diff --git a/src/cmd/compile/internal/gc/builtin.go b/src/cmd/compile/internal/gc/builtin.go
index 5f65d8135ab..675de836ce2 100644
--- a/src/cmd/compile/internal/gc/builtin.go
+++ b/src/cmd/compile/internal/gc/builtin.go
@@ -88,61 +88,64 @@ var runtimeDecls = [...]struct {
 	{"mapassign_faststr", funcTag, 61},
 	{"mapiterinit", funcTag, 66},
 	{"mapdelete", funcTag, 66},
-	{"mapiternext", funcTag, 67},
-	{"makechan", funcTag, 69},
-	{"chanrecv1", funcTag, 71},
-	{"chanrecv2", funcTag, 72},
-	{"chansend1", funcTag, 74},
+	{"mapdelete_fast32", funcTag, 67},
+	{"mapdelete_fast64", funcTag, 67},
+	{"mapdelete_faststr", funcTag, 67},
+	{"mapiternext", funcTag, 68},
+	{"makechan", funcTag, 70},
+	{"chanrecv1", funcTag, 72},
+	{"chanrecv2", funcTag, 73},
+	{"chansend1", funcTag, 75},
 	{"closechan", funcTag, 23},
-	{"writeBarrier", varTag, 76},
-	{"writebarrierptr", funcTag, 77},
-	{"typedmemmove", funcTag, 78},
-	{"typedmemclr", funcTag, 79},
-	{"typedslicecopy", funcTag, 80},
-	{"selectnbsend", funcTag, 81},
-	{"selectnbrecv", funcTag, 82},
-	{"selectnbrecv2", funcTag, 84},
-	{"newselect", funcTag, 85},
-	{"selectsend", funcTag, 74},
-	{"selectrecv", funcTag, 86},
+	{"writeBarrier", varTag, 77},
+	{"writebarrierptr", funcTag, 78},
+	{"typedmemmove", funcTag, 79},
+	{"typedmemclr", funcTag, 80},
+	{"typedslicecopy", funcTag, 81},
+	{"selectnbsend", funcTag, 82},
+	{"selectnbrecv", funcTag, 83},
+	{"selectnbrecv2", funcTag, 85},
+	{"newselect", funcTag, 86},
+	{"selectsend", funcTag, 75},
+	{"selectrecv", funcTag, 87},
 	{"selectdefault", funcTag, 56},
-	{"selectgo", funcTag, 87},
+	{"selectgo", funcTag, 88},
 	{"block", funcTag, 5},
-	{"makeslice", funcTag, 89},
-	{"makeslice64", funcTag, 90},
-	{"growslice", funcTag, 91},
-	{"memmove", funcTag, 92},
-	{"memclrNoHeapPointers", funcTag, 94},
-	{"memclrHasPointers", funcTag, 94},
-	{"memequal", funcTag, 95},
-	{"memequal8", funcTag, 96},
-	{"memequal16", funcTag, 96},
-	{"memequal32", funcTag, 96},
-	{"memequal64", funcTag, 96},
-	{"memequal128", funcTag, 96},
-	{"int64div", funcTag, 97},
-	{"uint64div", funcTag, 98},
-	{"int64mod", funcTag, 97},
-	{"uint64mod", funcTag, 98},
-	{"float64toint64", funcTag, 99},
-	{"float64touint64", funcTag, 100},
-	{"float64touint32", funcTag, 102},
-	{"int64tofloat64", funcTag, 103},
-	{"uint64tofloat64", funcTag, 104},
-	{"uint32tofloat64", funcTag, 105},
-	{"complex128div", funcTag, 106},
-	{"racefuncenter", funcTag, 107},
+	{"makeslice", funcTag, 90},
+	{"makeslice64", funcTag, 91},
+	{"growslice", funcTag, 92},
+	{"memmove", funcTag, 93},
+	{"memclrNoHeapPointers", funcTag, 95},
+	{"memclrHasPointers", funcTag, 95},
+	{"memequal", funcTag, 96},
+	{"memequal8", funcTag, 97},
+	{"memequal16", funcTag, 97},
+	{"memequal32", funcTag, 97},
+	{"memequal64", funcTag, 97},
+	{"memequal128", funcTag, 97},
+	{"int64div", funcTag, 98},
+	{"uint64div", funcTag, 99},
+	{"int64mod", funcTag, 98},
+	{"uint64mod", funcTag, 99},
+	{"float64toint64", funcTag, 100},
+	{"float64touint64", funcTag, 101},
+	{"float64touint32", funcTag, 103},
+	{"int64tofloat64", funcTag, 104},
+	{"uint64tofloat64", funcTag, 105},
+	{"uint32tofloat64", funcTag, 106},
+	{"complex128div", funcTag, 107},
+	{"racefuncenter", funcTag, 108},
 	{"racefuncexit", funcTag, 5},
-	{"raceread", funcTag, 107},
-	{"racewrite", funcTag, 107},
-	{"racereadrange", funcTag, 108},
-	{"racewriterange", funcTag, 108},
-	{"msanread", funcTag, 108},
-	{"msanwrite", funcTag, 108},
+	{"raceread", funcTag, 108},
+	{"racewrite", funcTag, 108},
+	{"racereadrange", funcTag, 109},
+	{"racewriterange", funcTag, 109},
+	{"msanread", funcTag, 109},
+	{"msanwrite", funcTag, 109},
 }
 
