UnwindPlan: pretty-print dwarf expressions

[labath]

Summary

Previously we were printing the dwarf expressions in unwind rules simply
as "dwarf-expr". This patch uses the existing dwarf-printing
capabilities in lldb to enhance this dump output, and print the full
decoded dwarf expression.

[jasonmolenda]

very nice.

lit/Unwind/Inputs/unwind-plan-dwarf-dump.s

+        .text
+        .globl  main
+        .type   main, @function
+main:
+.LFB0:
+        .cfi_startproc
+        .cfi_escape 0x0f, 0x05, 0x77, 0x00, 0x08, 0x00, 0x22
+        .cfi_escape 0x16, 0x10, 0x04, 0x09, 0xf8, 0x22, 0x06
+        movl    $47, %eax
+        ret
+        .cfi_endproc
+.LFE0:
+        .size   main, .-main

lit/Unwind/unwind-plan-dwarf-dump.test

+# REQUIRES: target-x86_64, system-linux, native
+
+# RUN: %clang %p/Inputs/unwind-plan-dwarf-dump.s -o %t
+# RUN: %lldb %t -s %s -o exit | FileCheck %s
+
+breakpoint set -n main
+# CHECK: Breakpoint 1:
+
+process launch
+# CHECK: stop reason = breakpoint 1.1
+
+target modules show-unwind -n main
+# CHECK: eh_frame UnwindPlan:
+# CHECK: row[0]:    0: CFA=DW_OP_breg7 +0, DW_OP_const1u 0x00, DW_OP_plus  => rip=DW_OP_const1s -8, DW_OP_plus , DW_OP_deref

source/Symbol/UnwindPlan.cpp

 //===-- UnwindPlan.cpp ----------------------------------*- C++ -*-===//
 //
 // 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 "lldb/Symbol/UnwindPlan.h"
 
+#include "lldb/Expression/DWARFExpression.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
+#include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/Log.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
 bool UnwindPlan::Row::RegisterLocation::

 // allocated memory for the lifespan of this UnwindPlan object.
 void UnwindPlan::Row::RegisterLocation::SetIsDWARFExpression(
     const uint8_t *opcodes, uint32_t len) {
   m_type = isDWARFExpression;
   m_location.expr.opcodes = opcodes;
   m_location.expr.length = len;
 }
 
+static llvm::Optional<std::pair<lldb::ByteOrder, uint32_t>>
+GetByteOrderAndAddrSize(Thread *thread) {
+  if (!thread)
+    return llvm::None;
+  ProcessSP process_sp = thread->GetProcess();
+  if (!process_sp)
+    return llvm::None;
+  ArchSpec arch = process_sp->GetTarget().GetArchitecture();
+  return std::make_pair(arch.GetByteOrder(), arch.GetAddressByteSize());
+}
+
+static void DumpDWARFExpr(Stream &s, llvm::ArrayRef<uint8_t> expr, Thread *thread) {
+  if (auto order_and_width = GetByteOrderAndAddrSize(thread)) {
+    DataExtractor extractor(expr.data(), expr.size(), order_and_width->first,
+                            order_and_width->second);
+    if (!DWARFExpression::PrintDWARFExpression(s, extractor,
+                                               order_and_width->second,
+                                               /*dwarf_ref_size*/ 4,
+                                               /*location_expression*/ false))
+      s.PutCString("invalid-dwarf-expr");
+  } else
+    s.PutCString("dwarf-expr");
+}
+
 void UnwindPlan::Row::RegisterLocation::Dump(Stream &s,
                                              const UnwindPlan *unwind_plan,
                                              const UnwindPlan::Row *row,
                                              Thread *thread,
                                              bool verbose) const {
   switch (m_type) {
   case unspecified:
     if (verbose)
case inOtherRegister: {
     else
       s.Printf("=reg(%u)", m_location.reg_num);
   } break;
 
   case atDWARFExpression:
   case isDWARFExpression: {
     s.PutChar('=');
     if (m_type == atDWARFExpression)
-      s.PutCString("[dwarf-expr]");
-    else
-      s.PutCString("dwarf-expr");
+      s.PutChar('[');
+    DumpDWARFExpr(
+        s, llvm::makeArrayRef(m_location.expr.opcodes, m_location.expr.length),
+        thread);
+    if (m_type == atDWARFExpression)
+      s.PutChar(']');
   } break;
   }
 }
 
 static void DumpRegisterName(Stream &s, const UnwindPlan *unwind_plan,
                              Thread *thread, uint32_t reg_num) {
   const RegisterInfo *reg_info = unwind_plan->GetRegisterInfo(thread, reg_num);
   if (reg_info)
case isRegisterPlusOffset:
     s.Printf("%+3d", m_value.reg.offset);
     break;
   case isRegisterDereferenced:
     s.PutChar('[');
     DumpRegisterName(s, unwind_plan, thread, m_value.reg.reg_num);
     s.PutChar(']');
     break;
   case isDWARFExpression:
-    s.PutCString("dwarf-expr");
+    DumpDWARFExpr(s,
+                  llvm::makeArrayRef(m_value.expr.opcodes, m_value.expr.length),
+                  thread);
     break;
   default:
     s.PutCString("unspecified");
     break;
   }
 }
 
 void UnwindPlan::Row::Clear() {