
+	"internal/runtime/maps"
 	"unsafe"
 )
 
-func mapaccess1_faststr(t *maptype, h *hmap, ky string) unsafe.Pointer {
+func mapaccess1_faststr(t *abi.SwissMapType, m *maps.Map, ky string) unsafe.Pointer {
 	throw("mapaccess1_faststr unimplemented")
 	panic("unreachable")
 }
 
-func mapaccess2_faststr(t *maptype, h *hmap, ky string) (unsafe.Pointer, bool) {
+func mapaccess2_faststr(t *abi.SwissMapType, m *maps.Map, ky string) (unsafe.Pointer, bool) {
 	throw("mapaccess2_faststr unimplemented")
 	panic("unreachable")
 }
 
-func mapassign_faststr(t *maptype, h *hmap, s string) unsafe.Pointer {
+func mapassign_faststr(t *abi.SwissMapType, m *maps.Map, s string) unsafe.Pointer {
 	throw("mapassign_faststr unimplemented")
 	panic("unreachable")
 }
 
-func mapdelete_faststr(t *maptype, h *hmap, ky string) {
+func mapdelete_faststr(t *abi.SwissMapType, m *maps.Map, ky string) {
 	throw("mapdelete_faststr unimplemented")
 }
diff --git a/src/runtime/map_noswiss_test.go b/src/runtime/map_noswiss_test.go
index 72d7e6d362..bda448471c 100644
--- a/src/runtime/map_noswiss_test.go
+++ b/src/runtime/map_noswiss_test.go
@@ -8,11 +8,37 @@ package runtime_test
 
 import (
 	"internal/abi"
+	"internal/goarch"
 	"runtime"
 	"slices"
 	"testing"
 )
 
+func TestHmapSize(t *testing.T) {
+	// The structure of hmap is defined in runtime/map.go
+	// and in cmd/compile/internal/reflectdata/map.go and must be in sync.
+	// The size of hmap should be 48 bytes on 64 bit and 28 bytes on 32 bit platforms.
+	var hmapSize = uintptr(8 + 5*goarch.PtrSize)
+	if runtime.RuntimeHmapSize != hmapSize {
+		t.Errorf("sizeof(runtime.hmap{})==%d, want %d", runtime.RuntimeHmapSize, hmapSize)
+	}
+}
+
+func TestLoadFactor(t *testing.T) {
+	for b := uint8(0); b < 20; b++ {
+		count := 13 * (1 << b) / 2 // 6.5
+		if b == 0 {
+			count = 8
+		}
+		if runtime.OverLoadFactor(count, b) {
+			t.Errorf("OverLoadFactor(%d,%d)=true, want false", count, b)
+		}
+		if !runtime.OverLoadFactor(count+1, b) {
+			t.Errorf("OverLoadFactor(%d,%d)=false, want true", count+1, b)
+		}
+	}
+}
+
 func TestMapIterOrder(t *testing.T) {
 	sizes := []int{3, 7, 9, 15}
 	if abi.OldMapBucketCountBits >= 5 {
diff --git a/src/runtime/map_swiss.go b/src/runtime/map_swiss.go
index 590fccc407..bd0d05d092 100644
--- a/src/runtime/map_swiss.go
+++ b/src/runtime/map_swiss.go
@@ -6,292 +6,65 @@
 
 package runtime
 
-// This file contains the implementation of Go's map type.
-//
-// A map is just a hash table. The data is arranged
-// into an array of buckets. Each bucket contains up to
-// 8 key/elem pairs. The low-order bits of the hash are
-// used to select a bucket. Each bucket contains a few
-// high-order bits of each hash to distinguish the entries
-// within a single bucket.
-//
-// If more than 8 keys hash to a bucket, we chain on
-// extra buckets.
-//
-// When the hashtable grows, we allocate a new array
-// of buckets twice as big. Buckets are incrementally
-// copied from the old bucket array to the new bucket array.
-//
-// Map iterators walk through the array of buckets and
-// return the keys in walk order (bucket #, then overflow
-// chain order, then bucket index).  To maintain iteration
-// semantics, we never move keys within their bucket (if
-// we did, keys might be returned 0 or 2 times).  When
-// growing the table, iterators remain iterating through the
-// old table and must check the new table if the bucket
-// they are iterating through has been moved ("evacuated")
-// to the new table.
-
-// Picking loadFactor: too large and we have lots of overflow
-// buckets, too small and we waste a lot of space. I wrote
-// a simple program to check some stats for different loads:
-// (64-bit, 8 byte keys and elems)
-//  loadFactor    %overflow  bytes/entry     hitprobe    missprobe
-//        4.00         2.13        20.77         3.00         4.00
-//        4.50         4.05        17.30         3.25         4.50
-//        5.00         6.85        14.77         3.50         5.00
-//        5.50        10.55        12.94         3.75         5.50
-//        6.00        15.27        11.67         4.00         6.00
-//        6.50        20.90        10.79         4.25         6.50
-//        7.00        27.14        10.15         4.50         7.00
-//        7.50        34.03         9.73         4.75         7.50
-//        8.00        41.10         9.40         5.00         8.00
-//
-// %overflow   = percentage of buckets which have an overflow bucket
-// bytes/entry = overhead bytes used per key/elem pair
-// hitprobe    = # of entries to check when looking up a present key
-// missprobe   = # of entries to check when looking up an absent key
-//
-// Keep in mind this data is for maximally loaded tables, i.e. just
-// before the table grows. Typical tables will be somewhat less loaded.
-
 import (
 	"internal/abi"
-	"internal/goarch"
-	"internal/runtime/atomic"
+	"internal/runtime/maps"
 	"internal/runtime/math"
 	"internal/runtime/sys"
 	"unsafe"
 )
 
-type maptype = abi.SwissMapType
-
 const (
-	// Maximum number of key/elem pairs a bucket can hold.
-	bucketCntBits = abi.SwissMapBucketCountBits
-
-	// Maximum average load of a bucket that triggers growth is bucketCnt*13/16 (about 80% full)
-	// Because of minimum alignment rules, bucketCnt is known to be at least 8.
-	// Represent as loadFactorNum/loadFactorDen, to allow integer math.
-	loadFactorDen = 2
-	loadFactorNum = loadFactorDen * abi.SwissMapBucketCount * 13 / 16
-
-	// data offset should be the size of the bmap struct, but needs to be
-	// aligned correctly. For amd64p32 this means 64-bit alignment
-	// even though pointers are 32 bit.
-	dataOffset = unsafe.Offsetof(struct {
-		b bmap
-		v int64
-	}{}.v)
-
-	// Possible tophash values. We reserve a few possibilities for special marks.
-	// Each bucket (including its overflow buckets, if any) will have either all or none of its
-	// entries in the evacuated* states (except during the evacuate() method, which only happens
-	// during map writes and thus no one else can observe the map during that time).
-	emptyRest      = 0 // this cell is empty, and there are no more non-empty cells at higher indexes or overflows.
-	emptyOne       = 1 // this cell is empty
-	evacuatedX     = 2 // key/elem is valid.  Entry has been evacuated to first half of larger table.
-	evacuatedY     = 3 // same as above, but evacuated to second half of larger table.
-	evacuatedEmpty = 4 // cell is empty, bucket is evacuated.
-	minTopHash     = 5 // minimum tophash for a normal filled cell.
-
-	// flags
-	iterator     = 1 // there may be an iterator using buckets
-	oldIterator  = 2 // there may be an iterator using oldbuckets
-	hashWriting  = 4 // a goroutine is writing to the map
-	sameSizeGrow = 8 // the current map growth is to a new map of the same size
-
-	// sentinel bucket ID for iterator checks
-	noCheck = 1<<(8*goarch.PtrSize) - 1
+	// TODO: remove? These are used by tests but not the actual map
+	loadFactorNum = 7
+	loadFactorDen = 8
 )
 
-// isEmpty reports whether the given tophash array entry represents an empty bucket entry.
-func isEmpty(x uint8) bool {
-	return x <= emptyOne
-}
-
-// A header for a Go map.
-type hmap struct {
-	// Note: the format of the hmap is also encoded in cmd/compile/internal/reflectdata/reflect.go.
-	// Make sure this stays in sync with the compiler's definition.
-	count     int // # live cells == size of map.  Must be first (used by len() builtin)
-	flags     uint8
-	B         uint8  // log_2 of # of buckets (can hold up to loadFactor * 2^B items)
-	noverflow uint16 // approximate number of overflow buckets; see incrnoverflow for details
-	hash0     uint32 // hash seed
-
-	buckets    unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.
-	oldbuckets unsafe.Pointer // previous bucket array of half the size, non-nil only when growing
-	nevacuate  uintptr        // progress counter for evacuation (buckets less than this have been evacuated)
-
-	extra *mapextra // optional fields
-}
-
-// mapextra holds fields that are not present on all maps.
-type mapextra struct {
-	// If both key and elem do not contain pointers and are inline, then we mark bucket
-	// type as containing no pointers. This avoids scanning such maps.
-	// However, bmap.overflow is a pointer. In order to keep overflow buckets
-	// alive, we store pointers to all overflow buckets in hmap.extra.overflow and hmap.extra.oldoverflow.
-	// overflow and oldoverflow are only used if key and elem do not contain pointers.
-	// overflow contains overflow buckets for hmap.buckets.
-	// oldoverflow contains overflow buckets for hmap.oldbuckets.
-	// The indirection allows to store a pointer to the slice in hiter.
-	overflow    *[]*bmap
-	oldoverflow *[]*bmap
-
-	// nextOverflow holds a pointer to a free overflow bucket.
-	nextOverflow *bmap
-}
-
-// A bucket for a Go map.
-type bmap struct {
-	// tophash generally contains the top byte of the hash value
-	// for each key in this bucket. If tophash[0] < minTopHash,
-	// tophash[0] is a bucket evacuation state instead.
-	tophash [abi.SwissMapBucketCount]uint8
-	// Followed by bucketCnt keys and then bucketCnt elems.
-	// NOTE: packing all the keys together and then all the elems together makes the
-	// code a bit more complicated than alternating key/elem/key/elem/... but it allows
-	// us to eliminate padding which would be needed for, e.g., map[int64]int8.
-	// Followed by an overflow pointer.
-}
-
-// A hash iteration structure.
-// If you modify hiter, also change cmd/compile/internal/reflectdata/reflect.go
-// and reflect/value.go to match the layout of this structure.
-type hiter struct {
-	key         unsafe.Pointer // Must be in first position.  Write nil to indicate iteration end (see cmd/compile/internal/walk/range.go).
-	elem        unsafe.Pointer // Must be in second position (see cmd/compile/internal/walk/range.go).
-	t           *maptype
-	h           *hmap
-	buckets     unsafe.Pointer // bucket ptr at hash_iter initialization time
-	bptr        *bmap          // current bucket
-	overflow    *[]*bmap       // keeps overflow buckets of hmap.buckets alive
-	oldoverflow *[]*bmap       // keeps overflow buckets of hmap.oldbuckets alive
-	startBucket uintptr        // bucket iteration started at
-	offset      uint8          // intra-bucket offset to start from during iteration (should be big enough to hold bucketCnt-1)
-	wrapped     bool           // already wrapped around from end of bucket array to beginning
-	B           uint8
-	i           uint8
-	bucket      uintptr
-	checkBucket uintptr
-}
-
-// bucketShift returns 1<<b, optimized for code generation.
-func bucketShift(b uint8) uintptr {
-	// Masking the shift amount allows overflow checks to be elided.
-	return uintptr(1) << (b & (goarch.PtrSize*8 - 1))
-}
-
-// bucketMask returns 1<<b - 1, optimized for code generation.
-func bucketMask(b uint8) uintptr {
-	return bucketShift(b) - 1
-}
+type maptype = abi.SwissMapType
 
