[lldb/breakpad] Fix register resolution on arm

In breakpad, only x86 (and mips) registers have a leading '$' in their
names. Arm architectures use plain register names.

Previously, lldb was assuming all registers have a '$'. Fix the code to
match the (unfortunately, inconsistent) reality.

lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.cpp

@@ -408,20 +408,25 @@ GetRule(llvm::StringRef &unwind_rules) {
 }
 
 static const RegisterInfo *
-ResolveRegister(const SymbolFile::RegisterInfoResolver &resolver,
+ResolveRegister(const llvm::Triple &triple,
+                const SymbolFile::RegisterInfoResolver &resolver,
                 llvm::StringRef name) {
-  if (name.consume_front("$"))
-    return resolver.ResolveName(name);
-
-  return nullptr;
+  if (triple.isX86() || triple.isMIPS()) {
+    // X86 and MIPS registers have '$' in front of their register names. Arm and
+    // AArch64 don't.
+    if (!name.consume_front("$"))
+      return nullptr;
+  }
+  return resolver.ResolveName(name);
 }
 
 static const RegisterInfo *
-ResolveRegisterOrRA(const SymbolFile::RegisterInfoResolver &resolver,
+ResolveRegisterOrRA(const llvm::Triple &triple,
+                    const SymbolFile::RegisterInfoResolver &resolver,
                     llvm::StringRef name) {
   if (name == ".ra")
     return resolver.ResolveNumber(eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC);
-  return ResolveRegister(resolver, name);
+  return ResolveRegister(triple, resolver, name);
 }
 
 llvm::ArrayRef<uint8_t> SymbolFileBreakpad::SaveAsDWARF(postfix::Node &node) {
@@ -440,6 +445,7 @@ bool SymbolFileBreakpad::ParseCFIUnwindRow(llvm::StringRef unwind_rules,
   Log *log = GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYMBOLS);
 
   llvm::BumpPtrAllocator node_alloc;
+  llvm::Triple triple = m_objfile_sp->GetArchitecture().GetTriple();
   while (auto rule = GetRule(unwind_rules)) {
     node_alloc.Reset();
     llvm::StringRef lhs = rule->first;
@@ -455,7 +461,8 @@ bool SymbolFileBreakpad::ParseCFIUnwindRow(llvm::StringRef unwind_rules,
           if (name == ".cfa" && lhs != ".cfa")
             return postfix::MakeNode<postfix::InitialValueNode>(node_alloc);
 
-          if (const RegisterInfo *info = ResolveRegister(resolver, name)) {
+          if (const RegisterInfo *info =
+                  ResolveRegister(triple, resolver, name)) {
             return postfix::MakeNode<postfix::RegisterNode>(
                 node_alloc, info->kinds[eRegisterKindLLDB]);
           }
@@ -470,7 +477,8 @@ bool SymbolFileBreakpad::ParseCFIUnwindRow(llvm::StringRef unwind_rules,
     llvm::ArrayRef<uint8_t> saved = SaveAsDWARF(*rhs);
     if (lhs == ".cfa") {
       row.GetCFAValue().SetIsDWARFExpression(saved.data(), saved.size());
-    } else if (const RegisterInfo *info = ResolveRegisterOrRA(resolver, lhs)) {
+    } else if (const RegisterInfo *info =
+                   ResolveRegisterOrRA(triple, resolver, lhs)) {
       UnwindPlan::Row::RegisterLocation loc;
       loc.SetIsDWARFExpression(saved.data(), saved.size());
       row.SetRegisterInfo(info->kinds[eRegisterKindLLDB], loc);
@@ -574,6 +582,7 @@ SymbolFileBreakpad::ParseWinUnwindPlan(const Bookmark &bookmark,
     return nullptr;
   }
   auto it = program.begin();
+  llvm::Triple triple = m_objfile_sp->GetArchitecture().GetTriple();
   const auto &symbol_resolver =
       [&](postfix::SymbolNode &symbol) -> postfix::Node * {
     llvm::StringRef name = symbol.GetName();
@@ -581,7 +590,7 @@ SymbolFileBreakpad::ParseWinUnwindPlan(const Bookmark &bookmark,
       if (rule.first == name)
         return rule.second;
     }
-    if (const RegisterInfo *info = ResolveRegister(resolver, name))
+    if (const RegisterInfo *info = ResolveRegister(triple, resolver, name))
       return postfix::MakeNode<postfix::RegisterNode>(
           node_alloc, info->kinds[eRegisterKindLLDB]);
     return nullptr;
@@ -611,7 +620,7 @@ SymbolFileBreakpad::ParseWinUnwindPlan(const Bookmark &bookmark,
 
   // Now process the rest of the assignments.
   for (++it; it != program.end(); ++it) {
-    const RegisterInfo *info = ResolveRegister(resolver, it->first);
+    const RegisterInfo *info = ResolveRegister(triple, resolver, it->first);
     // It is not an error if the resolution fails because the program may
     // contain temporary variables.
     if (!info)

lldb/test/Shell/SymbolFile/Breakpad/Inputs/stack-cfi-arm.syms

@@ -0,0 +1,5 @@
+MODULE Linux arm E5894855C35DCCCCCCCCCCCCCCCCCCCC0 linux.out
+INFO CODE_ID E35C283BC327C28762DB788BF5A4078BE2351448
+FUNC 0 2 0 func0
+STACK CFI INIT 0 2 .cfa: sp 0 + .ra: lr
+STACK CFI 2 .cfa: sp 8 + .ra: .cfa -4 + ^ r7: .cfa -8 + ^

lldb/test/Shell/SymbolFile/Breakpad/stack-cfi-arm.yaml

@@ -0,0 +1,32 @@
+# REQUIRES: arm
+
+# RUN: yaml2obj %s >%t
+# RUN: %lldb -c %t -o "target symbols add %S/Inputs/stack-cfi-arm.syms" \
+# RUN:   -o "image show-unwind -n func0" -b | FileCheck %s
+
+# CHECK:      Symbol file UnwindPlan:
+# CHECK:      row[0]:    0: CFA=DW_OP_breg13 +0, DW_OP_consts +0, DW_OP_plus  => pc=DW_OP_breg14 +0 
+# CHECK-NEXT: row[1]:    2: CFA=DW_OP_breg13 +0, DW_OP_consts +8, DW_OP_plus  => r7=DW_OP_pick 0x00, DW_OP_consts -8, DW_OP_plus , DW_OP_deref  pc=DW_OP_pick 0x00, DW_OP_consts -4, DW_OP_plus , DW_OP_deref  
+# 
+
+--- !minidump
+Streams:         
+  - Type:            ThreadList
+    Threads:         
+      - Thread Id:       0x00003E81
+        Context:         DEAD
+        Stack:           
+          Start of Memory Range: 0x00007FFCEB34A000
+          Content:         DEAD
+  - Type:            ModuleList
+    Modules:         
+      - Base of Image:   0x0000000000400000
+        Size of Image:   0x00001000
+        Module Name:     '/tmp/stack-cfi-arm.out'
+        CodeView Record: 4C457042E35C283BC327C28762DB788BF5A4078BE2351448
+  - Type:            SystemInfo
+    Processor Arch:  ARM
+    Platform ID:     Linux
+    CPU:             
+      CPUID:           0
+...