[VPlan] Set and use debug location for VPPredInstPHIRecipe.

Update the recipe it always set its debug location and use it during IR
generation.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -2839,12 +2839,12 @@ class VPPredInstPHIRecipe : public VPSingleDefRecipe {
 public:
   /// Construct a VPPredInstPHIRecipe given \p PredInst whose value needs a phi
   /// nodes after merging back from a Branch-on-Mask.
-  VPPredInstPHIRecipe(VPValue *PredV)
-      : VPSingleDefRecipe(VPDef::VPPredInstPHISC, PredV) {}
+  VPPredInstPHIRecipe(VPValue *PredV, DebugLoc DL)
+      : VPSingleDefRecipe(VPDef::VPPredInstPHISC, PredV, DL) {}
   ~VPPredInstPHIRecipe() override = default;
 
   VPPredInstPHIRecipe *clone() override {
-    return new VPPredInstPHIRecipe(getOperand(0));
+    return new VPPredInstPHIRecipe(getOperand(0), getDebugLoc());
   }
 
   VP_CLASSOF_IMPL(VPDef::VPPredInstPHISC)

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2392,6 +2392,7 @@ InstructionCost VPBranchOnMaskRecipe::computeCost(ElementCount VF,
 }
 
 void VPPredInstPHIRecipe::execute(VPTransformState &State) {
+  State.setDebugLocFrom(getDebugLoc());
   assert(State.Lane && "Predicated instruction PHI works per instance.");
   Instruction *ScalarPredInst =
       cast<Instruction>(State.get(getOperand(0), *State.Lane));

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -322,7 +322,8 @@ static VPRegionBlock *createReplicateRegion(VPReplicateRecipe *PredRecipe,
 
   VPPredInstPHIRecipe *PHIRecipe = nullptr;
   if (PredRecipe->getNumUsers() != 0) {
-    PHIRecipe = new VPPredInstPHIRecipe(RecipeWithoutMask);
+    PHIRecipe = new VPPredInstPHIRecipe(RecipeWithoutMask,
+                                        RecipeWithoutMask->getDebugLoc());
     PredRecipe->replaceAllUsesWith(PHIRecipe);
     PHIRecipe->setOperand(0, RecipeWithoutMask);
   }

llvm/test/Transforms/LoopVectorize/preserve-dbg-loc-and-loop-metadata.ll

@@ -1,6 +1,6 @@
-; RUN: opt < %s -passes=loop-vectorize -force-vector-width=4 -S 2>&1 | FileCheck %s
-; RUN: opt < %s -passes=debugify,loop-vectorize -force-vector-width=4 -S | FileCheck %s -check-prefix DEBUGLOC
-; RUN: opt < %s -passes=debugify,loop-vectorize -force-vector-width=4 -S --try-experimental-debuginfo-iterators | FileCheck %s -check-prefix DEBUGLOC
+; RUN: opt < %s -passes=loop-vectorize -force-vector-width=4 -force-widen-divrem-via-safe-divisor=0 -S 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=debugify,loop-vectorize -force-vector-width=4 -force-widen-divrem-via-safe-divisor=0 -S | FileCheck %s -check-prefix DEBUGLOC
+; RUN: opt < %s -passes=debugify,loop-vectorize -force-vector-width=4 -force-widen-divrem-via-safe-divisor=0 -S --try-experimental-debuginfo-iterators | FileCheck %s -check-prefix DEBUGLOC
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; This test makes sure we don't duplicate the loop vectorizer's metadata
@@ -54,6 +54,37 @@ exit:
   ret void
 }
 
+define void @predicated_phi_dbg(i64 %n, ptr %x) {
+; DEBUGLOC-LABEL: define void @predicated_phi_dbg(
+; DEBUGLOC: pred.udiv.continue{{.+}}:
+; DEBUGLOC-NEXT:   = phi <4 x i64> {{.+}}, !dbg [[PREDPHILOC:![0-9]+]]
+;
+; DEBUGLOC: for.body:
+; DEBUGLOC:   %tmp4 = udiv i64 %n, %i, !dbg [[PREDPHILOC]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i64 [ 0, %entry ], [ %i.next, %for.inc ]
+  %cmp = icmp ult i64 %i, 5
+  br i1 %cmp, label %if.then, label %for.inc
+
+if.then:
+  %tmp4 = udiv i64 %n, %i
+  br label %for.inc
+
+for.inc:
+  %d = phi i64 [ 0, %for.body ], [ %tmp4, %if.then ]
+  %idx = getelementptr i64, ptr %x, i64 %i
+  store i64 %d, ptr %idx
+  %i.next = add nuw nsw i64 %i, 1
+  %cond = icmp slt i64 %i.next, %n
+  br i1 %cond, label %for.body, label %for.end
+
+for.end:
+  ret void
+}
 
 !0 = !{!0, !1}
 !1 = !{!"llvm.loop.vectorize.width", i32 4}

llvm/unittests/Transforms/Vectorize/VPlanTest.cpp

@@ -1287,7 +1287,7 @@ TEST(VPRecipeTest, MayHaveSideEffectsAndMayReadWriteMemory) {
   }
   {
     VPValue Op1;
-    VPPredInstPHIRecipe Recipe(&Op1);
+    VPPredInstPHIRecipe Recipe(&Op1, {});
     EXPECT_FALSE(Recipe.mayHaveSideEffects());
     EXPECT_FALSE(Recipe.mayReadFromMemory());
     EXPECT_FALSE(Recipe.mayWriteToMemory());