-// tophash calculates the tophash value for hash.
-func tophash(hash uintptr) uint8 {
-	top := uint8(hash >> (goarch.PtrSize*8 - 8))
-	if top < minTopHash {
-		top += minTopHash
+func makemap64(t *abi.SwissMapType, hint int64, m *maps.Map) *maps.Map {
+	if int64(int(hint)) != hint {
+		hint = 0
 	}
-	return top
-}
-
-func evacuated(b *bmap) bool {
-	h := b.tophash[0]
-	return h > emptyOne && h < minTopHash
-}
-
-func (b *bmap) overflow(t *maptype) *bmap {
-	return *(**bmap)(add(unsafe.Pointer(b), uintptr(t.BucketSize)-goarch.PtrSize))
+	return makemap(t, int(hint), m)
 }
 
-func (b *bmap) setoverflow(t *maptype, ovf *bmap) {
-	*(**bmap)(add(unsafe.Pointer(b), uintptr(t.BucketSize)-goarch.PtrSize)) = ovf
-}
-
-func (b *bmap) keys() unsafe.Pointer {
-	return add(unsafe.Pointer(b), dataOffset)
+// makemap_small implements Go map creation for make(map[k]v) and
+// make(map[k]v, hint) when hint is known to be at most bucketCnt
+// at compile time and the map needs to be allocated on the heap.
+func makemap_small() *maps.Map {
+	panic("unimplemented")
 }
 
-// incrnoverflow increments h.noverflow.
-// noverflow counts the number of overflow buckets.
-// This is used to trigger same-size map growth.
-// See also tooManyOverflowBuckets.
-// To keep hmap small, noverflow is a uint16.
-// When there are few buckets, noverflow is an exact count.
-// When there are many buckets, noverflow is an approximate count.
-func (h *hmap) incrnoverflow() {
-	// We trigger same-size map growth if there are
-	// as many overflow buckets as buckets.
-	// We need to be able to count to 1<<h.B.
-	if h.B < 16 {
-		h.noverflow++
-		return
-	}
-	// Increment with probability 1/(1<<(h.B-15)).
-	// When we reach 1<<15 - 1, we will have approximately
-	// as many overflow buckets as buckets.
-	mask := uint32(1)<<(h.B-15) - 1
-	// Example: if h.B == 18, then mask == 7,
-	// and rand() & 7 == 0 with probability 1/8.
-	if uint32(rand())&mask == 0 {
-		h.noverflow++
+// checkHint verifies that hint is reasonable, adjusting as necessary.
+func checkHint(t *abi.SwissMapType, hint int) uint64 {
+	if hint <= 0 {
+		return 0
 	}
-}
 
-func (h *hmap) newoverflow(t *maptype, b *bmap) *bmap {
-	var ovf *bmap
-	if h.extra != nil && h.extra.nextOverflow != nil {
-		// We have preallocated overflow buckets available.
-		// See makeBucketArray for more details.
-		ovf = h.extra.nextOverflow
-		if ovf.overflow(t) == nil {
-			// We're not at the end of the preallocated overflow buckets. Bump the pointer.
-			h.extra.nextOverflow = (*bmap)(add(unsafe.Pointer(ovf), uintptr(t.BucketSize)))
-		} else {
-			// This is the last preallocated overflow bucket.
-			// Reset the overflow pointer on this bucket,
-			// which was set to a non-nil sentinel value.
-			ovf.setoverflow(t, nil)
-			h.extra.nextOverflow = nil
+	capacity := uint64(hint)
+
+	// Ensure a groups allocation for a capacity this high doesn't exceed
+	// the maximum allocation size.
+	//
+	// TODO(prattmic): Once we split tables, a large hint will result in
+	// splitting the tables up front, which will use smaller individual
+	// allocations.
+	//
+	// TODO(prattmic): This logic is largely duplicated from maps.newTable
+	// / maps.(*table).reset.
+	capacity, overflow := alignUpPow2(capacity)
+	if !overflow {
+		groupCount := capacity / abi.SwissMapGroupSlots
+		mem, overflow := math.MulUintptr(uintptr(groupCount), t.Group.Size_)
+		if overflow || mem > maxAlloc {
+			return 0
 		}
 	} else {
-		ovf = (*bmap)(newobject(t.Bucket))
-	}
-	h.incrnoverflow()
-	if !t.Bucket.Pointers() {
-		h.createOverflow()
-		*h.extra.overflow = append(*h.extra.overflow, ovf)
-	}
-	b.setoverflow(t, ovf)
-	return ovf
-}
-
-func (h *hmap) createOverflow() {
-	if h.extra == nil {
-		h.extra = new(mapextra)
-	}
-	if h.extra.overflow == nil {
-		h.extra.overflow = new([]*bmap)
-	}
-}
-
-func makemap64(t *maptype, hint int64, h *hmap) *hmap {
-	if int64(int(hint)) != hint {
-		hint = 0
+		return 0
 	}
-	return makemap(t, int(hint), h)
-}
 
-// makemap_small implements Go map creation for make(map[k]v) and
-// make(map[k]v, hint) when hint is known to be at most bucketCnt
-// at compile time and the map needs to be allocated on the heap.
-func makemap_small() *hmap {
-	h := new(hmap)
-	h.hash0 = uint32(rand())
-	return h
+	return capacity
 }
 
 // makemap implements Go map creation for make(map[k]v, hint).
@@ -299,90 +72,27 @@ func makemap_small() *hmap {
 // 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 h.buckets != nil, bucket pointed to can be used as the first bucket.
-func makemap(t *maptype, hint int, h *hmap) *hmap {
-	mem, overflow := math.MulUintptr(uintptr(hint), t.Bucket.Size_)
-	if overflow || mem > maxAlloc {
-		hint = 0
-	}
-
-	// initialize Hmap
-	if h == nil {
-		h = new(hmap)
-	}
-	h.hash0 = uint32(rand())
-
-	// Find the size parameter B which will hold the requested # of elements.
-	// For hint < 0 overLoadFactor returns false since hint < bucketCnt.
-	B := uint8(0)
-	for overLoadFactor(hint, B) {
-		B++
-	}
-	h.B = B
+func makemap(t *abi.SwissMapType, hint int, m *maps.Map) *maps.Map {
+	capacity := checkHint(t, hint)
 
-	// 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, nil)
-		if nextOverflow != nil {
-			h.extra = new(mapextra)
-			h.extra.nextOverflow = nextOverflow
-		}
-	}
-
-	return h
+	// TODO: use existing m
+	return maps.NewTable(t, capacity)
 }
 
-// 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, !t.Bucket.Pointers())
-		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.Pointers() {
-			memclrHasPointers(buckets, size)
-		} else {
-			memclrNoHeapPointers(buckets, size)
-		}
+// alignUpPow2 rounds n up to the next power of 2.
+//
+// Returns true if round up causes overflow.
+//
+// TODO(prattmic): deduplicate from internal/runtime/maps.
+func alignUpPow2(n uint64) (uint64, bool) {
+	if n == 0 {
+		return 0, false
 	}
-
-	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))
+	v := (uint64(1) << sys.Len64(n-1))
+	if v == 0 {
+		return 0, true
 	}
-	return buckets, nextOverflow
+	return v, false
 }
 
 // mapaccess1 returns a pointer to h[key].  Never returns nil, instead
@@ -390,197 +100,89 @@ func makeBucketArray(t *maptype, b uint8, dirtyalloc unsafe.Pointer) (buckets un
 // the key is not in the map.
 // NOTE: The returned pointer may keep the whole map live, so don't
 // hold onto it for very long.
-func mapaccess1(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
-	if raceenabled && h != nil {
+func mapaccess1(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) unsafe.Pointer {
+	// TODO: concurrent checks.
+	if raceenabled && m != nil {
 		callerpc := sys.GetCallerPC()
 		pc := abi.FuncPCABIInternal(mapaccess1)
-		racereadpc(unsafe.Pointer(h), callerpc, pc)
+		racereadpc(unsafe.Pointer(m), callerpc, pc)
 		raceReadObjectPC(t.Key, key, callerpc, pc)
 	}
-	if msanenabled && h != nil {
+	if msanenabled && m != nil {
 		msanread(key, t.Key.Size_)
 	}
-	if asanenabled && h != nil {
+	if asanenabled && m != nil {
 		asanread(key, t.Key.Size_)
 	}
-	if h == nil || h.count == 0 {
+
+	if m == nil || m.Used() == 0 {
 		if err := mapKeyError(t, key); err != nil {
 			panic(err) // see issue 23734
 		}
 		return unsafe.Pointer(&zeroVal[0])
 	}
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map read and map write")
-	}
-	hash := t.Hasher(key, uintptr(h.hash0))
-	m := bucketMask(h.B)
-	b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.BucketSize)))
-	if c := h.oldbuckets; c != nil {
-		if !h.sameSizeGrow() {
-			// There used to be half as many buckets; mask down one more power of two.
-			m >>= 1
-		}
-		oldb := (*bmap)(add(c, (hash&m)*uintptr(t.BucketSize)))
-		if !evacuated(oldb) {
-			b = oldb
-		}
-	}
-	top := tophash(hash)
-bucketloop:
-	for ; b != nil; b = b.overflow(t) {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			if b.tophash[i] != top {
-				if b.tophash[i] == emptyRest {
-					break bucketloop
-				}
-				continue
-			}
-			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-			if t.IndirectKey() {
-				k = *((*unsafe.Pointer)(k))
-			}
-			if t.Key.Equal(key, k) {
-				e := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-				if t.IndirectElem() {
-					e = *((*unsafe.Pointer)(e))
-				}
-				return e
-			}
-		}
+
+	elem, ok := m.Get(key)
+	if !ok {
+		return unsafe.Pointer(&zeroVal[0])
 	}
-	return unsafe.Pointer(&zeroVal[0])
+	return elem
 }
 
