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

src/IceAssemblerX86Base.h

Index: src/IceAssemblerX86Base.h
diff --git a/src/IceAssemblerX86Base.h b/src/IceAssemblerX86Base.h
index a7db6efb5f3fe6005575c9f206a0baaed54c8142..3823f0d1693b93035160813b3ddcebb0969e82e1 100644
--- a/src/IceAssemblerX86Base.h
+++ b/src/IceAssemblerX86Base.h
@@ -115,9 +115,8 @@ template <class Machine> class AssemblerX86Base : public Assembler {
   AssemblerX86Base &operator=(const AssemblerX86Base &) = delete;
 
 protected:
-  AssemblerX86Base(AssemblerKind Kind, GlobalContext *Ctx,
-                   bool use_far_branches)
-      : Assembler(Kind, Ctx) {
+  AssemblerX86Base(AssemblerKind Kind, bool use_far_branches)
+      : Assembler(Kind) {
     // This mode is only needed and implemented for MIPS and ARM.
     assert(!use_far_branches);
     (void)use_far_branches;