[LV] Assert no DbgInfoIntrinsic calls are passed to widening (NFC).

[fhahn]

Summary

When building a VPlan, BasicBlock::instructionsWithoutDebug() is used to
iterate over the instructions in a block. This means that no recipes
should be created for debug info intrinsics already and we can turn the
early exit into an assertion.

[Ayal]

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

7246–7247

Perhaps worth moving here the TODO comment about handling debug intrinsics / representing them in VPlan.

[fhahn]

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

7246–7247

Excellent suggestion, thanks! I've added a TODO here in the commit.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

default:
     // This instruction is not vectorized by simple widening.
     LLVM_DEBUG(dbgs() << "LV: Found an unhandled instruction: " << I);
     llvm_unreachable("Unhandled instruction!");
   } // end of switch.
 }
 
 void InnerLoopVectorizer::widenCallInstruction(CallInst &I, VPUser &ArgOperands,
                                                VPTransformState &State) {
-  // Ignore dbg intrinsics.
-  // TODO: Debug intrinsics should be skipped/handled during VPlan construction
-  // rather than dropping them here.
-  if (isa<DbgInfoIntrinsic>(I))
-    return;
+  assert(!isa<DbgInfoIntrinsic>(I) &&
+         "DbgInfoIntrinsic should have been dropped during VPlan construction");
   setDebugLocFromInst(Builder, &I);
 
   Module *M = I.getParent()->getParent()->getParent();
   auto *CI = cast<CallInst>(&I);
 
   SmallVector<Type *, 4> Tys;
   for (Value *ArgOperand : CI->arg_operands())
     Tys.push_back(ToVectorTy(ArgOperand->getType(), VF));
for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO())) {
     // Relevant instructions from basic block BB will be grouped into VPRecipe
     // ingredients and fill a new VPBasicBlock.
     unsigned VPBBsForBB = 0;
     auto *FirstVPBBForBB = new VPBasicBlock(BB->getName());
     VPBlockUtils::insertBlockAfter(FirstVPBBForBB, VPBB);
     VPBB = FirstVPBBForBB;
     Builder.setInsertPoint(VPBB);
 
     // Introduce each ingredient into VPlan.
+    // TODO: Model and preserve debug instrinsics in VPlan.
     for (Instruction &I : BB->instructionsWithoutDebug()) {
       Instruction *Instr = &I;
 
       // First filter out irrelevant instructions, to ensure no recipes are
       // built for them.
       if (isa<BranchInst>(Instr) ||
           DeadInstructions.find(Instr) != DeadInstructions.end())
         continue;