[lldb] [Process] Introduce common helpers to split/recombine YMM data

[mgorny]

Summary

Introduce two common helpers to take care of splitting and recombining
YMM registers to/from XSAVE-like data. Since FreeBSD, Linux and NetBSD
all use XSAVE-like data structures but with potentially different field
layouts, the function takes two pointers -- to XMM register and to YMM
high bits, and copies the data from/to YMMReg type.

While at it, remove support for big endian. To mine and Pavel Labath's
combined knowledge, there is no such thing on x86. Furthermore,
assuming that the YMM register data would be swapped for big endian
seems to be a weird assumption.

// NB: I have no clue why FreeBSD code claims to belong in 'POSIX', and Linux does not.

[labath]

It's not much, but it definitely does help.

// NB: I have no clue why FreeBSD code claims to belong in 'POSIX', and Linux does not.

I think that somehow fell out of the fact that FreeBSD uses an in-process debugging plugin, while linux uses lldb-server.

lldb/source/Plugins/Process/Utility/RegisterContext_x86.h

357

maybe call the last arg ymmh_bytes ?

[mgorny]

In D63610#1553143, @labath wrote:

It's not much, but it definitely does help.

// NB: I have no clue why FreeBSD code claims to belong in 'POSIX', and Linux does not.

I think that somehow fell out of the fact that FreeBSD uses an in-process debugging plugin, while linux uses lldb-server.

Ok, then I probably don't have to worry about porting NetBSD to reuse that stuff ;-).

lldb/source/Plugins/Process/Utility/RegisterContext_x86.h

357

Makes sense.

[labath]

In D63610#1553461, @mgorny wrote:

In D63610#1553143, @labath wrote:

It's not much, but it definitely does help.

// NB: I have no clue why FreeBSD code claims to belong in 'POSIX', and Linux does not.

I think that somehow fell out of the fact that FreeBSD uses an in-process debugging plugin, while linux uses lldb-server.

Ok, then I probably don't have to worry about porting NetBSD to reuse that stuff ;-).

No, but if you can figure out how to make Linux and NetBSD share more stuff, then that would be super-awesome. :)

lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp

 }
 
 bool NativeRegisterContextLinux_x86_64::CopyXSTATEtoYMM(
     uint32_t reg_index, lldb::ByteOrder byte_order) {
   if (!IsAVX(reg_index))
     return false;
 
   if (byte_order == lldb::eByteOrderLittle) {
-    ::memcpy(m_ymm_set.ymm[reg_index - m_reg_info.first_ymm].bytes,
-             m_xstate->fxsave.xmm[reg_index - m_reg_info.first_ymm].bytes,
-             sizeof(XMMReg));
-    ::memcpy(m_ymm_set.ymm[reg_index - m_reg_info.first_ymm].bytes +
-                 sizeof(XMMReg),
-             m_xstate->xsave.ymmh[reg_index - m_reg_info.first_ymm].bytes,
-             sizeof(YMMHReg));
+    uint32_t reg_no = reg_index - m_reg_info.first_ymm;
+    m_ymm_set.ymm[reg_no] = XStateToYMM(
+        m_xstate->fxsave.xmm[reg_no].bytes,
+        m_xstate->xsave.ymmh[reg_no].bytes);
     return true;
   }
 
-  if (byte_order == lldb::eByteOrderBig) {
-    ::memcpy(m_ymm_set.ymm[reg_index - m_reg_info.first_ymm].bytes +
-                 sizeof(XMMReg),
-             m_xstate->fxsave.xmm[reg_index - m_reg_info.first_ymm].bytes,
-             sizeof(XMMReg));
-    ::memcpy(m_ymm_set.ymm[reg_index - m_reg_info.first_ymm].bytes,
-             m_xstate->xsave.ymmh[reg_index - m_reg_info.first_ymm].bytes,
-             sizeof(YMMHReg));
-    return true;
-  }
   return false; // unsupported or invalid byte order
 }
 
 bool NativeRegisterContextLinux_x86_64::CopyYMMtoXSTATE(
     uint32_t reg, lldb::ByteOrder byte_order) {
   if (!IsAVX(reg))
     return false;
 
   if (byte_order == lldb::eByteOrderLittle) {
-    ::memcpy(m_xstate->fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes, sizeof(XMMReg));
-    ::memcpy(m_xstate->xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             sizeof(YMMHReg));
+    uint32_t reg_no = reg - m_reg_info.first_ymm;
+    YMMToXState(m_ymm_set.ymm[reg_no],
+        m_xstate->fxsave.xmm[reg_no].bytes,
+        m_xstate->xsave.ymmh[reg_no].bytes);
     return true;
   }
 