 func runtimeTypes() []*Type {
-	var typs [109]*Type
+	var typs [110]*Type
 	typs[0] = bytetype
 	typs[1] = typPtr(typs[0])
 	typs[2] = Types[TANY]
@@ -210,47 +213,48 @@ func runtimeTypes() []*Type {
 	typs[64] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[58]), anonfield(typs[2])}, []*Node{anonfield(typs[3]), anonfield(typs[11])})
 	typs[65] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[58]), anonfield(typs[3]), anonfield(typs[1])}, []*Node{anonfield(typs[3]), anonfield(typs[11])})
 	typs[66] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[58]), anonfield(typs[3])}, nil)
-	typs[67] = functype(nil, []*Node{anonfield(typs[3])}, nil)
-	typs[68] = typChan(typs[2], Cboth)
-	typs[69] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15])}, []*Node{anonfield(typs[68])})
-	typs[70] = typChan(typs[2], Crecv)
-	typs[71] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[70]), anonfield(typs[3])}, nil)
-	typs[72] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[70]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
-	typs[73] = typChan(typs[2], Csend)
-	typs[74] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[73]), anonfield(typs[3])}, nil)
-	typs[75] = typArray(typs[0], 3)
-	typs[76] = tostruct([]*Node{namedfield("enabled", typs[11]), namedfield("pad", typs[75]), namedfield("needed", typs[11]), namedfield("cgo", typs[11]), namedfield("alignme", typs[17])})
-	typs[77] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[2])}, nil)
-	typs[78] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[3])}, nil)
-	typs[79] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3])}, nil)
-	typs[80] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[2]), anonfield(typs[2])}, []*Node{anonfield(typs[32])})
-	typs[81] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[73]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
-	typs[82] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[70])}, []*Node{anonfield(typs[11])})
-	typs[83] = typPtr(typs[11])
-	typs[84] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[83]), anonfield(typs[70])}, []*Node{anonfield(typs[11])})
-	typs[85] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[8])}, nil)
-	typs[86] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[70]), anonfield(typs[3]), anonfield(typs[83])}, nil)
-	typs[87] = functype(nil, []*Node{anonfield(typs[1])}, []*Node{anonfield(typs[32])})
-	typs[88] = typSlice(typs[2])
-	typs[89] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[88])})
-	typs[90] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[88])})
-	typs[91] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[88]), anonfield(typs[32])}, []*Node{anonfield(typs[88])})
-	typs[92] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[49])}, nil)
-	typs[93] = Types[TUNSAFEPTR]
-	typs[94] = functype(nil, []*Node{anonfield(typs[93]), anonfield(typs[49])}, nil)
-	typs[95] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[49])}, []*Node{anonfield(typs[11])})
-	typs[96] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
-	typs[97] = functype(nil, []*Node{anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[15])})
-	typs[98] = functype(nil, []*Node{anonfield(typs[17]), anonfield(typs[17])}, []*Node{anonfield(typs[17])})
-	typs[99] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[15])})
-	typs[100] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[17])})
-	typs[101] = Types[TUINT32]
-	typs[102] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[101])})
-	typs[103] = functype(nil, []*Node{anonfield(typs[15])}, []*Node{anonfield(typs[13])})
-	typs[104] = functype(nil, []*Node{anonfield(typs[17])}, []*Node{anonfield(typs[13])})
-	typs[105] = functype(nil, []*Node{anonfield(typs[101])}, []*Node{anonfield(typs[13])})
-	typs[106] = functype(nil, []*Node{anonfield(typs[19]), anonfield(typs[19])}, []*Node{anonfield(typs[19])})
-	typs[107] = functype(nil, []*Node{anonfield(typs[49])}, nil)
-	typs[108] = functype(nil, []*Node{anonfield(typs[49]), anonfield(typs[49])}, nil)
+	typs[67] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[58]), anonfield(typs[2])}, nil)
