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

src/IceTargetLoweringX8632.cpp

Index: src/IceTargetLoweringX8632.cpp
diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index fec2d625f544eff323a05acacd436868da414501..49375a61ae122495f85974c97eeef28c4c38765c 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -2521,7 +2521,11 @@ 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