[NFC][DebugInfo] Use iterator moveBefore at many call-sites (#123583)

As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNonPHI and similar feed into
instruction insertion positions. Call-sites where that's necessary were
updated a year ago; but to ensure some type safety however, we'd like to
have all calls to moveBefore use iterators.

This patch adds a (guaranteed dereferenceable) iterator-taking
moveBefore, and changes a bunch of call-sites where it's obviously safe
to change to use it by just calling getIterator() on an instruction
pointer. A follow-up patch will contain less-obviously-safe changes.

We'll eventually deprecate and remove the instruction-pointer
insertBefore, but not before adding concise documentation of what
considerations are needed (very few).

1 files changed, 16 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 7106e53..7e9d705 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -1264,7 +1264,7 @@ simplifyRelocatesOffABase(GCRelocateInst *RelocatedBase,
     if (auto *RI = dyn_cast<GCRelocateInst>(R))
       if (RI->getStatepoint() == RelocatedBase->getStatepoint())
         if (RI->getBasePtrIndex() == RelocatedBase->getBasePtrIndex()) {
-          RelocatedBase->moveBefore(RI);
+          RelocatedBase->moveBefore(RI->getIterator());
           MadeChange = true;
           break;
         }
@@ -2690,7 +2690,7 @@ bool CodeGenPrepare::optimizeCallInst(CallInst *CI, ModifyDT &ModifiedDT) {
           ExtVal->getParent() == CI->getParent())
         return false;
       // Sink a zext feeding stlxr/stxr before it, so it can be folded into it.
-      ExtVal->moveBefore(CI);
+      ExtVal->moveBefore(CI->getIterator());
       // Mark this instruction as "inserted by CGP", so that other
       // optimizations don't touch it.
       InsertedInsts.insert(ExtVal);
@@ -3036,7 +3036,7 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB,
     for (auto *CI : CallInsts) {
       for (auto const *FakeUse : FakeUses) {
         auto *ClonedInst = FakeUse->clone();
-        ClonedInst->insertBefore(CI);
+        ClonedInst->insertBefore(CI->getIterator());
       }
     }
     BB->eraseFromParent();
@@ -7552,9 +7552,9 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
   // Sink expensive instructions into the conditional blocks to avoid executing
   // them speculatively.
   for (Instruction *I : TrueInstrs)
-    I->moveBefore(TrueBranch);
+    I->moveBefore(TrueBranch->getIterator());
   for (Instruction *I : FalseInstrs)
-    I->moveBefore(FalseBranch);
+    I->moveBefore(FalseBranch->getIterator());
 
   // If we did not create a new block for one of the 'true' or 'false' paths
   // of the condition, it means that side of the branch goes to the end block
@@ -7682,7 +7682,7 @@ bool CodeGenPrepare::tryToSinkFreeOperands(Instruction *I) {
     NewInstructions[UI] = NI;
     MaybeDead.insert(UI);
     LLVM_DEBUG(dbgs() << "Sinking " << *UI << " to user " << *I << "\n");
-    NI->insertBefore(InsertPoint);
+    NI->insertBefore(InsertPoint->getIterator());
     InsertPoint = NI;
     InsertedInsts.insert(NI);
 
@@ -7744,7 +7744,7 @@ bool CodeGenPrepare::optimizeSwitchType(SwitchInst *SI) {
   }
 
   auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
-  ExtInst->insertBefore(SI);
+  ExtInst->insertBefore(SI->getIterator());
   ExtInst->setDebugLoc(SI->getDebugLoc());
   SI->setCondition(ExtInst);
   for (auto Case : SI->cases()) {
@@ -8556,7 +8556,7 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI,
         match(UI, m_Shr(m_Specific(X), m_SpecificInt(CmpC.logBase2())))) {
       IRBuilder<> Builder(Branch);
       if (UI->getParent() != Branch->getParent())
-        UI->moveBefore(Branch);
+        UI->moveBefore(Branch->getIterator());
       UI->dropPoisonGeneratingFlags();
       Value *NewCmp = Builder.CreateCmp(ICmpInst::ICMP_EQ, UI,
                                         ConstantInt::get(UI->getType(), 0));
@@ -8570,7 +8570,7 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI,
          match(UI, m_Sub(m_Specific(X), m_SpecificInt(CmpC))))) {
       IRBuilder<> Builder(Branch);
       if (UI->getParent() != Branch->getParent())
-        UI->moveBefore(Branch);
+        UI->moveBefore(Branch->getIterator());
       UI->dropPoisonGeneratingFlags();
       Value *NewCmp = Builder.CreateCmp(Cmp->getPredicate(), UI,
                                         ConstantInt::get(UI->getType(), 0));
@@ -8890,21 +8890,21 @@ bool CodeGenPrepare::fixupDbgVariableRecord(DbgVariableRecord &DVR) {
   return AnyChange;
 }
 
-static void DbgInserterHelper(DbgValueInst *DVI, Instruction *VI) {
+static void DbgInserterHelper(DbgValueInst *DVI, BasicBlock::iterator VI) {
   DVI->removeFromParent();
   if (isa<PHINode>(VI))
-    DVI->insertBefore(&*VI->getParent()->getFirstInsertionPt());
+    DVI->insertBefore(VI->getParent()->getFirstInsertionPt());
   else
     DVI->insertAfter(VI);
 }
 
-static void DbgInserterHelper(DbgVariableRecord *DVR, Instruction *VI) {
+static void DbgInserterHelper(DbgVariableRecord *DVR, BasicBlock::iterator VI) {
   DVR->removeFromParent();
   BasicBlock *VIBB = VI->getParent();
   if (isa<PHINode>(VI))
     VIBB->insertDbgRecordBefore(DVR, VIBB->getFirstInsertionPt());
   else
-    VIBB->insertDbgRecordAfter(DVR, VI);
+    VIBB->insertDbgRecordAfter(DVR, &*VI);
 }
 
 // A llvm.dbg.value may be using a value before its definition, due to
@@ -8954,7 +8954,7 @@ bool CodeGenPrepare::placeDbgValues(Function &F) {
 
       LLVM_DEBUG(dbgs() << "Moving Debug Value before :\n"
                         << *DbgItem << ' ' << *VI);
-      DbgInserterHelper(DbgItem, VI);
+      DbgInserterHelper(DbgItem, VI->getIterator());
       MadeChange = true;
       ++NumDbgValueMoved;
     }
@@ -8997,7 +8997,7 @@ bool CodeGenPrepare::placePseudoProbes(Function &F) {
     I++;
     while (I != Block.end()) {
       if (auto *II = dyn_cast<PseudoProbeInst>(I++)) {
-        II->moveBefore(&*FirstInst);
+        II->moveBefore(FirstInst);
         MadeChange = true;
       }
     }
@@ -9105,7 +9105,7 @@ bool CodeGenPrepare::splitBranchCondition(Function &F, ModifyDT &ModifiedDT) {
     auto *Br2 = IRBuilder<>(TmpBB).CreateCondBr(Cond2, TBB, FBB);
     if (auto *I = dyn_cast<Instruction>(Cond2)) {
       I->removeFromParent();
-      I->insertBefore(Br2);
+      I->insertBefore(Br2->getIterator());
     }
 
     // Update PHI nodes in both successors. The original BB needs to be