-func mapaccess2(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, bool) {
-	if raceenabled && h != nil {
+func mapaccess2(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) (unsafe.Pointer, bool) {
+	// TODO: concurrent checks.
+	if raceenabled && m != nil {
 		callerpc := sys.GetCallerPC()
 		pc := abi.FuncPCABIInternal(mapaccess2)
-		racereadpc(unsafe.Pointer(h), callerpc, pc)
+		racereadpc(unsafe.Pointer(m), callerpc, pc)
 		raceReadObjectPC(t.Key, key, callerpc, pc)
 	}
-	if msanenabled && h != nil {
+	if msanenabled && m != nil {
 		msanread(key, t.Key.Size_)
 	}
-	if asanenabled && h != nil {
+	if asanenabled && m != nil {
 		asanread(key, t.Key.Size_)
 	}
-	if h == nil || h.count == 0 {
+
+	if m == nil || m.Used() == 0 {
 		if err := mapKeyError(t, key); err != nil {
 			panic(err) // see issue 23734
 		}
 		return unsafe.Pointer(&zeroVal[0]), false
 	}
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map read and map write")
-	}
-	hash := t.Hasher(key, uintptr(h.hash0))
-	m := bucketMask(h.B)
-	b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.BucketSize)))
-	if c := h.oldbuckets; c != nil {
-		if !h.sameSizeGrow() {
-			// There used to be half as many buckets; mask down one more power of two.
-			m >>= 1
-		}
-		oldb := (*bmap)(add(c, (hash&m)*uintptr(t.BucketSize)))
-		if !evacuated(oldb) {
-			b = oldb
-		}
-	}
-	top := tophash(hash)
-bucketloop:
-	for ; b != nil; b = b.overflow(t) {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			if b.tophash[i] != top {
-				if b.tophash[i] == emptyRest {
-					break bucketloop
-				}
-				continue
-			}
-			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-			if t.IndirectKey() {
-				k = *((*unsafe.Pointer)(k))
-			}
-			if t.Key.Equal(key, k) {
-				e := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-				if t.IndirectElem() {
-					e = *((*unsafe.Pointer)(e))
-				}
-				return e, true
-			}
-		}
-	}
-	return unsafe.Pointer(&zeroVal[0]), false
-}
 
-// returns both key and elem. Used by map iterator.
-func mapaccessK(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, unsafe.Pointer) {
-	if h == nil || h.count == 0 {
-		return nil, nil
-	}
-	hash := t.Hasher(key, uintptr(h.hash0))
-	m := bucketMask(h.B)
-	b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.BucketSize)))
-	if c := h.oldbuckets; c != nil {
-		if !h.sameSizeGrow() {
-			// There used to be half as many buckets; mask down one more power of two.
-			m >>= 1
-		}
-		oldb := (*bmap)(add(c, (hash&m)*uintptr(t.BucketSize)))
-		if !evacuated(oldb) {
-			b = oldb
-		}
-	}
-	top := tophash(hash)
-bucketloop:
-	for ; b != nil; b = b.overflow(t) {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			if b.tophash[i] != top {
-				if b.tophash[i] == emptyRest {
-					break bucketloop
-				}
-				continue
-			}
-			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-			if t.IndirectKey() {
-				k = *((*unsafe.Pointer)(k))
-			}
-			if t.Key.Equal(key, k) {
-				e := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-				if t.IndirectElem() {
-					e = *((*unsafe.Pointer)(e))
-				}
-				return k, e
-			}
-		}
+	elem, ok := m.Get(key)
+	if !ok {
+		return unsafe.Pointer(&zeroVal[0]), false
 	}
-	return nil, nil
+	return elem, true
 }
 
-func mapaccess1_fat(t *maptype, h *hmap, key, zero unsafe.Pointer) unsafe.Pointer {
-	e := mapaccess1(t, h, key)
+func mapaccess1_fat(t *abi.SwissMapType, m *maps.Map, key, zero unsafe.Pointer) unsafe.Pointer {
+	e := mapaccess1(t, m, key)
 	if e == unsafe.Pointer(&zeroVal[0]) {
 		return zero
 	}
 	return e
 }
 
-func mapaccess2_fat(t *maptype, h *hmap, key, zero unsafe.Pointer) (unsafe.Pointer, bool) {
-	e := mapaccess1(t, h, key)
+func mapaccess2_fat(t *abi.SwissMapType, m *maps.Map, key, zero unsafe.Pointer) (unsafe.Pointer, bool) {
+	e := mapaccess1(t, m, key)
 	if e == unsafe.Pointer(&zeroVal[0]) {
 		return zero, false
 	}
 	return e, true
 }
 
-// Like mapaccess, but allocates a slot for the key if it is not present in the map.
-func mapassign(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
-	if h == nil {
+func mapassign(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) unsafe.Pointer {
+	// TODO: concurrent checks.
+	if m == nil {
 		panic(plainError("assignment to entry in nil map"))
 	}
 	if raceenabled {
 		callerpc := sys.GetCallerPC()
 		pc := abi.FuncPCABIInternal(mapassign)
-		racewritepc(unsafe.Pointer(h), callerpc, pc)
+		racewritepc(unsafe.Pointer(m), callerpc, pc)
 		raceReadObjectPC(t.Key, key, callerpc, pc)
 	}
 	if msanenabled {
@@ -589,762 +191,91 @@ func mapassign(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 	if asanenabled {
 		asanread(key, t.Key.Size_)
 	}
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map writes")
-	}
-	hash := t.Hasher(key, uintptr(h.hash0))
-
-	// Set hashWriting after calling t.hasher, since t.hasher may panic,
-	// in which case we have not actually done a write.
-	h.flags ^= hashWriting
-
-	if h.buckets == nil {
-		h.buckets = newobject(t.Bucket) // newarray(t.Bucket, 1)
-	}
 
-again:
-	bucket := hash & bucketMask(h.B)
-	if h.growing() {
-		growWork(t, h, bucket)
-	}
-	b := (*bmap)(add(h.buckets, bucket*uintptr(t.BucketSize)))
-	top := tophash(hash)
-
-	var inserti *uint8
-	var insertk unsafe.Pointer
-	var elem unsafe.Pointer
-bucketloop:
-	for {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			if b.tophash[i] != top {
-				if isEmpty(b.tophash[i]) && inserti == nil {
-					inserti = &b.tophash[i]
-					insertk = add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-					elem = add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-				}
-				if b.tophash[i] == emptyRest {
-					break bucketloop
-				}
-				continue
-			}
-			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-			if t.IndirectKey() {
-				k = *((*unsafe.Pointer)(k))
-			}
-			if !t.Key.Equal(key, k) {
-				continue
-			}
-			// already have a mapping for key. Update it.
-			if t.NeedKeyUpdate() {
-				typedmemmove(t.Key, k, key)
-			}
-			elem = add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-			goto done
-		}
-		ovf := b.overflow(t)
-		if ovf == nil {
-			break
-		}
-		b = ovf
-	}
-
-	// Did not find mapping for key. Allocate new cell & add entry.
-
-	// If we hit the max load factor or we have too many overflow buckets,
-	// and we're not already in the middle of growing, start growing.
-	if !h.growing() && (overLoadFactor(h.count+1, h.B) || tooManyOverflowBuckets(h.noverflow, h.B)) {
-		hashGrow(t, h)
-		goto again // Growing the table invalidates everything, so try again
-	}
-
-	if inserti == nil {
-		// The current bucket and all the overflow buckets connected to it are full, allocate a new one.
-		newb := h.newoverflow(t, b)
-		inserti = &newb.tophash[0]
-		insertk = add(unsafe.Pointer(newb), dataOffset)
-		elem = add(insertk, abi.SwissMapBucketCount*uintptr(t.KeySize))
-	}
-
-	// store new key/elem at insert position
-	if t.IndirectKey() {
-		kmem := newobject(t.Key)
-		*(*unsafe.Pointer)(insertk) = kmem
-		insertk = kmem
-	}
-	if t.IndirectElem() {
-		vmem := newobject(t.Elem)
-		*(*unsafe.Pointer)(elem) = vmem
-	}
-	typedmemmove(t.Key, insertk, key)
-	*inserti = top
-	h.count++
-
-done:
-	if h.flags&hashWriting == 0 {
-		fatal("concurrent map writes")
-	}
-	h.flags &^= hashWriting
-	if t.IndirectElem() {
-		elem = *((*unsafe.Pointer)(elem))
-	}
-	return elem
+	return m.PutSlot(key)
 }
 
-func mapdelete(t *maptype, h *hmap, key unsafe.Pointer) {
-	if raceenabled && h != nil {
+func mapdelete(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) {
+	// TODO: concurrent checks.
+	if raceenabled && m != nil {
 		callerpc := sys.GetCallerPC()
 		pc := abi.FuncPCABIInternal(mapdelete)
-		racewritepc(unsafe.Pointer(h), callerpc, pc)
+		racewritepc(unsafe.Pointer(m), callerpc, pc)
 		raceReadObjectPC(t.Key, key, callerpc, pc)
 	}
-	if msanenabled && h != nil {
+	if msanenabled && m != nil {
 		msanread(key, t.Key.Size_)
 	}
-	if asanenabled && h != nil {
+	if asanenabled && m != nil {
 		asanread(key, t.Key.Size_)
 	}
-	if h == nil || h.count == 0 {
+
+	if m == nil || m.Used() == 0 {
 		if err := mapKeyError(t, key); err != nil {
 			panic(err) // see issue 23734
 		}
 		return
 	}
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map writes")
-	}
 
-	hash := t.Hasher(key, uintptr(h.hash0))
-
-	// Set hashWriting after calling t.hasher, since t.hasher may panic,
-	// in which case we have not actually done a write (delete).
-	h.flags ^= hashWriting
-
-	bucket := hash & bucketMask(h.B)
-	if h.growing() {
-		growWork(t, h, bucket)
-	}
-	b := (*bmap)(add(h.buckets, bucket*uintptr(t.BucketSize)))
-	bOrig := b
-	top := tophash(hash)
-search:
-	for ; b != nil; b = b.overflow(t) {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			if b.tophash[i] != top {
-				if b.tophash[i] == emptyRest {
-					break search
-				}
-				continue
-			}
-			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.KeySize))
-			k2 := k
-			if t.IndirectKey() {
-				k2 = *((*unsafe.Pointer)(k2))
-			}
-			if !t.Key.Equal(key, k2) {
-				continue
-			}
-			// Only clear key if there are pointers in it.
-			if t.IndirectKey() {
-				*(*unsafe.Pointer)(k) = nil
-			} else if t.Key.Pointers() {
-				memclrHasPointers(k, t.Key.Size_)
-			}
-			e := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-			if t.IndirectElem() {
-				*(*unsafe.Pointer)(e) = nil
-			} else if t.Elem.Pointers() {
-				memclrHasPointers(e, t.Elem.Size_)
-			} else {
-				memclrNoHeapPointers(e, t.Elem.Size_)
-			}
-			b.tophash[i] = emptyOne
-			// If the bucket now ends in a bunch of emptyOne states,
-			// change those to emptyRest states.
-			// It would be nice to make this a separate function, but
-			// for loops are not currently inlineable.
-			if i == abi.SwissMapBucketCount-1 {
-				if b.overflow(t) != nil && b.overflow(t).tophash[0] != emptyRest {
-					goto notLast
-				}
-			} else {
-				if b.tophash[i+1] != emptyRest {
-					goto notLast
-				}
-			}
-			for {
-				b.tophash[i] = emptyRest
-				if i == 0 {
-					if b == bOrig {
-						break // beginning of initial bucket, we're done.
-					}
-					// Find previous bucket, continue at its last entry.
-					c := b
-					for b = bOrig; b.overflow(t) != c; b = b.overflow(t) {
-					}
-					i = abi.SwissMapBucketCount - 1
-				} else {
-					i--
-				}
-				if b.tophash[i] != emptyOne {
-					break
-				}
-			}
-		notLast:
-			h.count--
-			// Reset the hash seed to make it more difficult for attackers to
-			// repeatedly trigger hash collisions. See issue 25237.
-			if h.count == 0 {
-				h.hash0 = uint32(rand())
-			}
-			break search
-		}
-	}
-
-	if h.flags&hashWriting == 0 {
-		fatal("concurrent map writes")
-	}
-	h.flags &^= hashWriting
+	m.Delete(key)
 }
 
