[csa] Add Unreachable() and use it after throw sites

src/builtins/builtins-sharedarraybuffer.cc

Index: src/builtins/builtins-sharedarraybuffer.cc
diff --git a/src/builtins/builtins-sharedarraybuffer.cc b/src/builtins/builtins-sharedarraybuffer.cc
index 7ee144901e1a074818704e50886065439ee1234f..742034929f5aa5875a5ddef7c8c012b1c7dbe6f6 100644
--- a/src/builtins/builtins-sharedarraybuffer.cc
+++ b/src/builtins/builtins-sharedarraybuffer.cc
@@ -85,7 +85,7 @@ void ValidateSharedTypedArray(CodeStubAssembler* a, compiler::Node* tagged,
   a->Bind(&invalid);
   a->CallRuntime(Runtime::kThrowNotIntegerSharedTypedArrayError, context,
                  tagged);
-  a->Return(a->UndefinedConstant());
+  a->Unreachable();
 
   a->Bind(&not_float_or_clamped);
   *out_instance_type = elements_instance_type;
@@ -136,8 +136,8 @@ compiler::Node* ConvertTaggedAtomicIndexToWord32(CodeStubAssembler* a,
     }
 
     a->Bind(&if_indexesarenotequal);
-    a->Return(
-        a->CallRuntime(Runtime::kThrowInvalidAtomicAccessIndexError, context));
+    a->CallRuntime(Runtime::kThrowInvalidAtomicAccessIndexError, context);
+    a->Unreachable();
   }
 
   a->Bind(&done);
@@ -156,8 +156,8 @@ void ValidateAtomicIndex(CodeStubAssembler* a, compiler::Node* index_word,
                   a->Int32GreaterThanOrEqual(index_word, array_length_word)),
       &if_notinbounds, &if_inbounds);
   a->Bind(&if_notinbounds);
-  a->Return(
-      a->CallRuntime(Runtime::kThrowInvalidAtomicAccessIndexError, context));
+  a->CallRuntime(Runtime::kThrowInvalidAtomicAccessIndexError, context);
+  a->Unreachable();
   a->Bind(&if_inbounds);
 }