[lldb] Add frame recognizer for __builtin_verbose_trap

This patch adds a frame recognizer for Clang's
`__builtin_verbose_trap`, which behaves like a
`__builtin_trap`, but emits a failure-reason string
into debug-info in order for debuggers to display
it to a user.

The frame recognizer triggers when we encounter
a frame with a function name that begins with
`__llvm_verbose_trap`, which is the magic prefix
Clang emits into debug-info for verbose traps.
Once such frame is encountered we display the
frame function name as the `Stop Reason` and display
that frame to the user.

Example output:
```
(lldb) run
warning: a.out was compiled with optimization - stepping may behave oddly; variables may not be available.
Process 35942 launched: 'a.out' (arm64)
Process 35942 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = __llvm_verbose_trap: Function is not implemented
    frame #1: 0x0000000100003fa4 a.out`main [inlined] Dummy::func(this=<unavailable>) at verbose_trap.cpp:3:5 [opt]
   1    struct Dummy {
   2      void func() {
-> 3        __builtin_verbose_trap("Function is not implemented");
   4      }
   5    };
   6
   7    int main() {
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = __llvm_verbose_trap: Function is not implemented
    frame #0: 0x0000000100003fa4 a.out`main [inlined] __llvm_verbose_trap: Function is not implemented at verbose_trap.cpp:0 [opt]
  * frame #1: 0x0000000100003fa4 a.out`main [inlined] Dummy::func(this=<unavailable>) at verbose_trap.cpp:3:5 [opt]
    frame #2: 0x0000000100003fa4 a.out`main at verbose_trap.cpp:8:13 [opt]
    frame #3: 0x0000000189d518b4 dyld`start + 1988
```

Author: Michael137

lldb/include/lldb/Target/VerboseTrapFrameRecognizer.h

@@ -0,0 +1,39 @@
+#ifndef LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H
+#define LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H
+
+#include "lldb/Target/StackFrameRecognizer.h"
+
+namespace lldb_private {
+
+void RegisterVerboseTrapFrameRecognizer(Process &process);
+
+/// Holds the stack frame that caused the Verbose trap and the inlined stop
+/// reason message.
+class VerboseTrapRecognizedStackFrame : public RecognizedStackFrame {
+public:
+  VerboseTrapRecognizedStackFrame(lldb::StackFrameSP most_relevant_frame_sp,
+                                  std::string stop_desc);
+
+  lldb::StackFrameSP GetMostRelevantFrame() override;
+
+private:
+  lldb::StackFrameSP m_most_relevant_frame;
+};
+
+/// When a thread stops, it checks the current frame contains a
+/// Verbose Trap diagnostic. If so, it returns a \a
+/// VerboseTrapRecognizedStackFrame holding the diagnostic a stop reason
+/// description with and the parent frame as the most relavant frame.
+class VerboseTrapFrameRecognizer : public StackFrameRecognizer {
+public:
+  std::string GetName() override {
+    return "Verbose Trap StackFrame Recognizer";
+  }
+
+  lldb::RecognizedStackFrameSP
+  RecognizeFrame(lldb::StackFrameSP frame) override;
+};
+
+} // namespace lldb_private
+
+#endif // LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H

lldb/source/Target/CMakeLists.txt

@@ -78,6 +78,7 @@ add_lldb_library(lldbTarget
   UnixSignals.cpp
   UnwindAssembly.cpp
   UnwindLLDB.cpp
+  VerboseTrapFrameRecognizer.cpp
 
   LINK_LIBS
     lldbBreakpoint

lldb/source/Target/Process.cpp

@@ -63,6 +63,7 @@
 #include "lldb/Target/ThreadPlanCallFunction.h"
 #include "lldb/Target/ThreadPlanStack.h"
 #include "lldb/Target/UnixSignals.h"
+#include "lldb/Target/VerboseTrapFrameRecognizer.h"
 #include "lldb/Utility/Event.h"
 #include "lldb/Utility/LLDBLog.h"
 #include "lldb/Utility/Log.h"
@@ -497,6 +498,7 @@ Process::Process(lldb::TargetSP target_sp, ListenerSP listener_sp,
     value_sp->SetValueAs(platform_cache_line_size);
 
   RegisterAssertFrameRecognizer(this);
+  RegisterVerboseTrapFrameRecognizer(*this);
 }
 
