[NFC] Use Unknown instead of empty location in VPlanTransforms

The default values for DebugLocs in LoopVectorizer/VPlan were recently
updated from empty DebugLocs to DebugLoc::getUnknown, as part of the Debug
Loc Coverage Tracking work. However, there are some cases where we also pass
an explicit empty DebugLoc, in some cases intentionally, and in others as a
filler argument. This patch updates all of these to `getUnknown` for now,
until a more principled approach to debug location propagation in the
vectorizers is implemented.

Author: SLTozer

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -349,7 +349,7 @@ static VPRegionBlock *createReplicateRegion(VPReplicateRecipe *PredRecipe,
   auto *BlockInMask = PredRecipe->getMask();
   auto *MaskDef = BlockInMask->getDefiningRecipe();
   auto *BOMRecipe = new VPBranchOnMaskRecipe(
-      BlockInMask, MaskDef ? MaskDef->getDebugLoc() : DebugLoc());
+      BlockInMask, MaskDef ? MaskDef->getDebugLoc() : DebugLoc::getUnknown());
   auto *Entry =
       Plan.createVPBasicBlock(Twine(RegionName) + ".entry", BOMRecipe);
 
@@ -864,8 +864,8 @@ static VPValue *optimizeLatchExitInductionUser(
     Type *StepTy = TypeInfo.inferScalarType(Step);
     auto *Zero = Plan.getOrAddLiveIn(ConstantInt::get(StepTy, 0));
     return B.createPtrAdd(EndValue,
-                          B.createNaryOp(Instruction::Sub, {Zero, Step}), {},
-                          "ind.escape");
+                          B.createNaryOp(Instruction::Sub, {Zero, Step}),
+                          DebugLoc::getUnknown(), "ind.escape");
   }
   if (ScalarTy->isFloatingPointTy()) {
     const auto &ID = WideIV->getInductionDescriptor();
@@ -2307,7 +2307,8 @@ static VPActiveLaneMaskPHIRecipe *addVPLaneMaskPhiAndUpdateExitBranch(
 
   // Now create the ActiveLaneMaskPhi recipe in the main loop using the
   // preheader ActiveLaneMask instruction.
-  auto *LaneMaskPhi = new VPActiveLaneMaskPHIRecipe(EntryALM, DebugLoc());
+  auto *LaneMaskPhi =
+      new VPActiveLaneMaskPHIRecipe(EntryALM, DebugLoc::getUnknown());
   LaneMaskPhi->insertAfter(CanonicalIVPHI);
 
   // Create the active lane mask for the next iteration of the loop before the
@@ -2534,11 +2535,11 @@ static void transformRecipestoEVLRecipes(VPlan &Plan, VPValue &EVL) {
     VPBuilder Builder(LoopRegion->getPreheaderVPBB());
     MaxEVL = Builder.createScalarZExtOrTrunc(
         MaxEVL, Type::getInt32Ty(Plan.getContext()),
-        TypeInfo.inferScalarType(MaxEVL), DebugLoc());
+        TypeInfo.inferScalarType(MaxEVL), DebugLoc::getUnknown());
 
     Builder.setInsertPoint(Header, Header->getFirstNonPhi());
-    VPValue *PrevEVL =
-        Builder.createScalarPhi({MaxEVL, &EVL}, DebugLoc(), "prev.evl");
+    VPValue *PrevEVL = Builder.createScalarPhi(
+        {MaxEVL, &EVL}, DebugLoc::getUnknown(), "prev.evl");
 
     for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
              vp_depth_first_deep(Plan.getVectorLoopRegion()->getEntry()))) {
@@ -2668,7 +2669,7 @@ void VPlanTransforms::addExplicitVectorLength(
   VPValue *StartV = CanonicalIVPHI->getStartValue();
 
   // Create the ExplicitVectorLengthPhi recipe in the main loop.
-  auto *EVLPhi = new VPEVLBasedIVPHIRecipe(StartV, DebugLoc());
+  auto *EVLPhi = new VPEVLBasedIVPHIRecipe(StartV, DebugLoc::getUnknown());
   EVLPhi->insertAfter(CanonicalIVPHI);
   VPBuilder Builder(Header, Header->getFirstNonPhi());
   // Create the AVL (application vector length), starting from TC -> 0 in steps
@@ -2682,10 +2683,11 @@ void VPlanTransforms::addExplicitVectorLength(
     VPValue *AVLSafe =
         Plan.getOrAddLiveIn(ConstantInt::get(CanIVTy, *MaxSafeElements));
     VPValue *Cmp = Builder.createICmp(ICmpInst::ICMP_ULT, AVL, AVLSafe);
-    AVL = Builder.createSelect(Cmp, AVL, AVLSafe, DebugLoc(), "safe_avl");
+    AVL = Builder.createSelect(Cmp, AVL, AVLSafe, DebugLoc::getUnknown(),
+                               "safe_avl");
   }
   auto *VPEVL = Builder.createNaryOp(VPInstruction::ExplicitVectorLength, AVL,
-                                     DebugLoc());
+                                     DebugLoc::getUnknown());
 
   auto *CanonicalIVIncrement =
       cast<VPInstruction>(CanonicalIVPHI->getBackedgeValue());
@@ -3112,8 +3114,8 @@ expandVPWidenIntOrFpInduction(VPWidenIntOrFpInductionRecipe *WidenIVR,
   VPValue *SplatStep = Builder.createNaryOp(VPInstruction::Broadcast, Step);
 
   Init = Builder.createNaryOp(MulOp, {Init, SplatStep}, Flags);
-  Init =
-      Builder.createNaryOp(AddOp, {SplatStart, Init}, Flags, {}, "induction");
+  Init = Builder.createNaryOp(AddOp, {SplatStart, Init}, Flags,
+                              DebugLoc::getUnknown(), "induction");
 
   // Create the widened phi of the vector IV.
   auto *WidePHI = new VPWidenPHIRecipe(WidenIVR->getPHINode(), nullptr,