[clang] [clang][AArch64] Pass down stack clash protection options to LLVM/Backend (PR #68993)

[Sam Tebbs via cfe-commits]

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@@ -85,17 +90,32 @@ static bool isPrologueCFIInstruction(const MachineInstr &MI) {
          MI.getFlag(MachineInstr::FrameSetup);
 }
 
-static bool containsPrologue(const MachineBasicBlock &MBB) {
-  return llvm::any_of(MBB.instrs(), isPrologueCFIInstruction);
-}
-
 static bool containsEpilogue(const MachineBasicBlock &MBB) {
   return llvm::any_of(llvm::reverse(MBB), [](const auto &MI) {
     return MI.getOpcode() == TargetOpcode::CFI_INSTRUCTION &&
            MI.getFlag(MachineInstr::FrameDestroy);
   });
 }
 
+static MachineBasicBlock *
+findPrologueEnd(MachineFunction &MF, MachineBasicBlock::iterator &PrologueEnd) {
+  MachineBasicBlock *PrologueBlock = nullptr;
+  for (auto It = po_begin(&MF.front()), End = po_end(&MF.front()); It != End;
+       ++It) {
+    MachineBasicBlock *MBB = *It;
+    llvm::for_each(MBB->instrs(), [&](MachineInstr &MI) {
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SamTebbs33 wrote:

Does it make sense here to go through the reversed list of the instructions and stop after you find the first prologue CFI instruction?

https://github.com/llvm/llvm-project/pull/68993