[x86] Fix issues with a realigned stack in MSVC compiled applications

Summary:
This patch fixes issues with a stack realignment.

MSVC maintains two frame pointers (`ebx` and `ebp`) for a realigned stack - one
is used for access to function parameters, while another is used for access to
locals. To support this the patch:
- adds an alternative frame pointer (`ebx`);
- considers stack realignment instructions (e.g. `and esp, -32`);
- along with CFA (Canonical Frame Address) which point to the position next to
  the saved return address (or to the first parameter on the stack) introduces
  AFA (Aligned Frame Address) which points to the position of the stack pointer
  right after realignment. AFA is used for access to registers saved after the
  realignment (see the test);

Here is an example of the code with the realignment:
```
struct __declspec(align(256)) OverAligned {
  char c;
};

void foo(int foo_arg) {
  OverAligned oa_foo = { 1 };
  auto aaa_foo = 1234;
}

void bar(int bar_arg) {
  OverAligned oa_bar = { 2 };
  auto aaa_bar = 5678;
  foo(1111);
}

int main() {
  bar(2222);
  return 0;
}
```
and here is the `bar` disassembly:
```
push    ebx
mov     ebx, esp
sub     esp, 8
and     esp, -100h
add     esp, 4
push    ebp
mov     ebp, [ebx+4]
mov     [esp+4], ebp
mov     ebp, esp
sub     esp, 200h
mov     byte ptr [ebp-200h], 2
mov     dword ptr [ebp-4], 5678
push    1111            ; foo_arg
call    j_?foo@@YAXH@Z  ; foo(int)
add     esp, 4
mov     esp, ebp
pop     ebp
mov     esp, ebx
pop     ebx
retn
```

Reviewers: labath, zturner, jasonmolenda, stella.stamenova

Reviewed By: jasonmolenda

Subscribers: abidh, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D53435

llvm-svn: 345577

6 files changed, 375 insertions, 134 deletions

diff --git a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
index e943c3dc1c9..3a1f2fb37b7 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
+++ b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
@@ -54,7 +54,8 @@ RegisterContextLLDB::RegisterContextLLDB(Thread &thread,
     : RegisterContext(thread, frame_number), m_thread(thread),
       m_fast_unwind_plan_sp(), m_full_unwind_plan_sp(),
       m_fallback_unwind_plan_sp(), m_all_registers_available(false),
-      m_frame_type(-1), m_cfa(LLDB_INVALID_ADDRESS), m_start_pc(),
+      m_frame_type(-1), m_cfa(LLDB_INVALID_ADDRESS),
+      m_afa(LLDB_INVALID_ADDRESS), m_start_pc(),
       m_current_pc(), m_current_offset(0), m_current_offset_backed_up_one(0),
       m_sym_ctx(sym_ctx), m_sym_ctx_valid(false), m_frame_number(frame_number),
       m_registers(), m_parent_unwind(unwind_lldb) {
@@ -228,7 +229,7 @@ void RegisterContextLLDB::InitializeZerothFrame() {
     return;
   }
 
-  if (!ReadCFAValueForRow(row_register_kind, active_row, m_cfa)) {
+  if (!ReadFrameAddress(row_register_kind, active_row->GetCFAValue(), m_cfa)) {
     // Try the fall back unwind plan since the
     // full unwind plan failed.
     FuncUnwindersSP func_unwinders_sp;
@@ -256,12 +257,14 @@ void RegisterContextLLDB::InitializeZerothFrame() {
       m_frame_type = eNotAValidFrame;
       return;
     }
-  }
+  } else
+    ReadFrameAddress(row_register_kind, active_row->GetAFAValue(), m_afa);
 
   UnwindLogMsg("initialized frame current pc is 0x%" PRIx64 " cfa is 0x%" PRIx64
-               " using %s UnwindPlan",
+               " afa is 0x%" PRIx64 " using %s UnwindPlan",
                (uint64_t)m_current_pc.GetLoadAddress(exe_ctx.GetTargetPtr()),
                (uint64_t)m_cfa,
+               (uint64_t)m_afa,
                m_full_unwind_plan_sp->GetSourceName().GetCString());
 }
 
@@ -379,7 +382,7 @@ void RegisterContextLLDB::InitializeNonZerothFrame() {
       RegisterKind row_register_kind = m_full_unwind_plan_sp->GetRegisterKind();
       UnwindPlan::RowSP row = m_full_unwind_plan_sp->GetRowForFunctionOffset(0);
       if (row.get()) {
-        if (!ReadCFAValueForRow(row_register_kind, row, m_cfa)) {
+        if (!ReadFrameAddress(row_register_kind, row->GetCFAValue(), m_cfa)) {
           UnwindLogMsg("failed to get cfa value");
           if (m_frame_type != eSkipFrame) // don't override eSkipFrame
           {
@@ -388,6 +391,8 @@ void RegisterContextLLDB::InitializeNonZerothFrame() {
           return;
         }
 
+        ReadFrameAddress(row_register_kind, row->GetAFAValue(), m_afa);
+
         // A couple of sanity checks..
         if (m_cfa == LLDB_INVALID_ADDRESS || m_cfa == 0 || m_cfa == 1) {
           UnwindLogMsg("could not find a valid cfa address");
@@ -420,7 +425,8 @@ void RegisterContextLLDB::InitializeNonZerothFrame() {
         }
       }
 
-      UnwindLogMsg("initialized frame cfa is 0x%" PRIx64, (uint64_t)m_cfa);
+      UnwindLogMsg("initialized frame cfa is 0x%" PRIx64 " afa is 0x%" PRIx64,
+                   (uint64_t)m_cfa, (uint64_t)m_afa);
       return;
     }
     m_frame_type = eNotAValidFrame;
@@ -584,13 +590,15 @@ void RegisterContextLLDB::InitializeNonZerothFrame() {
     return;
   }
 