-// mapiterinit initializes the hiter struct used for ranging over maps.
-// The hiter struct pointed to by 'it' is allocated on the stack
+// mapiterinit initializes the Iter struct used for ranging over maps.
+// The Iter struct pointed to by 'it' is allocated on the stack
 // by the compilers order pass or on the heap by reflect_mapiterinit.
 // Both need to have zeroed hiter since the struct contains pointers.
-func mapiterinit(t *maptype, h *hmap, it *hiter) {
-	if raceenabled && h != nil {
+func mapiterinit(t *abi.SwissMapType, m *maps.Map, it *maps.Iter) {
+	if raceenabled && m != nil {
 		callerpc := sys.GetCallerPC()
-		racereadpc(unsafe.Pointer(h), callerpc, abi.FuncPCABIInternal(mapiterinit))
-	}
-
-	it.t = t
-	if h == nil || h.count == 0 {
-		return
-	}
-
-	if unsafe.Sizeof(hiter{})/goarch.PtrSize != 12 {
-		throw("hash_iter size incorrect") // see cmd/compile/internal/reflectdata/reflect.go
-	}
-	it.h = h
-
-	// grab snapshot of bucket state
-	it.B = h.B
-	it.buckets = h.buckets
-	if !t.Bucket.Pointers() {
-		// Allocate the current slice and remember pointers to both current and old.
-		// This preserves all relevant overflow buckets alive even if
-		// the table grows and/or overflow buckets are added to the table
-		// while we are iterating.
-		h.createOverflow()
-		it.overflow = h.extra.overflow
-		it.oldoverflow = h.extra.oldoverflow
-	}
-
-	// decide where to start
-	r := uintptr(rand())
-	it.startBucket = r & bucketMask(h.B)
-	it.offset = uint8(r >> h.B & (abi.SwissMapBucketCount - 1))
-
-	// iterator state
-	it.bucket = it.startBucket
-
-	// Remember we have an iterator.
-	// Can run concurrently with another mapiterinit().
-	if old := h.flags; old&(iterator|oldIterator) != iterator|oldIterator {
-		atomic.Or8(&h.flags, iterator|oldIterator)
+		racereadpc(unsafe.Pointer(m), callerpc, abi.FuncPCABIInternal(mapiterinit))
 	}
 
-	mapiternext(it)
+	it.Init(t, m)
+	it.Next()
 }
 
-func mapiternext(it *hiter) {
-	h := it.h
+func mapiternext(it *maps.Iter) {
+	// TODO: concurrent checks.
 	if raceenabled {
 		callerpc := sys.GetCallerPC()
-		racereadpc(unsafe.Pointer(h), callerpc, abi.FuncPCABIInternal(mapiternext))
-	}
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map iteration and map write")
+		racereadpc(unsafe.Pointer(it.Map()), callerpc, abi.FuncPCABIInternal(mapiternext))
 	}
-	t := it.t
-	bucket := it.bucket
-	b := it.bptr
-	i := it.i
-	checkBucket := it.checkBucket
 
-next:
-	if b == nil {
-		if bucket == it.startBucket && it.wrapped {
-			// end of iteration
-			it.key = nil
-			it.elem = nil
-			return
-		}
-		if h.growing() && it.B == h.B {
-			// Iterator was started in the middle of a grow, and the grow isn't done yet.
-			// If the bucket we're looking at hasn't been filled in yet (i.e. the old
-			// bucket hasn't been evacuated) then we need to iterate through the old
-			// bucket and only return the ones that will be migrated to this bucket.
-			oldbucket := bucket & it.h.oldbucketmask()
-			b = (*bmap)(add(h.oldbuckets, oldbucket*uintptr(t.BucketSize)))
-			if !evacuated(b) {
-				checkBucket = bucket
-			} else {
-				b = (*bmap)(add(it.buckets, bucket*uintptr(t.BucketSize)))
-				checkBucket = noCheck
-			}
-		} else {
-			b = (*bmap)(add(it.buckets, bucket*uintptr(t.BucketSize)))
-			checkBucket = noCheck
-		}
-		bucket++
-		if bucket == bucketShift(it.B) {
-			bucket = 0
-			it.wrapped = true
-		}
-		i = 0
-	}
-	for ; i < abi.SwissMapBucketCount; i++ {
-		offi := (i + it.offset) & (abi.SwissMapBucketCount - 1)
-		if isEmpty(b.tophash[offi]) || b.tophash[offi] == evacuatedEmpty {
-			// TODO: emptyRest is hard to use here, as we start iterating
-			// in the middle of a bucket. It's feasible, just tricky.
-			continue
-		}
-		k := add(unsafe.Pointer(b), dataOffset+uintptr(offi)*uintptr(t.KeySize))
-		if t.IndirectKey() {
-			k = *((*unsafe.Pointer)(k))
-		}
-		e := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+uintptr(offi)*uintptr(t.ValueSize))
-		if checkBucket != noCheck && !h.sameSizeGrow() {
-			// Special case: iterator was started during a grow to a larger size
-			// and the grow is not done yet. We're working on a bucket whose
-			// oldbucket has not been evacuated yet. Or at least, it wasn't
-			// evacuated when we started the bucket. So we're iterating
-			// through the oldbucket, skipping any keys that will go
-			// to the other new bucket (each oldbucket expands to two
-			// buckets during a grow).
-			if t.ReflexiveKey() || t.Key.Equal(k, k) {
-				// If the item in the oldbucket is not destined for
-				// the current new bucket in the iteration, skip it.
-				hash := t.Hasher(k, uintptr(h.hash0))
-				if hash&bucketMask(it.B) != checkBucket {
-					continue
-				}
-			} else {
-				// Hash isn't repeatable if k != k (NaNs).  We need a
-				// repeatable and randomish choice of which direction
-				// to send NaNs during evacuation. We'll use the low
-				// bit of tophash to decide which way NaNs go.
-				// NOTE: this case is why we need two evacuate tophash
-				// values, evacuatedX and evacuatedY, that differ in
-				// their low bit.
-				if checkBucket>>(it.B-1) != uintptr(b.tophash[offi]&1) {
-					continue
-				}
-			}
-		}
-		if (b.tophash[offi] != evacuatedX && b.tophash[offi] != evacuatedY) ||
-			!(t.ReflexiveKey() || t.Key.Equal(k, k)) {
-			// This is the golden data, we can return it.
-			// OR
-			// key!=key, so the entry can't be deleted or updated, so we can just return it.
-			// That's lucky for us because when key!=key we can't look it up successfully.
-			it.key = k
-			if t.IndirectElem() {
-				e = *((*unsafe.Pointer)(e))
-			}
-			it.elem = e
-		} else {
-			// The hash table has grown since the iterator was started.
-			// The golden data for this key is now somewhere else.
-			// Check the current hash table for the data.
-			// This code handles the case where the key
-			// has been deleted, updated, or deleted and reinserted.
-			// NOTE: we need to regrab the key as it has potentially been
-			// updated to an equal() but not identical key (e.g. +0.0 vs -0.0).
-			rk, re := mapaccessK(t, h, k)
-			if rk == nil {
-				continue // key has been deleted
-			}
-			it.key = rk
-			it.elem = re
-		}
-		it.bucket = bucket
-		if it.bptr != b { // avoid unnecessary write barrier; see issue 14921
-			it.bptr = b
-		}
-		it.i = i + 1
-		it.checkBucket = checkBucket
-		return
-	}
-	b = b.overflow(t)
-	i = 0
-	goto next
+	it.Next()
 }
 
 // mapclear deletes all keys from a map.
-func mapclear(t *maptype, h *hmap) {
-	if raceenabled && h != nil {
+func mapclear(t *abi.SwissMapType, m *maps.Map) {
+	// TODO: concurrent checks.
+	if raceenabled && m != nil {
 		callerpc := sys.GetCallerPC()
 		pc := abi.FuncPCABIInternal(mapclear)
-		racewritepc(unsafe.Pointer(h), callerpc, pc)
+		racewritepc(unsafe.Pointer(m), callerpc, pc)
 	}
 