+	typs[68] = functype(nil, []*Node{anonfield(typs[3])}, nil)
+	typs[69] = typChan(typs[2], Cboth)
+	typs[70] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15])}, []*Node{anonfield(typs[69])})
+	typs[71] = typChan(typs[2], Crecv)
+	typs[72] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[71]), anonfield(typs[3])}, nil)
+	typs[73] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[71]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+	typs[74] = typChan(typs[2], Csend)
+	typs[75] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[74]), anonfield(typs[3])}, nil)
+	typs[76] = typArray(typs[0], 3)
+	typs[77] = tostruct([]*Node{namedfield("enabled", typs[11]), namedfield("pad", typs[76]), namedfield("needed", typs[11]), namedfield("cgo", typs[11]), namedfield("alignme", typs[17])})
+	typs[78] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[2])}, nil)
+	typs[79] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[3])}, nil)
+	typs[80] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3])}, nil)
+	typs[81] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[2]), anonfield(typs[2])}, []*Node{anonfield(typs[32])})
+	typs[82] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[74]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+	typs[83] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[71])}, []*Node{anonfield(typs[11])})
+	typs[84] = typPtr(typs[11])
+	typs[85] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[3]), anonfield(typs[84]), anonfield(typs[71])}, []*Node{anonfield(typs[11])})
+	typs[86] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[8])}, nil)
+	typs[87] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[71]), anonfield(typs[3]), anonfield(typs[84])}, nil)
+	typs[88] = functype(nil, []*Node{anonfield(typs[1])}, []*Node{anonfield(typs[32])})
+	typs[89] = typSlice(typs[2])
+	typs[90] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[89])})
+	typs[91] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[89])})
+	typs[92] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[89]), anonfield(typs[32])}, []*Node{anonfield(typs[89])})
+	typs[93] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[49])}, nil)
+	typs[94] = Types[TUNSAFEPTR]
+	typs[95] = functype(nil, []*Node{anonfield(typs[94]), anonfield(typs[49])}, nil)
+	typs[96] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[49])}, []*Node{anonfield(typs[11])})
+	typs[97] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3])}, []*Node{anonfield(typs[11])})
+	typs[98] = functype(nil, []*Node{anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[15])})
+	typs[99] = functype(nil, []*Node{anonfield(typs[17]), anonfield(typs[17])}, []*Node{anonfield(typs[17])})
+	typs[100] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[15])})
+	typs[101] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[17])})
+	typs[102] = Types[TUINT32]
+	typs[103] = functype(nil, []*Node{anonfield(typs[13])}, []*Node{anonfield(typs[102])})
+	typs[104] = functype(nil, []*Node{anonfield(typs[15])}, []*Node{anonfield(typs[13])})
+	typs[105] = functype(nil, []*Node{anonfield(typs[17])}, []*Node{anonfield(typs[13])})
+	typs[106] = functype(nil, []*Node{anonfield(typs[102])}, []*Node{anonfield(typs[13])})
+	typs[107] = functype(nil, []*Node{anonfield(typs[19]), anonfield(typs[19])}, []*Node{anonfield(typs[19])})
+	typs[108] = functype(nil, []*Node{anonfield(typs[49])}, nil)
+	typs[109] = functype(nil, []*Node{anonfield(typs[49]), anonfield(typs[49])}, nil)
 	return typs[:]
 }
diff --git a/src/cmd/compile/internal/gc/builtin/runtime.go b/src/cmd/compile/internal/gc/builtin/runtime.go
index cec04259476..168aaaf6f46 100644
--- a/src/cmd/compile/internal/gc/builtin/runtime.go
+++ b/src/cmd/compile/internal/gc/builtin/runtime.go
@@ -108,6 +108,9 @@ func mapassign_fast64(mapType *byte, hmap map[any]any, key any) (val *any)
 func mapassign_faststr(mapType *byte, hmap map[any]any, key any) (val *any)
 func mapiterinit(mapType *byte, hmap map[any]any, hiter *any)
 func mapdelete(mapType *byte, hmap map[any]any, key *any)
+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)
 