-  if (!ReadCFAValueForRow(row_register_kind, active_row, m_cfa)) {
+  if (!ReadFrameAddress(row_register_kind, active_row->GetCFAValue(), m_cfa)) {
     UnwindLogMsg("failed to get cfa");
     m_frame_type = eNotAValidFrame;
     return;
   }
 
-  UnwindLogMsg("m_cfa = 0x%" PRIx64, m_cfa);
+  ReadFrameAddress(row_register_kind, active_row->GetAFAValue(), m_afa);
+
+  UnwindLogMsg("m_cfa = 0x%" PRIx64 " m_afa = 0x%" PRIx64, m_cfa, m_afa);
 
   if (CheckIfLoopingStack()) {
     TryFallbackUnwindPlan();
@@ -603,9 +611,10 @@ void RegisterContextLLDB::InitializeNonZerothFrame() {
   }
 
   UnwindLogMsg("initialized frame current pc is 0x%" PRIx64
-               " cfa is 0x%" PRIx64,
+               " cfa is 0x%" PRIx64 " afa is 0x%" PRIx64,
                (uint64_t)m_current_pc.GetLoadAddress(exe_ctx.GetTargetPtr()),
-               (uint64_t)m_cfa);
+               (uint64_t)m_cfa,
+               (uint64_t)m_afa);
 }
 
 bool RegisterContextLLDB::CheckIfLoopingStack() {
@@ -1314,8 +1323,8 @@ RegisterContextLLDB::SavedLocationForRegister(
                     unwindplan_regloc)) {
               can_fetch_pc_value = true;
             }
-            if (ReadCFAValueForRow(unwindplan_registerkind, active_row,
-                                   cfa_value)) {
+            if (ReadFrameAddress(unwindplan_registerkind,
+                                 active_row->GetCFAValue(), cfa_value)) {
               can_fetch_cfa = true;
             }
           }
@@ -1444,6 +1453,36 @@ RegisterContextLLDB::SavedLocationForRegister(
     return UnwindLLDB::RegisterSearchResult::eRegisterFound;
   }
 
+  if (unwindplan_regloc.IsAFAPlusOffset()) {
+    if (m_afa == LLDB_INVALID_ADDRESS)
+        return UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
+
+    int offset = unwindplan_regloc.GetOffset();
+    regloc.type = UnwindLLDB::RegisterLocation::eRegisterValueInferred;
+    regloc.location.inferred_value = m_afa + offset;
+    m_registers[regnum.GetAsKind(eRegisterKindLLDB)] = regloc;
+    UnwindLogMsg("supplying caller's register %s (%d), value is AFA plus "
+                 "offset %d [value is 0x%" PRIx64 "]",
+                 regnum.GetName(), regnum.GetAsKind(eRegisterKindLLDB), offset,
+                 regloc.location.inferred_value);
+    return UnwindLLDB::RegisterSearchResult::eRegisterFound;
+  }
+
+  if (unwindplan_regloc.IsAtAFAPlusOffset()) {
+    if (m_afa == LLDB_INVALID_ADDRESS)
+        return UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
+
+    int offset = unwindplan_regloc.GetOffset();
+    regloc.type = UnwindLLDB::RegisterLocation::eRegisterSavedAtMemoryLocation;
+    regloc.location.target_memory_location = m_afa + offset;
+    m_registers[regnum.GetAsKind(eRegisterKindLLDB)] = regloc;
+    UnwindLogMsg("supplying caller's register %s (%d) from the stack, saved at "
+                 "AFA plus offset %d [saved at 0x%" PRIx64 "]",
+                 regnum.GetName(), regnum.GetAsKind(eRegisterKindLLDB), offset,
+                 regloc.location.target_memory_location);
+    return UnwindLLDB::RegisterSearchResult::eRegisterFound;
+  }
+
   if (unwindplan_regloc.IsInOtherRegister()) {
     uint32_t unwindplan_regnum = unwindplan_regloc.GetRegisterNumber();
     RegisterNumber row_regnum(m_thread, unwindplan_registerkind,
@@ -1558,7 +1597,6 @@ bool RegisterContextLLDB::TryFallbackUnwindPlan() {
 
   addr_t old_caller_pc_value = LLDB_INVALID_ADDRESS;
   addr_t new_caller_pc_value = LLDB_INVALID_ADDRESS;
-  addr_t old_this_frame_cfa_value = m_cfa;
   UnwindLLDB::RegisterLocation regloc;
   if (SavedLocationForRegister(pc_regnum.GetAsKind(eRegisterKindLLDB),
                                regloc) ==
@@ -1588,6 +1626,7 @@ bool RegisterContextLLDB::TryFallbackUnwindPlan() {
   // the value of the m_cfa ivar.  Save is down below a bit in 'old_cfa'.
   UnwindPlanSP original_full_unwind_plan_sp = m_full_unwind_plan_sp;
   addr_t old_cfa = m_cfa;
+  addr_t old_afa = m_afa;
 
   m_registers.clear();
 
@@ -1598,19 +1637,21 @@ bool RegisterContextLLDB::TryFallbackUnwindPlan() {
 
   if (active_row &&
       active_row->GetCFAValue().GetValueType() !=
-          UnwindPlan::Row::CFAValue::unspecified) {
+          UnwindPlan::Row::FAValue::unspecified) {
     addr_t new_cfa;
-    if (!ReadCFAValueForRow(m_fallback_unwind_plan_sp->GetRegisterKind(),
-                            active_row, new_cfa) ||
+    if (!ReadFrameAddress(m_fallback_unwind_plan_sp->GetRegisterKind(),
+                            active_row->GetCFAValue(), new_cfa) ||
         new_cfa == 0 || new_cfa == 1 || new_cfa == LLDB_INVALID_ADDRESS) {
       UnwindLogMsg("failed to get cfa with fallback unwindplan");
       m_fallback_unwind_plan_sp.reset();
       m_full_unwind_plan_sp = original_full_unwind_plan_sp;
-      m_cfa = old_cfa;
       return false;
     }
     m_cfa = new_cfa;
 
