Introduction of improved switch 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.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 49 matching lines @@
     Ret,
     Select,
     Store,
     Switch,
     Assign,       // not part of LLVM/PNaCl bitcode
     BundleLock,   // not part of LLVM/PNaCl bitcode
     BundleUnlock, // not part of LLVM/PNaCl bitcode
     FakeDef,      // not part of LLVM/PNaCl bitcode
     FakeUse,      // not part of LLVM/PNaCl bitcode
     FakeKill,     // not part of LLVM/PNaCl bitcode
+    JumpTable,    // not part of LLVM/PNaCl bitcode
     Target        // target-specific low-level ICE
                   // Anything >= Target is an InstTarget subclass.
                   // Note that the value-spaces are shared across targets.
                   // To avoid confusion over the definition of shared values,
                   // an object specific to one target should never be passed
                   // to a different target.
   };
   InstKind getKind() const { return Kind; }
 
   InstNumberT getNumber() const { return Number; }
@@ skipping 21 matching lines @@
   Operand *getSrc(SizeT I) const {
     assert(I < getSrcSize());
     return Srcs[I];
   }
 
   bool isLastUse(const Operand *Src) const;
   void spliceLivenessInfo(Inst *OrigInst, Inst *SpliceAssn);
 
   /// Returns a list of out-edges corresponding to a terminator
   /// instruction, which is the last instruction of the block.
+  /// The list must not contain duplicates.
   virtual NodeList getTerminatorEdges() const {
     // All valid terminator instructions override this method.  For
     // the default implementation, we assert in case some CfgNode
     // is constructed without a terminator instruction at the end.
     llvm_unreachable(
         "getTerminatorEdges() called on a non-terminator instruction");
     return NodeList();
   }
   virtual bool isUnconditionalBranch() const { return false; }
   /// If the instruction is a branch-type instruction with OldNode as a
   /// target, repoint it to NewNode and return true, otherwise return
-  /// false.  Only repoint one instance, even if the instruction has
-  /// multiple instances of OldNode as a target.
-  virtual bool repointEdge(CfgNode *OldNode, CfgNode *NewNode) {
+  /// false. Repoint all instances of OldNode as a target.
+  virtual bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) {
     (void)OldNode;
     (void)NewNode;
     return false;
   }
 
   virtual bool isSimpleAssign() const { return false; }
 
   void livenessLightweight(Cfg *Func, LivenessBV &Live);
   /// Calculates liveness for this instruction.  Returns true if this
   /// instruction is (tentatively) still live and should be retained,
@@ skipping 210 matching lines @@
     return getSrc(0);
   }
   CfgNode *getTargetTrue() const { return TargetTrue; }
   CfgNode *getTargetFalse() const { return TargetFalse; }
   CfgNode *getTargetUnconditional() const {
     assert(isUnconditional());
     return getTargetFalse();
   }
   NodeList getTerminatorEdges() const override;
   bool isUnconditionalBranch() const override { return isUnconditional(); }
-  bool repointEdge(CfgNode *OldNode, CfgNode *NewNode) override;
+  bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) override;
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Inst) { return Inst->getKind() == Br; }
 
 private:
   /// Conditional branch
   InstBr(Cfg *Func, Operand *Source, CfgNode *TargetTrue, CfgNode *TargetFalse);
   /// Unconditional branch
   InstBr(Cfg *Func, CfgNode *Target);
 
   CfgNode *TargetFalse; /// Doubles as unconditional branch target
@@ skipping 354 matching lines @@
   uint64_t getValue(SizeT I) const {
     assert(I < NumCases);
     return Values[I];
   }
   CfgNode *getLabel(SizeT I) const {
     assert(I < NumCases);
     return Labels[I];
   }
   void addBranch(SizeT CaseIndex, uint64_t Value, CfgNode *Label);
   NodeList getTerminatorEdges() const override;
-  bool repointEdge(CfgNode *OldNode, CfgNode *NewNode) override;
+  bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) override;
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Inst) { return Inst->getKind() == Switch; }
 
 private:
   InstSwitch(Cfg *Func, SizeT NumCases, Operand *Source, CfgNode *LabelDefault);
   void destroy(Cfg *Func) override {
     Func->deallocateArrayOf<uint64_t>(Values);
     Func->deallocateArrayOf<CfgNode *>(Labels);
     Inst::destroy(Func);
   }
@@ skipping 151 matching lines @@
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Inst) { return Inst->getKind() == FakeKill; }
 
 private:
   InstFakeKill(Cfg *Func, const Inst *Linked);
 
   /// This instruction is ignored if Linked->isDeleted() is true.
   const Inst *Linked;
 };
 
+/// JumpTable instruction. This represents a jump table that will be
+/// stored in the .rodata section. This is used to track and repoint
+/// the target CfgNodes which may change, for example due to
+/// splitting for phi lowering.
+class InstJumpTable : public InstHighLevel {
+  InstJumpTable() = delete;
+  InstJumpTable(const InstJumpTable &) = delete;
+  InstJumpTable &operator=(const InstJumpTable &) = delete;
+
+public:
+  static InstJumpTable *create(Cfg *Func, SizeT NumTargets, CfgNode *Default) {
+    return new (Func->allocate<InstJumpTable>())
+        InstJumpTable(Func, NumTargets, Default);
+  }
+  void emit(const Cfg *Func) const override;
+  void emitIAS(const Cfg *Func) const override;
+  void addTarget(SizeT TargetIndex, CfgNode *Target) {
+    assert(TargetIndex < NumTargets);
+    Targets[TargetIndex] = Target;
+  }
+  bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) override;
+  IceString getName(const Cfg *Func) const;
+  void dump(const Cfg *Func) const override;
+  static bool classof(const Inst *Inst) { return Inst->getKind() == JumpTable; }
+
+private:
+  InstJumpTable(Cfg *Func, SizeT NumTargets, CfgNode *Default);
+  void destroy(Cfg *Func) override {
+    Func->deallocateArrayOf<CfgNode *>(Targets);
+    Inst::destroy(Func);
+  }
+
+  const SizeT LabelNumber;
+  const SizeT NumTargets;
+  CfgNode **Targets;
+};
+
 /// The Target instruction is the base class for all target-specific
 /// instructions.
 class InstTarget : public Inst {
   InstTarget() = delete;
   InstTarget(const InstTarget &) = delete;
   InstTarget &operator=(const InstTarget &) = delete;
 
 public:
   uint32_t getEmitInstCount() const override { return 1; }
   void dump(const Cfg *Func) const override;
@@ skipping 25 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