 // *byte is really *runtime.Type
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index c15e9084e33..e6032c33d03 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -206,23 +206,15 @@ func orderaddrtemp(n *Node, order *Order) *Node {
 	return ordercopyexpr(n, n.Type, order, 0)
 }
 
-// ordermapkeytemp prepares n.Right to be a key in a map runtime call.
-func ordermapkeytemp(n *Node, order *Order) {
+// ordermapkeytemp prepares n to be a key in a map runtime call and returns n.
+// It should only be used for map runtime calls which have *_fast* versions.
+func ordermapkeytemp(t *Type, n *Node, order *Order) *Node {
 	// Most map calls need to take the address of the key.
-	// Exception: map(accessN|assign)_fast* calls. See golang.org/issue/19015.
-	var p string
-	switch n.Etype {
-	case 0: // n is an rvalue
-		p, _ = mapaccessfast(n.Left.Type)
-	case 1: // n is an lvalue
-		p = mapassignfast(n.Left.Type)
-	default:
-		Fatalf("unexpected node type: %+v", n)
+	// Exception: map*_fast* calls. See golang.org/issue/19015.
+	if mapfast(t) == mapslow {
+		return orderaddrtemp(n, order)
 	}
-	if p != "" {
-		return
-	}
-	n.Right = orderaddrtemp(n.Right, order)
+	return n
 }
 
 type ordermarker int
@@ -560,7 +552,7 @@ func orderstmt(n *Node, order *Order) {
 		if r.Right.Op == OARRAYBYTESTR {
 			r.Right.Op = OARRAYBYTESTRTMP
 		}
-		ordermapkeytemp(r, order)
+		r.Right = ordermapkeytemp(r.Left.Type, r.Right, order)
 		orderokas2(n, order)
 		cleantemp(t, order)
 
@@ -640,10 +632,12 @@ func orderstmt(n *Node, order *Order) {
 		case ODELETE:
 			orderexprlist(n.Left.List, order)
 
-			t1 := marktemp(order)
-			np := n.Left.List.Addr(1) // map key
-			*np = ordercopyexpr(*np, (*np).Type, order, 0)
-			poptemp(t1, order)
+			if mapfast(n.Left.List.First().Type) == mapslow {
+				t1 := marktemp(order)
+				np := n.Left.List.Addr(1) // map key
+				*np = ordercopyexpr(*np, (*np).Type, order, 0)
+				poptemp(t1, order)
+			}
 
 		default:
 			ordercall(n.Left, order)
@@ -656,7 +650,7 @@ func orderstmt(n *Node, order *Order) {
 		t := marktemp(order)
 		n.List.SetFirst(orderexpr(n.List.First(), order, nil))
 		n.List.SetSecond(orderexpr(n.List.Second(), order, nil))
-		n.List.SetSecond(orderaddrtemp(n.List.Second(), order)) // map key
+		n.List.SetSecond(ordermapkeytemp(n.List.First().Type, n.List.Second(), order))
 		order.out = append(order.out, n)
 		cleantemp(t, order)
 
@@ -1069,7 +1063,7 @@ func orderexpr(n *Node, order *Order, lhs *Node) *Node {
 			needCopy = true
 		}
 
-		ordermapkeytemp(n, order)
+		n.Right = ordermapkeytemp(n.Left.Type, n.Right, order)
 		if needCopy {
 			n = ordercopyexpr(n, n.Type, order, 0)
 		}
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 96b564df7c0..e21816653b9 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -804,16 +804,15 @@ opswitch:
 		r.Right = walkexpr(r.Right, init)
 		t := r.Left.Type
 
