Minor refactoring regarding Cast::isNoopCast(), NFC

[uabelho]

Summary

FastISel::hasTrivialKill() was the only user of the "IntPtrTy" version of
Cast::isNoopCast(). According to review comments in D37894 we could instead
use the "DataLayout" version of the method, and thus get rid of the
"IntPtrTy" versions of isNoopCast() completely.

With the above done, the remaining isNoopCast() could then be simplified
a bit more.

[arsenm]

LGTM

llvm/trunk/include/llvm/IR/InstrTypes.h

public:
   /// a no-op cast but is more stringent, preventing things like int->float,
   /// long->double, or int->ptr.
   /// @returns true iff the cast is lossless.
   /// @brief Determine if this is a lossless cast.
   bool isLosslessCast() const;
 
   /// A no-op cast is one that can be effected without changing any bits.
   /// It implies that the source and destination types are the same size. The
-  /// IntPtrTy argument is used to make accurate determinations for casts
+  /// DataLayout argument is to determine the pointer size when examining casts
   /// involving Integer and Pointer types. They are no-op casts if the integer
   /// is the same size as the pointer. However, pointer size varies with
-  /// platform. Generally, the result of DataLayout::getIntPtrType() should be
-  /// passed in. If that's not available, use Type::Int64Ty, which will make
-  /// the isNoopCast call conservative.
-  /// @brief Determine if the described cast is a no-op cast.
-  static bool isNoopCast(
-    Instruction::CastOps Opcode,  ///< Opcode of cast
-    Type *SrcTy,   ///< SrcTy of cast
-    Type *DstTy,   ///< DstTy of cast
-    Type *IntPtrTy ///< Integer type corresponding to Ptr types
-  );
-
+  /// platform.
   /// @brief Determine if the described cast is a no-op cast.
   static bool isNoopCast(
     Instruction::CastOps Opcode, ///< Opcode of cast
     Type *SrcTy,         ///< SrcTy of cast
     Type *DstTy,         ///< DstTy of cast
     const DataLayout &DL ///< DataLayout to get the Int Ptr type from.
   );
 
   /// @brief Determine if this cast is a no-op cast.
-  bool isNoopCast(
-    Type *IntPtrTy ///< Integer type corresponding to pointer
-  ) const;
-
-  /// @brief Determine if this cast is a no-op cast.
   ///
-  /// \param DL is the DataLayout to get the Int Ptr type from.
+  /// \param DL is the DataLayout to determine pointer size.
   bool isNoopCast(const DataLayout &DL) const;
 
   /// Determine how a pair of casts can be eliminated, if they can be at all.
   /// This is a helper function for both CastInst and ConstantExpr.
   /// @returns 0 if the CastInst pair can't be eliminated, otherwise
   /// returns Instruction::CastOps value for a cast that can replace
   /// the pair, casting SrcTy to DstTy.
   /// @brief Determine if a cast pair is eliminable

llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp

 bool FastISel::hasTrivialKill(const Value *V) {
   // Don't consider constants or arguments to have trivial kills.
   const Instruction *I = dyn_cast<Instruction>(V);
   if (!I)
     return false;
 
   // No-op casts are trivially coalesced by fast-isel.
   if (const auto *Cast = dyn_cast<CastInst>(I))
-    if (Cast->isNoopCast(DL.getIntPtrType(Cast->getContext())) &&
-        !hasTrivialKill(Cast->getOperand(0)))
+    if (Cast->isNoopCast(DL) && !hasTrivialKill(Cast->getOperand(0)))
       return false;
 
   // Even the value might have only one use in the LLVM IR, it is possible that
   // FastISel might fold the use into another instruction and now there is more
   // than one use at the Machine Instruction level.
   unsigned Reg = lookUpRegForValue(V);
   if (Reg && !MRI.use_empty(Reg))
     return false;

llvm/trunk/lib/IR/Instructions.cpp

 /// example, the following are all no-op casts:
 /// # bitcast i32* %x to i8*
 /// # bitcast <2 x i32> %x to <4 x i16> 
 /// # ptrtoint i32* %x to i32     ; on 32-bit plaforms only
 /// @brief Determine if the described cast is a no-op.
 bool CastInst::isNoopCast(Instruction::CastOps Opcode,
                           Type *SrcTy,
                           Type *DestTy,
-                          Type *IntPtrTy) {
+                          const DataLayout &DL) {
   switch (Opcode) {
     default: llvm_unreachable("Invalid CastOp");
     case Instruction::Trunc:
     case Instruction::ZExt:
     case Instruction::SExt: 
     case Instruction::FPTrunc:
     case Instruction::FPExt:
     case Instruction::UIToFP:
     case Instruction::SIToFP:
     case Instruction::FPToUI:
     case Instruction::FPToSI:
     case Instruction::AddrSpaceCast:
       // TODO: Target informations may give a more accurate answer here.
       return false;
     case Instruction::BitCast:
       return true;  // BitCast never modifies bits.
     case Instruction::PtrToInt:
-      return IntPtrTy->getScalarSizeInBits() ==
+      return DL.getIntPtrType(SrcTy)->getScalarSizeInBits() ==
              DestTy->getScalarSizeInBits();
     case Instruction::IntToPtr:
-      return IntPtrTy->getScalarSizeInBits() ==
+      return DL.getIntPtrType(DestTy)->getScalarSizeInBits() ==
              SrcTy->getScalarSizeInBits();
   }
 }
 
-/// @brief Determine if a cast is a no-op.
-bool CastInst::isNoopCast(Instruction::CastOps Opcode,
-                          Type *SrcTy,
-                          Type *DestTy,
-                          const DataLayout &DL) {
-  Type *PtrOpTy = nullptr;
-  if (Opcode == Instruction::PtrToInt)
-    PtrOpTy = SrcTy;
-  else if (Opcode == Instruction::IntToPtr)
-    PtrOpTy = DestTy;
-
-  Type *IntPtrTy = PtrOpTy ? DL.getIntPtrType(PtrOpTy) :
-                             DL.getIntPtrType(SrcTy->getContext(), 0);
-
-  return isNoopCast(Opcode, SrcTy, DestTy, IntPtrTy);
-}
-
-/// @brief Determine if a cast is a no-op.
-bool CastInst::isNoopCast(Type *IntPtrTy) const {
-  return isNoopCast(getOpcode(), getOperand(0)->getType(), getType(), IntPtrTy);
-}
-
 bool CastInst::isNoopCast(const DataLayout &DL) const {
   return isNoopCast(getOpcode(), getOperand(0)->getType(), getType(), DL);
 }
 
 /// This function determines if a pair of casts can be eliminated and what
 /// opcode should be used in the elimination. This assumes that there are two
 /// instructions like this:
 /// *  %F = firstOpcode SrcTy %x to MidTy