Add recognition for another x86 epilogue sequence (ret followed by

a nop).  Fixes an instruction stepping problem when trying to step
over the final instructions of an epilogue.
<rdar://problem/18068877> 

llvm-svn: 221241

1 files changed, 11 insertions, 0 deletions

diff --git a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
index 32a21d2b8bb..d6f8f2457f0 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
@@ -804,6 +804,12 @@ loopnext:
     //  [ 0xc3 ] ret
     //  [ 0xe8 xx xx xx xx ] call __stack_chk_fail  (this is sometimes the final insn in the function)
 
+    // or
+
+    //  [ 0x5d ] mov %rbp, %rsp  (aka pop %rbp)
+    //  [ 0xc3 ] ret
+    //  [ 0x0f 0x1f 0x44 xx xx ] nopl (%rax,%rax)   (aka nop)
+
     // We want to add a Row describing how to unwind when we're stopped on the 'ret' instruction where the
     // CFA is no longer defined in terms of rbp, but is now defined in terms of rsp like on function entry.
     // (or the 'jmp' instruction in the second case)
@@ -834,6 +840,11 @@ loopnext:
             {
                 ret_insn_offset = m_func_bounds.GetByteSize() - 6;
             }
+            else if (bytebuf[0] == 0x5d && bytebuf[1] == 0xc3 
+                     && bytebuf[2] == 0x0f && bytebuf[3] == 0x1f & bytebuf[4] == 0x44) // mov & ret & nop
+            {
+                ret_insn_offset = m_func_bounds.GetByteSize() - 6;
+            }
         }
     }
     else if (m_func_bounds.GetByteSize() > 2)