[PATCH] D128755: [VPlan] Make sure optimizeInductions removes wide ind from scalar plan.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 440945.
fhahn marked 3 inline comments as done.
fhahn added a comment.

Address latest comments, thanks!

In D128755#3617144 <https://reviews.llvm.org/D128755#3617144>, @bmahjour wrote:

> could you please add the crashing IR from https://reviews.llvm.org/D123720 as an additional test? It still seems to crash with this patch!

Is it still crashing with this patch applied to current `main`? It needs b18141a8f29f638be0602aa6ffbfc2d434b0b74a <https://reviews.llvm.org/rGb18141a8f29f638be0602aa6ffbfc2d434b0b74a> as well.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D128755/new/

https://reviews.llvm.org/D128755

Files:
  llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
  llvm/test/Transforms/LoopVectorize/interleave-and-scalarize-only.ll


Index: llvm/test/Transforms/LoopVectorize/interleave-and-scalarize-only.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/interleave-and-scalarize-only.ll
+++ llvm/test/Transforms/LoopVectorize/interleave-and-scalarize-only.ll
@@ -168,3 +168,62 @@
 exit:
   ret void
 }
+
+; Make sure the widened induction gets replaced by scalar-steps for plans
+; including the scalar VF, if it is used in first-order recurrences.
+
+; DBG-LABEL: 'first_order_recurrence_using_induction'
+; DBG:      VPlan 'Initial VPlan for VF={1},UF>=1' {
+; DBG-NEXT: Live-in vp<%1> = vector-trip-count
+; DBG-EMPTY:
+; DBG-NEXT: vector.ph:
+; DBG-NEXT: Successor(s): vector loop
+; DBG-EMPTY:
+; DBG-NEXT: <x1> vector loop: {
+; DBG-NEXT:   vector.body:
+; DBG-NEXT:     EMIT vp<%2> = CANONICAL-INDUCTION
+; DBG-NEXT:     FIRST-ORDER-RECURRENCE-PHI ir<%for> = phi ir<0>, vp<%4>
+; DBG-NEXT:     vp<%4>    = SCALAR-STEPS vp<%2>, ir<0>, ir<1>
+; DBG-NEXT:     EMIT vp<%5> = first-order splice ir<%for> vp<%4>
+; DBG-NEXT:     CLONE store vp<%5>, ir<%dst>
+; DBG-NEXT:     EMIT vp<%7> = VF * UF +(nuw)  vp<%2>
+; DBG-NEXT:     EMIT branch-on-count  vp<%7> vp<%1>
+; DBG-NEXT:   No successors
+; DBG-NEXT: }
+; DBG-NEXT: Successor(s): middle.block
+; DBG-EMPTY:
+; DBG-NEXT: middle.block:
+; DBG-NEXT: No successors
+; DBG-NEXT: }
+
+define void @first_order_recurrence_using_induction(i32 %n, ptr %dst) {
+; CHECK-LABEL: @first_order_recurrence_using_induction(
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %vector.body ]
+; CHECK-NEXT:    [[VECTOR_RECUR:%.*]] = phi i32 [ 0, %vector.ph ], [ [[INDUCTION1:%.*]], %vector.body ]
+; CHECK-NEXT:    [[TMP3:%.*]] = trunc i64 [[INDEX]] to i32
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add i32 [[TMP3]], 0
+; CHECK-NEXT:    [[INDUCTION1]] = add i32 [[TMP3]], 1
+; CHECK-NEXT:    store i32 [[VECTOR_RECUR]], ptr [[DST:%.*]], align 4
+; CHECK-NEXT:    store i32 [[INDUCTION]], ptr [[DST]], align 4
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i64 [[INDEX_NEXT]], %n.vec
+; CHECK-NEXT:    br i1 [[TMP4]], label %middle.block, label %vector.body
+; CHECK:       middle.block:
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ],[ %iv.next, %loop ]
+  %for = phi i32 [ 0, %entry ], [ %iv.trunc, %loop ]
+  %iv.trunc = trunc i64 %iv to i32
+  store i32 %for, ptr %dst
+  %iv.next = add nuw nsw i64 %iv, 1
+  %iv.next.trunc = trunc i64 %iv.next to i32
+  %ec = icmp slt i32 %iv.next.trunc, %n
+  br i1 %ec, label %loop, label %exit
+
+exit:
+  ret void
+}
Index: llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -381,10 +381,13 @@
 void VPlanTransforms::optimizeInductions(VPlan &Plan, ScalarEvolution &SE) {
   SmallVector<VPRecipeBase *> ToRemove;
   VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock();
+  bool HasScalarVF = Plan.hasVF(ElementCount::getFixed(1));
   for (VPRecipeBase &Phi : HeaderVPBB->phis()) {
     auto *IV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi);
-    if (!IV ||
-        all_of(IV->users(), [IV](VPUser *U) { return !U->usesScalars(IV); }))
+    if (!IV)
+      continue;
+    if (!HasScalarVF &&
+        none_of(IV->users(), [IV](VPUser *U) { return U->usesScalars(IV); }))
       continue;
 
     const InductionDescriptor &ID = IV->getInductionDescriptor();
@@ -400,7 +403,7 @@
     // the list of users doesn't contain duplicates.
     SetVector<VPUser *> Users(IV->user_begin(), IV->user_end());
     for (VPUser *U : Users) {
-      if (!U->usesScalars(IV))
+      if (!HasScalarVF && !U->usesScalars(IV))
         continue;
       for (unsigned I = 0, E = U->getNumOperands(); I != E; I++) {
         if (U->getOperand(I) != IV)


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