GPU/SW: Split out rasterizer, add dynamic selection

src/core/gpu_sw_rasterizer.cpp

@@ -0,0 +1,100 @@
+// SPDX-FileCopyrightText: 2019-2024 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-License-Identifier: CC-BY-NC-ND-4.0
+
+#include "gpu_sw_rasterizer.h"
+#include "gpu.h"
+
+#include "cpuinfo.h"
+
+#include "common/log.h"
+#include "common/string_util.h"
+
+Log_SetChannel(GPU_SW_Rasterizer);
+
+namespace GPU_SW_Rasterizer {
+// Default implementation, compatible with all ISAs.
+extern const DrawRectangleFunctionTable DrawRectangleFunctions;
+extern const DrawTriangleFunctionTable DrawTriangleFunctions;
+extern const DrawLineFunctionTable DrawLineFunctions;
+
+constinit const DitherLUT g_dither_lut = []() constexpr {
+  DitherLUT lut = {};
+  for (u32 i = 0; i < DITHER_MATRIX_SIZE; i++)
+  {
+    for (u32 j = 0; j < DITHER_MATRIX_SIZE; j++)
+    {
+      for (u32 value = 0; value < DITHER_LUT_SIZE; value++)
+      {
+        const s32 dithered_value = (static_cast<s32>(value) + DITHER_MATRIX[i][j]) >> 3;
+        lut[i][j][value] = static_cast<u8>((dithered_value < 0) ? 0 : ((dithered_value > 31) ? 31 : dithered_value));
+      }
+    }
+  }
+  return lut;
+}();
+
+GPUDrawingArea g_drawing_area = {};
+} // namespace GPU_SW_Rasterizer
+
+// Default implementation definitions.
+namespace GPU_SW_Rasterizer {
+#include "gpu_sw_rasterizer.inl"
+}
+
+// Default vector implementation definitions.
+#if defined(CPU_ARCH_SSE) || defined(CPU_ARCH_NEON)
+namespace GPU_SW_Rasterizer::SIMD {
+#include "gpu_sw_rasterizer.inl"
+}
+#endif
+
+// Initialize with default implementation.
+namespace GPU_SW_Rasterizer {
+const DrawRectangleFunctionTable* SelectedDrawRectangleFunctions = &DrawRectangleFunctions;
+const DrawTriangleFunctionTable* SelectedDrawTriangleFunctions = &DrawTriangleFunctions;
+const DrawLineFunctionTable* SelectedDrawLineFunctions = &DrawLineFunctions;
+} // namespace GPU_SW_Rasterizer
+
+// Declare alternative implementations.
+void GPU_SW_Rasterizer::SelectImplementation()
+{
+  static bool selected = false;
+  if (selected)
+    return;
+
+  selected = true;
+
+#define SELECT_ALTERNATIVE_RASTERIZER(isa)                                                                             \
+  do                                                                                                                   \
+  {                                                                                                                    \
+    INFO_LOG("Using " #isa " software rasterizer implementation.");                                                    \
+    SelectedDrawRectangleFunctions = &isa::DrawRectangleFunctions;                                                     \
+    SelectedDrawTriangleFunctions = &isa::DrawTriangleFunctions;                                                       \
+    SelectedDrawLineFunctions = &isa::DrawLineFunctions;                                                               \
+  } while (0)
+
+#if defined(CPU_ARCH_SSE) || defined(CPU_ARCH_NEON)
+  const char* use_isa = std::getenv("SW_USE_ISA");
+
+  // Default to scalar for now, until vector is finished.
+  use_isa = use_isa ? use_isa : "Scalar";
+
+#if defined(CPU_ARCH_SSE) && defined(_MSC_VER)
+  if (cpuinfo_has_x86_avx2() && (!use_isa || StringUtil::Strcasecmp(use_isa, "AVX2") == 0))
+  {
+    SELECT_ALTERNATIVE_RASTERIZER(AVX2);
+    return;
+  }
+#endif
+
+  if (!use_isa || StringUtil::Strcasecmp(use_isa, "SIMD") == 0)
+  {
+    SELECT_ALTERNATIVE_RASTERIZER(SIMD);
+    return;
+  }
+#endif
+
+  INFO_LOG("Using scalar software rasterizer implementation.");
+
+#undef SELECT_ALTERNATIVE_RASTERIZER
+}