Revert "Revert "[optimizing] Enable x86 long support.""

This reverts commit 154552e666347d41d95d7619c6ee56249ff4feca.

Change-Id: Idc726551c249a888b7ff5fde8508ae50e81b2e13
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 3470595..475d98c 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -520,7 +520,7 @@
                             dex_file,
                             dex_compilation_unit,
                             &pass_info_printer);
-  } else if (shouldOptimize && RegisterAllocator::Supports(instruction_set)) {
+  } else if (shouldOptimize && can_allocate_registers) {
     LOG(FATAL) << "Could not allocate registers in optimizing compiler";
     UNREACHABLE();
   } else {