-		_, p := mapaccessfast(t)
+		fast := mapfast(t)
 		var key *Node
-		if p != "" {
+		if fast != mapslow {
 			// fast versions take key by value
 			key = r.Right
 		} else {
 			// standard version takes key by reference
 			// orderexpr made sure key is addressable.
 			key = nod(OADDR, r.Right, nil)
-			p = "mapaccess2"
 		}
 
 		// from:
@@ -824,7 +823,7 @@ opswitch:
 		a := n.List.First()
 
 		if w := t.Val().Width; w <= 1024 { // 1024 must match ../../../../runtime/hashmap.go:maxZero
-			fn := mapfn(p, t)
+			fn := mapfn(mapaccess2[fast], t)
 			r = mkcall1(fn, fn.Type.Results(), init, typename(t), r.Left, key)
 		} else {
 			fn := mapfn("mapaccess2_fat", t)
@@ -862,11 +861,13 @@ opswitch:
 		map_ = walkexpr(map_, init)
 		key = walkexpr(key, init)
 
-		// orderstmt made sure key is addressable.
-		key = nod(OADDR, key, nil)
-
 		t := map_.Type
-		n = mkcall1(mapfndel("mapdelete", t), nil, init, typename(t), map_, key)
+		fast := mapfast(t)
+		if fast == mapslow {
+			// orderstmt made sure key is addressable.
+			key = nod(OADDR, key, nil)
+		}
+		n = mkcall1(mapfndel(mapdelete[fast], t), nil, init, typename(t), map_, key)
 
 	case OAS2DOTTYPE:
 		walkexprlistsafe(n.List.Slice(), init)
@@ -1184,30 +1185,27 @@ opswitch:
 		t := map_.Type
 		if n.Etype == 1 {
 			// This m[k] expression is on the left-hand side of an assignment.
-			p := mapassignfast(t)
-			if p == "" {
+			fast := mapfast(t)
+			if fast == mapslow {
 				// standard version takes key by reference.
 				// orderexpr made sure key is addressable.
 				key = nod(OADDR, key, nil)
-				p = "mapassign"
 			}
-			n = mkcall1(mapfn(p, t), nil, init, typename(t), map_, key)
+			n = mkcall1(mapfn(mapassign[fast], t), nil, init, typename(t), map_, key)
 		} else {
 			// m[k] is not the target of an assignment.
-			p, _ := mapaccessfast(t)
-			if p == "" {
+			fast := mapfast(t)
+			if fast == mapslow {
 				// standard version takes key by reference.
 				// orderexpr made sure key is addressable.
 				key = nod(OADDR, key, nil)
-				p = "mapaccess1"
 			}
 
 			if w := t.Val().Width; w <= 1024 { // 1024 must match ../../../../runtime/hashmap.go:maxZero
-				n = mkcall1(mapfn(p, t), typPtr(t.Val()), init, typename(t), map_, key)
+				n = mkcall1(mapfn(mapaccess1[fast], t), typPtr(t.Val()), init, typename(t), map_, key)
 			} else {
-				p = "mapaccess1_fat"
 				z := zeroaddr(w)
-				n = mkcall1(mapfn(p, t), typPtr(t.Val()), init, typename(t), map_, key, z)
+				n = mkcall1(mapfn("mapaccess1_fat", t), typPtr(t.Val()), init, typename(t), map_, key, z)
 			}
 		}
 		n.Type = typPtr(t.Val())
@@ -2633,38 +2631,39 @@ func mapfndel(name string, t *Type) *Node {
 	return fn
 }
 
