[llvm] 3277f6c - [LV] Explicitly disable in-loop reductions for AnyOf and FindIV. nfc (#163541)

[via llvm-commits]

Author: Mel Chen
Date: 2025-11-14T09:14:07Z
New Revision: 3277f6caef110359046e32983fee37932b8f9ac2

URL: https://github.com/llvm/llvm-project/commit/3277f6caef110359046e32983fee37932b8f9ac2
DIFF: https://github.com/llvm/llvm-project/commit/3277f6caef110359046e32983fee37932b8f9ac2.diff

LOG: [LV] Explicitly disable in-loop reductions for AnyOf and FindIV. nfc (#163541)

Currently, in-loop reductions for AnyOf and FindIV are not supported.
They were implicitly blocked. This happened because
RecurrenceDescriptor::getReductionOpChain could not detect their
recurrence chain. The reason is that RecurrenceDescriptor::getOpcode was
set to Instruction::Or, but the recurrence chains of AnyOf and FindIV do
not actually contain an Instruction::Or.

This patch explicitly disables in-loop reductions for AnyOf and FindIV
instead of relying on getReductionOpChain to implicitly prevent them.

Added: 
    

Modified: 
    llvm/lib/Analysis/IVDescriptors.cpp
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index 9f8ac6e8e2e0b..641850b46bbd8 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -1220,11 +1220,6 @@ unsigned RecurrenceDescriptor::getOpcode(RecurKind Kind) {
     return Instruction::Add;
   case RecurKind::Mul:
     return Instruction::Mul;
-  case RecurKind::AnyOf:
-  case RecurKind::FindFirstIVSMin:
-  case RecurKind::FindFirstIVUMin:
-  case RecurKind::FindLastIVSMax:
-  case RecurKind::FindLastIVUMax:
   case RecurKind::Or:
     return Instruction::Or;
   case RecurKind::And:
@@ -1248,6 +1243,13 @@ unsigned RecurrenceDescriptor::getOpcode(RecurKind Kind) {
   case RecurKind::FMaximumNum:
   case RecurKind::FMinimumNum:
     return Instruction::FCmp;
+  case RecurKind::AnyOf:
+  case RecurKind::FindFirstIVSMin:
+  case RecurKind::FindFirstIVUMin:
+  case RecurKind::FindLastIVSMax:
+  case RecurKind::FindLastIVUMax:
+    // TODO: Set AnyOf and FindIV to Instruction::Select once in-loop reductions
+    // are supported.
   default:
     llvm_unreachable("Unknown recurrence operation");
   }

diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 9f0d6fcb237ef..58fcab40d5894 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6591,9 +6591,14 @@ void LoopVectorizationCostModel::collectInLoopReductions() {
     if (RdxDesc.getRecurrenceType() != Phi->getType())
       continue;
 
+    // In-loop AnyOf and FindIV reductions are not yet supported.
+    RecurKind Kind = RdxDesc.getRecurrenceKind();
+    if (RecurrenceDescriptor::isAnyOfRecurrenceKind(Kind) ||
+        RecurrenceDescriptor::isFindIVRecurrenceKind(Kind))
+      continue;
+
     // If the target would prefer this reduction to happen "in-loop", then we
     // want to record it as such.
-    RecurKind Kind = RdxDesc.getRecurrenceKind();
     if (!PreferInLoopReductions && !useOrderedReductions(RdxDesc) &&
         !TTI.preferInLoopReduction(Kind, Phi->getType()))
       continue;

diff  --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index e0e6990c56ec7..aa85bd435ee9e 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -821,10 +821,9 @@ Value *VPInstruction::generate(VPTransformState &State) {
     auto *OrigPhi = cast<PHINode>(PhiR->getUnderlyingValue());
     Value *ReducedPartRdx = State.get(getOperand(2));
     for (unsigned Idx = 3; Idx < getNumOperands(); ++Idx)
-      ReducedPartRdx = Builder.CreateBinOp(
-          (Instruction::BinaryOps)RecurrenceDescriptor::getOpcode(
-              RecurKind::AnyOf),
-          State.get(getOperand(Idx)), ReducedPartRdx, "bin.rdx");
+      ReducedPartRdx =
+          Builder.CreateBinOp(Instruction::Or, State.get(getOperand(Idx)),
+                              ReducedPartRdx, "bin.rdx");
     return createAnyOfReduction(Builder, ReducedPartRdx,
                                 State.get(getOperand(1), VPLane(0)), OrigPhi);
   }