[lldb] [Process/NetBSD] Set xs_xstate_bv correctly when setting regs

[mgorny]

Summary

Ensure that xs_xstate_bv is set correctly before calling
WriteRegisterSet(). The bit can be clear if the relevant registers
were at their initial state when they were read, and it needs to be set
in order to apply changes from the XState structure.

[mgorny]

Hmm, I have an idea how to avoid all this repetition.

[mgorny]

Reduce the repetition by bringing the most common case out.

[labath]

Linux has this factored into a separate function (UpdateXSTATEforWrite), but this isn't too bad either. Could be another candidate for factoring...

lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp

Status NativeRegisterContextNetBSD_x86_64::WriteRegister(
   if (set == -1) {
     // This is likely an internal register for lldb use only and should not be
     // directly queried.
     error.SetErrorStringWithFormat("register \"%s\" is in unrecognized set",
                                    reg_info->name);
     return error;
   }
 
+  uint64_t new_xstate_bv = XCR0_X87;  // the most common case
+
   switch (GetRegisterInfoInterface().GetTargetArchitecture().GetMachine()) {
   case llvm::Triple::x86_64:
     break;
   case llvm::Triple::x86:
     reg = RegNumX86ToX86_64(reg);
     break;
   default:
     llvm_unreachable("Unhandled target architecture.");
#endif
   case lldb_foseg_x86_64:
     m_xstate.xs_fxsave.fx_dp.fa_32.fa_seg = reg_value.GetAsUInt32();
     break;
   case lldb_fooff_x86_64:
     m_xstate.xs_fxsave.fx_dp.fa_32.fa_off = reg_value.GetAsUInt32();
     break;
   case lldb_mxcsr_x86_64:
     m_xstate.xs_fxsave.fx_mxcsr = reg_value.GetAsUInt32();
+    new_xstate_bv = XCR0_SSE;
     break;
   case lldb_mxcsrmask_x86_64:
     m_xstate.xs_fxsave.fx_mxcsr_mask = reg_value.GetAsUInt32();
+    new_xstate_bv = XCR0_SSE;
     break;
   case lldb_st0_x86_64:
   case lldb_st1_x86_64:
   case lldb_st2_x86_64:
   case lldb_st3_x86_64:
   case lldb_st4_x86_64:
   case lldb_st5_x86_64:
   case lldb_st6_x86_64:
#endif
   case lldb_xmm14_x86_64:
   case lldb_xmm15_x86_64:
     if (!(m_xstate.xs_rfbm & XCR0_SSE)) {
       error.SetErrorStringWithFormat(
           "register \"%s\" not supported by CPU/kernel", reg_info->name);
     } else {
       ::memcpy(&m_xstate.xs_fxsave.fx_xmm[reg - lldb_xmm0_x86_64],
                reg_value.GetBytes(), reg_value.GetByteSize());
+      new_xstate_bv = XCR0_SSE;
     }
     break;
   case lldb_ymm0_x86_64:
   case lldb_ymm1_x86_64:
   case lldb_ymm2_x86_64:
   case lldb_ymm3_x86_64:
   case lldb_ymm4_x86_64:
   case lldb_ymm5_x86_64:
if (!(m_xstate.xs_rfbm & XCR0_SSE) ||
       error.SetErrorStringWithFormat(
           "register \"%s\" not supported by CPU/kernel", reg_info->name);
     } else {
       uint32_t reg_index = reg - lldb_ymm0_x86_64;
       YMMReg ymm;
       ::memcpy(ymm.bytes, reg_value.GetBytes(), reg_value.GetByteSize());
       YMMToXState(ymm, m_xstate.xs_fxsave.fx_xmm[reg_index].xmm_bytes,
                   m_xstate.xs_ymm_hi128.xs_ymm[reg_index].ymm_bytes);
+      new_xstate_bv = XCR0_SSE | XCR0_YMM_Hi128;
     }
     break;
   case lldb_dr0_x86_64:
   case lldb_dr1_x86_64:
   case lldb_dr2_x86_64:
   case lldb_dr3_x86_64:
   case lldb_dr4_x86_64:
   case lldb_dr5_x86_64:
   case lldb_dr6_x86_64:
   case lldb_dr7_x86_64:
     m_dbr.dr[reg - lldb_dr0_x86_64] = reg_value.GetAsUInt64();
     break;
   default:
     llvm_unreachable("Reading unknown/unsupported register");
   }
 
+  if (set == XStateRegSet)
+    m_xstate.xs_xstate_bv |= new_xstate_bv;
+
   return WriteRegisterSet(set);
 }
 
 Status NativeRegisterContextNetBSD_x86_64::ReadAllRegisterValues(
     lldb::DataBufferSP &data_sp) {
   Status error;
 
   data_sp.reset(new DataBufferHeap(REG_CONTEXT_SIZE, 0));