[llvm] Minimal unwinding information (DWARF CFI) checker (PR #145633)

[Paul Kirth via llvm-commits]

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@@ -0,0 +1,96 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/UnwindInfoChecker/FunctionUnitStreamer.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCStreamer.h"
+#include <cstdio>
+#include <optional>
+
+using namespace llvm;
+
+std::pair<unsigned, unsigned> FunctionUnitStreamer::updateDirectivesRange() {
+  auto Frames = getDwarfFrameInfos();
+  unsigned CurrentCFIDirectiveIndex = 0;
+  if (hasUnfinishedDwarfFrameInfo()) {
+    assert(!FrameIndices.empty() && "FunctionUnitStreamer frame indices should "
+                                    "be synced with MCStreamer's");
+    assert(FrameIndices.back() < Frames.size());
+    CurrentCFIDirectiveIndex = Frames[FrameIndices.back()].Instructions.size();
+  }
+
+  assert(CurrentCFIDirectiveIndex >= LastDirectiveIndex);
+  std::pair<unsigned, unsigned> CFIDirectivesRange(LastDirectiveIndex,
+                                                   CurrentCFIDirectiveIndex);
+  LastDirectiveIndex = CurrentCFIDirectiveIndex;
+  return CFIDirectivesRange;
+}
+
+void FunctionUnitStreamer::updateAnalyzer() {
+  if (FrameIndices.empty()) {
+    auto CFIDirectivesRange = updateDirectivesRange();
+    assert(CFIDirectivesRange.first == CFIDirectivesRange.second &&
+           "CFI directives should be in some frame");
+    return;
+  }
+
+  const auto *LastFrame = &getDwarfFrameInfos()[FrameIndices.back()];
----------------
ilovepi wrote:

Nit: generally prefer to use a real type over `auto`.  `using` statements are a good option if you have some types that are hard to spell, plus that usually makes the code easier to read anyway.  The style guide has more to say here: https://llvm.org/docs/CodingStandards.html#use-auto-type-deduction-to-make-code-more-readable


https://github.com/llvm/llvm-project/pull/145633