[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, 4 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index 5dc1686..5a395c9 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -1251,11 +1251,12 @@ void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
   llvm::BasicBlock *WasmCatchStartBlock = nullptr;
   if (EHPersonality::get(*this).isWasmPersonality()) {
     auto *CatchSwitch =
-        cast<llvm::CatchSwitchInst>(DispatchBlock->getFirstNonPHI());
+        cast<llvm::CatchSwitchInst>(DispatchBlock->getFirstNonPHIIt());
     WasmCatchStartBlock = CatchSwitch->hasUnwindDest()
                               ? CatchSwitch->getSuccessor(1)
                               : CatchSwitch->getSuccessor(0);
-    auto *CPI = cast<llvm::CatchPadInst>(WasmCatchStartBlock->getFirstNonPHI());
+    auto *CPI =
+        cast<llvm::CatchPadInst>(WasmCatchStartBlock->getFirstNonPHIIt());
     CurrentFuncletPad = CPI;
   }
 
@@ -2252,7 +2253,7 @@ void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
   // __except blocks don't get outlined into funclets, so immediately do a
   // catchret.
   llvm::CatchPadInst *CPI =
-      cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI());
+      cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHIIt());
   llvm::BasicBlock *ExceptBB = createBasicBlock("__except");
   Builder.CreateCatchRet(CPI, ExceptBB);
   EmitBlock(ExceptBB);