Fix x64 patching of asllocation stub: the pool pointer must be set-up before patching jump is execu…

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
===================================================================
--- runtime/vm/assembler_x64.cc	(revision 40325)
+++ runtime/vm/assembler_x64.cc	(working copy)
@@ -3135,6 +3135,27 @@
 }
 
 
+void Assembler::SetupPP(Register new_pp, Register temp_pc) {
+  Label next;
+  nop(4);  // Need a fixed size sequence on frame entry.
+  call(&next);
+  Bind(&next);
+
+  const intptr_t object_pool_pc_dist =
+      Instructions::HeaderSize() - Instructions::object_pool_offset() +
+      CodeSize();
+  const intptr_t offset =
+      Assembler::EntryPointToPcMarkerOffset() - CodeSize();
+  popq(temp_pc);
+  if (offset != 0) {
+    addq(temp_pc, Immediate(offset));
+  }
+
+  // Load callee's pool pointer.
+  movq(new_pp, Address(temp_pc, -object_pool_pc_dist - offset));
+}
+
+
 void Assembler::ComputeCounterAddressesForCid(intptr_t cid,
                                               Heap::Space space,
                                               Address* count_address,