+    ReadFrameAddress(m_fallback_unwind_plan_sp->GetRegisterKind(),
+                     active_row->GetAFAValue(), m_afa);
+
     if (SavedLocationForRegister(pc_regnum.GetAsKind(eRegisterKindLLDB),
                                  regloc) ==
         UnwindLLDB::RegisterSearchResult::eRegisterFound) {
@@ -1631,19 +1672,18 @@ bool RegisterContextLLDB::TryFallbackUnwindPlan() {
       m_fallback_unwind_plan_sp.reset();
       m_full_unwind_plan_sp = original_full_unwind_plan_sp;
       m_cfa = old_cfa;
+      m_afa = old_afa;
       return false;
     }
 
-    if (old_caller_pc_value != LLDB_INVALID_ADDRESS) {
-      if (old_caller_pc_value == new_caller_pc_value &&
-          new_cfa == old_this_frame_cfa_value) {
-        UnwindLogMsg("fallback unwind plan got the same values for this frame "
-                     "CFA and caller frame pc, not using");
-        m_fallback_unwind_plan_sp.reset();
-        m_full_unwind_plan_sp = original_full_unwind_plan_sp;
-        m_cfa = old_cfa;
-        return false;
-      }
+    if (old_caller_pc_value == new_caller_pc_value &&
+        m_cfa == old_cfa &&
+        m_afa == old_afa) {
+      UnwindLogMsg("fallback unwind plan got the same values for this frame "
+                   "CFA and caller frame pc, not using");
+      m_fallback_unwind_plan_sp.reset();
+      m_full_unwind_plan_sp = original_full_unwind_plan_sp;
+      return false;
     }
 
     UnwindLogMsg("trying to unwind from this function with the UnwindPlan '%s' "
@@ -1677,16 +1717,19 @@ bool RegisterContextLLDB::ForceSwitchToFallbackUnwindPlan() {
 
   if (active_row &&
       active_row->GetCFAValue().GetValueType() !=
-          UnwindPlan::Row::CFAValue::unspecified) {
+          UnwindPlan::Row::FAValue::unspecified) {
     addr_t new_cfa;
-    if (!ReadCFAValueForRow(m_fallback_unwind_plan_sp->GetRegisterKind(),
-                            active_row, new_cfa) ||
+    if (!ReadFrameAddress(m_fallback_unwind_plan_sp->GetRegisterKind(),
+                            active_row->GetCFAValue(), new_cfa) ||
         new_cfa == 0 || new_cfa == 1 || new_cfa == LLDB_INVALID_ADDRESS) {
       UnwindLogMsg("failed to get cfa with fallback unwindplan");
       m_fallback_unwind_plan_sp.reset();
       return false;
     }
 
+    ReadFrameAddress(m_fallback_unwind_plan_sp->GetRegisterKind(),
+                     active_row->GetAFAValue(), m_afa);
+
     m_full_unwind_plan_sp = m_fallback_unwind_plan_sp;
     m_fallback_unwind_plan_sp.reset();
 
@@ -1701,18 +1744,18 @@ bool RegisterContextLLDB::ForceSwitchToFallbackUnwindPlan() {
   return false;
 }
 
-bool RegisterContextLLDB::ReadCFAValueForRow(
-    lldb::RegisterKind row_register_kind, const UnwindPlan::RowSP &row,
-    addr_t &cfa_value) {
+bool RegisterContextLLDB::ReadFrameAddress(
+    lldb::RegisterKind row_register_kind, UnwindPlan::Row::FAValue &fa,
+    addr_t &address) {
   RegisterValue reg_value;
 
-  cfa_value = LLDB_INVALID_ADDRESS;
+  address = LLDB_INVALID_ADDRESS;
   addr_t cfa_reg_contents;
 
-  switch (row->GetCFAValue().GetValueType()) {
-  case UnwindPlan::Row::CFAValue::isRegisterDereferenced: {
+  switch (fa.GetValueType()) {
+  case UnwindPlan::Row::FAValue::isRegisterDereferenced: {
     RegisterNumber cfa_reg(m_thread, row_register_kind,
-                           row->GetCFAValue().GetRegisterNumber());
+                           fa.GetRegisterNumber());
     if (ReadGPRValue(cfa_reg, cfa_reg_contents)) {
       const RegisterInfo *reg_info =
           GetRegisterInfoAtIndex(cfa_reg.GetAsKind(eRegisterKindLLDB));
@@ -1721,12 +1764,12 @@ bool RegisterContextLLDB::ReadCFAValueForRow(
         Status error = ReadRegisterValueFromMemory(
             reg_info, cfa_reg_contents, reg_info->byte_size, reg_value);
         if (error.Success()) {
-          cfa_value = reg_value.GetAsUInt64();
+          address = reg_value.GetAsUInt64();
           UnwindLogMsg(
               "CFA value via dereferencing reg %s (%d): reg has val 0x%" PRIx64
               ", CFA value is 0x%" PRIx64,
               cfa_reg.GetName(), cfa_reg.GetAsKind(eRegisterKindLLDB),
-              cfa_reg_contents, cfa_value);
+              cfa_reg_contents, address);
           return true;
         } else {
           UnwindLogMsg("Tried to deref reg %s (%d) [0x%" PRIx64
@@ -1738,9 +1781,9 @@ bool RegisterContextLLDB::ReadCFAValueForRow(
     }
     break;
   }
-  case UnwindPlan::Row::CFAValue::isRegisterPlusOffset: {
+  case UnwindPlan::Row::FAValue::isRegisterPlusOffset: {
     RegisterNumber cfa_reg(m_thread, row_register_kind,
-                           row->GetCFAValue().GetRegisterNumber());
+                           fa.GetRegisterNumber());
     if (ReadGPRValue(cfa_reg, cfa_reg_contents)) {
       if (cfa_reg_contents == LLDB_INVALID_ADDRESS || cfa_reg_contents == 0 ||
           cfa_reg_contents == 1) {
@@ -1751,35 +1794,35 @@ bool RegisterContextLLDB::ReadCFAValueForRow(
         cfa_reg_contents = LLDB_INVALID_ADDRESS;
         return false;
       }
-      cfa_value = cfa_reg_contents + row->GetCFAValue().GetOffset();
+      address = cfa_reg_contents + fa.GetOffset();
       UnwindLogMsg(
           "CFA is 0x%" PRIx64 ": Register %s (%d) contents are 0x%" PRIx64
           ", offset is %d",
-          cfa_value, cfa_reg.GetName(), cfa_reg.GetAsKind(eRegisterKindLLDB),
-          cfa_reg_contents, row->GetCFAValue().GetOffset());
+          address, cfa_reg.GetName(), cfa_reg.GetAsKind(eRegisterKindLLDB),
+          cfa_reg_contents, fa.GetOffset());
       return true;
     }
     break;
   }
-  case UnwindPlan::Row::CFAValue::isDWARFExpression: {
+  case UnwindPlan::Row::FAValue::isDWARFExpression: {
     ExecutionContext exe_ctx(m_thread.shared_from_this());
     Process *process = exe_ctx.GetProcessPtr();
-    DataExtractor dwarfdata(row->GetCFAValue().GetDWARFExpressionBytes(),
-                            row->GetCFAValue().GetDWARFExpressionLength(),
+    DataExtractor dwarfdata(fa.GetDWARFExpressionBytes(),
+                            fa.GetDWARFExpressionLength(),
                             process->GetByteOrder(),
                             process->GetAddressByteSize());
     ModuleSP opcode_ctx;
     DWARFExpression dwarfexpr(opcode_ctx, dwarfdata, nullptr, 0,
-                              row->GetCFAValue().GetDWARFExpressionLength());
+                              fa.GetDWARFExpressionLength());
     dwarfexpr.SetRegisterKind(row_register_kind);
     Value result;
     Status error;
     if (dwarfexpr.Evaluate(&exe_ctx, this, 0, nullptr, nullptr, result,
                            &error)) {
-      cfa_value = result.GetScalar().ULongLong();
+      address = result.GetScalar().ULongLong();
 
