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

src/IceTargetLoweringX8632.cpp

 //===- subzero/src/IceTargetLoweringX8632.cpp - x86-32 lowering -----------===//
 //
 //                        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 TargetLoweringX8632 class, which
@@ skipping 2503 matching lines @@
     Reg->setWeightInfinite();
   else
     Reg->setRegNum(RegNum);
   return Reg;
 }
 
 void TargetX8632::postLower() {
   if (Ctx->getOptLevel() != Opt_m1)
     return;
   // TODO: Avoid recomputing WhiteList every instruction.
-  llvm::SmallBitVector WhiteList = getRegisterSet(RegSet_All, RegSet_None);
+  RegSetMask RegInclude = RegSet_All;
+  RegSetMask RegExclude = RegSet_None | RegSet_StackPointer;

[Jim Stichnoth, 2014/07/02 23:03:36]

Could probably just use
  RegSetMask RegExclude = RegSet_StackPointer;

[Jim Stichnoth, 2014/07/02 23:23:44]

Actually, it would be even better to use RegSet_None, except that for some
reason Reg_esp is marked as isInt in IceInstX8632.def.  I don't know if there
would be any problems setting isInt to 0, but I think the existing lit tests and
cross tests would flag any problems.

[jvoung (off chromium), 2014/07/02 23:43:38]

Okay so the idea is mark esp as a non-int register and the calls to
getRegisterSetForType() will never return it.

I tried it out, and at least the existing lit tests/crosstests are okay with
it... but let's chat about it next week, you're on vacation!

+  if (hasFramePointer())
+    RegExclude |= RegSet_FramePointer;
+  llvm::SmallBitVector WhiteList = getRegisterSet(RegInclude, RegExclude);
   // Make one pass to black-list pre-colored registers.  TODO: If
   // there was some prior register allocation pass that made register
   // assignments, those registers need to be black-listed here as
   // well.
   for (InstList::iterator I = Context.getCur(), E = Context.getEnd(); I != E;
        ++I) {
     const Inst *Inst = *I;
     if (Inst->isDeleted())
       continue;
     if (llvm::isa<InstFakeKill>(Inst))
@@ skipping 146 matching lines @@
     for (SizeT i = 0; i < Size; ++i) {
       Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
     }
     Str << "\t.size\t" << MangledName << ", " << Size << "\n";
   }
   Str << "\t" << (IsInternal ? ".local" : ".global") << "\t" << MangledName
       << "\n";
 }
 
 } // end of namespace Ice