[IR] Remove CastInst::isCastable since it is not used

It was removed back in 2013 (f63dfbb) by Matt Arsenault but then
reverted since DragonEgg used it, but that project is no longer
maintained.

Reviewed By: ldionne, dexonsmith

Differential Revision: https://reviews.llvm.org/D92571

Author: c-rhodes

llvm/include/llvm/IR/InstrTypes.h

@@ -599,12 +599,6 @@ class CastInst : public UnaryInstruction {
     BasicBlock *InsertAtEnd  ///< The block to insert the instruction into
   );
 
-  /// Check whether it is valid to call getCastOpcode for these types.
-  static bool isCastable(
-    Type *SrcTy, ///< The Type from which the value should be cast.
-    Type *DestTy ///< The Type to which the value should be cast.
-  );
-
   /// Check whether a bitcast between these types is valid
   static bool isBitCastable(
     Type *SrcTy, ///< The Type from which the value should be cast.

llvm/lib/IR/Instructions.cpp

@@ -3142,64 +3142,6 @@ CastInst *CastInst::CreateFPCast(Value *C, Type *Ty,
   return Create(opcode, C, Ty, Name, InsertAtEnd);
 }
 
-// Check whether it is valid to call getCastOpcode for these types.
-// This routine must be kept in sync with getCastOpcode.
-bool CastInst::isCastable(Type *SrcTy, Type *DestTy) {
-  if (!SrcTy->isFirstClassType() || !DestTy->isFirstClassType())
-    return false;
-
-  if (SrcTy == DestTy)
-    return true;
-
-  if (VectorType *SrcVecTy = dyn_cast<VectorType>(SrcTy))
-    if (VectorType *DestVecTy = dyn_cast<VectorType>(DestTy))
-      if (cast<FixedVectorType>(SrcVecTy)->getNumElements() ==
-          cast<FixedVectorType>(DestVecTy)->getNumElements()) {
-        // An element by element cast.  Valid if casting the elements is valid.
-        SrcTy = SrcVecTy->getElementType();
-        DestTy = DestVecTy->getElementType();
-      }
-
-  // Get the bit sizes, we'll need these
-  TypeSize SrcBits = SrcTy->getPrimitiveSizeInBits();   // 0 for ptr
-  TypeSize DestBits = DestTy->getPrimitiveSizeInBits(); // 0 for ptr
-
-  // Run through the possibilities ...
-  if (DestTy->isIntegerTy()) {               // Casting to integral
-    if (SrcTy->isIntegerTy())                // Casting from integral
-        return true;
-    if (SrcTy->isFloatingPointTy())   // Casting from floating pt
-      return true;
-    if (SrcTy->isVectorTy())          // Casting from vector
-      return DestBits == SrcBits;
-                                      // Casting from something else
-    return SrcTy->isPointerTy();
-  }
-  if (DestTy->isFloatingPointTy()) {  // Casting to floating pt
-    if (SrcTy->isIntegerTy())                // Casting from integral
-      return true;
-    if (SrcTy->isFloatingPointTy())   // Casting from floating pt
-      return true;
-    if (SrcTy->isVectorTy())          // Casting from vector
-      return DestBits == SrcBits;
-                                    // Casting from something else
-    return false;
-  }
-  if (DestTy->isVectorTy())         // Casting to vector
-    return DestBits == SrcBits;
-  if (DestTy->isPointerTy()) {        // Casting to pointer
-    if (SrcTy->isPointerTy())                // Casting from pointer
-      return true;
-    return SrcTy->isIntegerTy();             // Casting from integral
-  }
-  if (DestTy->isX86_MMXTy()) {
-    if (SrcTy->isVectorTy())
-      return DestBits == SrcBits;       // 64-bit vector to MMX
-    return false;
-  }                                    // Casting to something else
-  return false;
-}
-
 bool CastInst::isBitCastable(Type *SrcTy, Type *DestTy) {
   if (!SrcTy->isFirstClassType() || !DestTy->isFirstClassType())
     return false;
@@ -3261,7 +3203,6 @@ bool CastInst::isBitOrNoopPointerCastable(Type *SrcTy, Type *DestTy,
 //   castIsValid( getCastOpcode(Val, Ty), Val, Ty)
 // should not assert in castIsValid. In other words, this produces a "correct"
 // casting opcode for the arguments passed to it.
-// This routine must be kept in sync with isCastable.
 Instruction::CastOps
 CastInst::getCastOpcode(
   const Value *Src, bool SrcIsSigned, Type *DestTy, bool DestIsSigned) {

llvm/unittests/IR/InstructionsTest.cpp

@@ -229,11 +229,6 @@ TEST(InstructionsTest, CastInst) {
 
   const Constant *v2ptr32 = Constant::getNullValue(V2Int32PtrTy);
 
-  EXPECT_TRUE(CastInst::isCastable(V8x8Ty, X86MMXTy));
-  EXPECT_TRUE(CastInst::isCastable(X86MMXTy, V8x8Ty));
-  EXPECT_FALSE(CastInst::isCastable(Int64Ty, X86MMXTy));
-  EXPECT_TRUE(CastInst::isCastable(V8x64Ty, V8x8Ty));
-  EXPECT_TRUE(CastInst::isCastable(V8x8Ty, V8x64Ty));
   EXPECT_EQ(CastInst::Trunc, CastInst::getCastOpcode(c64, true, V8x8Ty, true));
   EXPECT_EQ(CastInst::SExt, CastInst::getCastOpcode(c8, true, V8x64Ty, true));
 
@@ -249,7 +244,6 @@ TEST(InstructionsTest, CastInst) {
   EXPECT_FALSE(CastInst::isBitCastable(V2Int32PtrTy, V2Int32PtrAS1Ty));
   EXPECT_FALSE(CastInst::isBitCastable(V2Int32PtrAS1Ty, V2Int32PtrTy));
   EXPECT_TRUE(CastInst::isBitCastable(V2Int32PtrAS1Ty, V2Int64PtrAS1Ty));
-  EXPECT_TRUE(CastInst::isCastable(V2Int32PtrAS1Ty, V2Int32PtrTy));
   EXPECT_EQ(CastInst::AddrSpaceCast, CastInst::getCastOpcode(v2ptr32, true,
                                                              V2Int32PtrAS1Ty,
                                                              true));