       UnwindLogMsg("CFA value set by DWARF expression is 0x%" PRIx64,
-                   cfa_value);
+                   address);
       return true;
     }
     UnwindLogMsg("Failed to set CFA value via DWARF expression: %s",
diff --git a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.h b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.h
index 7e9e77dcf06..d436bc1890c 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.h
+++ b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.h
@@ -192,9 +192,9 @@ private:
 
   bool ReadGPRValue(const RegisterNumber &reg_num, lldb::addr_t &value);
 
-  // Get the CFA register for a given frame.
-  bool ReadCFAValueForRow(lldb::RegisterKind register_kind,
-                          const UnwindPlan::RowSP &row, lldb::addr_t &value);
+  // Get the Frame Address register for a given frame.
+  bool ReadFrameAddress(lldb::RegisterKind register_kind,
+                          UnwindPlan::Row::FAValue &fa, lldb::addr_t &address);
 
   lldb::UnwindPlanSP GetFastUnwindPlanForFrame();
 
@@ -225,6 +225,7 @@ private:
   int m_frame_type;               // enum FrameType
 
   lldb::addr_t m_cfa;
+  lldb::addr_t m_afa;
   lldb_private::Address m_start_pc;
   lldb_private::Address m_current_pc;
 
diff --git a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
index 327d0b0e4f7..9295a095353 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
@@ -92,7 +92,7 @@ bool UnwindAssembly_x86::AugmentUnwindPlanFromCallSite(
   // assembly parsing instead.
 
   if (first_row->GetCFAValue().GetValueType() !=
-          UnwindPlan::Row::CFAValue::isRegisterPlusOffset ||
+          UnwindPlan::Row::FAValue::isRegisterPlusOffset ||
       RegisterNumber(thread, unwind_plan.GetRegisterKind(),
                      first_row->GetCFAValue().GetRegisterNumber()) !=
           sp_regnum ||
diff --git a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
index 10a56980594..eb1989895af 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
@@ -59,6 +59,7 @@ void x86AssemblyInspectionEngine::Initialize(RegisterContextSP &reg_ctx) {
     m_machine_ip_regnum = k_machine_eip;
     m_machine_sp_regnum = k_machine_esp;
     m_machine_fp_regnum = k_machine_ebp;
+    m_machine_alt_fp_regnum = k_machine_ebx;
     m_wordsize = 4;
 
     struct lldb_reg_info reginfo;
@@ -84,6 +85,7 @@ void x86AssemblyInspectionEngine::Initialize(RegisterContextSP &reg_ctx) {
     m_machine_ip_regnum = k_machine_rip;
     m_machine_sp_regnum = k_machine_rsp;
     m_machine_fp_regnum = k_machine_rbp;
+    m_machine_alt_fp_regnum = k_machine_rbx;
     m_wordsize = 8;
 
     struct lldb_reg_info reginfo;
@@ -135,6 +137,8 @@ void x86AssemblyInspectionEngine::Initialize(RegisterContextSP &reg_ctx) {
     m_lldb_sp_regnum = lldb_regno;
   if (machine_regno_to_lldb_regno(m_machine_fp_regnum, lldb_regno))
     m_lldb_fp_regnum = lldb_regno;
+  if (machine_regno_to_lldb_regno(m_machine_alt_fp_regnum, lldb_regno))
+    m_lldb_alt_fp_regnum = lldb_regno;
   if (machine_regno_to_lldb_regno(m_machine_ip_regnum, lldb_regno))
     m_lldb_ip_regnum = lldb_regno;
 
