[NFC][DebugInfo] Use iterators for insertion at some final callsites

These are the callsites that have materialised in the last three weeks
since I last built with deprecation warnings.

llvm/examples/IRTransforms/SimplifyCFG.cpp

@@ -286,7 +286,7 @@ static bool mergeIntoSinglePredecessor_v1(Function &F) {
     }
     // Move all instructions from BB to Pred.
     for (Instruction &I : make_early_inc_range(BB))
-      I.moveBefore(Pred->getTerminator());
+      I.moveBefore(Pred->getTerminator()->getIterator());
 
     // Remove the Pred's terminator (which jumped to BB). BB's terminator
     // will become Pred's terminator.
@@ -337,7 +337,7 @@ static bool mergeIntoSinglePredecessor_v2(Function &F, DominatorTree &DT) {
     }
     // Move all instructions from BB to Pred.
     for (Instruction &I : make_early_inc_range(BB))
-      I.moveBefore(Pred->getTerminator());
+      I.moveBefore(Pred->getTerminator()->getIterator());
 
     // Remove the Pred's terminator (which jumped to BB). BB's terminator
     // will become Pred's terminator.

llvm/lib/Analysis/Loads.cpp

@@ -361,7 +361,7 @@ bool llvm::isDereferenceableAndAlignedInLoop(
   } else
     return false;
 
-  Instruction *HeaderFirstNonPHI = L->getHeader()->getFirstNonPHI();
+  Instruction *HeaderFirstNonPHI = &*L->getHeader()->getFirstNonPHIIt();
   return isDereferenceableAndAlignedPointer(Base, Alignment, AccessSize, DL,
                                             HeaderFirstNonPHI, AC, &DT);
 }

llvm/lib/Target/SPIRV/SPIRVRegularizer.cpp

@@ -83,7 +83,7 @@ void SPIRVRegularizer::runLowerConstExpr(Function &F) {
       LLVM_DEBUG(dbgs() << "[lowerConstantExpressions] " << *CE);
       auto ReplInst = CE->getAsInstruction();
       auto InsPoint = II->getParent() == &*FBegin ? II : &FBegin->back();
-      ReplInst->insertBefore(InsPoint);
+      ReplInst->insertBefore(InsPoint->getIterator());
       LLVM_DEBUG(dbgs() << " -> " << *ReplInst << '\n');
       std::vector<Instruction *> Users;
       // Do not replace use during iteration of use. Do it in another loop.
@@ -97,7 +97,7 @@ void SPIRVRegularizer::runLowerConstExpr(Function &F) {
       for (auto &User : Users) {
         if (ReplInst->getParent() == User->getParent() &&
             User->comesBefore(ReplInst))
-          ReplInst->moveBefore(User);
+          ReplInst->moveBefore(User->getIterator());
         User->replaceUsesOfWith(CE, ReplInst);
       }
       return ReplInst;

llvm/lib/Target/SPIRV/SPIRVStructurizer.cpp

@@ -683,7 +683,7 @@ class SPIRVStructurizer : public FunctionPass {
               });
 
     for (Instruction *I : MergeInstructions) {
-      I->moveBefore(InsertionPoint);
+      I->moveBefore(InsertionPoint->getIterator());
       InsertionPoint = I;
     }
 

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -2044,7 +2044,7 @@ convertFSqrtDivIntoFMul(CallInst *CI, Instruction *X,
   // instructions in R2 and get the most common fpmath metadata and fast-math
   // flags on it.
   auto *FSqrt = cast<CallInst>(CI->clone());
-  FSqrt->insertBefore(CI);
+  FSqrt->insertBefore(CI->getIterator());
   auto *R2FPMathMDNode = (*R2.begin())->getMetadata(LLVMContext::MD_fpmath);
   FastMathFlags R2FMF = (*R2.begin())->getFastMathFlags(); // Common FMF
   for (Instruction *I : R2) {

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -10301,8 +10301,8 @@ preparePlanForEpilogueVectorLoop(VPlan &Plan, Loop *L,
         // value. This ensures correctness when the start value might not be
         // less than the minimum value of a monotonically increasing induction
         // variable.
-        IRBuilder<> Builder(
+        BasicBlock *ResumeBB = cast<Instruction>(ResumeV)->getParent();
-            cast<Instruction>(ResumeV)->getParent()->getFirstNonPHI());
+        IRBuilder<> Builder(ResumeBB, ResumeBB->getFirstNonPHIIt());
         Value *Cmp =
             Builder.CreateICmpEQ(ResumeV, RdxDesc.getRecurrenceStartValue());
         ResumeV =