[csa] CSA type checks: allow the empty FixedArray to be CAST() to Fix…

…edDoubleArray

This should allow to re-land https://crrev.com/c/1039190

Bug: chromium:871886

Change-Id: If815537410b3fa09902026dc26205421f5c36ae5
Reviewed-on: https://chromium-review.googlesource.com/1169019
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55015}

src/compiler/code-assembler.cc

@@ -1709,6 +1709,11 @@ void CodeAssemblerLabel::UpdateVariablesAfterBind() {
 }  // namespace compiler
 
 Smi* CheckObjectType(Object* value, Smi* type, String* location) {
+  // Allow the empty FixedArray to be treated as a FixedDoubleArray.
+  if (static_cast<ObjectType>(type->value()) == ObjectType::kFixedDoubleArray &&
+      value->IsFixedArray() && FixedArray::cast(value)->length() == 0) {
+    return Smi::FromInt(0);
+  }
 #ifdef DEBUG
   const char* expected;
   switch (static_cast<ObjectType>(type->value())) {