[NFC][DebugInfo] Use iterator-flavour getFirstNonPHI at many call-sites (#123737)

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 getFirstNonPHI use the iterator-returning version.

This patch changes a bunch of call-sites calling getFirstNonPHI to use
getFirstNonPHIIt, which returns an iterator. All these call sites are
where it's obviously safe to fetch the iterator then dereference it. A
follow-up patch will contain less-obviously-safe changes.

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

---------

Co-authored-by: Stephen Tozer <Melamoto@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index e482418..ab3609b 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -833,7 +833,8 @@ MCSymbol *MachineFunction::addLandingPad(MachineBasicBlock *LandingPad) {
   LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
   LP.LandingPadLabel = LandingPadLabel;
 
-  const Instruction *FirstI = LandingPad->getBasicBlock()->getFirstNonPHI();
+  BasicBlock::const_iterator FirstI =
+      LandingPad->getBasicBlock()->getFirstNonPHIIt();
   if (const auto *LPI = dyn_cast<LandingPadInst>(FirstI)) {
     // If there's no typeid list specified, then "cleanup" is implicit.
     // Otherwise, id 0 is reserved for the cleanup action.