[LV] Support sinking recipe in replicate region after another region.

This patch handles sinking a replicate region after another replicate
region. In that case, we can connect the sink region after the target
region. This properly handles the case for which an assertion has been
added in 337d765.

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=34842.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D103514

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -9192,52 +9192,60 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
     auto GetReplicateRegion = [](VPRecipeBase *R) -> VPRegionBlock * {
       auto *Region =
           dyn_cast_or_null<VPRegionBlock>(R->getParent()->getParent());
-      if (Region && Region->isReplicator())
+      if (Region && Region->isReplicator()) {
+        assert(Region->getNumSuccessors() == 1 &&
+               Region->getNumPredecessors() == 1 && "Expected SESE region!");
+        assert(R->getParent()->size() == 1 &&
+               "A recipe in an original replicator region must be the only "
+               "recipe in its block");
         return Region;
+      }
       return nullptr;
     };
-
-    // If the target is in a replication region, make sure to move Sink to the
-    // block after it, not into the replication region itself.
-    if (auto *TargetRegion = GetReplicateRegion(Target)) {
-      assert(TargetRegion->getNumSuccessors() == 1 && "Expected SESE region!");
-      assert(!GetReplicateRegion(Sink) &&
-             "cannot sink a region into another region yet");
-      VPBasicBlock *NextBlock =
-          cast<VPBasicBlock>(TargetRegion->getSuccessors().front());
-      Sink->moveBefore(*NextBlock, NextBlock->getFirstNonPhi());
-      continue;
-    }
-
+    auto *TargetRegion = GetReplicateRegion(Target);
     auto *SinkRegion = GetReplicateRegion(Sink);
-    // Unless the sink source is in a replicate region, sink the recipe
-    // directly.
     if (!SinkRegion) {
-      Sink->moveAfter(Target);
+      // If the sink source is not a replicate region, sink the recipe directly.
+      if (TargetRegion) {
+        // The target is in a replication region, make sure to move Sink to
+        // the block after it, not into the replication region itself.
+        VPBasicBlock *NextBlock =
+            cast<VPBasicBlock>(TargetRegion->getSuccessors().front());
+        Sink->moveBefore(*NextBlock, NextBlock->getFirstNonPhi());
+      } else
+        Sink->moveAfter(Target);
       continue;
     }
 
-    // If the sink source is in a replicate region, we need to move the whole
-    // replicate region, which should only contain a single recipe in the main
-    // block.
-    assert(Sink->getParent()->size() == 1 &&
-           "parent must be a replicator with a single recipe");
-    auto *SplitBlock =
-        Target->getParent()->splitAt(std::next(Target->getIterator()));
-
-    auto *Pred = SinkRegion->getSinglePredecessor();
-    auto *Succ = SinkRegion->getSingleSuccessor();
-    VPBlockUtils::disconnectBlocks(Pred, SinkRegion);
-    VPBlockUtils::disconnectBlocks(SinkRegion, Succ);
-    VPBlockUtils::connectBlocks(Pred, Succ);
-
-    auto *SplitPred = SplitBlock->getSinglePredecessor();
-
-    VPBlockUtils::disconnectBlocks(SplitPred, SplitBlock);
-    VPBlockUtils::connectBlocks(SplitPred, SinkRegion);
-    VPBlockUtils::connectBlocks(SinkRegion, SplitBlock);
-    if (VPBB == SplitPred)
-      VPBB = SplitBlock;
+    // The sink source is in a replicate region. Unhook the region from the CFG.
+    auto *SinkPred = SinkRegion->getSinglePredecessor();
+    auto *SinkSucc = SinkRegion->getSingleSuccessor();
+    VPBlockUtils::disconnectBlocks(SinkPred, SinkRegion);
+    VPBlockUtils::disconnectBlocks(SinkRegion, SinkSucc);
+    VPBlockUtils::connectBlocks(SinkPred, SinkSucc);
+
+    if (TargetRegion) {
+      // The target recipe is also in a replicate region, move the sink region
+      // after the target region.
+      auto *TargetSucc = TargetRegion->getSingleSuccessor();
+      VPBlockUtils::disconnectBlocks(TargetRegion, TargetSucc);
+      VPBlockUtils::connectBlocks(TargetRegion, SinkRegion);
+      VPBlockUtils::connectBlocks(SinkRegion, TargetSucc);
+    } else {
+      // The sink source is in a replicate region, we need to move the whole
+      // replicate region, which should only contain a single recipe in the main
+      // block.
+      auto *SplitBlock =
+          Target->getParent()->splitAt(std::next(Target->getIterator()));
+
+      auto *SplitPred = SplitBlock->getSinglePredecessor();
+
+      VPBlockUtils::disconnectBlocks(SplitPred, SplitBlock);
+      VPBlockUtils::connectBlocks(SplitPred, SinkRegion);
+      VPBlockUtils::connectBlocks(SinkRegion, SplitBlock);
+      if (VPBB == SplitPred)
+        VPBB = SplitBlock;
+    }
   }
 
   // Interleave memory: for each Interleave Group we marked earlier as relevant

llvm/test/Transforms/LoopVectorize/first-order-recurrence-sink-replicate-region.ll

