Reland - Arm64: Ensure that csp is always aligned to 16 byte values even if jssp is not.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index d0c1a446a8beb9e80e5ddce6fab385d74468363c..b523450e2880dcd174e7c384f3251ddf43079dd3 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1604,9 +1604,13 @@ void Builtins::SetUp(Isolate* isolate, bool create_heap_objects) {
   // For now we generate builtin adaptor code into a stack-allocated
   // buffer, before copying it into individual code objects. Be careful
   // with alignment, some platforms don't like unaligned code.
-  // TODO(jbramley): I had to increase the size of this buffer from 8KB because
-  // we can generate a lot of debug code on ARM64.
-  union { int force_alignment; byte buffer[16*KB]; } u;
+#ifdef DEBUG
+  // We can generate a lot of debug code on Arm64.
+  const size_t buffer_size = 32*KB;
+#else
+  const size_t buffer_size = 8*KB;
+#endif
+  union { int force_alignment; byte buffer[buffer_size]; } u;
 
   // Traverse the list of builtins and generate an adaptor in a
   // separate code object for each one.