[DebugInfo][RemoveDIs] Switch some insertion routines to use iterators (#75330)

As part of RemoveDIs, we need instruction insertion to be done with
iterators rather than instruction pointers, so that we can communicate
some debug-info facts about the position. This patch is an entirely
mechanical replacement of Instruction * with BasicBlock::iterator, plus
using insertBefore to insert some instructions because we don't have
iterator-taking constructors yet.

Sadly it's not NFC because it causes dbg.value intrinsics / their
DPValue equivalents to shift location.

Author: jmorse

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -1384,7 +1384,8 @@ static bool SinkCast(CastInst *CI) {
       BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
       assert(InsertPt != UserBB->end());
       InsertedCast = CastInst::Create(CI->getOpcode(), CI->getOperand(0),
-                                      CI->getType(), "", &*InsertPt);
+                                      CI->getType(), "");
+      InsertedCast->insertBefore(*UserBB, InsertPt);
       InsertedCast->setDebugLoc(CI->getDebugLoc());
     }
 
@@ -2058,12 +2059,13 @@ SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
       assert(InsertPt != TruncUserBB->end());
       // Sink the shift
       if (ShiftI->getOpcode() == Instruction::AShr)
-        InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
-                                                   "", &*InsertPt);
+        InsertedShift =
+            BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "");
       else
-        InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
-                                                   "", &*InsertPt);
+        InsertedShift =
+            BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "");
       InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
+      InsertedShift->insertBefore(*TruncUserBB, InsertPt);
 
       // Sink the trunc
       BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
@@ -2162,11 +2164,12 @@ static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
       assert(InsertPt != UserBB->end());
 
       if (ShiftI->getOpcode() == Instruction::AShr)
-        InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
-                                                   "", &*InsertPt);
+        InsertedShift =
+            BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "");
       else
-        InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
-                                                   "", &*InsertPt);
+        InsertedShift =
+            BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "");
+      InsertedShift->insertBefore(*UserBB, InsertPt);
       InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
 
       MadeChange = true;
@@ -6628,7 +6631,8 @@ bool CodeGenPrepare::optimizeExtUses(Instruction *I) {
     if (!InsertedTrunc) {
       BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
       assert(InsertPt != UserBB->end());
-      InsertedTrunc = new TruncInst(I, Src->getType(), "", &*InsertPt);
+      InsertedTrunc = new TruncInst(I, Src->getType(), "");
+      InsertedTrunc->insertBefore(*UserBB, InsertPt);
       InsertedInsts.insert(InsertedTrunc);
     }
 

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -193,7 +193,7 @@ static Instruction *cloneInstructionInExitBlock(
 static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
                              MemorySSAUpdater &MSSAU);
 
-static void moveInstructionBefore(Instruction &I, Instruction &Dest,
+static void moveInstructionBefore(Instruction &I, BasicBlock::iterator Dest,
                                   ICFLoopSafetyInfo &SafetyInfo,
                                   MemorySSAUpdater &MSSAU, ScalarEvolution *SE);
 
@@ -1011,7 +1011,8 @@ bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
         LLVM_DEBUG(dbgs() << "LICM rehoisting to "
                           << HoistPoint->getParent()->getNameOrAsOperand()
                           << ": " << *I << "\n");
-        moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU, SE);
+        moveInstructionBefore(*I, HoistPoint->getIterator(), *SafetyInfo, MSSAU,
+                              SE);
         HoistPoint = I;
         Changed = true;
       }
@@ -1491,16 +1492,17 @@ static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
   I.eraseFromParent();
 }
 
-static void moveInstructionBefore(Instruction &I, Instruction &Dest,
+static void moveInstructionBefore(Instruction &I, BasicBlock::iterator Dest,
                                   ICFLoopSafetyInfo &SafetyInfo,
                                   MemorySSAUpdater &MSSAU,
                                   ScalarEvolution *SE) {
   SafetyInfo.removeInstruction(&I);
-  SafetyInfo.insertInstructionTo(&I, Dest.getParent());
-  I.moveBefore(&Dest);
+  SafetyInfo.insertInstructionTo(&I, Dest->getParent());
+  I.moveBefore(*Dest->getParent(), Dest);
   if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>(
           MSSAU.getMemorySSA()->getMemoryAccess(&I)))
-    MSSAU.moveToPlace(OldMemAcc, Dest.getParent(), MemorySSA::BeforeTerminator);
+    MSSAU.moveToPlace(OldMemAcc, Dest->getParent(),
+                      MemorySSA::BeforeTerminator);
   if (SE)
     SE->forgetBlockAndLoopDispositions(&I);
 }
@@ -1747,10 +1749,11 @@ static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
 
   if (isa<PHINode>(I))
     // Move the new node to the end of the phi list in the destination block.
-    moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU, SE);
+    moveInstructionBefore(I, Dest->getFirstNonPHIIt(), *SafetyInfo, MSSAU, SE);
   else
     // Move the new node to the destination block, before its terminator.
-    moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU, SE);
+    moveInstructionBefore(I, Dest->getTerminator()->getIterator(), *SafetyInfo,
+                          MSSAU, SE);
 
   I.updateLocationAfterHoist();
 

llvm/lib/Transforms/Utils/LoopRotationUtils.cpp

@@ -708,12 +708,13 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
       // as U1'' and U1' scopes will not be compatible wrt to the local restrict
 
       // Clone the llvm.experimental.noalias.decl again for the NewHeader.
-      Instruction *NewHeaderInsertionPoint = &(*NewHeader->getFirstNonPHI());
+      BasicBlock::iterator NewHeaderInsertionPoint =
+          NewHeader->getFirstNonPHIIt();
       for (NoAliasScopeDeclInst *NAD : NoAliasDeclInstructions) {
         LLVM_DEBUG(dbgs() << "  Cloning llvm.experimental.noalias.scope.decl:"
                           << *NAD << "\n");
         Instruction *NewNAD = NAD->clone();
-        NewNAD->insertBefore(NewHeaderInsertionPoint);
+        NewNAD->insertBefore(*NewHeader, NewHeaderInsertionPoint);
       }
 
       // Scopes must now be duplicated, once for OrigHeader and once for