Subzero: Fold icmp into br/select lowering.

src/IceInst.h

 //===- subzero/src/IceInst.h - High-level instructions ----------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the Inst class and its target-independent
@@ skipping 63 matching lines @@
   void renumber(Cfg *Func);
   enum {
     NumberDeleted = -1,
     NumberSentinel = 0,
     NumberInitial = 2,
     NumberExtended = NumberInitial - 1
   };
 
   bool isDeleted() const { return Deleted; }
   void setDeleted() { Deleted = true; }
+  void setDead(bool Value = true) { Dead = Value; }
   void deleteIfDead();
 
   bool hasSideEffects() const { return HasSideEffects; }
 
   bool isDestNonKillable() const { return IsDestNonKillable; }
   void setDestNonKillable() { IsDestNonKillable = true; }
 
   Variable *getDest() const { return Dest; }
 
   SizeT getSrcSize() const { return NumSrcs; }
@@ skipping 77 matching lines @@
   void resetLastUses() { LiveRangesEnded = 0; }
   // The destroy() method lets the instruction cleanly release any
   // memory that was allocated via the Cfg's allocator.
   virtual void destroy(Cfg *Func) { Func->deallocateArrayOf<Operand *>(Srcs); }
 
   const InstKind Kind;
   // Number is the instruction number for describing live ranges.
   InstNumberT Number;
   // Deleted means irrevocably deleted.
   bool Deleted;
-  // Dead means pending deletion after liveness analysis converges.
+  // Dead means one of two things depending on context: (1) pending
+  // deletion after liveness analysis converges, or (2) marked for
+  // deletion during lowering due to a folded bool operation.
   bool Dead;
   // HasSideEffects means the instruction is something like a function
   // call or a volatile load that can't be removed even if its Dest
   // variable is not live.
   bool HasSideEffects;
   // IsDestNonKillable means that liveness analysis shouldn't consider
   // this instruction to kill the Dest variable.  This is used when
   // lowering produces two assignments to the same variable.
   bool IsDestNonKillable;
 
@@ skipping 748 matching lines @@
   static void noteHead(Ice::Inst *, Ice::Inst *) {}
   void deleteNode(Ice::Inst *) {}
 
 private:
   mutable ilist_half_node<Ice::Inst> Sentinel;
 };
 
 } // end of namespace llvm
 
 #endif // SUBZERO_SRC_ICEINST_H