 Process::~Process() {

lldb/source/Target/VerboseTrapFrameRecognizer.cpp

@@ -0,0 +1,85 @@
+#include "lldb/Target/VerboseTrapFrameRecognizer.h"
+
+#include "lldb/Core/Module.h"
+#include "lldb/Symbol/Function.h"
+#include "lldb/Symbol/SymbolContext.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Target/Target.h"
+
+#include "lldb/Utility/LLDBLog.h"
+#include "lldb/Utility/Log.h"
+
+using namespace llvm;
+using namespace lldb;
+using namespace lldb_private;
+
+VerboseTrapRecognizedStackFrame::VerboseTrapRecognizedStackFrame(
+    StackFrameSP most_relevant_frame_sp, std::string stop_desc)
+    : m_most_relevant_frame(most_relevant_frame_sp) {
+  m_stop_desc = std::move(stop_desc);
+}
+
+lldb::RecognizedStackFrameSP
+VerboseTrapFrameRecognizer::RecognizeFrame(lldb::StackFrameSP frame_sp) {
+  if (frame_sp->GetFrameIndex())
+    return {};
+
+  ThreadSP thread_sp = frame_sp->GetThread();
+  ProcessSP process_sp = thread_sp->GetProcess();
+
+  StackFrameSP most_relevant_frame_sp = thread_sp->GetStackFrameAtIndex(1);
+
+  if (!most_relevant_frame_sp) {
+    Log *log = GetLog(LLDBLog::Unwind);
+    LLDB_LOG(
+        log,
+        "Failed to find most relevant frame: Hit unwinding bound (1 frame)!");
+    return {};
+  }
+
+  SymbolContext sc = frame_sp->GetSymbolContext(eSymbolContextEverything);
+
+  if (!sc.block)
+    return {};
+
+  // The runtime error is set as the function name in the inlined function info
+  // of frame #0 by the compiler
+  const InlineFunctionInfo *inline_info = nullptr;
+  Block *inline_block = sc.block->GetContainingInlinedBlock();
+
+  if (!inline_block)
+    return {};
+
+  inline_info = sc.block->GetInlinedFunctionInfo();
+
+  if (!inline_info)
+    return {};
+
+  auto runtime_error = inline_info->GetName().GetString();
+
+  if (runtime_error.empty())
+    return {};
+
+  return lldb::RecognizedStackFrameSP(new VerboseTrapRecognizedStackFrame(
+      most_relevant_frame_sp, std::move(runtime_error)));
+}
+
+lldb::StackFrameSP VerboseTrapRecognizedStackFrame::GetMostRelevantFrame() {
+  return m_most_relevant_frame;
+}
+
+namespace lldb_private {
+
+void RegisterVerboseTrapFrameRecognizer(Process &process) {
+  RegularExpressionSP module_regex_sp = nullptr;
+  RegularExpressionSP symbol_regex_sp(
+      new RegularExpression("(__llvm_verbose_trap)"));
+
+  StackFrameRecognizerSP srf_recognizer_sp =
+      std::make_shared<VerboseTrapFrameRecognizer>();
+
+  process.GetTarget().GetFrameRecognizerManager().AddRecognizer(
+      srf_recognizer_sp, module_regex_sp, symbol_regex_sp, false);
+}
+
+} // namespace lldb_private

lldb/test/Shell/Recognizer/Inputs/verbose_trap.cpp

@@ -0,0 +1,8 @@
+struct Dummy {
+  void func() { __builtin_verbose_trap("Function is not implemented"); }
+};
+
+int main() {
+  Dummy{}.func();
+  return 0;
+}

lldb/test/Shell/Recognizer/verbose_trap.test

@@ -0,0 +1,9 @@
+# RUN: %clang_host -g -O0 %S/Inputs/verbose_trap.cpp -o %t.out
+# RUN: %lldb -b -s %s %t.out | FileCheck %s
+run
+# CHECK: thread #{{.*}}stop reason = __llvm_verbose_trap: Function is not implemented
+frame info
+# CHECK: frame #{{.*}}`Dummy::func(this={{.*}}) at verbose_trap.cpp
+frame recognizer info 0
+# CHECK: frame 0 is recognized by Verbose Trap StackFrame Recognizer
+q