Use enums instead of literals for X86 subregisters.

The cases in getMatchingSuperRegClass cannot be broken up until the enums have
unique values.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104611 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index a7b75fa..34e12ca 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -744,17 +744,17 @@
     case X86::MOVZX32rr8:
     case X86::MOVSX64rr8:
     case X86::MOVZX64rr8:
-      SubIdx = 1;
+      SubIdx = X86::sub_8bit;
       break;
     case X86::MOVSX32rr16:
     case X86::MOVZX32rr16:
     case X86::MOVSX64rr16:
     case X86::MOVZX64rr16:
-      SubIdx = 3;
+      SubIdx = X86::sub_16bit;
       break;
     case X86::MOVSX64rr32:
     case X86::MOVZX64rr32:
-      SubIdx = 4;
+      SubIdx = X86::sub_32bit;
       break;
     }
     return true;