-	if h == nil || h.count == 0 {
+	if m == nil || m.Used() == 0 {
 		return
 	}
 
-	if h.flags&hashWriting != 0 {
-		fatal("concurrent map writes")
-	}
-
-	h.flags ^= hashWriting
-
-	// Mark buckets empty, so existing iterators can be terminated, see issue #59411.
-	markBucketsEmpty := func(bucket unsafe.Pointer, mask uintptr) {
-		for i := uintptr(0); i <= mask; i++ {
-			b := (*bmap)(add(bucket, i*uintptr(t.BucketSize)))
-			for ; b != nil; b = b.overflow(t) {
-				for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-					b.tophash[i] = emptyRest
-				}
-			}
-		}
-	}
-	markBucketsEmpty(h.buckets, bucketMask(h.B))
-	if oldBuckets := h.oldbuckets; oldBuckets != nil {
-		markBucketsEmpty(oldBuckets, h.oldbucketmask())
-	}
-
-	h.flags &^= sameSizeGrow
-	h.oldbuckets = nil
-	h.nevacuate = 0
-	h.noverflow = 0
-	h.count = 0
-
-	// Reset the hash seed to make it more difficult for attackers to
-	// repeatedly trigger hash collisions. See issue 25237.
-	h.hash0 = uint32(rand())
-
-	// 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 {
-		fatal("concurrent map writes")
-	}
-	h.flags &^= hashWriting
-}
-
-func hashGrow(t *maptype, h *hmap) {
-	// If we've hit the load factor, get bigger.
-	// Otherwise, there are too many overflow buckets,
-	// so keep the same number of buckets and "grow" laterally.
-	bigger := uint8(1)
-	if !overLoadFactor(h.count+1, h.B) {
-		bigger = 0
-		h.flags |= sameSizeGrow
-	}
-	oldbuckets := h.buckets
-	newbuckets, nextOverflow := makeBucketArray(t, h.B+bigger, nil)
-
-	flags := h.flags &^ (iterator | oldIterator)
-	if h.flags&iterator != 0 {
-		flags |= oldIterator
-	}
-	// commit the grow (atomic wrt gc)
-	h.B += bigger
-	h.flags = flags
-	h.oldbuckets = oldbuckets
-	h.buckets = newbuckets
-	h.nevacuate = 0
-	h.noverflow = 0
-
-	if h.extra != nil && h.extra.overflow != nil {
-		// Promote current overflow buckets to the old generation.
-		if h.extra.oldoverflow != nil {
-			throw("oldoverflow is not nil")
-		}
-		h.extra.oldoverflow = h.extra.overflow
-		h.extra.overflow = nil
-	}
-	if nextOverflow != nil {
-		if h.extra == nil {
-			h.extra = new(mapextra)
-		}
-		h.extra.nextOverflow = nextOverflow
-	}
-
-	// the actual copying of the hash table data is done incrementally
-	// by growWork() and evacuate().
-}
-
-// overLoadFactor reports whether count items placed in 1<<B buckets is over loadFactor.
-func overLoadFactor(count int, B uint8) bool {
-	return count > abi.SwissMapBucketCount && uintptr(count) > loadFactorNum*(bucketShift(B)/loadFactorDen)
-}
-
-// tooManyOverflowBuckets reports whether noverflow buckets is too many for a map with 1<<B buckets.
-// Note that most of these overflow buckets must be in sparse use;
-// if use was dense, then we'd have already triggered regular map growth.
-func tooManyOverflowBuckets(noverflow uint16, B uint8) bool {
-	// If the threshold is too low, we do extraneous work.
-	// If the threshold is too high, maps that grow and shrink can hold on to lots of unused memory.
-	// "too many" means (approximately) as many overflow buckets as regular buckets.
-	// See incrnoverflow for more details.
-	if B > 15 {
-		B = 15
-	}
-	// The compiler doesn't see here that B < 16; mask B to generate shorter shift code.
-	return noverflow >= uint16(1)<<(B&15)
-}
-
-// growing reports whether h is growing. The growth may be to the same size or bigger.
-func (h *hmap) growing() bool {
-	return h.oldbuckets != nil
-}
-
-// sameSizeGrow reports whether the current growth is to a map of the same size.
-func (h *hmap) sameSizeGrow() bool {
-	return h.flags&sameSizeGrow != 0
-}
-
-//go:linkname sameSizeGrowForIssue69110Test
-func sameSizeGrowForIssue69110Test(h *hmap) bool {
-	return h.sameSizeGrow()
-}
-
-// noldbuckets calculates the number of buckets prior to the current map growth.
-func (h *hmap) noldbuckets() uintptr {
-	oldB := h.B
-	if !h.sameSizeGrow() {
-		oldB--
-	}
-	return bucketShift(oldB)
-}
-
-// oldbucketmask provides a mask that can be applied to calculate n % noldbuckets().
-func (h *hmap) oldbucketmask() uintptr {
-	return h.noldbuckets() - 1
-}
-
-func growWork(t *maptype, h *hmap, bucket uintptr) {
-	// make sure we evacuate the oldbucket corresponding
-	// to the bucket we're about to use
-	evacuate(t, h, bucket&h.oldbucketmask())
-
-	// evacuate one more oldbucket to make progress on growing
-	if h.growing() {
-		evacuate(t, h, h.nevacuate)
-	}
-}
-
-func bucketEvacuated(t *maptype, h *hmap, bucket uintptr) bool {
-	b := (*bmap)(add(h.oldbuckets, bucket*uintptr(t.BucketSize)))
-	return evacuated(b)
-}
-
-// evacDst is an evacuation destination.
-type evacDst struct {
-	b *bmap          // current destination bucket
-	i int            // key/elem index into b
-	k unsafe.Pointer // pointer to current key storage
-	e unsafe.Pointer // pointer to current elem storage
-}
-
-func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
-	b := (*bmap)(add(h.oldbuckets, oldbucket*uintptr(t.BucketSize)))
-	newbit := h.noldbuckets()
-	if !evacuated(b) {
-		// TODO: reuse overflow buckets instead of using new ones, if there
-		// is no iterator using the old buckets.  (If !oldIterator.)
-
-		// xy contains the x and y (low and high) evacuation destinations.
-		var xy [2]evacDst
-		x := &xy[0]
-		x.b = (*bmap)(add(h.buckets, oldbucket*uintptr(t.BucketSize)))
-		x.k = add(unsafe.Pointer(x.b), dataOffset)
-		x.e = add(x.k, abi.SwissMapBucketCount*uintptr(t.KeySize))
-
-		if !h.sameSizeGrow() {
-			// Only calculate y pointers if we're growing bigger.
-			// Otherwise GC can see bad pointers.
-			y := &xy[1]
-			y.b = (*bmap)(add(h.buckets, (oldbucket+newbit)*uintptr(t.BucketSize)))
-			y.k = add(unsafe.Pointer(y.b), dataOffset)
-			y.e = add(y.k, abi.SwissMapBucketCount*uintptr(t.KeySize))
-		}
-
-		for ; b != nil; b = b.overflow(t) {
-			k := add(unsafe.Pointer(b), dataOffset)
-			e := add(k, abi.SwissMapBucketCount*uintptr(t.KeySize))
-			for i := 0; i < abi.SwissMapBucketCount; i, k, e = i+1, add(k, uintptr(t.KeySize)), add(e, uintptr(t.ValueSize)) {
-				top := b.tophash[i]
-				if isEmpty(top) {
-					b.tophash[i] = evacuatedEmpty
-					continue
-				}
-				if top < minTopHash {
-					throw("bad map state")
-				}
-				k2 := k
-				if t.IndirectKey() {
-					k2 = *((*unsafe.Pointer)(k2))
-				}
-				var useY uint8
-				if !h.sameSizeGrow() {
-					// Compute hash to make our evacuation decision (whether we need
-					// to send this key/elem to bucket x or bucket y).
-					hash := t.Hasher(k2, uintptr(h.hash0))
-					if h.flags&iterator != 0 && !t.ReflexiveKey() && !t.Key.Equal(k2, k2) {
-						// If key != key (NaNs), then the hash could be (and probably
-						// will be) entirely different from the old hash. Moreover,
-						// it isn't reproducible. Reproducibility is required in the
-						// presence of iterators, as our evacuation decision must
-						// match whatever decision the iterator made.
-						// Fortunately, we have the freedom to send these keys either
-						// way. Also, tophash is meaningless for these kinds of keys.
-						// We let the low bit of tophash drive the evacuation decision.
-						// We recompute a new random tophash for the next level so
-						// these keys will get evenly distributed across all buckets
-						// after multiple grows.
-						useY = top & 1
-						top = tophash(hash)
-					} else {
-						if hash&newbit != 0 {
-							useY = 1
-						}
-					}
-				}
-
-				if evacuatedX+1 != evacuatedY || evacuatedX^1 != evacuatedY {
-					throw("bad evacuatedN")
-				}
-
-				b.tophash[i] = evacuatedX + useY // evacuatedX + 1 == evacuatedY
-				dst := &xy[useY]                 // evacuation destination
-
-				if dst.i == abi.SwissMapBucketCount {
-					dst.b = h.newoverflow(t, dst.b)
-					dst.i = 0
-					dst.k = add(unsafe.Pointer(dst.b), dataOffset)
-					dst.e = add(dst.k, abi.SwissMapBucketCount*uintptr(t.KeySize))
-				}
-				dst.b.tophash[dst.i&(abi.SwissMapBucketCount-1)] = top // mask dst.i as an optimization, to avoid a bounds check
-				if t.IndirectKey() {
-					*(*unsafe.Pointer)(dst.k) = k2 // copy pointer
-				} else {
-					typedmemmove(t.Key, dst.k, k) // copy elem
-				}
-				if t.IndirectElem() {
-					*(*unsafe.Pointer)(dst.e) = *(*unsafe.Pointer)(e)
-				} else {
-					typedmemmove(t.Elem, dst.e, e)
-				}
-				dst.i++
-				// These updates might push these pointers past the end of the
-				// key or elem arrays.  That's ok, as we have the overflow pointer
-				// at the end of the bucket to protect against pointing past the
-				// end of the bucket.
-				dst.k = add(dst.k, uintptr(t.KeySize))
-				dst.e = add(dst.e, uintptr(t.ValueSize))
-			}
-		}
-		// Unlink the overflow buckets & clear key/elem to help GC.
-		if h.flags&oldIterator == 0 && t.Bucket.Pointers() {
-			b := add(h.oldbuckets, oldbucket*uintptr(t.BucketSize))
-			// Preserve b.tophash because the evacuation
-			// state is maintained there.
-			ptr := add(b, dataOffset)
-			n := uintptr(t.BucketSize) - dataOffset
-			memclrHasPointers(ptr, n)
-		}
-	}
-
-	if oldbucket == h.nevacuate {
-		advanceEvacuationMark(h, t, newbit)
-	}
-}
-
-func advanceEvacuationMark(h *hmap, t *maptype, newbit uintptr) {
-	h.nevacuate++
-	// Experiments suggest that 1024 is overkill by at least an order of magnitude.
-	// Put it in there as a safeguard anyway, to ensure O(1) behavior.
-	stop := h.nevacuate + 1024
-	if stop > newbit {
-		stop = newbit
-	}
-	for h.nevacuate != stop && bucketEvacuated(t, h, h.nevacuate) {
-		h.nevacuate++
-	}
-	if h.nevacuate == newbit { // newbit == # of oldbuckets
-		// Growing is all done. Free old main bucket array.
-		h.oldbuckets = nil
-		// Can discard old overflow buckets as well.
-		// If they are still referenced by an iterator,
-		// then the iterator holds a pointers to the slice.
-		if h.extra != nil {
-			h.extra.oldoverflow = nil
-		}
-		h.flags &^= sameSizeGrow
-	}
+	m.Clear()
 }
 
