Subzero: Initial implementation of multithreaded translation.

src/IceTargetLoweringX8632.h

 //===- subzero/src/IceTargetLoweringX8632.h - x86-32 lowering ---*- 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 TargetLoweringX8632 class, which
@@ skipping 38 matching lines @@
   }
   size_t typeWidthInBytesOnStack(Type Ty) const override {
     // Round up to the next multiple of 4 bytes.  In particular, i1,
     // i8, and i16 are rounded up to 4 bytes.
     return (typeWidthInBytes(Ty) + 3) & ~3;
   }
   void emitVariable(const Variable *Var) const override;
   void lowerArguments() override;
   void addProlog(CfgNode *Node) override;
   void addEpilog(CfgNode *Node) override;
-  void emitConstants() const override;
+  static void emitConstants(GlobalContext *Ctx);

[JF, 2015/01/22 20:50:56]

Why not keep this as override, and implement per target?

I wouldn't go the static route, I'd instead do static polymorphism through
templates (which is easy to move towards from virtual functions).

[Jim Stichnoth, 2015/01/23 07:55:55]

The reason was explained in the CL description:

"TargetLowering::emitConstants() and related methods are changed to be static,
so that a valid TargetLowering object isn't required.  This is because the
TargetLowering object wants to hold a valid Cfg, and none really exists after
all functions are translated and the constant pool is ready for emission."

That is, emitConstants has nothing to do with a Cfg, and only needs to know the
GlobalContext in which the constant pool is stored.

Not sure why I didn't think of this before, but the existing
TargetGlobalInitLowering abstract class, and its target-specific concrete class,
is the perfect place for this.  I changed the name to TargetGlobalLowering to
reflect the more general functionality.

   SizeT makeNextLabelNumber() { return NextLabelNumber++; }
   // Ensure that a 64-bit Variable has been split into 2 32-bit
   // Variables, creating them if necessary.  This is needed for all
   // I64 operations, and it is needed for pushing F64 arguments for
   // function calls using the 32-bit push instruction (though the
   // latter could be done by directly writing to the stack).
   void split64(Variable *Var);
   void finishArgumentLowering(Variable *Arg, Variable *FramePtr,
                               size_t BasicFrameOffset, size_t &InArgsSizeBytes);
   Operand *loOperand(Operand *Operand);
@@ skipping 410 matching lines @@
   size_t SpillAreaSizeBytes;
   llvm::SmallBitVector TypeToRegisterSet[IceType_NUM];
   llvm::SmallBitVector ScratchRegs;
   llvm::SmallBitVector RegsUsed;
   SizeT NextLabelNumber;
   VarList PhysicalRegisters[IceType_NUM];
   static IceString RegNames[];
 
 private:
   ~TargetX8632() override {}
-  template <typename T> void emitConstantPool() const;
+  template <typename T> static void emitConstantPool(GlobalContext *Ctx);
 };
 
 class TargetGlobalInitX8632 : public TargetGlobalInitLowering {
   TargetGlobalInitX8632(const TargetGlobalInitX8632 &) = delete;
   TargetGlobalInitX8632 &operator=(const TargetGlobalInitX8632 &) = delete;
 
 public:
   static TargetGlobalInitLowering *create(GlobalContext *Ctx) {
     return new TargetGlobalInitX8632(Ctx);
   }
 
   virtual void lower(const VariableDeclaration &Var) final;
 
 protected:
   TargetGlobalInitX8632(GlobalContext *Ctx);
 
 private:
   ~TargetGlobalInitX8632() override {}
 };
 
 template <> void ConstantInteger32::emit(GlobalContext *Ctx) const;
 template <> void ConstantInteger64::emit(GlobalContext *Ctx) const;
 template <> void ConstantFloat::emit(GlobalContext *Ctx) const;
 template <> void ConstantDouble::emit(GlobalContext *Ctx) const;
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX8632_H