compiler: make map and channel panics recoverable

Change hashmap set operations and channel send/close from
createRuntimeCall to createRuntimeInvoke. This places a setjmp
checkpoint before each call, allowing runtimePanicAt to safely
longjmp when these operations panic.

compiler/channel.go

@@ -48,7 +48,7 @@ func (b *builder) createChanSend(instr *ssa.Send) {
 	channelOpAlloca, channelOpAllocaSize := b.createTemporaryAlloca(channelOp, "chan.op")
 
 	// Do the send.
-	b.createRuntimeCall("chanSend", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "")
+	b.createRuntimeInvoke("chanSend", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "")
 
 	// End the lifetime of the allocas.
 	// This also works around a bug in CoroSplit, at least in LLVM 8:
@@ -101,7 +101,7 @@ func (b *builder) createChanRecv(unop *ssa.UnOp) llvm.Value {
 
 // createChanClose closes the given channel.
 func (b *builder) createChanClose(ch llvm.Value) {
-	b.createRuntimeCall("chanClose", []llvm.Value{ch}, "")
+	b.createRuntimeInvoke("chanClose", []llvm.Value{ch}, "")
 }
 
 // createSelect emits all IR necessary for a select statements. That's a

compiler/map.go

@@ -133,7 +133,7 @@ func (b *builder) createMapUpdate(keyType types.Type, m, key, value llvm.Value,
 	if t, ok := keyType.(*types.Basic); ok && t.Info()&types.IsString != 0 {
 		// key is a string
 		params := []llvm.Value{m, key, valueAlloca}
-		b.createRuntimeCall("hashmapStringSet", params, "")
+		b.createRuntimeInvoke("hashmapStringSet", params, "")
 	} else {
 		// Key stored at actual type.
 		keyAlloca, keySize := b.createTemporaryAlloca(key.Type(), "hashmap.key")
@@ -143,7 +143,7 @@ func (b *builder) createMapUpdate(keyType types.Type, m, key, value llvm.Value,
 			fnName = "hashmapGenericSet"
 		}
 		params := []llvm.Value{m, keyAlloca, valueAlloca}
-		b.createRuntimeCall(fnName, params, "")
+		b.createRuntimeInvoke(fnName, params, "")
 		b.emitLifetimeEnd(keyAlloca, keySize)
 	}
 	b.emitLifetimeEnd(valueAlloca, valueSize)

testdata/recover.go

@@ -41,6 +41,9 @@ func main() {
 
 	println("\n# recover runtime errors")
 	recoverRuntimeError()
+
+	println("\n# recover from nil map and closed channel")
+	recoverNilMapAndChan()
 }
 
 func recoverSimple() {
@@ -241,3 +244,20 @@ func recoverMustPanic(name string, f func()) {
 	}()
 	f()
 }
+
+// Test recovering from nil map assignment and closed channel send.
+func recoverNilMapAndChan() {
+	recoverMustPanic("nil map", func() {
+		var m map[string]int
+		m["x"] = 1
+	})
+	recoverMustPanic("closed chan", func() {
+		ch := make(chan int)
+		close(ch)
+		ch <- 1
+	})
+	recoverMustPanic("close nil chan", func() {
+		var ch chan int
+		close(ch)
+	})
+}

testdata/recover.txt

@@ -44,3 +44,8 @@ outer recovered: repanic value
   recovered: slice
   recovered: type assert
   recovered: empty interface type assert
+
+# recover from nil map and closed channel
+  recovered: nil map
+  recovered: closed chan
+  recovered: close nil chan