[idd] lgmp: stream staged copies to WC memory

idd/LGCommon/LGCommon.vcxproj

@@ -74,6 +74,10 @@
     <ClCompile Include="WCCopyAVX2.cpp">
       <EnableEnhancedInstructionSet>AdvancedVectorExtensions2</EnableEnhancedInstructionSet>
     </ClCompile>
+    <ClCompile Include="WCWrite.cpp" />
+    <ClCompile Include="WCWriteAVX2.cpp">
+      <EnableEnhancedInstructionSet>AdvancedVectorExtensions2</EnableEnhancedInstructionSet>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="CClipboardChannel.h" />
@@ -90,6 +94,7 @@
     <ClInclude Include="RefreshRate.h" />
     <ClInclude Include="Seq.h" />
     <ClInclude Include="WCCopy.h" />
+    <ClInclude Include="WCWrite.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets" />

idd/LGCommon/LGCommon.vcxproj.filters

@@ -33,6 +33,12 @@
     <ClCompile Include="WCCopyAVX2.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="WCWrite.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="WCWriteAVX2.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Atomic.h">
@@ -77,5 +83,8 @@
     <ClInclude Include="WCCopy.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="WCWrite.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

idd/LGCommon/WCWrite.cpp

@@ -0,0 +1,146 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "WCWrite.h"
+
+#include <atomic>
+#include <immintrin.h>
+#include <intrin.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace WCWrite
+{
+  namespace Detail
+  {
+    void CopyAVX2(void * destination, const void * source, size_t size);
+  }
+
+  namespace
+  {
+    using CopyFn = void (*)(void *, const void *, size_t);
+    static constexpr unsigned __int64 AVX_XSTATE_MASK = 0x6U;
+
+    void CopyFallback(void * destination, const void * source, size_t size)
+    {
+      memcpy(destination, source, size);
+    }
+
+#if defined(_M_IX86) || defined(_M_X64)
+    __declspec(noinline) void CopySSE41(
+      void * destination, const void * source, size_t size)
+    {
+      uint8_t * dst       = static_cast<uint8_t *>(destination);
+      const uint8_t * src = static_cast<const uint8_t *>(source);
+
+      const size_t prefix =
+        (16U - (reinterpret_cast<uintptr_t>(dst) & 15U)) & 15U;
+      if (prefix)
+      {
+        const size_t copy = prefix < size ? prefix : size;
+        memcpy(dst, src, copy);
+        dst  += copy;
+        src  += copy;
+        size -= copy;
+      }
+
+      while (size >= 64U)
+      {
+        const __m128i v0 = _mm_loadu_si128(
+          reinterpret_cast<const __m128i *>(src +  0));
+        const __m128i v1 = _mm_loadu_si128(
+          reinterpret_cast<const __m128i *>(src + 16));
+        const __m128i v2 = _mm_loadu_si128(
+          reinterpret_cast<const __m128i *>(src + 32));
+        const __m128i v3 = _mm_loadu_si128(
+          reinterpret_cast<const __m128i *>(src + 48));
+        __m128i * output = reinterpret_cast<__m128i *>(dst);
+        _mm_stream_si128(output + 0, v0);
+        _mm_stream_si128(output + 1, v1);
+        _mm_stream_si128(output + 2, v2);
+        _mm_stream_si128(output + 3, v3);
+        dst  += 64U;
+        src  += 64U;
+        size -= 64U;
+      }
+
+      while (size >= 16U)
+      {
+        const __m128i value = _mm_loadu_si128(
+          reinterpret_cast<const __m128i *>(src));
+        _mm_stream_si128(reinterpret_cast<__m128i *>(dst), value);
+        dst  += 16U;
+        src  += 16U;
+        size -= 16U;
+      }
+
+      if (size)
+        memcpy(dst, src, size);
+    }
+
+    CopyFn SelectCopy()
+    {
+      int registers[4] = {};
+      __cpuid(registers, 0);
+      const int maximumLeaf = registers[0];
+      if (maximumLeaf < 1)
+        return &CopyFallback;
+
+      __cpuidex(registers, 1, 0);
+      const bool sse41   = (registers[2] & (1 << 19)) != 0;
+      const bool avx     = (registers[2] & (1 << 28)) != 0;
+      const bool osxsave = (registers[2] & (1 << 27)) != 0;
+
+      if (maximumLeaf >= 7 && avx && osxsave &&
+        (_xgetbv(0) & AVX_XSTATE_MASK) == AVX_XSTATE_MASK)
+      {
+        __cpuidex(registers, 7, 0);
+        if ((registers[1] & (1 << 5)) != 0)
+          return &Detail::CopyAVX2;
+      }
+
+      return sse41 ? &CopySSE41 : &CopyFallback;
+    }
+#else
+    CopyFn SelectCopy()
+    {
+      return &CopyFallback;
+    }
+#endif
+  }
+
+  void Copy(void * destination, const void * source, size_t size)
+  {
+    if (!size)
+      return;
+
+    static const CopyFn copy = SelectCopy();
+    copy(destination, source, size);
+  }
+
+  void Flush()
+  {
+#if defined(_M_IX86) || defined(_M_X64)
+    _mm_sfence();
+#else
+    std::atomic_thread_fence(std::memory_order_release);
+#endif
+  }
+}

