Re-reland: Remove register index/code indirection

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 884067b776e417e086b948c93d52d9d362d78083..262e16bcbd8c5230ce5f8bcc7d5c3af3df379fde 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -482,14 +482,13 @@ LPlatformChunk* LChunkBuilder::Build() {
 
 
 LUnallocated* LChunkBuilder::ToUnallocated(Register reg) {
-  return new(zone()) LUnallocated(LUnallocated::FIXED_REGISTER,
-                                  Register::ToAllocationIndex(reg));
+  return new (zone()) LUnallocated(LUnallocated::FIXED_REGISTER, reg.code());
 }
 
 
 LUnallocated* LChunkBuilder::ToUnallocated(XMMRegister reg) {
-  return new(zone()) LUnallocated(LUnallocated::FIXED_DOUBLE_REGISTER,
-                                  XMMRegister::ToAllocationIndex(reg));
+  return new (zone())
+      LUnallocated(LUnallocated::FIXED_DOUBLE_REGISTER, reg.code());
 }