[Compiler] Only look in optimized code cache if function is compiled.

We make assumptions that baseline code exists if we run the optimized code
(e.g., to deopt to the baseline code). If the baseline code has been
cleared by code flushing (only full-codegen) then it might not exist
but there is still optimized code in the map.

BUG=v8:6389

Change-Id: Id4db664afee96c2da3a36a177f425293aae9a0a3
Reviewed-on: https://chromium-review.googlesource.com/503010Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45278}

src/compiler.cc

@@ -1051,6 +1051,9 @@ MaybeHandle<Code> GetLazyCode(Handle<JSFunction> function) {
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"), "V8.CompileCode");
   AggregatedHistogramTimerScope timer(isolate->counters()->compile_lazy());
 
+  if (function->shared()->is_compiled()) {
+    // Function has already been compiled, get the optimized code if possible,
+    // otherwise return baseline code.
     Handle<Code> cached_code;
     if (GetCodeFromOptimizedCodeCache(function, BailoutId::None())
             .ToHandle(&cached_code)) {
@@ -1063,8 +1066,7 @@ MaybeHandle<Code> GetLazyCode(Handle<JSFunction> function) {
       return cached_code;
     }
 
-  if (function->shared()->is_compiled() &&
-      function->shared()->marked_for_tier_up()) {
+    if (function->shared()->marked_for_tier_up()) {
       DCHECK(FLAG_mark_shared_functions_for_tier_up);
 
       function->shared()->set_marked_for_tier_up(false);
@@ -1081,15 +1083,10 @@ MaybeHandle<Code> GetLazyCode(Handle<JSFunction> function) {
       }
     }
 
-  if (function->shared()->is_compiled()) {
     return Handle<Code>(function->shared()->code());
-  }
-
-  if (function->shared()->HasBytecodeArray()) {
-    Handle<Code> entry = isolate->builtins()->InterpreterEntryTrampoline();
-    function->shared()->ReplaceCode(*entry);
-    return entry;
-  }
+  } else {
+    // Function doesn't have any baseline compiled code, compile now.
+    DCHECK(!function->shared()->HasBytecodeArray());
 
     ParseInfo parse_info(handle(function->shared()));
     Zone compile_zone(isolate->allocator(), ZONE_NAME);
@@ -1118,6 +1115,7 @@ MaybeHandle<Code> GetLazyCode(Handle<JSFunction> function) {
     }
 
     return result;
+  }
 }