[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, 2 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
index fffff29..b07f345 100644
--- a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
@@ -650,7 +650,7 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
 
         NextDbgInsts = I->getDbgRecordRange();
 
-        Inst->moveBefore(LoopEntryBranch);
+        Inst->moveBefore(LoopEntryBranch->getIterator());
 
         ++NumInstrsHoisted;
         continue;
@@ -658,7 +658,7 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
 
       // Otherwise, create a duplicate of the instruction.
       Instruction *C = Inst->clone();
-      C->insertBefore(LoopEntryBranch);
+      C->insertBefore(LoopEntryBranch->getIterator());
 
       ++NumInstrsDuplicated;