[VPlan] Do not create VPWidenCall recipes for scalar vector factors.

[fhahn]

Summary

'Widen' recipe are only used when actual vector values are generated.
Fix tryToWidenCall to do not create VPWidenCallRecipes for scalar vector
factors.

This was exposed by D123720, because the widened recipes are considered
vector users.

[Ayal]

Looks good to me, adding a couple of nits.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

8331–8333

Early exit here as done in tryToWidenMemory's willWiden?

if (VF.isScalar())
  return false;

(Perhaps recipe creation for VF.isScalar() should be handled more systematically rather than individually by each try-to-widen/will-widen.)

llvm/test/Transforms/LoopVectorize/interleave-with-call.ll

15

nit: retain dumping of callee name as in call @llvm.smin.i32(...) rather than as an operand , ir<@llvm.smin.i32>?

[fhahn]

Thanks Ayal!

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

8331–8333

I added the early exit to willWiden to start with. We could add this as general check at the start of tryToWiden as follow up?

llvm/test/Transforms/LoopVectorize/interleave-with-call.ll

15

Thanks, I'll put up a separate patch for that!

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

VPWidenCallRecipe *VPRecipeBuilder::tryToWidenCall(CallInst *CI,
 
   Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
   if (ID && (ID == Intrinsic::assume || ID == Intrinsic::lifetime_end ||
              ID == Intrinsic::lifetime_start || ID == Intrinsic::sideeffect ||
              ID == Intrinsic::pseudoprobe ||
              ID == Intrinsic::experimental_noalias_scope_decl))
     return nullptr;
 
   auto willWiden = [&](ElementCount VF) -> bool {
+    if (VF.isScalar())
+       return false;
     Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
     // The following case may be scalarized depending on the VF.
     // The flag shows whether we use Intrinsic or a usual Call for vectorized
     // version of the instruction.
     // Is it beneficial to perform intrinsic call compared to lib call?
     bool NeedToScalarize = false;
     InstructionCost CallCost = CM.getVectorCallCost(CI, VF, NeedToScalarize);
     InstructionCost IntrinsicCost = ID ? CM.getVectorIntrinsicCost(CI, VF) : 0;

llvm/test/Transforms/LoopVectorize/AArch64/strict-fadd.ll

 ; CHECK-UNORDERED: [[LOAD:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD1:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD2:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD3:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD4:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD5:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD6:%.*]] = load float, float*
 ; CHECK-UNORDERED: [[LOAD7:%.*]] = load float, float*
-; CHECK-UNORDERED: [[FMULADD]] = call float @llvm.fmuladd.f32(float [[LOAD]], float [[LOAD4]], float [[VEC_PHI]])
-; CHECK-UNORDERED: [[FMULADD1]] = call float @llvm.fmuladd.f32(float [[LOAD1]], float [[LOAD5]], float [[VEC_PHI1]])
-; CHECK-UNORDERED: [[FMULADD2]] = call float @llvm.fmuladd.f32(float [[LOAD2]], float [[LOAD6]], float [[VEC_PHI2]])
-; CHECK-UNORDERED: [[FMULADD3]] = call float @llvm.fmuladd.f32(float [[LOAD3]], float [[LOAD7]], float [[VEC_PHI3]])
+; CHECK-UNORDERED: [[FMULADD]] = tail call float @llvm.fmuladd.f32(float [[LOAD]], float [[LOAD4]], float [[VEC_PHI]])
+; CHECK-UNORDERED: [[FMULADD1]] = tail call float @llvm.fmuladd.f32(float [[LOAD1]], float [[LOAD5]], float [[VEC_PHI1]])
+; CHECK-UNORDERED: [[FMULADD2]] = tail call float @llvm.fmuladd.f32(float [[LOAD2]], float [[LOAD6]], float [[VEC_PHI2]])
+; CHECK-UNORDERED: [[FMULADD3]] = tail call float @llvm.fmuladd.f32(float [[LOAD3]], float [[LOAD7]], float [[VEC_PHI3]])
 ; CHECK-UNORDERED-NOT: llvm.vector.reduce.fadd
 ; CHECK-UNORDERED: middle.block:
 ; CHECK-UNORDERED: [[BIN_RDX:%.*]] = fadd float [[FMULADD1]], [[FMULADD]]
 ; CHECK-UNORDERED: [[BIN_RDX1:%.*]] = fadd float [[FMULADD2]], [[BIN_RDX]]
 ; CHECK-UNORDERED: [[BIN_RDX2:%.*]] = fadd float [[FMULADD3]], [[BIN_RDX1]]
 ; CHECK-UNORDERED: scalar.ph:
 ; CHECK-UNORDERED: [[MERGE_RDX:%.*]] = phi float [ 0.000000e+00, %entry ], [ [[BIN_RDX2]], %middle.block ]
 ; CHECK-UNORDERED: for.body:

llvm/test/Transforms/LoopVectorize/interleave-with-call.ll

 ; REQUIRES: asserts
 
 ; RUN: opt -passes=loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -debug -S %s 2>&1 | FileCheck %s
 
 ; CHECK:      VPlan 'Initial VPlan for VF={1},UF>=1' {
 ; CHECK-NEXT: Live-in vp<[[VEC_TC:%.+]]> = vector-trip-count
 ; CHECK-EMPTY:
 ; CHECK-NEXT: vector.ph:
 ; CHECK-NEXT: Successor(s): vector loop
 ; CHECK-EMPTY:
 ; CHECK-NEXT: <x1> vector loop: {
 ; CHECK-NEXT:   vector.body:
 ; CHECK-NEXT:     EMIT vp<[[CAN_IV:%.+]]> = CANONICAL-INDUCTION
 ; CHECK-NEXT:     vp<[[IV_STEPS:%.]]>    = SCALAR-STEPS vp<[[CAN_IV]]>, ir<%start>, ir<1>
-; CHECK-NEXT:     WIDEN-CALL ir<%min> = call @llvm.smin.i32(vp<[[IV_STEPS]]>, ir<65535>)
+; CHECK-NEXT:     CLONE ir<%min> = call vp<[[IV_STEPS]]>, ir<65535>, ir<@llvm.smin.i32>
 ; CHECK-NEXT:     CLONE ir<%arrayidx> = getelementptr ir<%dst>, vp<[[IV_STEPS]]>
 ; CHECK-NEXT:     CLONE store ir<%min>, ir<%arrayidx>
 ; CHECK-NEXT:     EMIT vp<[[INC:%.+]]> = VF * UF +(nuw)  vp<[[CAN_IV]]>
 ; CHECK-NEXT:     EMIT branch-on-count  vp<[[INC]]> vp<[[VEC_TC]]>
 ; CHECK-NEXT:   No successors
 ; CHECK-NEXT: }
 ;
 define void @test(i32 %start, ptr %dst) {
 ; CHECK-LABEL: @test(
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %vector.body ]
 ; CHECK-NEXT:    [[OFFSET_IDX:%.*]] = add i32 %start, [[INDEX]]
 ; CHECK-NEXT:    [[INDUCTION:%.*]] = add i32 [[OFFSET_IDX]], 0
 ; CHECK-NEXT:    [[INDUCTION1:%.*]] = add i32 [[OFFSET_IDX]], 1
-; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.smin.i32(i32 [[INDUCTION]], i32 65535)
-; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.smin.i32(i32 [[INDUCTION1]], i32 65535)
+; CHECK-NEXT:    [[TMP1:%.*]] = tail call i32 @llvm.smin.i32(i32 [[INDUCTION]], i32 65535)
+; CHECK-NEXT:    [[TMP2:%.*]] = tail call i32 @llvm.smin.i32(i32 [[INDUCTION1]], i32 65535)
 ; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i32, ptr [[DST:%.*]], i32 [[INDUCTION]]
 ; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i32, ptr [[DST]], i32 [[INDUCTION1]]
 ; CHECK-NEXT:    store i32 [[TMP1]], ptr [[TMP3]], align 8
 ; CHECK-NEXT:    store i32 [[TMP2]], ptr [[TMP4]], align 8
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 2
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[INDEX_NEXT]], %n.vec
 ; CHECK-NEXT:    br i1 [[TMP5]], label %middle.block, label %vector.body
 ; CHECK:       middle.block: