diff --git a/src/cmd/compile/internal/gc/asm_test.go b/src/cmd/compile/internal/gc/asm_test.go
index 29ed0739cf..d07988b2ab 100644
--- a/src/cmd/compile/internal/gc/asm_test.go
+++ b/src/cmd/compile/internal/gc/asm_test.go
@@ -440,6 +440,38 @@ func f(t *T) {
 `,
 		[]string{"\tROLL\t[$]7,"},
 	},
+
+	// Direct use of constants in fast map access calls. Issue 19015.
+	{"amd64", "linux", `
+	func f(m map[int]int) int {
+		return m[5]
+	}
+`,
+		[]string{"\tMOVQ\t[$]5,"},
+	},
+	{"amd64", "linux", `
+	func f(m map[int]int) bool {
+		_, ok := m[5]
+		return ok
+	}
+`,
+		[]string{"\tMOVQ\t[$]5,"},
+	},
+	{"amd64", "linux", `
+	func f(m map[string]int) int {
+		return m["abc"]
+	}
+`,
+		[]string{"\"abc\""},
+	},
+	{"amd64", "linux", `
+	func f(m map[string]int) bool {
+		_, ok := m["abc"]
+		return ok
+	}
+`,
+		[]string{"\"abc\""},
+	},
 }
 
 // mergeEnvLists merges the two environment lists such that
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index 4f2cc831fe..9530d4d928 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -206,6 +206,18 @@ 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 lookup.
+func ordermapkeytemp(n *Node, order *Order) {
+	// Most map calls need to take the address of the key.
+	// Exception: mapaccessN_fast* calls. See golang.org/issue/19015.
+	p, _ := mapaccessfast(n.Left.Type)
+	fastaccess := p != "" && n.Etype == 0 // Etype == 0 iff n is an rvalue
+	if fastaccess {
+		return
+	}
+	n.Right = orderaddrtemp(n.Right, order)
+}
+
 type ordermarker int
 
 // Marktemp returns the top of the temporary variable stack.
@@ -527,7 +539,7 @@ func orderstmt(n *Node, order *Order) {
 		ordermapassign(n, order)
 		cleantemp(t, order)
 
-	// Special: make sure key is addressable,
+	// Special: make sure key is addressable if needed,
 	// and make sure OINDEXMAP is not copied out.
 	case OAS2MAPR:
 		t := marktemp(order)
@@ -541,7 +553,7 @@ func orderstmt(n *Node, order *Order) {
 		if r.Right.Op == OARRAYBYTESTR {
 			r.Right.Op = OARRAYBYTESTRTMP
 		}
-		r.Right = orderaddrtemp(r.Right, order)
+		ordermapkeytemp(r, order)
 		ordermapassign(n, order)
 		cleantemp(t, order)
 
@@ -1074,9 +1086,7 @@ func orderexpr(n *Node, order *Order, lhs *Node) *Node {
 			needCopy = true
 		}
 
-		// Map calls need to take the address of the key.
-		n.Right = orderaddrtemp(n.Right, order)
-
+		ordermapkeytemp(n, 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 8fb33cd949..772e86bfab 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -791,18 +791,8 @@ opswitch:
 		r.Left = walkexpr(r.Left, init)
 		r.Right = walkexpr(r.Right, init)
 		t := r.Left.Type
-		p := ""
-		if t.Val().Width <= 128 { // Check ../../runtime/hashmap.go:maxValueSize before changing.
-			switch algtype(t.Key()) {
-			case AMEM32:
-				p = "mapaccess2_fast32"
-			case AMEM64:
-				p = "mapaccess2_fast64"
-			case ASTRING:
-				p = "mapaccess2_faststr"
-			}
-		}
 
+		_, p := mapaccessfast(t)
 		var key *Node
 		if p != "" {
 			// fast versions take key by value
@@ -811,7 +801,6 @@ opswitch:
 			// standard version takes key by reference
 			// orderexpr made sure key is addressable.
 			key = nod(OADDR, r.Right, nil)
-
 			p = "mapaccess2"
 		}
 
@@ -1173,18 +1162,7 @@ opswitch:
 			n = mkcall1(mapfn("mapassign", t), nil, init, typename(t), map_, key)
 		} else {
 			// m[k] is not the target of an assignment.
-			p := ""
-			if t.Val().Width <= 128 { // Check ../../runtime/hashmap.go:maxValueSize before changing.
-				switch algtype(t.Key()) {
-				case AMEM32:
-					p = "mapaccess1_fast32"
-				case AMEM64:
-					p = "mapaccess1_fast64"
-				case ASTRING:
-					p = "mapaccess1_faststr"
-				}
-			}
-
+			p, _ := mapaccessfast(t)
 			if p == "" {
 				// standard version takes key by reference.
 				// orderexpr made sure key is addressable.
@@ -2700,6 +2678,23 @@ func mapfndel(name string, t *Type) *Node {
 	return fn
 }
 
+// mapaccessfast returns the names of the fast map access runtime routines 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 "", ""
+}
+
 func writebarrierfn(name string, l *Type, r *Type) *Node {
 	fn := syslook(name)
 	fn = substArgTypes(fn, l, r)