[SimplifyLibCalls] Drop redundant CreatePointerCast in optimizeSPrintFString

Given the transition into using opaque pointers we no longer need to
add casts to handle "mismatched pointer types" as all pointers types
involved now are the same.

Author: bjope

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -3103,9 +3103,6 @@ Value *LibCallSimplifier::optimizeSPrintFString(CallInst *CI,
       return ConstantInt::get(CI->getType(), SrcLen - 1);
     } else if (Value *V = emitStpCpy(Dest, CI->getArgOperand(2), B, TLI)) {
       // sprintf(dest, "%s", str) -> stpcpy(dest, str) - dest
-      // Handle mismatched pointer types (goes away with typeless pointers?).
-      V = B.CreatePointerCast(V, B.getInt8PtrTy());
-      Dest = B.CreatePointerCast(Dest, B.getInt8PtrTy());
       Value *PtrDiff = B.CreatePtrDiff(B.getInt8Ty(), V, Dest);
       return B.CreateIntCast(PtrDiff, CI->getType(), false);
     }