[VPlan] Assign custom opcodes to recipes not mapping to IR opcodes. (#162267)

We can perform CSE on recipes that do not directly map to Instruction opcodes. One example is VPVectorPointerRecipe. Currently this is handled by supporting them in ::canHandle, but currently that means that we return std::nullopt from getOpcodeOrIntrinsicID() for it. This currently only works, because the only case we return std::nullopt and perform CSE is VPVectorPointerRecipe. But that does not work if we support more such recipes, like VPPredInstPHIRecipe (#162110). To fix this, return a custom opcode from getOpcodeOrIntrinsicID for recipes like VPVectorPointerRecipe, using the VPDefID after all regular instruction opcodes. PR: #162267

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -1064,6 +1064,7 @@ class LLVM_ABI_FOR_TEST VPInstruction : public VPRecipeWithIRFlags,
  ResumeForEpilogue,
  /// Returns the value for vscale.
  VScale,
+ OpsEnd = VScale,
  };
 
  /// Returns true if this VPInstruction generates scalar values for all lanes.

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1991,6 +1991,13 @@ struct VPCSEDenseMapInfo : public DenseMapInfo<VPSingleDefRecipe *> {
  .Case<VPWidenIntrinsicRecipe>([](auto *I) {
  return std::make_pair(true, I->getVectorIntrinsicID());
  })
+ .Case<VPVectorPointerRecipe>([](auto *I) {
+ // For recipes that do not directly map to LLVM IR instructions,
+ // assign opcodes after the last VPInstruction opcode (which is also
+ // after the last IR Instruction opcode), based on the VPDefID.
+ return std::make_pair(false,
+ VPInstruction::OpsEnd + 1 + I->getVPDefID());
+ })
  .Default([](auto *) { return std::nullopt; });
  }
 
@@ -2014,11 +2021,8 @@ struct VPCSEDenseMapInfo : public DenseMapInfo<VPSingleDefRecipe *> {
  static bool canHandle(const VPSingleDefRecipe *Def) {
  // We can extend the list of handled recipes in the future,
  // provided we account for the data embedded in them while checking for
- // equality or hashing. We assign VPVectorEndPointerRecipe the GEP opcode,
- // as it is essentially a GEP with different semantics.
- auto C = isa<VPVectorPointerRecipe>(Def)
- ? std::make_pair(false, Instruction::GetElementPtr)
- : getOpcodeOrIntrinsicID(Def);
+ // equality or hashing.
+ auto C = getOpcodeOrIntrinsicID(Def);
 
  // The issue with (Insert|Extract)Value is that the index of the
  // insert/extract is not a proper operand in LLVM IR, and hence also not in
@@ -2057,6 +2061,8 @@ struct VPCSEDenseMapInfo : public DenseMapInfo<VPSingleDefRecipe *> {
  vputils::isSingleScalar(L) != vputils::isSingleScalar(R) ||
  !equal(L->operands(), R->operands()))
  return false;
+ assert(getOpcodeOrIntrinsicID(L) && getOpcodeOrIntrinsicID(R) &&
+ "must have valid opcode info for both recipes");
  if (auto *LFlags = dyn_cast<VPRecipeWithIRFlags>(L))
  if (LFlags->hasPredicate() &&
  LFlags->getPredicate() !=