diff --git a/src/cmd/gc/racewalk.c b/src/cmd/gc/racewalk.c
index 269c0b2..3e5e592 100644
--- a/src/cmd/gc/racewalk.c
+++ b/src/cmd/gc/racewalk.c
@@ -196,6 +196,7 @@
 	case OPLUS:
 	case OREAL:
 	case OIMAG:
+	case OCOM:
 		racewalknode(&n->left, init, wr, 0);
 		goto ret;
 
@@ -222,23 +223,17 @@
 	case OCAP:
 		racewalknode(&n->left, init, 0, 0);
 		if(istype(n->left->type, TMAP)) {
-			// crashes on len(m[0]) or len(f())
-			SET(n1);
-			USED(n1);
-			/*
-			n1 = nod(OADDR, n->left, N);
-			n1 = conv(n1, types[TUNSAFEPTR]);
-			n1 = conv(n1, ptrto(ptrto(types[TINT8])));
-			n1 = nod(OIND, n1, N);
+			n1 = nod(OCONVNOP, n->left, N);
+			n1->type = ptrto(types[TUINT8]);
 			n1 = nod(OIND, n1, N);
 			typecheck(&n1, Erv);
 			callinstr(&n1, init, 0, skip);
-			*/
 		}
 		goto ret;
 
 	case OLSH:
 	case ORSH:
+	case OLROT:
 	case OAND:
 	case OANDNOT:
 	case OOR:
@@ -279,7 +274,6 @@
 
 	case ODIV:
 	case OMOD:
-		// TODO(dvyukov): add a test for this
 		racewalknode(&n->left, init, wr, 0);
 		racewalknode(&n->right, init, wr, 0);
 		goto ret;
@@ -324,9 +318,30 @@
 	case OPANIC:
 	case ORECOVER:
 	case OCONVIFACE:
+	case OMAKECHAN:
+	case OMAKEMAP:
+	case OMAKESLICE:
+	case OCALL:
+	case OCOPY:
+	case ORUNESTR:
+	case OARRAYBYTESTR:
+	case OARRAYRUNESTR:
+	case OSTRARRAYBYTE:
+	case OSTRARRAYRUNE:
+	case OINDEXMAP:  // lowered to call
+	case OCMPSTR:
+	case OADDSTR:
+	case ODOTTYPE:
+	case ODOTTYPE2:
 		yyerror("racewalk: %O must be lowered by now", n->op);
 		goto ret;
 
+	// impossible nodes: only appear in backend.
+	case ORROTC:
+	case OEXTEND:
+		yyerror("racewalk: %O cannot exist now", n->op);
+		goto ret;
+
 	// just do generic traversal
 	case OFOR:
 	case OIF:
@@ -334,43 +349,28 @@
 	case ORETURN:
 	case OSELECT:
 	case OEMPTY:
+	case OBREAK:
+	case OCONTINUE:
+	case OFALL:
+	case OGOTO:
+	case OLABEL:
 		goto ret;
 
 	// does not require instrumentation
-	case OINDEXMAP:  // implemented in runtime
 	case OPRINT:     // don't bother instrumenting it
 	case OPRINTN:    // don't bother instrumenting it
 	case OPARAM:     // it appears only in fn->exit to copy heap params back
 		goto ret;
 
 	// unimplemented
-	case OCMPSTR:
-	case OADDSTR:
 	case OSLICESTR:
 	case OAPPEND:
-	case OCOPY:
-	case OMAKECHAN:
-	case OMAKEMAP:
-	case OMAKESLICE:
-	case ORUNESTR:
-	case OARRAYBYTESTR:
-	case OARRAYRUNESTR:
-	case OSTRARRAYBYTE:
-	case OSTRARRAYRUNE:
 	case OCMPIFACE:
 	case OARRAYLIT:
 	case OMAPLIT:
 	case OSTRUCTLIT:
 	case OCLOSURE:
-	case ODOTTYPE:
-	case ODOTTYPE2:
-	case OCALL:
-	case OBREAK:
 	case ODCL:
-	case OCONTINUE:
-	case OFALL:
-	case OGOTO:
-	case OLABEL:
 	case ODCLCONST:
 	case ODCLTYPE:
 	case OLITERAL:
@@ -378,14 +378,11 @@
 	case OTYPE:
 	case ONONAME:
 	case OINDREG:
-	case OCOM:
 	case ODOTMETH:
 	case OITAB:
-	case OEXTEND:
 	case OHMUL:
-	case OLROT:
-	case ORROTC:
 	case OCHECKNOTNIL:
+	case OCLOSUREVAR:
 		goto ret;
 	}
 
diff --git a/src/pkg/runtime/race/testdata/map_test.go b/src/pkg/runtime/race/testdata/map_test.go
index 6f86a50..35db8db 100644
--- a/src/pkg/runtime/race/testdata/map_test.go
+++ b/src/pkg/runtime/race/testdata/map_test.go
@@ -94,8 +94,7 @@
 	<-ch
 }
 
