Introduction of improved switch lowering.

src/IceTargetLoweringX86Base.h

 //===- subzero/src/IceTargetLoweringX86Base.h - x86 lowering ----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// This file declares the TargetLoweringX86 template class, which
 /// implements the TargetLowering base interface for the x86
 /// architecture.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICETARGETLOWERINGX86BASE_H
 #define SUBZERO_SRC_ICETARGETLOWERINGX86BASE_H
 
 #include "IceDefs.h"
 #include "IceInst.h"
+#include "IceSwitchLowering.h"
 #include "IceTargetLowering.h"
 
 #include <type_traits>
 #include <unordered_map>
 
 namespace Ice {
 namespace X86Internal {
 
 template <class MachineTraits> class BoolFolding;
 
@@ skipping 91 matching lines @@
   SizeT getFrameOrStackReg() const override {
     return IsEbpBasedFrame ? Traits::RegisterSet::Reg_ebp
                            : Traits::RegisterSet::Reg_esp;
   }
   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;
   }
 
+  SizeT getMinJumpTableSize() const override { return 4; }
+
   void emitVariable(const Variable *Var) const override;
 
   const char *getConstantPrefix() const final { return "$"; }
   void emit(const ConstantUndef *C) const final;
   void emit(const ConstantInteger32 *C) const final;
   void emit(const ConstantInteger64 *C) const final;
   void emit(const ConstantFloat *C) const final;
   void emit(const ConstantDouble *C) const final;
 
   void lowerArguments() override;
@@ skipping 53 matching lines @@
   void lowerAtomicCmpxchg(Variable *DestPrev, Operand *Ptr, Operand *Expected,
                           Operand *Desired);
   /// Attempt a more optimized lowering of cmpxchg. Returns true if optimized.
   bool tryOptimizedCmpxchgCmpBr(Variable *DestPrev, Operand *Ptr,
                                 Operand *Expected, Operand *Desired);
   void lowerAtomicRMW(Variable *Dest, uint32_t Operation, Operand *Ptr,
                       Operand *Val);
   void lowerCountZeros(bool Cttz, Type Ty, Variable *Dest, Operand *FirstVal,
                        Operand *SecondVal);
 
+  /// Check the comparison is in [Min,Max]. If not in the range, above will be
+  /// set, if in the range below equal will be set. The index into the range is

[jvoung (off chromium), 2015/07/15 18:32:01]

For "above will be set" and "below equal will be..." I think it would be good to
clarify that you mean the x86 flags register (due to insert cmp instructions).

[ascull, 2015/07/16 19:38:45]

Done.

+  /// returned.
+  Operand *lowerCmpRange(Operand *Comparison, uint64_t Min, uint64_t Max);
+  /// Lowering of a cluster of switch cases. If the case is not matched control
+  /// will pass to the default label provided. If the default label is nullptr
+  /// then control will fall through to the next instruction.
+  void lowerCaseCluster(const CaseCluster &Case, Operand *Src0,
+                        CfgNode *DefaultLabel=nullptr);
+
   typedef void (TargetX86Base::*LowerBinOp)(Variable *, Operand *);
   void expandAtomicRMWAsCmpxchg(LowerBinOp op_lo, LowerBinOp op_hi,
                                 Variable *Dest, Operand *Ptr, Operand *Val);
 
   void eliminateNextVectorSextInstruction(Variable *SignExtendedResult);
 
   void scalarizeArithmetic(InstArithmetic::OpKind K, Variable *Dest,
                            Operand *Src0, Operand *Src1);
 
   /// Operand legalization helpers.  To deal with address mode
@@ skipping 397 matching lines @@
 private:
   ~TargetX86Base() override {}
   BoolFolding FoldingInfo;
 };
 } // end of namespace X86Internal
 } // end of namespace Ice
 
 #include "IceTargetLoweringX86BaseImpl.h"
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX86BASE_H