Subzero: Improve the representation and handling of the FakeKill instruction.

src/IceInst.h

Index: src/IceInst.h
diff --git a/src/IceInst.h b/src/IceInst.h
index e6edb4c6d6f62d7a82fd1a81e30c3da198ddc3b6..7c96e3f9e9b4cd74e4162bca5303f05ae3350e30 100644
--- a/src/IceInst.h
+++ b/src/IceInst.h
@@ -801,6 +801,7 @@ public:
     return new (Func->allocateInst<InstFakeKill>())
         InstFakeKill(Func, KilledRegs, Linked);
   }
+  const VarList &getKilledRegs() const { return KilledRegs; }
   const Inst *getLinked() const { return Linked; }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
@@ -811,6 +812,7 @@ private:
   InstFakeKill(Cfg *Func, const VarList &KilledRegs, const Inst *Linked);
   ~InstFakeKill() override {}
 
+  const VarList &KilledRegs;
   // This instruction is ignored if Linked->isDeleted() is true.
   const Inst *Linked;
 };