[regexp] fix v8_interpreted_regexp build.

R=jgruber@chromium.org

Change-Id: I8328fdaf5d53850b87dd16867255d4325ab9cd9c
Reviewed-on: https://chromium-review.googlesource.com/936644Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51570}

src/regexp/interpreter-irregexp.cc

@@ -519,6 +519,7 @@ static RegExpImpl::IrregexpResult RawMatch(Isolate* isolate,
         break;
       }
       BYTECODE(CHECK_NOT_BACK_REF_NO_CASE_UNICODE)
+      V8_FALLTHROUGH;
       BYTECODE(CHECK_NOT_BACK_REF_NO_CASE) {
         bool unicode =
             (insn & BYTECODE_MASK) == BC_CHECK_NOT_BACK_REF_NO_CASE_UNICODE;
@@ -537,6 +538,7 @@ static RegExpImpl::IrregexpResult RawMatch(Isolate* isolate,
         break;
       }
       BYTECODE(CHECK_NOT_BACK_REF_NO_CASE_UNICODE_BACKWARD)
+      V8_FALLTHROUGH;
       BYTECODE(CHECK_NOT_BACK_REF_NO_CASE_BACKWARD) {
         bool unicode = (insn & BYTECODE_MASK) ==
                        BC_CHECK_NOT_BACK_REF_NO_CASE_UNICODE_BACKWARD;

test/cctest/test-thread-termination.cc

@@ -634,6 +634,8 @@ class TerminatorSleeperThread : public v8::base::Thread {
 };
 
 TEST(TerminateRegExp) {
+// regexp interpreter does not support preemption.
+#ifndef V8_INTERPRETED_REGEXP
   i::FLAG_allow_natives_syntax = true;
   v8::Isolate* isolate = CcTest::isolate();
   ConsoleImpl console;
@@ -653,4 +655,5 @@ TEST(TerminateRegExp) {
             .IsEmpty());
   CHECK(try_catch.HasCaught());
   CHECK(!isolate->IsExecutionTerminating());
+#endif  // V8_INTERPRETED_REGEXP
 }