-// Map len is not instrumented.
-func TestRaceFailingMapLen(t *testing.T) {
+func TestRaceMapLen(t *testing.T) {
 	m := make(map[string]bool)
 	ch := make(chan bool, 1)
 	go func() {
@@ -117,8 +116,7 @@
 	<-ch
 }
 
-// Map len is not instrumented.
-func TestRaceFailingMapLenDelete(t *testing.T) {
+func TestRaceMapLenDelete(t *testing.T) {
 	m := make(map[string]bool)
 	ch := make(chan bool, 1)
 	go func() {
diff --git a/src/pkg/runtime/race/testdata/mop_test.go b/src/pkg/runtime/race/testdata/mop_test.go
index f2daa37..26cd3a4 100644
--- a/src/pkg/runtime/race/testdata/mop_test.go
+++ b/src/pkg/runtime/race/testdata/mop_test.go
@@ -306,6 +306,102 @@
 	<-ch
 }
 
+func TestRaceComplement(t *testing.T) {
+	var x, y, z int
+	ch := make(chan int, 2)
+
+	go func() {
+		x = ^y
+		ch <- 1
+	}()
+	go func() {
+		y = ^z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
+func TestRaceDiv(t *testing.T) {
+	var x, y, z int
+	ch := make(chan int, 2)
+
+	go func() {
+		x = y / (z + 1)
+		ch <- 1
+	}()
+	go func() {
+		y = z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
+func TestRaceDivConst(t *testing.T) {
+	var x, y, z int
+	ch := make(chan int, 2)
+
+	go func() {
+		x = y / 3
+		ch <- 1
+	}()
+	go func() {
+		y = z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
+func TestRaceMod(t *testing.T) {
+	var x, y, z int
+	ch := make(chan int, 2)
+
+	go func() {
+		x = y % (z + 1)
+		ch <- 1
+	}()
+	go func() {
+		y = z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
+func TestRaceModConst(t *testing.T) {
+	var x, y, z int
+	ch := make(chan int, 2)
+
+	go func() {
+		x = y % 3
+		ch <- 1
+	}()
+	go func() {
+		y = z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
+func TestRaceRotate(t *testing.T) {
+	var x, y, z uint32
+	ch := make(chan int, 2)
+
+	go func() {
+		x = y<<12 | y>>20
+		ch <- 1
+	}()
+	go func() {
+		y = z
+		ch <- 1
+	}()
+	<-ch
+	<-ch
+}
+
 // May crash if the instrumentation is reckless.
 func TestNoRaceEnoughRegisters(t *testing.T) {
 	// from erf.go
diff --git a/src/pkg/runtime/race/testdata/regression_test.go b/src/pkg/runtime/race/testdata/regression_test.go
index afe8cc5..f08ee3e 100644
--- a/src/pkg/runtime/race/testdata/regression_test.go
+++ b/src/pkg/runtime/race/testdata/regression_test.go
@@ -45,6 +45,18 @@
 	_ = len(*m[0])
 }
 
+func TestRaceUnaddressableMapLen(t *testing.T) {
+	m := make(map[int]map[int]int)
+	ch := make(chan int, 1)
+	m[0] = make(map[int]int)
+	go func() {
+		_ = len(m[0])
+		ch <- 0
+	}()
+	m[0][0] = 1
+	<-ch
+}
+
 type Rect struct {
 	x, y int
 }
diff --git a/src/pkg/runtime/race/testdata/slice_test.go b/src/pkg/runtime/race/testdata/slice_test.go
index 7734636..1fe051b 100644
--- a/src/pkg/runtime/race/testdata/slice_test.go
+++ b/src/pkg/runtime/race/testdata/slice_test.go
@@ -463,3 +463,24 @@
 	s[9] = 42
 	<-c
 }
+
+func TestRaceConcatString(t *testing.T) {
+	s := "hello"
+	c := make(chan string, 1)
+	go func() {
+		c <- s + " world"
+	}()
+	s = "world"
+	<-c
+}
+
+func TestRaceCompareString(t *testing.T) {
+	s1 := "hello"
+	s2 := "world"
+	c := make(chan bool, 1)
+	go func() {
+		c <- s1 == s2
+	}()
+	s1 = s2
+	<-c
+}