@@ -160,6 +164,7 @@ void x86AssemblyInspectionEngine::Initialize(
     m_machine_ip_regnum = k_machine_eip;
     m_machine_sp_regnum = k_machine_esp;
     m_machine_fp_regnum = k_machine_ebp;
+    m_machine_alt_fp_regnum = k_machine_ebx;
     m_wordsize = 4;
 
     struct lldb_reg_info reginfo;
@@ -185,6 +190,7 @@ void x86AssemblyInspectionEngine::Initialize(
     m_machine_ip_regnum = k_machine_rip;
     m_machine_sp_regnum = k_machine_rsp;
     m_machine_fp_regnum = k_machine_rbp;
+    m_machine_alt_fp_regnum = k_machine_rbx;
     m_wordsize = 8;
 
     struct lldb_reg_info reginfo;
@@ -239,6 +245,8 @@ void x86AssemblyInspectionEngine::Initialize(
     m_lldb_sp_regnum = lldb_regno;
   if (machine_regno_to_lldb_regno(m_machine_fp_regnum, lldb_regno))
     m_lldb_fp_regnum = lldb_regno;
+  if (machine_regno_to_lldb_regno(m_machine_alt_fp_regnum, lldb_regno))
+    m_lldb_alt_fp_regnum = lldb_regno;
   if (machine_regno_to_lldb_regno(m_machine_ip_regnum, lldb_regno))
     m_lldb_ip_regnum = lldb_regno;
 
@@ -387,6 +395,45 @@ bool x86AssemblyInspectionEngine::mov_rsp_rbp_pattern_p() {
   return false;
 }
 
+// movq %rsp, %rbx [0x48 0x8b 0xdc] or [0x48 0x89 0xe3]
+// movl %esp, %ebx [0x8b 0xdc] or [0x89 0xe3]
+bool x86AssemblyInspectionEngine::mov_rsp_rbx_pattern_p() {
+  uint8_t *p = m_cur_insn;
+  if (m_wordsize == 8 && *p == 0x48)
+    p++;
+  if (*(p) == 0x8b && *(p + 1) == 0xdc)
+    return true;
+  if (*(p) == 0x89 && *(p + 1) == 0xe3)
+    return true;
+  return false;
+}
+
+// movq %rbp, %rsp [0x48 0x8b 0xe5] or [0x48 0x89 0xec]
+// movl %ebp, %esp [0x8b 0xe5] or [0x89 0xec]
+bool x86AssemblyInspectionEngine::mov_rbp_rsp_pattern_p() {
+  uint8_t *p = m_cur_insn;
+  if (m_wordsize == 8 && *p == 0x48)
+    p++;
+  if (*(p) == 0x8b && *(p + 1) == 0xe5)
+    return true;
+  if (*(p) == 0x89 && *(p + 1) == 0xec)
+    return true;
+  return false;
+}
+
+// movq %rbx, %rsp [0x48 0x8b 0xe3] or [0x48 0x89 0xdc]
+// movl %ebx, %esp [0x8b 0xe3] or [0x89 0xdc]
+bool x86AssemblyInspectionEngine::mov_rbx_rsp_pattern_p() {
+  uint8_t *p = m_cur_insn;
+  if (m_wordsize == 8 && *p == 0x48)
+    p++;
+  if (*(p) == 0x8b && *(p + 1) == 0xe3)
+    return true;
+  if (*(p) == 0x89 && *(p + 1) == 0xdc)
+    return true;
+  return false;
+}
+
 // subq $0x20, %rsp
 bool x86AssemblyInspectionEngine::sub_rsp_pattern_p(int &amount) {
   uint8_t *p = m_cur_insn;
@@ -476,6 +523,46 @@ bool x86AssemblyInspectionEngine::lea_rbp_rsp_pattern_p(int &amount) {
   return false;
 }
 
+// lea -0x28(%ebx), %esp
+// (32-bit and 64-bit variants, 8-bit and 32-bit displacement)
+bool x86AssemblyInspectionEngine::lea_rbx_rsp_pattern_p(int &amount) {
+  uint8_t *p = m_cur_insn;
+  if (m_wordsize == 8 && *p == 0x48)
+    p++;
+
+  // Check opcode
+  if (*p != 0x8d)
+    return false;
+  ++p;
+
+  // 8 bit displacement
+  if (*p == 0x63) {
+    amount = (int8_t)p[1];
+    return true;
+  }
+
+  // 32 bit displacement
+  if (*p == 0xa3) {
+    amount = (int32_t)extract_4(p + 1);
+    return true;
+  }
+
+  return false;
+}
+
+// and -0xfffffff0, %esp
+// (32-bit and 64-bit variants, 8-bit and 32-bit displacement)
+bool x86AssemblyInspectionEngine::and_rsp_pattern_p() {
+  uint8_t *p = m_cur_insn;
+  if (m_wordsize == 8 && *p == 0x48)
+    p++;
+
+  if (*p != 0x81 && *p != 0x83)
+    return false;
+
+  return *++p == 0xe4;
+}
+
 // popq %rbx
 // popl %ebx
 bool x86AssemblyInspectionEngine::pop_reg_p(int &regno) {
@@ -640,7 +727,8 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     return false;
 
   addr_t current_func_text_offset = 0;
-  int current_sp_bytes_offset_from_cfa = 0;
+  int current_sp_bytes_offset_from_fa = 0;
+  bool is_aligned = false;
   UnwindPlan::Row::RegisterLocation initial_regloc;
   UnwindPlan::RowSP row(new UnwindPlan::Row);
 
@@ -657,8 +745,8 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
   row->SetRegisterInfo(m_lldb_sp_regnum, initial_regloc);
 
   // saved instruction pointer can be found at CFA - wordsize.
-  current_sp_bytes_offset_from_cfa = m_wordsize;
-  initial_regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_cfa);
+  current_sp_bytes_offset_from_fa = m_wordsize;
+  initial_regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_fa);
   row->SetRegisterInfo(m_lldb_ip_regnum, initial_regloc);
 
   unwind_plan.AppendRow(row);
@@ -682,6 +770,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
   UnwindPlan::RowSP prologue_completed_row; // copy of prologue row of CFI
   int prologue_completed_sp_bytes_offset_from_cfa; // The sp value before the
                                                    // epilogue started executed
+  bool prologue_completed_is_aligned;
   std::vector<bool> prologue_completed_saved_registers;
 
   while (current_func_text_offset < size) {
@@ -701,22 +790,59 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
       break;
     }
 
