irgen: do not emit an extra terminator for panic thunks

Found with GoSmith.

Differential Revision: http://reviews.llvm.org/D6714

llvm-svn: 224904

llgo/irgen/builtins.go

@@ -110,7 +110,9 @@ func (fr *frame) callRecover(isDeferredRecover bool) *govalue {
 	return newValue(llv, eface)
 }
 
-func (fr *frame) callPanic(arg *govalue) {
+func (fr *frame) callPanic(arg *govalue, term bool) {
 	fr.runtime.panic.call(fr, arg.value)
-	fr.builder.CreateUnreachable()
+	if term {
+		fr.builder.CreateUnreachable()
+	}
 }

llgo/irgen/ssa.go

@@ -1079,7 +1079,7 @@ func (fr *frame) instruction(instr ssa.Instruction) {
 
 	case *ssa.Panic:
 		arg := fr.value(instr.X)
-		fr.callPanic(arg)
+		fr.callPanic(arg, true)
 
 	case *ssa.Phi:
 		typ := instr.Type()
@@ -1190,7 +1190,7 @@ func (fr *frame) callBuiltin(typ types.Type, builtin *ssa.Builtin, args []ssa.Va
 		return nil
 
 	case "panic":
-		fr.callPanic(fr.value(args[0]))
+		fr.callPanic(fr.value(args[0]), false)
 		return nil
 
 	case "recover":

llgo/test/irgen/go-panic.go

@@ -0,0 +1,10 @@
+// RUN: llgo -S -emit-llvm -o - %s | FileCheck %s
+
+package foo
+
+func F() {
+	// CHECK: call void @__go_panic
+	// CHECK-NEXT: ret void
+	// CHECK-NEXT: }
+	go panic("")
+}