-// mapaccessfast returns the name of the fast map access runtime routine for t.
-func mapaccessfast(t *Type) (access1, access2 string) {
-	// Check ../../runtime/hashmap.go:maxValueSize before changing.
-	if t.Val().Width > 128 {
-		return "", ""
-	}
-	switch algtype(t.Key()) {
-	case AMEM32:
-		return "mapaccess1_fast32", "mapaccess2_fast32"
-	case AMEM64:
-		return "mapaccess1_fast64", "mapaccess2_fast64"
-	case ASTRING:
-		return "mapaccess1_faststr", "mapaccess2_faststr"
-	}
-	return "", ""
+const (
+	mapslow = iota
+	mapfast32
+	mapfast64
+	mapfaststr
+	nmapfast
+)
+
+type mapnames [nmapfast]string
+
+func mkmapnames(base string) mapnames {
+	return mapnames{base, base + "_fast32", base + "_fast64", base + "_faststr"}
 }
 
-// mapassignfast returns the name of the fast map assign runtime routine for t.
-func mapassignfast(t *Type) (assign string) {
+var mapaccess1 mapnames = mkmapnames("mapaccess1")
+var mapaccess2 mapnames = mkmapnames("mapaccess2")
+var mapassign mapnames = mkmapnames("mapassign")
+var mapdelete mapnames = mkmapnames("mapdelete")
+
+func mapfast(t *Type) int {
 	// Check ../../runtime/hashmap.go:maxValueSize before changing.
 	if t.Val().Width > 128 {
-		return ""
+		return mapslow
 	}
 	switch algtype(t.Key()) {
 	case AMEM32:
-		return "mapassign_fast32"
+		return mapfast32
 	case AMEM64:
-		return "mapassign_fast64"
+		return mapfast64
 	case ASTRING:
-		return "mapassign_faststr"
+		return mapfaststr
 	}
-	return ""
+	return mapslow
 }
 