 // Reflect stubs. Called from ../reflect/asm_*.s
 
 //go:linkname reflect_makemap reflect.makemap
-func reflect_makemap(t *maptype, cap int) *hmap {
+func reflect_makemap(t *abi.SwissMapType, cap int) *maps.Map {
 	// Check invariants and reflects math.
 	if t.Key.Equal == nil {
 		throw("runtime.reflect_makemap: unsupported map key type")
 	}
-	if t.Key.Size_ > abi.SwissMapMaxKeyBytes && (!t.IndirectKey() || t.KeySize != uint8(goarch.PtrSize)) ||
-		t.Key.Size_ <= abi.SwissMapMaxKeyBytes && (t.IndirectKey() || t.KeySize != uint8(t.Key.Size_)) {
-		throw("key size wrong")
-	}
-	if t.Elem.Size_ > abi.SwissMapMaxElemBytes && (!t.IndirectElem() || t.ValueSize != uint8(goarch.PtrSize)) ||
-		t.Elem.Size_ <= abi.SwissMapMaxElemBytes && (t.IndirectElem() || t.ValueSize != uint8(t.Elem.Size_)) {
-		throw("elem size wrong")
-	}
-	if t.Key.Align_ > abi.SwissMapBucketCount {
-		throw("key align too big")
-	}
-	if t.Elem.Align_ > abi.SwissMapBucketCount {
-		throw("elem align too big")
-	}
-	if t.Key.Size_%uintptr(t.Key.Align_) != 0 {
-		throw("key size not a multiple of key align")
-	}
-	if t.Elem.Size_%uintptr(t.Elem.Align_) != 0 {
-		throw("elem size not a multiple of elem align")
-	}
-	if abi.SwissMapBucketCount < 8 {
-		throw("bucketsize too small for proper alignment")
-	}
-	if dataOffset%uintptr(t.Key.Align_) != 0 {
-		throw("need padding in bucket (key)")
-	}
-	if dataOffset%uintptr(t.Elem.Align_) != 0 {
-		throw("need padding in bucket (elem)")
-	}
+	// TODO: other checks
 
 	return makemap(t, cap, nil)
 }
 
 //go:linkname reflect_mapaccess reflect.mapaccess
-func reflect_mapaccess(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
-	elem, ok := mapaccess2(t, h, key)
+func reflect_mapaccess(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) unsafe.Pointer {
+	elem, ok := mapaccess2(t, m, key)
 	if !ok {
 		// reflect wants nil for a missing element
 		elem = nil
@@ -1353,8 +284,8 @@ func reflect_mapaccess(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 }
 
 //go:linkname reflect_mapaccess_faststr reflect.mapaccess_faststr
-func reflect_mapaccess_faststr(t *maptype, h *hmap, key string) unsafe.Pointer {
-	elem, ok := mapaccess2_faststr(t, h, key)
+func reflect_mapaccess_faststr(t *abi.SwissMapType, m *maps.Map, key string) unsafe.Pointer {
+	elem, ok := mapaccess2_faststr(t, m, key)
 	if !ok {
 		// reflect wants nil for a missing element
 		elem = nil
@@ -1363,74 +294,74 @@ func reflect_mapaccess_faststr(t *maptype, h *hmap, key string) unsafe.Pointer {
 }
 
 //go:linkname reflect_mapassign reflect.mapassign0
-func reflect_mapassign(t *maptype, h *hmap, key unsafe.Pointer, elem unsafe.Pointer) {
-	p := mapassign(t, h, key)
+func reflect_mapassign(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer, elem unsafe.Pointer) {
+	p := mapassign(t, m, key)
 	typedmemmove(t.Elem, p, elem)
 }
 
 //go:linkname reflect_mapassign_faststr reflect.mapassign_faststr0
-func reflect_mapassign_faststr(t *maptype, h *hmap, key string, elem unsafe.Pointer) {
-	p := mapassign_faststr(t, h, key)
+func reflect_mapassign_faststr(t *abi.SwissMapType, m *maps.Map, key string, elem unsafe.Pointer) {
+	p := mapassign_faststr(t, m, key)
 	typedmemmove(t.Elem, p, elem)
 }
 
 //go:linkname reflect_mapdelete reflect.mapdelete
-func reflect_mapdelete(t *maptype, h *hmap, key unsafe.Pointer) {
-	mapdelete(t, h, key)
+func reflect_mapdelete(t *abi.SwissMapType, m *maps.Map, key unsafe.Pointer) {
+	mapdelete(t, m, key)
 }
 
 //go:linkname reflect_mapdelete_faststr reflect.mapdelete_faststr
-func reflect_mapdelete_faststr(t *maptype, h *hmap, key string) {
-	mapdelete_faststr(t, h, key)
+func reflect_mapdelete_faststr(t *abi.SwissMapType, m *maps.Map, key string) {
+	mapdelete_faststr(t, m, key)
 }
 
 //go:linkname reflect_mapiterinit reflect.mapiterinit
-func reflect_mapiterinit(t *maptype, h *hmap, it *hiter) {
-	mapiterinit(t, h, it)
+func reflect_mapiterinit(t *abi.SwissMapType, m *maps.Map, it *maps.Iter) {
+	mapiterinit(t, m, it)
 }
 
 //go:linkname reflect_mapiternext reflect.mapiternext
-func reflect_mapiternext(it *hiter) {
+func reflect_mapiternext(it *maps.Iter) {
 	mapiternext(it)
 }
 
 //go:linkname reflect_mapiterkey reflect.mapiterkey
-func reflect_mapiterkey(it *hiter) unsafe.Pointer {
-	return it.key
+func reflect_mapiterkey(it *maps.Iter) unsafe.Pointer {
+	return it.Key()
 }
 
 //go:linkname reflect_mapiterelem reflect.mapiterelem
-func reflect_mapiterelem(it *hiter) unsafe.Pointer {
-	return it.elem
+func reflect_mapiterelem(it *maps.Iter) unsafe.Pointer {
+	return it.Elem()
 }
 
 //go:linkname reflect_maplen reflect.maplen
-func reflect_maplen(h *hmap) int {
-	if h == nil {
+func reflect_maplen(m *maps.Map) int {
+	if m == nil {
 		return 0
 	}
 	if raceenabled {
 		callerpc := sys.GetCallerPC()
-		racereadpc(unsafe.Pointer(h), callerpc, abi.FuncPCABIInternal(reflect_maplen))
+		racereadpc(unsafe.Pointer(m), callerpc, abi.FuncPCABIInternal(reflect_maplen))
 	}
-	return h.count
+	return int(m.Used())
 }
 
 //go:linkname reflect_mapclear reflect.mapclear
-func reflect_mapclear(t *maptype, h *hmap) {
-	mapclear(t, h)
+func reflect_mapclear(t *abi.SwissMapType, m *maps.Map) {
+	mapclear(t, m)
 }
 
 //go:linkname reflectlite_maplen internal/reflectlite.maplen
-func reflectlite_maplen(h *hmap) int {
-	if h == nil {
+func reflectlite_maplen(m *maps.Map) int {
+	if m == nil {
 		return 0
 	}
 	if raceenabled {
 		callerpc := sys.GetCallerPC()
-		racereadpc(unsafe.Pointer(h), callerpc, abi.FuncPCABIInternal(reflect_maplen))
+		racereadpc(unsafe.Pointer(m), callerpc, abi.FuncPCABIInternal(reflect_maplen))
 	}
-	return h.count
+	return int(m.Used())
 }
 
 // mapinitnoop is a no-op function known the Go linker; if a given global
@@ -1445,169 +376,19 @@ func mapinitnoop()
 //go:linkname mapclone maps.clone
 func mapclone(m any) any {
 	e := efaceOf(&m)
-	e.data = unsafe.Pointer(mapclone2((*maptype)(unsafe.Pointer(e._type)), (*hmap)(e.data)))
+	e.data = unsafe.Pointer(mapclone2((*abi.SwissMapType)(unsafe.Pointer(e._type)), (*maps.Map)(e.data)))
 	return m
 }
 
-// moveToBmap moves a bucket from src to dst. It returns the destination bucket or new destination bucket if it overflows
-// and the pos that the next key/value will be written, if pos == bucketCnt means needs to written in overflow bucket.
-func moveToBmap(t *maptype, h *hmap, dst *bmap, pos int, src *bmap) (*bmap, int) {
-	for i := 0; i < abi.SwissMapBucketCount; i++ {
-		if isEmpty(src.tophash[i]) {
-			continue
-		}
-
-		for ; pos < abi.SwissMapBucketCount; pos++ {
-			if isEmpty(dst.tophash[pos]) {
-				break
-			}
-		}
-
-		if pos == abi.SwissMapBucketCount {
-			dst = h.newoverflow(t, dst)
-			pos = 0
-		}
-
-		srcK := add(unsafe.Pointer(src), dataOffset+uintptr(i)*uintptr(t.KeySize))
-		srcEle := add(unsafe.Pointer(src), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+uintptr(i)*uintptr(t.ValueSize))
-		dstK := add(unsafe.Pointer(dst), dataOffset+uintptr(pos)*uintptr(t.KeySize))
-		dstEle := add(unsafe.Pointer(dst), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+uintptr(pos)*uintptr(t.ValueSize))
-
-		dst.tophash[pos] = src.tophash[i]
-		if t.IndirectKey() {
-			srcK = *(*unsafe.Pointer)(srcK)
-			if t.NeedKeyUpdate() {
-				kStore := newobject(t.Key)
-				typedmemmove(t.Key, kStore, srcK)
-				srcK = kStore
-			}
-			// Note: if NeedKeyUpdate is false, then the memory
-			// used to store the key is immutable, so we can share
-			// it between the original map and its clone.
-			*(*unsafe.Pointer)(dstK) = srcK
-		} else {
-			typedmemmove(t.Key, dstK, srcK)
-		}
-		if t.IndirectElem() {
-			srcEle = *(*unsafe.Pointer)(srcEle)
-			eStore := newobject(t.Elem)
-			typedmemmove(t.Elem, eStore, srcEle)
-			*(*unsafe.Pointer)(dstEle) = eStore
-		} else {
-			typedmemmove(t.Elem, dstEle, srcEle)
-		}
-		pos++
-		h.count++
-	}
-	return dst, pos
-}
-
-func mapclone2(t *maptype, src *hmap) *hmap {
-	hint := src.count
-	if overLoadFactor(hint, src.B) {
-		// Note: in rare cases (e.g. during a same-sized grow) the map
-		// can be overloaded. Make sure we don't allocate a destination
-		// bucket array larger than the source bucket array.
-		// This will cause the cloned map to be overloaded also,
-		// but that's better than crashing. See issue 69110.
-		hint = int(loadFactorNum * (bucketShift(src.B) / loadFactorDen))
-	}
-	dst := makemap(t, hint, nil)
-	dst.hash0 = src.hash0
-	dst.nevacuate = 0
-	// flags do not need to be copied here, just like a new map has no flags.
-
-	if src.count == 0 {
-		return dst
-	}
-
-	if src.flags&hashWriting != 0 {
-		fatal("concurrent map clone and map write")
-	}
+func mapclone2(t *abi.SwissMapType, src *maps.Map) *maps.Map {
+	dst := makemap(t, int(src.Used()), nil)
 
-	if src.B == 0 && !(t.IndirectKey() && t.NeedKeyUpdate()) && !t.IndirectElem() {
-		// Quick copy for small maps.
-		dst.buckets = newobject(t.Bucket)
-		dst.count = src.count
-		typedmemmove(t.Bucket, dst.buckets, src.buckets)
-		return dst
+	var iter maps.Iter
+	iter.Init(t, src)
+	for iter.Next(); iter.Key() != nil; iter.Next() {
+		dst.Put(iter.Key(), iter.Elem())
 	}
 
