Subzero: Refactor x86 register definitions to use the alias mechanism.

src/IceAssemblerX8664.h

Index: src/IceAssemblerX8664.h
diff --git a/src/IceAssemblerX8664.h b/src/IceAssemblerX8664.h
index 43b50be75cebb3364bddcfd8cfca12e4cebf73b2..566681016e10d1d687eb134e709b9baeb70446dc 100644
--- a/src/IceAssemblerX8664.h
+++ b/src/IceAssemblerX8664.h
@@ -45,8 +45,8 @@ class AssemblerX8664 : public X86Internal::AssemblerX86Base<TargetX8664> {
   AssemblerX8664 &operator=(const AssemblerX8664 &) = delete;
 
 public:
-  explicit AssemblerX8664(GlobalContext *Ctx, bool use_far_branches = false)
-      : X86Internal::AssemblerX86Base<TargetX8664>(Asm_X8664, Ctx,
+  explicit AssemblerX8664(bool use_far_branches = false)
+      : X86Internal::AssemblerX86Base<TargetX8664>(Asm_X8664,
                                                    use_far_branches) {}
   ~AssemblerX8664() override = default;