 func writebarrierfn(name string, l *Type, r *Type) *Node {
diff --git a/src/runtime/hashmap_fast.go b/src/runtime/hashmap_fast.go
index f1a5bf3fc3d..0a625cca56c 100644
--- a/src/runtime/hashmap_fast.go
+++ b/src/runtime/hashmap_fast.go
@@ -692,3 +692,172 @@ done:
 	h.flags &^= hashWriting
 	return val
 }
+
+func mapdelete_fast32(t *maptype, h *hmap, key uint32) {
+	if raceenabled && h != nil {
+		callerpc := getcallerpc(unsafe.Pointer(&t))
+		racewritepc(unsafe.Pointer(h), callerpc, funcPC(mapdelete_fast32))
+	}
+	if h == nil || h.count == 0 {
+		return
+	}
+	if h.flags&hashWriting != 0 {
+		throw("concurrent map writes")
+	}
+
+	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
+
+	// Set hashWriting after calling alg.hash for consistency with mapdelete
+	h.flags |= hashWriting
+
+	bucket := hash & (uintptr(1)<<h.B - 1)
+	if h.growing() {
+		growWork(t, h, bucket)
+	}
+	b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize)))
+	top := uint8(hash >> (sys.PtrSize*8 - 8))
+	if top < minTopHash {
+		top += minTopHash
+	}
+	for {
+		for i := uintptr(0); i < bucketCnt; i++ {
+			if b.tophash[i] != top {
+				continue
+			}
+			k := (*uint32)(add(unsafe.Pointer(b), dataOffset+i*4))
+			if key != *k {
+				continue
+			}
+			*k = 0
+			v := unsafe.Pointer(uintptr(unsafe.Pointer(b)) + dataOffset + bucketCnt*4 + i*uintptr(t.valuesize))
+			typedmemclr(t.elem, v)
+			b.tophash[i] = empty
+			h.count--
+			goto done
+		}
+		b = b.overflow(t)
+		if b == nil {
+			goto done
+		}
+	}
+
+done:
+	if h.flags&hashWriting == 0 {
+		throw("concurrent map writes")
+	}
+	h.flags &^= hashWriting
+}
+
+func mapdelete_fast64(t *maptype, h *hmap, key uint64) {
+	if raceenabled && h != nil {
+		callerpc := getcallerpc(unsafe.Pointer(&t))
+		racewritepc(unsafe.Pointer(h), callerpc, funcPC(mapdelete_fast64))
+	}
+	if h == nil || h.count == 0 {
+		return
+	}
+	if h.flags&hashWriting != 0 {
+		throw("concurrent map writes")
+	}
+
+	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
+
+	// Set hashWriting after calling alg.hash for consistency with mapdelete
+	h.flags |= hashWriting
+
+	bucket := hash & (uintptr(1)<<h.B - 1)
+	if h.growing() {
+		growWork(t, h, bucket)
+	}
+	b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize)))
+	top := uint8(hash >> (sys.PtrSize*8 - 8))
+	if top < minTopHash {
+		top += minTopHash
+	}
+	for {
+		for i := uintptr(0); i < bucketCnt; i++ {
+			if b.tophash[i] != top {
+				continue
+			}
+			k := (*uint64)(add(unsafe.Pointer(b), dataOffset+i*8))
+			if key != *k {
+				continue
+			}
+			*k = 0
+			v := unsafe.Pointer(uintptr(unsafe.Pointer(b)) + dataOffset + bucketCnt*8 + i*uintptr(t.valuesize))
+			typedmemclr(t.elem, v)
+			b.tophash[i] = empty
+			h.count--
+			goto done
+		}
+		b = b.overflow(t)
+		if b == nil {
+			goto done
+		}
+	}
+
+done:
+	if h.flags&hashWriting == 0 {
+		throw("concurrent map writes")
+	}
+	h.flags &^= hashWriting
+}
+
+func mapdelete_faststr(t *maptype, h *hmap, ky string) {
+	if raceenabled && h != nil {
+		callerpc := getcallerpc(unsafe.Pointer(&t))
+		racewritepc(unsafe.Pointer(h), callerpc, funcPC(mapdelete_faststr))
+	}
+	if h == nil || h.count == 0 {
+		return
+	}
+	if h.flags&hashWriting != 0 {
+		throw("concurrent map writes")
+	}
+
+	key := stringStructOf(&ky)
+	hash := t.key.alg.hash(noescape(unsafe.Pointer(&ky)), uintptr(h.hash0))
+
+	// Set hashWriting after calling alg.hash for consistency with mapdelete
+	h.flags |= hashWriting
+
+	bucket := hash & (uintptr(1)<<h.B - 1)
+	if h.growing() {
+		growWork(t, h, bucket)
+	}
+	b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize)))
+	top := uint8(hash >> (sys.PtrSize*8 - 8))
+	if top < minTopHash {
+		top += minTopHash
+	}
+	for {
+		for i := uintptr(0); i < bucketCnt; i++ {
+			if b.tophash[i] != top {
+				continue
+			}
+			k := (*stringStruct)(add(unsafe.Pointer(b), dataOffset+i*2*sys.PtrSize))
+			if k.len != key.len {
+				continue
+			}
+			if k.str != key.str && !memequal(k.str, key.str, uintptr(key.len)) {
+				continue
+			}
+			typedmemclr(t.key, unsafe.Pointer(k))
+			v := unsafe.Pointer(uintptr(unsafe.Pointer(b)) + dataOffset + bucketCnt*2*sys.PtrSize + i*uintptr(t.valuesize))
+			typedmemclr(t.elem, v)
+			b.tophash[i] = empty
+			h.count--
+			goto done
+		}
+		b = b.overflow(t)
+		if b == nil {
+			goto done
+		}
+	}
+
+done:
+	if h.flags&hashWriting == 0 {
+		throw("concurrent map writes")
+	}
+	h.flags &^= hashWriting
+}
diff --git a/src/runtime/map_test.go b/src/runtime/map_test.go
index 8ec67d5ab03..45d14126c2e 100644
--- a/src/runtime/map_test.go
+++ b/src/runtime/map_test.go
@@ -619,35 +619,85 @@ func TestNonEscapingMap(t *testing.T) {
 	}
 }
 
-func benchmarkMapAssignInt32(b *testing.B, pow uint) {
+func benchmarkMapAssignInt32(b *testing.B, n int) {
 	a := make(map[int32]int)
 	for i := 0; i < b.N; i++ {
-		a[int32(i&((1<<pow)-1))] = i
+		a[int32(i&(n-1))] = i
 	}
 }
-func BenchmarkMapAssignInt32_255(b *testing.B) { benchmarkMapAssignInt32(b, 8) }
-func BenchmarkMapAssignInt32_64k(b *testing.B) { benchmarkMapAssignInt32(b, 16) }
 