-    if (push_rbp_pattern_p()) {
-      current_sp_bytes_offset_from_cfa += m_wordsize;
-      row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
-      UnwindPlan::Row::RegisterLocation regloc;
-      regloc.SetAtCFAPlusOffset(-row->GetCFAValue().GetOffset());
-      row->SetRegisterInfo(m_lldb_fp_regnum, regloc);
-      saved_registers[m_machine_fp_regnum] = true;
-      row_updated = true;
+    auto &cfa_value = row->GetCFAValue();
+    auto &afa_value = row->GetAFAValue();
+    auto fa_value_ptr = is_aligned ? &afa_value : &cfa_value;
+
+    if (mov_rsp_rbp_pattern_p()) {
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_fp_regnum, fa_value_ptr->GetOffset());
+        row_updated = true;
+      }
     }
 
-    else if (mov_rsp_rbp_pattern_p()) {
-      row->GetCFAValue().SetIsRegisterPlusOffset(
-          m_lldb_fp_regnum, row->GetCFAValue().GetOffset());
+    else if (mov_rsp_rbx_pattern_p()) {
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_alt_fp_regnum, fa_value_ptr->GetOffset());
+        row_updated = true;
+      }
+    }
+
+    else if (and_rsp_pattern_p()) {
+      current_sp_bytes_offset_from_fa = 0;
+      afa_value.SetIsRegisterPlusOffset(
+          m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
+      fa_value_ptr = &afa_value;
+      is_aligned = true;
       row_updated = true;
     }
 
+    else if (mov_rbp_rsp_pattern_p()) {
+      if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_fp_regnum)
+      {
+        is_aligned = false;
+        fa_value_ptr = &cfa_value;
+        afa_value.SetUnspecified();
+        row_updated = true;
+      }
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum)
+        current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
+    }
+
+    else if (mov_rbx_rsp_pattern_p()) {
+      if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_alt_fp_regnum)
+      {
+        is_aligned = false;
+        fa_value_ptr = &cfa_value;
+        afa_value.SetUnspecified();
+        row_updated = true;
+      }
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum)
+        current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
+    }
+
     // This is the start() function (or a pthread equivalent), it starts with a
     // pushl $0x0 which puts the saved pc value of 0 on the stack.  In this
     // case we want to pretend we didn't see a stack movement at all --
@@ -726,12 +852,12 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     }
 
     else if (push_reg_p(machine_regno)) {
-      current_sp_bytes_offset_from_cfa += m_wordsize;
-      // the PUSH instruction has moved the stack pointer - if the CFA is set
+      current_sp_bytes_offset_from_fa += m_wordsize;
+      // the PUSH instruction has moved the stack pointer - if the FA is set
       // in terms of the stack pointer, we need to add a new row of
       // instructions.
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
       // record where non-volatile (callee-saved, spilled) registers are saved
@@ -740,7 +866,10 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
           machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
           saved_registers[machine_regno] == false) {
         UnwindPlan::Row::RegisterLocation regloc;
-        regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_cfa);
+        if (is_aligned)
+            regloc.SetAtAFAPlusOffset(-current_sp_bytes_offset_from_fa);
+        else
+            regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_fa);
         row->SetRegisterInfo(lldb_regno, regloc);
         saved_registers[machine_regno] = true;
         row_updated = true;
@@ -748,7 +877,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     }
 
     else if (pop_reg_p(machine_regno)) {
-      current_sp_bytes_offset_from_cfa -= m_wordsize;
+      current_sp_bytes_offset_from_fa -= m_wordsize;
 
       if (nonvolatile_reg_p(machine_regno) &&
           machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
@@ -756,29 +885,29 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
         saved_registers[machine_regno] = false;
         row->RemoveRegisterInfo(lldb_regno);
 
-        if (machine_regno == (int)m_machine_fp_regnum) {
-          row->GetCFAValue().SetIsRegisterPlusOffset(
-              m_lldb_sp_regnum, row->GetCFAValue().GetOffset());
+        if (lldb_regno == fa_value_ptr->GetRegisterNumber()) {
+          fa_value_ptr->SetIsRegisterPlusOffset(
+              m_lldb_sp_regnum, fa_value_ptr->GetOffset());
         }
 
         in_epilogue = true;
         row_updated = true;
       }
 
-      // the POP instruction has moved the stack pointer - if the CFA is set in
+      // the POP instruction has moved the stack pointer - if the FA is set in
       // terms of the stack pointer, we need to add a new row of instructions.
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetIsRegisterPlusOffset(
-            m_lldb_sp_regnum, current_sp_bytes_offset_from_cfa);
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
     }
 
     else if (pop_misc_reg_p()) {
-      current_sp_bytes_offset_from_cfa -= m_wordsize;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetIsRegisterPlusOffset(
-            m_lldb_sp_regnum, current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa -= m_wordsize;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
     }
@@ -787,24 +916,38 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     // off the stack into rbp (restoring the caller's rbp value). It is the
     // opposite of ENTER, or 'push rbp, mov rsp rbp'.
     else if (leave_pattern_p()) {
-      // We're going to copy the value in rbp into rsp, so re-set the sp offset
-      // based on the CFAValue.  Also, adjust it to recognize that we're
-      // popping the saved rbp value off the stack.
-      current_sp_bytes_offset_from_cfa = row->GetCFAValue().GetOffset();
-      current_sp_bytes_offset_from_cfa -= m_wordsize;
-      row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
-
-      // rbp is restored to the caller's value
-      saved_registers[m_machine_fp_regnum] = false;
-      row->RemoveRegisterInfo(m_lldb_fp_regnum);
-
-      // cfa is now in terms of rsp again.
-      row->GetCFAValue().SetIsRegisterPlusOffset(
-          m_lldb_sp_regnum, row->GetCFAValue().GetOffset());
-      row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      if (saved_registers[m_machine_fp_regnum]) {
+        saved_registers[m_machine_fp_regnum] = false;
+        row->RemoveRegisterInfo(m_lldb_fp_regnum);
+
+        row_updated = true;
+      }
+
+      if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_fp_regnum)
+      {
+        is_aligned = false;
+        fa_value_ptr = &cfa_value;
+        afa_value.SetUnspecified();
+        row_updated = true;
+      }
+
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum)
+      {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_sp_regnum, fa_value_ptr->GetOffset());
+
+        current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
+      }
+
+      current_sp_bytes_offset_from_fa -= m_wordsize;
+
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetIsRegisterPlusOffset(
+            m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
+        row_updated = true;
+      }
 
