[InstCombine][WIP] Explicitly disable simplifyIntToPtrRoundTripCast for vectors.

[craig.topper]

Summary

This code compares getPointerTypeSizeInBits and getTypeSizeInBits.
getPointerTypeSizeInBits contains a call to getScalarType while
getTypeSizeInBits does not. This makes the code incorrect for vectors.

Additionally, for scalable vectors getTypeSizeInBits returns a scalable
TypeSize but getPointerTypeSizeInBits always returns an unsigned
integer. I believe the comparison forces the scalable TypeSize to
be converted to unsigned which triggers a warning.

Fixes PR59480.

Still need to add a test.

[pirama]

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

376

Would the control flow be clearer with:

if (CastTy->isVectorTy())
  return nullptr;
if (DL.get...)

?

377

Is the >> a tab or misalignment?

[nikic]

Can't we just use getTypeSizeInBits() on both sides? ptrtoint/inttoptr can't change number of vector elements anyway.

[craig.topper]

Will post a new version with Nikita's suggestion.

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
static bool simplifyAssocCastAssoc(BinaryOperator *BinOp1,
   IC.replaceOperand(*BinOp1, 1, FoldedC);
   return true;
 }
 
 // Simplifies IntToPtr/PtrToInt RoundTrip Cast To BitCast.
 // inttoptr ( ptrtoint (x) ) --> x
 Value *InstCombinerImpl::simplifyIntToPtrRoundTripCast(Value *Val) {
   auto *IntToPtr = dyn_cast<IntToPtrInst>(Val);
-  if (IntToPtr && DL.getPointerTypeSizeInBits(IntToPtr->getDestTy()) ==
+  if (!IntToPtr)
+    return nullptr;
+  Type *CastTy = IntToPtr->getDestTy();
+  if (!CastTy->isVectorTy() && DL.getPointerTypeSizeInBits(CastTy) ==
                                    DL.getTypeSizeInBits(IntToPtr->getSrcTy())) {
     auto *PtrToInt = dyn_cast<PtrToIntInst>(IntToPtr->getOperand(0));
-    Type *CastTy = IntToPtr->getDestTy();
     if (PtrToInt &&
         CastTy->getPointerAddressSpace() ==
             PtrToInt->getSrcTy()->getPointerAddressSpace() &&
         DL.getPointerTypeSizeInBits(PtrToInt->getSrcTy()) ==
             DL.getTypeSizeInBits(PtrToInt->getDestTy())) {
       return CastInst::CreateBitOrPointerCast(PtrToInt->getOperand(0), CastTy,
                                               "", PtrToInt);
     }