[llvm] [BOLT][AArch64] Handle OpNegateRAState to enable optimizing binaries with pac-ret hardening (PR #120064)

[Maksim Panchenko via llvm-commits]

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@@ -0,0 +1,160 @@
+//===- bolt/Passes/MarkRAStates.cpp ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the MarkRAStates class.
+// Three CFIs have an influence on the RA State of an instruction:
+// - NegateRAState flips the RA State,
+// - RememberState pushes the RA State to a stack,
+// - RestoreState pops the RA State from the stack.
+// These are saved as MCAnnotations on instructions they refer to at CFI
+// reading (in CFIReaderWriter::fillCFIInfoFor). In this pass, we can work out
+// the RA State of each instruction, and save it as new MCAnnotations. The new
+// annotations are Signing, Signed, Authenticating and Unsigned. After
+// optimizations, .cfi_negate_ra_state CFIs are added to the places where the
+// state changes in InsertNegateRAStatePass.
+//
+//===----------------------------------------------------------------------===//
+#include "bolt/Passes/MarkRAStates.h"
+#include "bolt/Core/BinaryFunction.h"
+#include "bolt/Core/ParallelUtilities.h"
+#include <cstdlib>
+#include <optional>
+#include <stack>
+
+using namespace llvm;
+
+namespace llvm {
+namespace bolt {
+
+bool MarkRAStates::runOnFunction(BinaryFunction &BF) {
+
+  BinaryContext &BC = BF.getBinaryContext();
+
+  for (BinaryBasicBlock &BB : BF) {
+    for (auto It = BB.begin(); It != BB.end(); ++It) {
+      MCInst &Inst = *It;
----------------
maksfb wrote:

```suggestion
    for (const MCInst &Inst : BB) {
```

https://github.com/llvm/llvm-project/pull/120064