Avoid assigning esp (or ebp for framepointer-using frames) in Om1.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the skeleton of the TargetLowering class,
@@ skipping 149 matching lines @@
 // Drives register allocation, allowing all physical registers (except
 // perhaps for the frame pointer) to be allocated.  This set of
 // registers could potentially be parameterized if we want to restrict
 // registers e.g. for performance testing.
 void TargetLowering::regAlloc() {
   LinearScan LinearScan(Func);
   RegSetMask RegInclude = RegSet_None;
   RegSetMask RegExclude = RegSet_None;
   RegInclude |= RegSet_CallerSave;
   RegInclude |= RegSet_CalleeSave;
-  RegExclude |= RegSet_StackPointer;
   if (hasFramePointer())
     RegExclude |= RegSet_FramePointer;
   llvm::SmallBitVector RegMask = getRegisterSet(RegInclude, RegExclude);
   LinearScan.scan(RegMask);
 }
 
 TargetGlobalInitLowering *
 TargetGlobalInitLowering::createLowering(TargetArch Target,
                                          GlobalContext *Ctx) {
   // These statements can be #ifdef'd to specialize the code generator
   // to a subset of the available targets.  TODO: use CRTP.
   if (Target == Target_X8632)
     return TargetGlobalInitX8632::create(Ctx);
 #if 0
   if (Target == Target_X8664)
     return IceTargetGlobalInitX8664::create(Ctx);
   if (Target == Target_ARM32)
     return IceTargetGlobalInitARM32::create(Ctx);
   if (Target == Target_ARM64)
     return IceTargetGlobalInitARM64::create(Ctx);
 #endif
   llvm_unreachable("Unsupported target");
   return NULL;
 }
 
 } // end of namespace Ice