       in_epilogue = true;
-      row_updated = true;
     }
 
     else if (mov_reg_to_local_stack_frame_p(machine_regno, stack_offset) &&
@@ -816,12 +959,14 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
       UnwindPlan::Row::RegisterLocation regloc;
 
       // stack_offset for 'movq %r15, -80(%rbp)' will be 80. In the Row, we
-      // want to express this as the offset from the CFA.  If the frame base is
-      // rbp (like the above instruction), the CFA offset for rbp is probably
-      // 16.  So we want to say that the value is stored at the CFA address -
+      // want to express this as the offset from the FA.  If the frame base is
+      // rbp (like the above instruction), the FA offset for rbp is probably
+      // 16.  So we want to say that the value is stored at the FA address -
       // 96.
-      regloc.SetAtCFAPlusOffset(
-          -(stack_offset + row->GetCFAValue().GetOffset()));
+      if (is_aligned)
+          regloc.SetAtAFAPlusOffset(-(stack_offset + fa_value_ptr->GetOffset()));
+      else
+          regloc.SetAtCFAPlusOffset(-(stack_offset + fa_value_ptr->GetOffset()));
 
       row->SetRegisterInfo(lldb_regno, regloc);
 
@@ -829,17 +974,17 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     }
 
     else if (sub_rsp_pattern_p(stack_offset)) {
-      current_sp_bytes_offset_from_cfa += stack_offset;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa += stack_offset;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
     }
 
     else if (add_rsp_pattern_p(stack_offset)) {
-      current_sp_bytes_offset_from_cfa -= stack_offset;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa -= stack_offset;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
       in_epilogue = true;
@@ -847,27 +992,48 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
 
     else if (push_extended_pattern_p() || push_imm_pattern_p() ||
              push_misc_reg_p()) {
-      current_sp_bytes_offset_from_cfa += m_wordsize;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa += m_wordsize;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
     }
 
     else if (lea_rsp_pattern_p(stack_offset)) {
-      current_sp_bytes_offset_from_cfa -= stack_offset;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa -= stack_offset;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
       if (stack_offset > 0)
         in_epilogue = true;
     }
 
-    else if (lea_rbp_rsp_pattern_p(stack_offset) &&
-             row->GetCFAValue().GetRegisterNumber() == m_lldb_fp_regnum) {
-      current_sp_bytes_offset_from_cfa =
-          row->GetCFAValue().GetOffset() - stack_offset;
+    else if (lea_rbp_rsp_pattern_p(stack_offset)) {
+      if (is_aligned &&
+          cfa_value.GetRegisterNumber() == m_lldb_fp_regnum) {
+        is_aligned = false;
+        fa_value_ptr = &cfa_value;
+        afa_value.SetUnspecified();
+        row_updated = true;
+      }
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum) {
+        current_sp_bytes_offset_from_fa =
+          fa_value_ptr->GetOffset() - stack_offset;
+      }
+    }
+
+    else if (lea_rbx_rsp_pattern_p(stack_offset)) {
+      if (is_aligned &&
+          cfa_value.GetRegisterNumber() == m_lldb_alt_fp_regnum) {
+        is_aligned = false;
+        fa_value_ptr = &cfa_value;
+        afa_value.SetUnspecified();
+        row_updated = true;
+      }
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum) {
+        current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset() - stack_offset;
+      }
     }
 
     else if (ret_pattern_p() && prologue_completed_row.get()) {
@@ -877,8 +1043,9 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
       UnwindPlan::Row *newrow = new UnwindPlan::Row;
       *newrow = *prologue_completed_row.get();
       row.reset(newrow);
-      current_sp_bytes_offset_from_cfa =
+      current_sp_bytes_offset_from_fa =
           prologue_completed_sp_bytes_offset_from_cfa;
+      is_aligned = prologue_completed_is_aligned;
 
       saved_registers.clear();
       saved_registers.resize(prologue_completed_saved_registers.size(), false);
@@ -896,9 +1063,9 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     // This is used in i386 programs to get the PIC base address for finding
     // global data
     else if (call_next_insn_pattern_p()) {
-      current_sp_bytes_offset_from_cfa += m_wordsize;
-      if (row->GetCFAValue().GetRegisterNumber() == m_lldb_sp_regnum) {
-        row->GetCFAValue().SetOffset(current_sp_bytes_offset_from_cfa);
+      current_sp_bytes_offset_from_fa += m_wordsize;
+      if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
+        fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
         row_updated = true;
       }
     }
@@ -931,7 +1098,8 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
     // track of it either way.
     if (in_epilogue == false) {
       prologue_completed_sp_bytes_offset_from_cfa =
-          current_sp_bytes_offset_from_cfa;
+          current_sp_bytes_offset_from_fa;
+      prologue_completed_is_aligned = is_aligned;
     }
 