-	if dst.B == 0 {
-		dst.buckets = newobject(t.Bucket)
-	}
-	dstArraySize := int(bucketShift(dst.B))
-	srcArraySize := int(bucketShift(src.B))
-	for i := 0; i < dstArraySize; i++ {
-		dstBmap := (*bmap)(add(dst.buckets, uintptr(i*int(t.BucketSize))))
-		pos := 0
-		for j := 0; j < srcArraySize; j += dstArraySize {
-			srcBmap := (*bmap)(add(src.buckets, uintptr((i+j)*int(t.BucketSize))))
-			for srcBmap != nil {
-				dstBmap, pos = moveToBmap(t, dst, dstBmap, pos, srcBmap)
-				srcBmap = srcBmap.overflow(t)
-			}
-		}
-	}
-
-	if src.oldbuckets == nil {
-		return dst
-	}
-
-	oldB := src.B
-	srcOldbuckets := src.oldbuckets
-	if !src.sameSizeGrow() {
-		oldB--
-	}
-	oldSrcArraySize := int(bucketShift(oldB))
-
-	for i := 0; i < oldSrcArraySize; i++ {
-		srcBmap := (*bmap)(add(srcOldbuckets, uintptr(i*int(t.BucketSize))))
-		if evacuated(srcBmap) {
-			continue
-		}
-
-		if oldB >= dst.B { // main bucket bits in dst is less than oldB bits in src
-			dstBmap := (*bmap)(add(dst.buckets, (uintptr(i)&bucketMask(dst.B))*uintptr(t.BucketSize)))
-			for dstBmap.overflow(t) != nil {
-				dstBmap = dstBmap.overflow(t)
-			}
-			pos := 0
-			for srcBmap != nil {
-				dstBmap, pos = moveToBmap(t, dst, dstBmap, pos, srcBmap)
-				srcBmap = srcBmap.overflow(t)
-			}
-			continue
-		}
-
-		// oldB < dst.B, so a single source bucket may go to multiple destination buckets.
-		// Process entries one at a time.
-		for srcBmap != nil {
-			// move from oldBlucket to new bucket
-			for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-				if isEmpty(srcBmap.tophash[i]) {
-					continue
-				}
-
-				if src.flags&hashWriting != 0 {
-					fatal("concurrent map clone and map write")
-				}
-
-				srcK := add(unsafe.Pointer(srcBmap), dataOffset+i*uintptr(t.KeySize))
-				if t.IndirectKey() {
-					srcK = *((*unsafe.Pointer)(srcK))
-				}
-
-				srcEle := add(unsafe.Pointer(srcBmap), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+i*uintptr(t.ValueSize))
-				if t.IndirectElem() {
-					srcEle = *((*unsafe.Pointer)(srcEle))
-				}
-				dstEle := mapassign(t, dst, srcK)
-				typedmemmove(t.Elem, dstEle, srcEle)
-			}
-			srcBmap = srcBmap.overflow(t)
-		}
-	}
 	return dst
 }
 
@@ -1615,127 +396,14 @@ func mapclone2(t *maptype, src *hmap) *hmap {
 //
 //go:linkname keys maps.keys
 func keys(m any, p unsafe.Pointer) {
-	e := efaceOf(&m)
-	t := (*maptype)(unsafe.Pointer(e._type))
-	h := (*hmap)(e.data)
-
-	if h == nil || h.count == 0 {
-		return
-	}
-	s := (*slice)(p)
-	r := int(rand())
-	offset := uint8(r >> h.B & (abi.SwissMapBucketCount - 1))
-	if h.B == 0 {
-		copyKeys(t, h, (*bmap)(h.buckets), s, offset)
-		return
-	}
-	arraySize := int(bucketShift(h.B))
-	buckets := h.buckets
-	for i := 0; i < arraySize; i++ {
-		bucket := (i + r) & (arraySize - 1)
-		b := (*bmap)(add(buckets, uintptr(bucket)*uintptr(t.BucketSize)))
-		copyKeys(t, h, b, s, offset)
-	}
-
-	if h.growing() {
-		oldArraySize := int(h.noldbuckets())
-		for i := 0; i < oldArraySize; i++ {
-			bucket := (i + r) & (oldArraySize - 1)
-			b := (*bmap)(add(h.oldbuckets, uintptr(bucket)*uintptr(t.BucketSize)))
-			if evacuated(b) {
-				continue
-			}
-			copyKeys(t, h, b, s, offset)
-		}
-	}
-	return
-}
-
-func copyKeys(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
-	for b != nil {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			offi := (i + uintptr(offset)) & (abi.SwissMapBucketCount - 1)
-			if isEmpty(b.tophash[offi]) {
-				continue
-			}
-			if h.flags&hashWriting != 0 {
-				fatal("concurrent map read and map write")
-			}
-			k := add(unsafe.Pointer(b), dataOffset+offi*uintptr(t.KeySize))
-			if t.IndirectKey() {
-				k = *((*unsafe.Pointer)(k))
-			}
-			if s.len >= s.cap {
-				fatal("concurrent map read and map write")
-			}
-			typedmemmove(t.Key, add(s.array, uintptr(s.len)*uintptr(t.Key.Size())), k)
-			s.len++
-		}
-		b = b.overflow(t)
-	}
+	// Currently unused in the maps package.
+	panic("unimplemented")
 }
 
 // values for implementing maps.values
 //
 //go:linkname values maps.values
 func values(m any, p unsafe.Pointer) {
-	e := efaceOf(&m)
-	t := (*maptype)(unsafe.Pointer(e._type))
-	h := (*hmap)(e.data)
-	if h == nil || h.count == 0 {
-		return
-	}
-	s := (*slice)(p)
-	r := int(rand())
-	offset := uint8(r >> h.B & (abi.SwissMapBucketCount - 1))
-	if h.B == 0 {
-		copyValues(t, h, (*bmap)(h.buckets), s, offset)
-		return
-	}
-	arraySize := int(bucketShift(h.B))
-	buckets := h.buckets
-	for i := 0; i < arraySize; i++ {
-		bucket := (i + r) & (arraySize - 1)
-		b := (*bmap)(add(buckets, uintptr(bucket)*uintptr(t.BucketSize)))
-		copyValues(t, h, b, s, offset)
-	}
-
-	if h.growing() {
-		oldArraySize := int(h.noldbuckets())
-		for i := 0; i < oldArraySize; i++ {
-			bucket := (i + r) & (oldArraySize - 1)
-			b := (*bmap)(add(h.oldbuckets, uintptr(bucket)*uintptr(t.BucketSize)))
-			if evacuated(b) {
-				continue
-			}
-			copyValues(t, h, b, s, offset)
-		}
-	}
-	return
-}
-
-func copyValues(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
-	for b != nil {
-		for i := uintptr(0); i < abi.SwissMapBucketCount; i++ {
-			offi := (i + uintptr(offset)) & (abi.SwissMapBucketCount - 1)
-			if isEmpty(b.tophash[offi]) {
-				continue
-			}
-
-			if h.flags&hashWriting != 0 {
-				fatal("concurrent map read and map write")
-			}
-
-			ele := add(unsafe.Pointer(b), dataOffset+abi.SwissMapBucketCount*uintptr(t.KeySize)+offi*uintptr(t.ValueSize))
-			if t.IndirectElem() {
-				ele = *((*unsafe.Pointer)(ele))
-			}
-			if s.len >= s.cap {
-				fatal("concurrent map read and map write")
-			}
-			typedmemmove(t.Elem, add(s.array, uintptr(s.len)*uintptr(t.Elem.Size())), ele)
-			s.len++
-		}
-		b = b.overflow(t)
-	}
+	// Currently unused in the maps package.
+	panic("unimplemented")
 }
diff --git a/src/runtime/map_swiss_test.go b/src/runtime/map_swiss_test.go
index 78db4aa926..aa019e1c31 100644
--- a/src/runtime/map_swiss_test.go
+++ b/src/runtime/map_swiss_test.go
@@ -8,17 +8,41 @@ package runtime_test
 
 import (
 	"internal/abi"
-	"runtime"
+	"internal/goarch"
+	"internal/runtime/maps"
 	"slices"
 	"testing"
+	"unsafe"
 )
 
+func TestHmapSize(t *testing.T) {
+	// The structure of Map is defined in internal/runtime/maps/map.go
+	// and in cmd/compile/internal/reflectdata/map_swiss.go and must be in sync.
+	// The size of Map should be 72 bytes on 64 bit and 56 bytes on 32 bit platforms.
+	wantSize := uintptr(4*goarch.PtrSize + 5*8)
+	gotSize := unsafe.Sizeof(maps.Map{})
+	if gotSize != wantSize {
+		t.Errorf("sizeof(maps.Map{})==%d, want %d", gotSize, wantSize)
+	}
+}
+
+// See also reflect_test.TestGroupSizeZero.
+func TestGroupSizeZero(t *testing.T) {
+	var m map[struct{}]struct{}
+	mTyp := abi.TypeOf(m)
+	mt := (*abi.SwissMapType)(unsafe.Pointer(mTyp))
+
+	// internal/runtime/maps when create pointers to slots, even if slots
+	// are size 0. The compiler should have reserved an extra word to
+	// ensure that pointers to the zero-size type at the end of group are
+	// valid.
+	if mt.Group.Size() <= 8 {
+		t.Errorf("Group size got %d want >8", mt.Group.Size())
+	}
+}
+
 func TestMapIterOrder(t *testing.T) {
 	sizes := []int{3, 7, 9, 15}
-	if abi.SwissMapBucketCountBits >= 5 {
-		// it gets flaky (often only one iteration order) at size 3 when abi.MapBucketCountBits >=5.
-		t.Fatalf("This test becomes flaky if abi.MapBucketCountBits(=%d) is 5 or larger", abi.SwissMapBucketCountBits)
-	}
 	for _, n := range sizes {
 		for i := 0; i < 1000; i++ {
 			// Make m be {0: true, 1: true, ..., n-1: true}.
@@ -50,139 +74,6 @@ func TestMapIterOrder(t *testing.T) {
 	}
 }
 
