[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

@@ -130,6 +130,24 @@ bool VPlanTransforms::tryToConvertVPInstructionsToVPRecipes(
   return true;
 }
 
+/// Return true if we do not know how to (mechanically) hoist or sink \p R out
+/// of a loop region.
+static bool cannotHoistOrSinkRecipe(const VPRecipeBase &R) {
+  // Assumes don't alias anything or throw; as long as they're guaranteed to
+  // execute, they're safe to hoist.
+  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.mayHaveSideEffects() || R.mayReadFromMemory() || R.isPhi())
+    return true;
+
+  // Allocas cannot be hoisted.
+  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;
@@ -1825,7 +1843,7 @@ sinkRecurrenceUsersAfterPrevious(VPFirstOrderRecurrencePHIRecipe *FOR,
         VPDT.properlyDominates(Previous, SinkCandidate))
       return true;
 
-    if (SinkCandidate->mayHaveSideEffects())
+    if (cannotHoistOrSinkRecipe(*SinkCandidate))
       return false;
 
     WorkList.push_back(SinkCandidate);
@@ -1865,7 +1883,7 @@ 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.
@@ -1912,11 +1930,6 @@ 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;
@@ -1928,7 +1941,7 @@ 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()) {
@@ -2143,24 +2156,6 @@ void VPlanTransforms::cse(VPlan &Plan) {
 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.
-  auto CannotHoistRecipe = [](VPRecipeBase &R) {
-    // Assumes don't alias anything or throw; as long as they're guaranteed to
-    // execute, they're safe to hoist.
-    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.mayHaveSideEffects() || R.mayReadFromMemory() || 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. Since the top-level blocks in the
@@ -2172,7 +2167,7 @@ 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 (any_of(R.operands(), [](VPValue *Op) {
             return !Op->isDefinedOutsideLoopRegions();

llvm/test/Transforms/LoopVectorize/first-order-recurrence-multiply-recurrences.ll

@@ -429,41 +429,18 @@ exit:
 define void @hoist_previous_value_and_operand_load(ptr %dst) {
 ; CHECK-LABEL: @hoist_previous_value_and_operand_load(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    br label [[VECTOR_PH:%.*]]
-; CHECK:       vector.ph:
-; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
-; CHECK:       vector.body:
-; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VECTOR_RECUR:%.*]] = phi <4 x i32> [ <i32 poison, i32 poison, i32 poison, i32 1>, [[VECTOR_PH]] ], [ [[BROADCAST_SPLAT:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VECTOR_RECUR1:%.*]] = phi <4 x i32> [ <i32 poison, i32 poison, i32 poison, i32 0>, [[VECTOR_PH]] ], [ [[TMP3:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[OFFSET_IDX:%.*]] = add i64 1, [[INDEX]]
-; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds i32, ptr [[DST:%.*]], i64 [[OFFSET_IDX]]
-; CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[DST]], align 4
-; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i32> poison, i32 [[TMP1]], i64 0
-; CHECK-NEXT:    [[BROADCAST_SPLAT]] = shufflevector <4 x i32> [[BROADCAST_SPLATINSERT]], <4 x i32> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <4 x i32> [[VECTOR_RECUR]], <4 x i32> [[BROADCAST_SPLAT]], <4 x i32> <i32 3, i32 4, i32 5, i32 6>
-; CHECK-NEXT:    [[TMP3]] = or <4 x i32> [[TMP2]], splat (i32 3)
-; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <4 x i32> [[VECTOR_RECUR1]], <4 x i32> [[TMP3]], <4 x i32> <i32 3, i32 4, i32 5, i32 6>
-; CHECK-NEXT:    store <4 x i32> [[TMP4]], ptr [[TMP0]], align 4
-; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
-; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i64 [[INDEX_NEXT]], 336
-; CHECK-NEXT:    br i1 [[TMP5]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP7:![0-9]+]]
-; CHECK:       middle.block:
-; CHECK-NEXT:    [[VECTOR_RECUR_EXTRACT:%.*]] = extractelement <4 x i32> [[TMP3]], i32 3
-; CHECK-NEXT:    br label [[SCALAR_PH:%.*]]
-; CHECK:       scalar.ph:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 337, [[SCALAR_PH]] ], [ [[ADD:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[FOR_1:%.*]] = phi i32 [ [[TMP1]], [[SCALAR_PH]] ], [ [[LOAD:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[FOR_2:%.*]] = phi i32 [ [[VECTOR_RECUR_EXTRACT]], [[SCALAR_PH]] ], [ [[OR:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 1, [[ENTRY:%.*]] ], [ [[ADD:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[FOR_1:%.*]] = phi i32 [ 1, [[ENTRY]] ], [ [[LOAD:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[FOR_2:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[OR:%.*]], [[LOOP]] ]
 ; CHECK-NEXT:    [[OR]] = or i32 [[FOR_1]], 3
 ; CHECK-NEXT:    [[ADD]] = add i64 [[IV]], 1
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i32, ptr [[DST]], i64 [[IV]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i32, ptr [[DST:%.*]], i64 [[IV]]
 ; CHECK-NEXT:    store i32 [[FOR_2]], ptr [[GEP]], align 4
 ; CHECK-NEXT:    [[ICMP:%.*]] = icmp ult i64 [[IV]], 337
 ; CHECK-NEXT:    [[LOAD]] = load i32, ptr [[DST]], align 4
-; CHECK-NEXT:    br i1 [[ICMP]], label [[LOOP]], label [[EXIT:%.*]], !llvm.loop [[LOOP8:![0-9]+]]
+; CHECK-NEXT:    br i1 [[ICMP]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;