-  if (byte_order == lldb::eByteOrderBig) {
-    ::memcpy(m_xstate->fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             sizeof(XMMReg));
-    ::memcpy(m_xstate->xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes, sizeof(YMMHReg));
-    return true;
-  }
   return false; // unsupported or invalid byte order
 }
 
 void *NativeRegisterContextLinux_x86_64::GetFPRBuffer() {
   switch (m_xstate_type) {
   case XStateType::FXSAVE:
     return &m_xstate->fxsave;
   case XStateType::XSAVE:

lldb/source/Plugins/Process/Utility/RegisterContextPOSIX_x86.cpp

 
 // Parse ymm registers and into xmm.bytes and ymmh.bytes.
 bool RegisterContextPOSIX_x86::CopyYMMtoXSTATE(uint32_t reg,
                                                lldb::ByteOrder byte_order) {
   if (!IsAVX(reg))
     return false;
 
   if (byte_order == eByteOrderLittle) {
-    ::memcpy(m_fpr.fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes, sizeof(XMMReg));
-    ::memcpy(m_fpr.xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             sizeof(YMMHReg));
+    uint32_t reg_no = reg - m_reg_info.first_ymm;
+    YMMToXState(m_ymm_set.ymm[reg_no],
+        m_fpr.fxsave.xmm[reg_no].bytes,
+        m_fpr.xsave.ymmh[reg_no].bytes);
     return true;
   }
 
-  if (byte_order == eByteOrderBig) {
-    ::memcpy(m_fpr.fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             sizeof(XMMReg));
-    ::memcpy(m_fpr.xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes, sizeof(YMMHReg));
-    return true;
-  }
   return false; // unsupported or invalid byte order
 }
 
 // Concatenate xmm.bytes with ymmh.bytes
 bool RegisterContextPOSIX_x86::CopyXSTATEtoYMM(uint32_t reg,
                                                lldb::ByteOrder byte_order) {
   if (!IsAVX(reg))
     return false;
 
   if (byte_order == eByteOrderLittle) {
-    ::memcpy(m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes,
-             m_fpr.fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             sizeof(XMMReg));
-    ::memcpy(m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             m_fpr.xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             sizeof(YMMHReg));
+    uint32_t reg_no = reg - m_reg_info.first_ymm;
+    m_ymm_set.ymm[reg_no] = XStateToYMM(
+        m_fpr.fxsave.xmm[reg_no].bytes,
+        m_fpr.xsave.ymmh[reg_no].bytes);
     return true;
   }
 
-  if (byte_order == eByteOrderBig) {
-    ::memcpy(m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes + sizeof(XMMReg),
-             m_fpr.fxsave.xmm[reg - m_reg_info.first_ymm].bytes,
-             sizeof(XMMReg));
-    ::memcpy(m_ymm_set.ymm[reg - m_reg_info.first_ymm].bytes,
-             m_fpr.xsave.ymmh[reg - m_reg_info.first_ymm].bytes,
-             sizeof(YMMHReg));
-    return true;
-  }
   return false; // unsupported or invalid byte order
 }
 
 bool RegisterContextPOSIX_x86::IsRegisterSetAvailable(size_t set_index) {
   // Note: Extended register sets are assumed to be at the end of g_reg_sets...
   size_t num_sets = k_num_register_sets - k_num_extended_register_sets;
 
   if (GetFPRType() == eXSAVE) // ...and to start with AVX registers.

lldb/source/Plugins/Process/Utility/RegisterContext_x86.h

 // Floating-point registers
 union FPR {
   FXSAVE fxsave; // Generic floating-point registers.
   XSAVE xsave;   // x86 extended processor state.
 };
 
 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
 
+// Convenience function to combine YMM register data from XSAVE-style input.
+inline YMMReg XStateToYMM(const void* xmm_bytes, const void* ymm_bytes) {
+  YMMReg ret;
+
+  ::memcpy(ret.bytes, xmm_bytes, sizeof(XMMReg));
+  ::memcpy(ret.bytes + sizeof(XMMReg), ymm_bytes, sizeof(YMMHReg));
+
+  return ret;
+}
+
+// Convenience function to copy YMM register data into XSAVE-style output.
+inline void YMMToXState(const YMMReg& input, void* xmm_bytes, void* ymm_bytes) {
+  ::memcpy(xmm_bytes, input.bytes, sizeof(XMMReg));
+  ::memcpy(ymm_bytes, input.bytes + sizeof(XMMReg), sizeof(YMMHReg));
+}
+
 } // namespace lldb_private
 
 #endif