-const bs = abi.SwissMapBucketCount
-
-// belowOverflow should be a pretty-full pair of buckets;
-// atOverflow is 1/8 bs larger = 13/8 buckets or two buckets
-// that are 13/16 full each, which is the overflow boundary.
-// Adding one to that should ensure overflow to the next higher size.
-const (
-	belowOverflow = bs * 3 / 2           // 1.5 bs = 2 buckets @ 75%
-	atOverflow    = belowOverflow + bs/8 // 2 buckets at 13/16 fill.
-)
-
-var mapBucketTests = [...]struct {
-	n        int // n is the number of map elements
-	noescape int // number of expected buckets for non-escaping map
-	escape   int // number of expected buckets for escaping map
-}{
-	{-(1 << 30), 1, 1},
-	{-1, 1, 1},
-	{0, 1, 1},
-	{1, 1, 1},
-	{bs, 1, 1},
-	{bs + 1, 2, 2},
-	{belowOverflow, 2, 2},  // 1.5 bs = 2 buckets @ 75%
-	{atOverflow + 1, 4, 4}, // 13/8 bs + 1 == overflow to 4
-
-	{2 * belowOverflow, 4, 4}, // 3 bs = 4 buckets @75%
-	{2*atOverflow + 1, 8, 8},  // 13/4 bs + 1 = overflow to 8
-
-	{4 * belowOverflow, 8, 8},  // 6 bs = 8 buckets @ 75%
-	{4*atOverflow + 1, 16, 16}, // 13/2 bs + 1 = overflow to 16
-}
-
 func TestMapBuckets(t *testing.T) {
-	// Test that maps of different sizes have the right number of buckets.
-	// Non-escaping maps with small buckets (like map[int]int) never
-	// have a nil bucket pointer due to starting with preallocated buckets
-	// on the stack. Escaping maps start with a non-nil bucket pointer if
-	// hint size is above bucketCnt and thereby have more than one bucket.
-	// These tests depend on bucketCnt and loadFactor* in map.go.
-	t.Run("mapliteral", func(t *testing.T) {
-		for _, tt := range mapBucketTests {
-			localMap := map[int]int{}
-			if runtime.MapBucketsPointerIsNil(localMap) {
-				t.Errorf("no escape: buckets pointer is nil for non-escaping map")
-			}
-			for i := 0; i < tt.n; i++ {
-				localMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(localMap); got != tt.noescape {
-				t.Errorf("no escape: n=%d want %d buckets, got %d", tt.n, tt.noescape, got)
-			}
-			escapingMap := runtime.Escape(map[int]int{})
-			if count := runtime.MapBucketsCount(escapingMap); count > 1 && runtime.MapBucketsPointerIsNil(escapingMap) {
-				t.Errorf("escape: buckets pointer is nil for n=%d buckets", count)
-			}
-			for i := 0; i < tt.n; i++ {
-				escapingMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(escapingMap); got != tt.escape {
-				t.Errorf("escape n=%d want %d buckets, got %d", tt.n, tt.escape, got)
-			}
-		}
-	})
-	t.Run("nohint", func(t *testing.T) {
-		for _, tt := range mapBucketTests {
-			localMap := make(map[int]int)
-			if runtime.MapBucketsPointerIsNil(localMap) {
-				t.Errorf("no escape: buckets pointer is nil for non-escaping map")
-			}
-			for i := 0; i < tt.n; i++ {
-				localMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(localMap); got != tt.noescape {
-				t.Errorf("no escape: n=%d want %d buckets, got %d", tt.n, tt.noescape, got)
-			}
-			escapingMap := runtime.Escape(make(map[int]int))
-			if count := runtime.MapBucketsCount(escapingMap); count > 1 && runtime.MapBucketsPointerIsNil(escapingMap) {
-				t.Errorf("escape: buckets pointer is nil for n=%d buckets", count)
-			}
-			for i := 0; i < tt.n; i++ {
-				escapingMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(escapingMap); got != tt.escape {
-				t.Errorf("escape: n=%d want %d buckets, got %d", tt.n, tt.escape, got)
-			}
-		}
-	})
-	t.Run("makemap", func(t *testing.T) {
-		for _, tt := range mapBucketTests {
-			localMap := make(map[int]int, tt.n)
-			if runtime.MapBucketsPointerIsNil(localMap) {
-				t.Errorf("no escape: buckets pointer is nil for non-escaping map")
-			}
-			for i := 0; i < tt.n; i++ {
-				localMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(localMap); got != tt.noescape {
-				t.Errorf("no escape: n=%d want %d buckets, got %d", tt.n, tt.noescape, got)
-			}
-			escapingMap := runtime.Escape(make(map[int]int, tt.n))
-			if count := runtime.MapBucketsCount(escapingMap); count > 1 && runtime.MapBucketsPointerIsNil(escapingMap) {
-				t.Errorf("escape: buckets pointer is nil for n=%d buckets", count)
-			}
-			for i := 0; i < tt.n; i++ {
-				escapingMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(escapingMap); got != tt.escape {
-				t.Errorf("escape: n=%d want %d buckets, got %d", tt.n, tt.escape, got)
-			}
-		}
-	})
-	t.Run("makemap64", func(t *testing.T) {
-		for _, tt := range mapBucketTests {
-			localMap := make(map[int]int, int64(tt.n))
-			if runtime.MapBucketsPointerIsNil(localMap) {
-				t.Errorf("no escape: buckets pointer is nil for non-escaping map")
-			}
-			for i := 0; i < tt.n; i++ {
-				localMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(localMap); got != tt.noescape {
-				t.Errorf("no escape: n=%d want %d buckets, got %d", tt.n, tt.noescape, got)
-			}
-			escapingMap := runtime.Escape(make(map[int]int, tt.n))
-			if count := runtime.MapBucketsCount(escapingMap); count > 1 && runtime.MapBucketsPointerIsNil(escapingMap) {
-				t.Errorf("escape: buckets pointer is nil for n=%d buckets", count)
-			}
-			for i := 0; i < tt.n; i++ {
-				escapingMap[i] = i
-			}
-			if got := runtime.MapBucketsCount(escapingMap); got != tt.escape {
-				t.Errorf("escape: n=%d want %d buckets, got %d", tt.n, tt.escape, got)
-			}
-		}
-	})
+	t.Skipf("todo")
 }
diff --git a/src/runtime/map_test.go b/src/runtime/map_test.go
index 7d884c4922..8a73b9ff6f 100644
--- a/src/runtime/map_test.go
+++ b/src/runtime/map_test.go
@@ -6,7 +6,7 @@ package runtime_test
 
 import (
 	"fmt"
-	"internal/goarch"
+	"internal/goexperiment"
 	"internal/testenv"
 	"math"
 	"os"
@@ -20,17 +20,6 @@ import (
 	"unsafe"
 )
 
-func TestHmapSize(t *testing.T) {
-	// The structure of hmap is defined in runtime/map.go
-	// and in cmd/compile/internal/gc/reflect.go and must be in sync.
-	// The size of hmap should be 48 bytes on 64 bit and 28 bytes on 32 bit platforms.
-	var hmapSize = uintptr(8 + 5*goarch.PtrSize)
-	if runtime.RuntimeHmapSize != hmapSize {
-		t.Errorf("sizeof(runtime.hmap{})==%d, want %d", runtime.RuntimeHmapSize, hmapSize)
-	}
-
-}
-
 // negative zero is a good test because:
 //  1. 0 and -0 are equal, yet have distinct representations.
 //  2. 0 is represented as all zeros, -0 isn't.
@@ -430,6 +419,12 @@ func TestEmptyKeyAndValue(t *testing.T) {
 	if len(a) != 1 {
 		t.Errorf("empty value insert problem")
 	}
+	if len(b) != 1 {
+		t.Errorf("empty key insert problem")
+	}
+	if len(c) != 1 {
+		t.Errorf("empty key+value insert problem")
+	}
 	if b[empty{}] != 1 {
 		t.Errorf("empty key returned wrong value")
 	}
@@ -668,33 +663,37 @@ func BenchmarkMapPop10000(b *testing.B) { benchmarkMapPop(b, 10000) }
 var testNonEscapingMapVariable int = 8
 
 func TestNonEscapingMap(t *testing.T) {
+	if goexperiment.SwissMap {
+		t.Skip("TODO(go.dev/issue/54766): implement stack allocated maps")
+	}
+
 	n := testing.AllocsPerRun(1000, func() {
 		m := map[int]int{}
 		m[0] = 0
 	})
 	if n != 0 {
-		t.Fatalf("mapliteral: want 0 allocs, got %v", n)
+		t.Errorf("mapliteral: want 0 allocs, got %v", n)
 	}
 	n = testing.AllocsPerRun(1000, func() {
 		m := make(map[int]int)
 		m[0] = 0
 	})
 	if n != 0 {
-		t.Fatalf("no hint: want 0 allocs, got %v", n)
+		t.Errorf("no hint: want 0 allocs, got %v", n)
 	}
 	n = testing.AllocsPerRun(1000, func() {
 		m := make(map[int]int, 8)
 		m[0] = 0
 	})
 	if n != 0 {
-		t.Fatalf("with small hint: want 0 allocs, got %v", n)
+		t.Errorf("with small hint: want 0 allocs, got %v", n)
 	}
 	n = testing.AllocsPerRun(1000, func() {
 		m := make(map[int]int, testNonEscapingMapVariable)
 		m[0] = 0
 	})
 	if n != 0 {
-		t.Fatalf("with variable hint: want 0 allocs, got %v", n)
+		t.Errorf("with variable hint: want 0 allocs, got %v", n)
 	}
 
 }
@@ -1246,22 +1245,11 @@ func TestEmptyMapWithInterfaceKey(t *testing.T) {
 	})
 }
 
-func TestLoadFactor(t *testing.T) {
-	for b := uint8(0); b < 20; b++ {
-		count := 13 * (1 << b) / 2 // 6.5
-		if b == 0 {
-			count = 8
-		}
-		if runtime.OverLoadFactor(count, b) {
-			t.Errorf("OverLoadFactor(%d,%d)=true, want false", count, b)
-		}
-		if !runtime.OverLoadFactor(count+1, b) {
-			t.Errorf("OverLoadFactor(%d,%d)=false, want true", count+1, b)
-		}
+func TestMapKeys(t *testing.T) {
+	if goexperiment.SwissMap {
+		t.Skip("mapkeys not implemented for swissmaps")
 	}
-}
 
-func TestMapKeys(t *testing.T) {
 	type key struct {
 		s   string
 		pad [128]byte // sizeof(key) > abi.MapMaxKeyBytes
@@ -1277,6 +1265,10 @@ func TestMapKeys(t *testing.T) {
 }
 
 func TestMapValues(t *testing.T) {
+	if goexperiment.SwissMap {
+		t.Skip("mapvalues not implemented for swissmaps")
+	}
+
 	type val struct {
 		s   string
 		pad [128]byte // sizeof(val) > abi.MapMaxElemBytes
diff --git a/src/runtime/runtime-gdb_test.go b/src/runtime/runtime-gdb_test.go
index f2a9bd055a..ef01d6a194 100644
--- a/src/runtime/runtime-gdb_test.go
+++ b/src/runtime/runtime-gdb_test.go
@@ -9,6 +9,7 @@ import (
 	"flag"
 	"fmt"
 	"internal/abi"
+	"internal/goexperiment"
 	"internal/testenv"
 	"os"
 	"os/exec"
@@ -185,6 +186,9 @@ func TestGdbPythonCgo(t *testing.T) {
 }
 
 func testGdbPython(t *testing.T, cgo bool) {
+	if goexperiment.SwissMap {
+		t.Skip("TODO(prattmic): swissmap DWARF")
+	}
 	if cgo {
 		testenv.MustHaveCGO(t)
 	}
@@ -527,6 +531,10 @@ func main() {
 // TestGdbAutotmpTypes ensures that types of autotmp variables appear in .debug_info
 // See bug #17830.
 func TestGdbAutotmpTypes(t *testing.T) {
+	if goexperiment.SwissMap {
+		t.Skip("TODO(prattmic): swissmap DWARF")
+	}
+
 	checkGdbEnvironment(t)
 	t.Parallel()
 	checkGdbVersion(t)