Add a flag for flushing icache for embedded builtins

It will be used in a Finch experiment to evaluate if icache flushing
helps with crashes on certain CPUs.

Bug: chromium:889460
Change-Id: I1218ce93db001833e29fdeca8fde3e863e26dfdd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2267297Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68545}

src/execution/isolate.cc

@@ -25,6 +25,7 @@
 #include "src/builtins/constants-table-builder.h"
 #include "src/codegen/assembler-inl.h"
 #include "src/codegen/compilation-cache.h"
+#include "src/codegen/flush-instruction-cache.h"
 #include "src/common/ptr-compr.h"
 #include "src/compiler-dispatcher/compiler-dispatcher.h"
 #include "src/compiler-dispatcher/optimizing-compile-dispatcher.h"
@@ -239,6 +240,10 @@ void Isolate::SetEmbeddedBlob(const uint8_t* blob, uint32_t blob_size) {
         "cause is a debugging breakpoint set within builtin code.");
   }
 #endif  // DEBUG
+
+  if (FLAG_experimental_flush_embedded_blob_icache) {
+    FlushInstructionCache(const_cast<uint8_t*>(blob), blob_size);
+  }
 }
 
 void Isolate::ClearEmbeddedBlob() {

src/flags/flag-definitions.h

@@ -1337,6 +1337,8 @@ DEFINE_BOOL(
     "includes arguments for each function call in the error stack frames array")
 DEFINE_BOOL(adjust_os_scheduling_parameters, true,
             "adjust OS specific scheduling params for the isolate")
+DEFINE_BOOL(experimental_flush_embedded_blob_icache, false,
+            "Used in an experiment to evaluate icache flushing on certain CPUs")
 
 // runtime.cc
 DEFINE_BOOL(runtime_call_stats, false, "report runtime call counts and times")