idd/LGCommon/WCWrite.h

@@ -0,0 +1,32 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+
+#include <stddef.h>
+
+namespace WCWrite
+{
+  // Copy from normal cacheable memory into write-combined memory. The source
+  // and destination ranges must not overlap. Call Flush before publishing the
+  // written range to another processor or device.
+  void Copy(void * destination, const void * source, size_t size);
+  void Flush();
+}

idd/LGCommon/WCWriteAVX2.cpp

@@ -0,0 +1,84 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "WCWrite.h"
+
+#include <immintrin.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace WCWrite
+{
+  namespace Detail
+  {
+    __declspec(noinline) void CopyAVX2(
+      void * destination, const void * source, size_t size)
+    {
+      uint8_t * dst       = static_cast<uint8_t *>(destination);
+      const uint8_t * src = static_cast<const uint8_t *>(source);
+
+      const size_t prefix =
+        (32U - (reinterpret_cast<uintptr_t>(dst) & 31U)) & 31U;
+      if (prefix)
+      {
+        const size_t copy = prefix < size ? prefix : size;
+        memcpy(dst, src, copy);
+        dst  += copy;
+        src  += copy;
+        size -= copy;
+      }
+
+      while (size >= 128U)
+      {
+        const __m256i v0 = _mm256_loadu_si256(
+          reinterpret_cast<const __m256i *>(src +  0));
+        const __m256i v1 = _mm256_loadu_si256(
+          reinterpret_cast<const __m256i *>(src + 32));
+        const __m256i v2 = _mm256_loadu_si256(
+          reinterpret_cast<const __m256i *>(src + 64));
+        const __m256i v3 = _mm256_loadu_si256(
+          reinterpret_cast<const __m256i *>(src + 96));
+        __m256i * output = reinterpret_cast<__m256i *>(dst);
+        _mm256_stream_si256(output + 0, v0);
+        _mm256_stream_si256(output + 1, v1);
+        _mm256_stream_si256(output + 2, v2);
+        _mm256_stream_si256(output + 3, v3);
+        dst  += 128U;
+        src  += 128U;
+        size -= 128U;
+      }
+
+      while (size >= 32U)
+      {
+        const __m256i value = _mm256_loadu_si256(
+          reinterpret_cast<const __m256i *>(src));
+        _mm256_stream_si256(reinterpret_cast<__m256i *>(dst), value);
+        dst  += 32U;
+        src  += 32U;
+        size -= 32U;
+      }
+
+      if (size)
+        memcpy(dst, src, size);
+
+      _mm256_zeroupper();
+    }
+  }
+}

idd/LGIdd/transport/lgmp/CLGMPFrameTransport.cpp

@@ -25,6 +25,7 @@
 #include "transport/lgmp/CLGMPHost.h"
 #include "Atomic.h"
 #include "CDebug.h"
+#include "WCWrite.h"
 
 #include <cstring>
 #include <memory>
@@ -1335,15 +1336,14 @@ void CLGMPFrameTransport::WriteFrameBuffer(unsigned frameIndex, void * src,
 {
   LGMPBuffer * fb = m_frameBuffer[frameIndex];
 
-  memcpy(
+  WCWrite::Copy(fb->data + offset,
-    reinterpret_cast<void *>(
+    static_cast<uint8_t *>(src) + offset, len);
-      reinterpret_cast<uintptr_t>(fb->data) + offset),
-    reinterpret_cast<void *>(
-      reinterpret_cast<uintptr_t>(src) + offset),
-    len);
 
   if (setWritePos)
+  {
+    WCWrite::Flush();
     fb->wp = (uint32_t)(offset + len);
+  }
 }
 
 void CLGMPFrameTransport::WriteFrameBufferRows(unsigned frameIndex,
@@ -1355,7 +1355,7 @@ void CLGMPFrameTransport::WriteFrameBufferRows(unsigned frameIndex,
   uint8_t * source = static_cast<uint8_t *>(src) + offset;
   for (unsigned row = 0; row < rows; ++row)
   {
-    memcpy(dst, source, rowBytes);
+    WCWrite::Copy(dst, source, rowBytes);
     dst    += pitch;
     source += pitch;
   }
@@ -1365,5 +1365,6 @@ void CLGMPFrameTransport::FinalizeFrameBuffer(unsigned frameIndex) const
 {
   const KVMFRFrame * frame = m_frame[frameIndex];
   LGMPBuffer       * fb    = m_frameBuffer[frameIndex];
+  WCWrite::Flush();
   fb->wp = frame->dataHeight * frame->pitch;
 }