     m_cur_insn = m_cur_insn + insn_len;
diff --git a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.h b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.h
index cec9803c8a4..e02b510ba1f 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.h
+++ b/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.h
@@ -98,10 +98,15 @@ private:
   bool push_extended_pattern_p();
   bool push_misc_reg_p();
   bool mov_rsp_rbp_pattern_p();
+  bool mov_rsp_rbx_pattern_p();
+  bool mov_rbp_rsp_pattern_p();
+  bool mov_rbx_rsp_pattern_p();
   bool sub_rsp_pattern_p(int &amount);
   bool add_rsp_pattern_p(int &amount);
   bool lea_rsp_pattern_p(int &amount);
   bool lea_rbp_rsp_pattern_p(int &amount);
+  bool lea_rbx_rsp_pattern_p(int &amount);
+  bool and_rsp_pattern_p();
   bool push_reg_p(int &regno);
   bool pop_reg_p(int &regno);
   bool pop_rbp_pattern_p();
@@ -157,9 +162,11 @@ private:
   uint32_t m_machine_ip_regnum;
   uint32_t m_machine_sp_regnum;
   uint32_t m_machine_fp_regnum;
+  uint32_t m_machine_alt_fp_regnum;
   uint32_t m_lldb_ip_regnum;
   uint32_t m_lldb_sp_regnum;
   uint32_t m_lldb_fp_regnum;
+  uint32_t m_lldb_alt_fp_regnum;
 
   typedef std::map<uint32_t, lldb_reg_info> MachineRegnumToNameAndLLDBRegnum;
 
diff --git a/lldb/source/Symbol/UnwindPlan.cpp b/lldb/source/Symbol/UnwindPlan.cpp
index 23ca1324ab0..0f8d9bf7e5a 100644
--- a/lldb/source/Symbol/UnwindPlan.cpp
+++ b/lldb/source/Symbol/UnwindPlan.cpp
@@ -29,6 +29,8 @@ operator==(const UnwindPlan::Row::RegisterLocation &rhs) const {
 
     case atCFAPlusOffset:
     case isCFAPlusOffset:
+    case atAFAPlusOffset:
+    case isAFAPlusOffset:
       return m_location.offset == rhs.m_location.offset;
 
     case inOtherRegister:
@@ -95,6 +97,16 @@ void UnwindPlan::Row::RegisterLocation::Dump(Stream &s,
       s.PutChar(']');
   } break;
 
+  case atAFAPlusOffset:
+  case isAFAPlusOffset: {
+    s.PutChar('=');
+    if (m_type == atAFAPlusOffset)
+      s.PutChar('[');
+    s.Printf("AFA%+d", m_location.offset);
+    if (m_type == atAFAPlusOffset)
+      s.PutChar(']');
+  } break;
+
   case inOtherRegister: {
     const RegisterInfo *other_reg_info = nullptr;
     if (unwind_plan)
@@ -125,8 +137,8 @@ static void DumpRegisterName(Stream &s, const UnwindPlan *unwind_plan,
     s.Printf("reg(%u)", reg_num);
 }
 
-bool UnwindPlan::Row::CFAValue::
-operator==(const UnwindPlan::Row::CFAValue &rhs) const {
+bool UnwindPlan::Row::FAValue::
+operator==(const UnwindPlan::Row::FAValue &rhs) const {
   if (m_type == rhs.m_type) {
     switch (m_type) {
     case unspecified:
@@ -148,7 +160,7 @@ operator==(const UnwindPlan::Row::CFAValue &rhs) const {
   return false;
 }
 
-void UnwindPlan::Row::CFAValue::Dump(Stream &s, const UnwindPlan *unwind_plan,
+void UnwindPlan::Row::FAValue::Dump(Stream &s, const UnwindPlan *unwind_plan,
                                      Thread *thread) const {
   switch (m_type) {
   case isRegisterPlusOffset:
@@ -171,6 +183,7 @@ void UnwindPlan::Row::CFAValue::Dump(Stream &s, const UnwindPlan *unwind_plan,
 
 void UnwindPlan::Row::Clear() {
   m_cfa_value.SetUnspecified();
+  m_afa_value.SetUnspecified();
   m_offset = 0;
   m_register_locations.clear();
 }
@@ -183,6 +196,12 @@ void UnwindPlan::Row::Dump(Stream &s, const UnwindPlan *unwind_plan,
     s.Printf("%4" PRId64 ": CFA=", GetOffset());
 
   m_cfa_value.Dump(s, unwind_plan, thread);
+
+  if (!m_afa_value.IsUnspecified()) {
+    s.Printf(" AFA=");
+    m_afa_value.Dump(s, unwind_plan, thread);
+  }
+
   s.Printf(" => ");
   for (collection::const_iterator idx = m_register_locations.begin();
        idx != m_register_locations.end(); ++idx) {
@@ -194,7 +213,8 @@ void UnwindPlan::Row::Dump(Stream &s, const UnwindPlan *unwind_plan,
   s.EOL();
 }
 
-UnwindPlan::Row::Row() : m_offset(0), m_cfa_value(), m_register_locations() {}
+UnwindPlan::Row::Row()
+    : m_offset(0), m_cfa_value(), m_afa_value(), m_register_locations() {}
 
 bool UnwindPlan::Row::GetRegisterInfo(
     uint32_t reg_num,
@@ -296,8 +316,10 @@ bool UnwindPlan::Row::SetRegisterLocationToSame(uint32_t reg_num,
 }
 
 bool UnwindPlan::Row::operator==(const UnwindPlan::Row &rhs) const {
-  return m_offset == rhs.m_offset && m_cfa_value == rhs.m_cfa_value &&
-         m_register_locations == rhs.m_register_locations;
+  return m_offset == rhs.m_offset &&
+      m_cfa_value == rhs.m_cfa_value &&
+      m_afa_value == rhs.m_afa_value &&
+      m_register_locations == rhs.m_register_locations;
 }
 
 void UnwindPlan::AppendRow(const UnwindPlan::RowSP &row_sp) {
@@ -399,7 +421,7 @@ bool UnwindPlan::PlanValidAtAddress(Address addr) {
   // UnwindPlan.
   if (GetRowAtIndex(0).get() == nullptr ||
       GetRowAtIndex(0)->GetCFAValue().GetValueType() ==
-          Row::CFAValue::unspecified) {
+          Row::FAValue::unspecified) {
     Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
     if (log) {
       StreamString s;