Subzero: Completely remove tracking of stack pointer live range.

src/IceRegAlloc.cpp

 //===- subzero/src/IceRegAlloc.cpp - Linear-scan implementation -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 160 matching lines @@
   // Iterate across all instructions and record the begin and end of
   // the live range for each variable that is pre-colored or infinite
   // weight.
   std::vector<InstNumberT> LRBegin(Vars.size(), Inst::NumberSentinel);
   std::vector<InstNumberT> LREnd(Vars.size(), Inst::NumberSentinel);
   for (CfgNode *Node : Func->getNodes()) {
     for (Inst &Inst : Node->getInsts()) {
       if (Inst.isDeleted())
         continue;
       if (const Variable *Var = Inst.getDest()) {
-        if (Var->hasReg() || Var->getWeight().isInf()) {
+        if (!Var->getIgnoreLiveness() &&
+            (Var->hasReg() || Var->getWeight().isInf())) {
           if (LRBegin[Var->getIndex()] == Inst::NumberSentinel) {
             LRBegin[Var->getIndex()] = Inst.getNumber();
             ++NumVars;
           }
         }
       }
       for (SizeT I = 0; I < Inst.getSrcSize(); ++I) {
         Operand *Src = Inst.getSrc(I);
         SizeT NumVars = Src->getNumVars();
         for (SizeT J = 0; J < NumVars; ++J) {
           const Variable *Var = Src->getVar(J);
+          if (Var->getIgnoreLiveness())
+            continue;
           if (Var->hasReg() || Var->getWeight().isInf())
             LREnd[Var->getIndex()] = Inst.getNumber();
         }
       }
     }
   }
 
   Unhandled.reserve(NumVars);
   UnhandledPrecolored.reserve(NumVars);
   for (SizeT i = 0; i < Vars.size(); ++i) {
@@ skipping 644 matching lines @@
     Str << "\n";
   }
   Str << "++++++ Inactive:\n";
   for (const Variable *Item : Inactive) {
     dumpLiveRange(Item, Func);
     Str << "\n";
   }
 }
 
 } // end of namespace Ice