@@ -1,5 +1,5 @@
 ; REQUIRES: asserts
-; RUN: opt < %s -loop-vectorize -force-vector-width=2 -force-vector-interleave=1 -debug-only=loop-vectorize 2>&1 | FileCheck %s
+; RUN: opt < %s -loop-vectorize -force-vector-width=2 -force-vector-interleave=1 -disable-output -debug-only=loop-vectorize 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
 
@@ -306,3 +306,92 @@ loop:
 exit:
   ret void
 }
+
+; Test case that requires sinking a recipe in a replicate region after another replicate region.
+define void @sink_replicate_region_after_replicate_region(i32* %ptr, i32 %x, i8 %y) optsize {
+; CHECK-LABEL: sink_replicate_region_after_replicate_region
+; CHECK:      VPlan 'Initial VPlan for VF={2},UF>=1' {
+; CHECK-NEXT: loop:
+; CHECK-NEXT:   WIDEN-PHI %recur = phi 0, %recur.next
+; CHECK-NEXT:   WIDEN-INDUCTION %iv = phi 0, %iv.next
+; CHECK-NEXT:   EMIT vp<%3> = icmp ule ir<%iv> vp<%0>
+; CHECK-NEXT: Successor(s): loop.0
+; CHECK-EMPTY:
+; CHECK-NEXT: loop.0:
+; CHECK-NEXT: Successor(s): loop.1
+; CHECK-EMPTY:
+; CHECK-NEXT:  loop.1:
+; CHECK-NEXT:   WIDEN ir<%recur.next> = sext ir<%y>
+; CHECK-NEXT: Successor(s): pred.srem
+; CHECK-EMPTY:
+; CHECK-NEXT: <xVFxUF> pred.srem: {
+; CHECK-NEXT:   pred.srem.entry:
+; CHECK-NEXT:     BRANCH-ON-MASK vp<%3>
+; CHECK-NEXT:   Successor(s): pred.srem.if, pred.srem.continue
+; CHECK-NEXT:   CondBit: vp<%3> (loop)
+; CHECK-EMPTY:
+; CHECK-NEXT:   pred.srem.if:
+; CHECK-NEXT:     REPLICATE ir<%rem> = srem ir<%recur>, ir<%x>
+; CHECK-NEXT:   Successor(s): pred.srem.continue
+; CHECK-EMPTY:
+; CHECK-NEXT:   pred.srem.continue:
+; CHECK-NEXT:     PHI-PREDICATED-INSTRUCTION vp<%6> = ir<%rem>
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+
+; CHECK:      <xVFxUF> pred.sdiv: {
+; CHECK-NEXT:  pred.sdiv.entry:
+; CHECK-NEXT:    BRANCH-ON-MASK vp<%3>
+; CHECK-NEXT:  Successor(s): pred.sdiv.if, pred.sdiv.continue
+; CHECK-NEXT:  CondBit: vp<%3> (loop)
+; CHECK-EMPTY:
+; CHECK-NEXT:       pred.sdiv.if:
+; CHECK-NEXT:    REPLICATE ir<%rem.div> = sdiv ir<20>, vp<%6>
+; CHECK-NEXT:  Successor(s): pred.sdiv.continue
+; CHECK-EMPTY:
+; CHECK-NEXT:       pred.sdiv.continue:
+; CHECK-NEXT:    PHI-PREDICATED-INSTRUCTION vp<%8> = ir<%rem.div>
+; CHECK-NEXT:  No successors
+; CHECK-NEXT: }
+; CHECK-NEXT: Successor(s): loop.1.split
+; CHECK-EMPTY:
+; CHECK-NEXT:      loop.1.split:
+; CHECK-NEXT: Successor(s): pred.store
+; CHECK-EMPTY:
+; CHECK-NEXT:       <xVFxUF> pred.store: {
+; CHECK-NEXT:   pred.store.entry:
+; CHECK-NEXT:     BRANCH-ON-MASK vp<%3>
+; CHECK-NEXT:   Successor(s): pred.store.if, pred.store.continue
+; CHECK-NEXT:   CondBit: vp<%3> (loop)
+; CHECK-EMPTY:
+; CHECK-NEXT:   pred.store.if:
+; CHECK-NEXT:     REPLICATE ir<%gep> = getelementptr ir<%ptr>, ir<%iv>
+; CHECK-NEXT:     REPLICATE store vp<%8>, ir<%gep>
+; CHECK-NEXT:   Successor(s): pred.store.continue
+; CHECK-EMPTY:
+; CHECK-NEXT:   pred.store.continue:
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+
+; CHECK:      loop.2:
+; CHECK-NEXT: No successors
+; CHECK-NEXT: }
+;
+entry:
+  br label %loop
+
+loop:                                             ; preds = %loop, %entry
+  %recur = phi i32 [ 0, %entry ], [ %recur.next, %loop ]
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+  %rem = srem i32 %recur, %x
+  %rem.div = sdiv i32 20, %rem
+  %recur.next = sext i8 %y to i32
+  %gep = getelementptr i32, i32* %ptr, i32 %iv
+  store i32 %rem.div, i32* %gep
+  %iv.next = add nsw i32 %iv, 1
+  %C = icmp sgt i32 %iv.next, %recur.next
+  br i1 %C, label %exit, label %loop
+
+exit:                                             ; preds = %loop
+  ret void
+}