-func benchmarkMapAssignInt64(b *testing.B, pow uint) {
+func benchmarkMapDeleteInt32(b *testing.B, n int) {
+	a := make(map[int32]int)
+	for i := 0; i < n*b.N; i++ {
+		a[int32(i)] = i
+	}
+	b.ResetTimer()
+	for i := 0; i < n*b.N; i = i + n {
+		delete(a, int32(i))
+	}
+}
+
+func benchmarkMapAssignInt64(b *testing.B, n int) {
 	a := make(map[int64]int)
 	for i := 0; i < b.N; i++ {
-		a[int64(i&((1<<pow)-1))] = i
+		a[int64(i&(n-1))] = i
 	}
 }
-func BenchmarkMapAssignInt64_255(b *testing.B) { benchmarkMapAssignInt64(b, 8) }
-func BenchmarkMapAssignInt64_64k(b *testing.B) { benchmarkMapAssignInt64(b, 16) }
 
-func benchmarkMapAssignStr(b *testing.B, pow uint) {
-	k := make([]string, (1 << pow))
+func benchmarkMapDeleteInt64(b *testing.B, n int) {
+	a := make(map[int64]int)
+	for i := 0; i < n*b.N; i++ {
+		a[int64(i)] = i
+	}
+	b.ResetTimer()
+	for i := 0; i < n*b.N; i = i + n {
+		delete(a, int64(i))
+	}
+}
+
+func benchmarkMapAssignStr(b *testing.B, n int) {
+	k := make([]string, n)
 	for i := 0; i < len(k); i++ {
 		k[i] = strconv.Itoa(i)
 	}
 	b.ResetTimer()
 	a := make(map[string]int)
 	for i := 0; i < b.N; i++ {
-		a[k[i&((1<<pow)-1)]] = i
+		a[k[i&(n-1)]] = i
 	}
 }
 
-func BenchmarkMapAssignStr_255(b *testing.B) { benchmarkMapAssignStr(b, 8) }
-func BenchmarkMapAssignStr_64k(b *testing.B) { benchmarkMapAssignStr(b, 16) }
+func benchmarkMapDeleteStr(b *testing.B, n int) {
+	k := make([]string, n*b.N)
+	for i := 0; i < n*b.N; i++ {
+		k[i] = strconv.Itoa(i)
+	}
+	a := make(map[string]int)
+	for i := 0; i < n*b.N; i++ {
+		a[k[i]] = i
+	}
+	b.ResetTimer()
+	for i := 0; i < n*b.N; i = i + n {
+		delete(a, k[i])
+	}
+}
+
+func runWith(f func(*testing.B, int), v ...int) func(*testing.B) {
+	return func(b *testing.B) {
+		for _, n := range v {
+			b.Run(strconv.Itoa(n), func(b *testing.B) { f(b, n) })
+		}
+	}
+}
+
+func BenchmarkMapAssign(b *testing.B) {
+	b.Run("Int32", runWith(benchmarkMapAssignInt32, 1<<8, 1<<16))
+	b.Run("Int64", runWith(benchmarkMapAssignInt64, 1<<8, 1<<16))
+	b.Run("Str", runWith(benchmarkMapAssignStr, 1<<8, 1<<16))
+}
+
+func BenchmarkMapDelete(b *testing.B) {
+	b.Run("Int32", runWith(benchmarkMapDeleteInt32, 1, 2, 4))
+	b.Run("Int64", runWith(benchmarkMapDeleteInt64, 1, 2, 4))
+	b.Run("Str", runWith(benchmarkMapDeleteStr, 1, 2, 4))
+}
diff --git a/test/live.go b/test/live.go
index 0c1be2504cf..ef988a05e5c 100644
--- a/test/live.go
+++ b/test/live.go
@@ -255,16 +255,18 @@ func g15() string
 // and also that none show up in "ambiguously live" messages.
 
 var m map[string]int
+var mi map[interface{}]int
 
-// str is used to ensure that a temp is required for runtime calls below.
+// str and iface are used to ensure that a temp is required for runtime calls below.
 func str() string
+func iface() interface{}
 
 func f16() {
 	if b {
-		delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+		delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
 	}
-	delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
-	delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+	delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+	delete(mi, iface()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
 }
 
 var m2s map[string]*byte