Add option to force filetype=asm for testing

src/IceTargetLoweringX8632Traits.h

 //===- subzero/src/IceTargetLoweringX8632Traits.h - x86-32 traits -*- C++ -*-=//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 346 matching lines @@
     assert(RegNum >= 0);
     assert(RegNum < RegisterSet::Reg_NUM);
     return BaseRegs[RegNum];
   }
 
   // Return a register in RegNum's alias set that is suitable for Ty.
   static int32_t getGprForType(Type Ty, int32_t RegNum) {
     assert(RegNum != Variable::NoRegister);
     // TODO(stichnot): Rewrite this as a table lookup from a table computed in a
     // TargetLowering static initializer.
+    // [abcd]h registers are not convertible to their ?l, ?x, and e?x versions.
+    switch (RegNum) {
+    default:
+      break;
+    case RegisterSet::Reg_ah:
+    case RegisterSet::Reg_bh:
+    case RegisterSet::Reg_ch:
+    case RegisterSet::Reg_dh:
+      assert(isByteSizedType(Ty));
+      return RegNum;
+    }
     RegNum = getBaseReg(RegNum);
-    if (Ty == IceType_i8 || Ty == IceType_i1) {
+    if (isByteSizedType(Ty)) {
       switch (RegNum) {
       default:
         assert(0);
       case RegisterSet::Reg_eax:
         return RegisterSet::Reg_al;
       case RegisterSet::Reg_ecx:
         return RegisterSet::Reg_cl;
       case RegisterSet::Reg_edx:
         return RegisterSet::Reg_dl;
       case RegisterSet::Reg_ebx:
@@ skipping 561 matching lines @@
 
   static uint8_t InstSegmentPrefixes[];
 };
 
 using Traits = ::Ice::X8632::TargetX8632Traits;
 } // end of namespace X8632
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX8632TRAITS_H