[VPlan] Introduce cannotHoistOrSinkRecipe

Factor out common code to determine legality of hoisting and sinking. In
the case of the additonal use-sites, functional changes, if any, would
amount to esoteric bugs being fixed.

Author: artagnon

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -70,6 +70,7 @@ bool VPRecipeBase::mayWriteToMemory() const {
     return cast<VPWidenIntrinsicRecipe>(this)->mayWriteToMemory();
   case VPCanonicalIVPHISC:
   case VPBranchOnMaskSC:
+  case VPDerivedIVSC:
   case VPFirstOrderRecurrencePHISC:
   case VPReductionPHISC:
   case VPScalarIVStepsSC:
@@ -86,6 +87,7 @@ bool VPRecipeBase::mayWriteToMemory() const {
   case VPWidenLoadEVLSC:
   case VPWidenLoadSC:
   case VPWidenPHISC:
+  case VPWidenPointerInductionSC:
   case VPWidenSC:
   case VPWidenSelectSC: {
     const Instruction *I =
@@ -119,6 +121,7 @@ bool VPRecipeBase::mayReadFromMemory() const {
   case VPWidenIntrinsicSC:
     return cast<VPWidenIntrinsicRecipe>(this)->mayReadFromMemory();
   case VPBranchOnMaskSC:
+  case VPDerivedIVSC:
   case VPFirstOrderRecurrencePHISC:
   case VPPredInstPHISC:
   case VPScalarIVStepsSC:
@@ -134,6 +137,7 @@ bool VPRecipeBase::mayReadFromMemory() const {
   case VPWidenGEPSC:
   case VPWidenIntOrFpInductionSC:
   case VPWidenPHISC:
+  case VPWidenPointerInductionSC:
   case VPWidenSC:
   case VPWidenSelectSC: {
     const Instruction *I =

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -131,6 +131,24 @@ bool VPlanTransforms::tryToConvertVPInstructionsToVPRecipes(
   return true;
 }
 
+// Return true if we do not know how to (mechanically) hoist or sink a given
+// recipe out of a loop region. Does not address legality concerns such as
+// aliasing or speculation safety.
+static bool cannotHoistOrSinkRecipe(const VPRecipeBase &R) {
+  // Assumes don't alias anything or throw.
+  if (match(&R, m_Intrinsic<Intrinsic::assume>()))
+    return false;
+
+  // TODO: Relax checks in the future, e.g. we could also hoist or sink reads,
+  // if their memory location is not modified in the vector loop.
+  if (R.mayReadOrWriteMemory() || R.isPhi())
+    return true;
+
+  // Allocas cannot be hoisted or sunk.
+  auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
+  return RepR && RepR->getOpcode() == Instruction::Alloca;
+}
+
 static bool sinkScalarOperands(VPlan &Plan) {
   auto Iter = vp_depth_first_deep(Plan.getEntry());
   bool Changed = false;
@@ -1765,7 +1783,7 @@ sinkRecurrenceUsersAfterPrevious(VPFirstOrderRecurrencePHIRecipe *FOR,
         VPDT.properlyDominates(Previous, SinkCandidate))
       return true;
 
-    if (SinkCandidate->mayHaveSideEffects())
+    if (cannotHoistOrSinkRecipe(*SinkCandidate))
       return false;
 
     WorkList.push_back(SinkCandidate);
@@ -1805,7 +1823,7 @@ sinkRecurrenceUsersAfterPrevious(VPFirstOrderRecurrencePHIRecipe *FOR,
 static bool hoistPreviousBeforeFORUsers(VPFirstOrderRecurrencePHIRecipe *FOR,
                                         VPRecipeBase *Previous,
                                         VPDominatorTree &VPDT) {
-  if (Previous->mayHaveSideEffects() || Previous->mayReadFromMemory())
+  if (cannotHoistOrSinkRecipe(*Previous))
     return false;
 
   // Collect recipes that need hoisting.
@@ -1852,11 +1870,6 @@ static bool hoistPreviousBeforeFORUsers(VPFirstOrderRecurrencePHIRecipe *FOR,
       return nullptr;
     return HoistCandidate;
   };
-  auto CanHoist = [&](VPRecipeBase *HoistCandidate) {
-    // Avoid hoisting candidates with side-effects, as we do not yet analyze
-    // associated dependencies.
-    return !HoistCandidate->mayHaveSideEffects();
-  };
 
   if (!NeedsHoisting(Previous->getVPSingleValue()))
     return true;
@@ -1868,7 +1881,7 @@ static bool hoistPreviousBeforeFORUsers(VPFirstOrderRecurrencePHIRecipe *FOR,
     VPRecipeBase *Current = HoistCandidates[I];
     assert(Current->getNumDefinedValues() == 1 &&
            "only recipes with a single defined value expected");
-    if (!CanHoist(Current))
+    if (cannotHoistOrSinkRecipe(*Current))
       return false;
 
     for (VPValue *Op : Current->operands()) {
@@ -2102,24 +2115,6 @@ static bool isSafeToSpeculativelyExecute(VPRecipeBase *R) {
 static void licm(VPlan &Plan) {
   VPBasicBlock *Preheader = Plan.getVectorPreheader();
 
-  // Return true if we do not know how to (mechanically) hoist a given recipe
-  // out of a loop region. Does not address legality concerns such as aliasing
-  // or speculation safety.
-  auto CannotHoistRecipe = [](VPRecipeBase &R) {
-    // Assumes don't alias anything or throw.
-    if (match(&R, m_Intrinsic<Intrinsic::assume>()))
-      return false;
-
-    // TODO: Relax checks in the future, e.g. we could also hoist reads, if
-    // their memory location is not modified in the vector loop.
-    if (R.mayReadOrWriteMemory() || R.isPhi())
-      return true;
-
-    // Allocas cannot be hoisted.
-    auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
-    return RepR && RepR->getOpcode() == Instruction::Alloca;
-  };
-
   // Hoist any loop invariant recipes from the vector loop region to the
   // preheader. Preform a shallow traversal of the vector loop region, to
   // exclude recipes in replicate regions.
@@ -2128,7 +2123,7 @@ static void licm(VPlan &Plan) {
   for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
            vp_depth_first_shallow(LoopRegion->getEntry()))) {
     for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
-      if (CannotHoistRecipe(R))
+      if (cannotHoistOrSinkRecipe(R))
         continue;
       if ((!GuaranteedToExecute && !isSafeToSpeculativelyExecute(&R)) ||
           any_of(R.operands(), [](VPValue *Op) {