From f83809f7a10433c6c4f94d489b4595c877443aa1 Mon Sep 17 00:00:00 2001
From: Triang3l <triang3l@yandex.ru>
Date: Sun, 19 Apr 2020 23:11:52 +0300
Subject: [PATCH] [D3D12] Non-adaptive quad tessellation

---
 .../gpu/d3d12/d3d12_command_processor.cc      |  1 +
 src/xenia/gpu/d3d12/pipeline_cache.cc         | 13 +++++++
 src/xenia/gpu/dxbc_shader_translator.cc       | 34 +++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/src/xenia/gpu/d3d12/d3d12_command_processor.cc b/src/xenia/gpu/d3d12/d3d12_command_processor.cc
index 1575173c8..0c4b96c52 100644
--- a/src/xenia/gpu/d3d12/d3d12_command_processor.cc
+++ b/src/xenia/gpu/d3d12/d3d12_command_processor.cc
@@ -1358,6 +1358,7 @@ bool D3D12CommandProcessor::IssueDraw(PrimitiveType primitive_type,
       case PrimitiveType::kTrianglePatch:
         primitive_topology = D3D_PRIMITIVE_TOPOLOGY_3_CONTROL_POINT_PATCHLIST;
         break;
+      case PrimitiveType::kQuadList:
       case PrimitiveType::kQuadPatch:
         primitive_topology = D3D_PRIMITIVE_TOPOLOGY_4_CONTROL_POINT_PATCHLIST;
         break;
diff --git a/src/xenia/gpu/d3d12/pipeline_cache.cc b/src/xenia/gpu/d3d12/pipeline_cache.cc
index c31dbd0ab..8151d90eb 100644
--- a/src/xenia/gpu/d3d12/pipeline_cache.cc
+++ b/src/xenia/gpu/d3d12/pipeline_cache.cc
@@ -769,6 +769,19 @@ Shader::HostVertexShaderType PipelineCache::GetHostVertexShaderTypeIfValid()
           break;
       }
       break;
+    case PrimitiveType::kQuadList:
+      switch (tessellation_mode) {
+        // Also supported by quad strips according to:
+        // https://www.khronos.org/registry/OpenGL/extensions/AMD/AMD_vertex_shader_tessellator.txt
+        // Would need to convert those to quad lists, but haven't seen any games
+        // using tessellated strips so far.
+        case xenos::TessellationMode::kContinuous:
+          // - Defender - retro screen and beams in the main menu - kQuadList.
+          return Shader::HostVertexShaderType::kQuadDomainConstant;
+        default:
+          break;
+      }
+      break;
     case PrimitiveType::kTrianglePatch:
       if (tessellation_mode == xenos::TessellationMode::kAdaptive) {
         // - Banjo-Kazooie: Nuts & Bolts - water.
diff --git a/src/xenia/gpu/dxbc_shader_translator.cc b/src/xenia/gpu/dxbc_shader_translator.cc
index 79185d0fd..bf5eba966 100644
--- a/src/xenia/gpu/dxbc_shader_translator.cc
+++ b/src/xenia/gpu/dxbc_shader_translator.cc
@@ -530,6 +530,40 @@ void DxbcShaderTranslator::StartVertexOrDomainShader() {
       }
       break;
 
+    case Shader::HostVertexShaderType::kQuadDomainConstant:
+      assert_true(register_count() >= 2);
+      if (register_count() >= 1) {
+        // Copy the domain location to r0.xy.
+        DxbcOpMov(uses_register_dynamic_addressing() ? DxbcDest::X(0, 0, 0b0011)
+                                                     : DxbcDest::R(0, 0b0011),
+                  DxbcSrc::VDomain());
+        // Control point indices according to the shader from the main menu of
+        // Defender, which starts from `cndeq r2, c255.xxxy, r1.xyzz, r0.zzzz`,
+        // where c255.x is 0, and c255.y is 1.
+        // r0.z for (1 - r0.x) * (1 - r0.y)
+        // r1.x for r0.x * (1 - r0.y)
+        // r1.y for r0.x * r0.y
+        // r1.z for (1 - r0.x) * r0.y
+        DxbcOpMov(
+            uses_register_dynamic_addressing() ? DxbcDest::X(0, 0, 0b0100)
+                                               : DxbcDest::R(0, 0b0100),
+            DxbcSrc::VICP(0, uint32_t(InOutRegister::kDSInControlPointIndex),
+                          DxbcSrc::kXXXX));
+        if (register_count() >= 2) {
+          DxbcDest r1_dest(uses_register_dynamic_addressing()
+                               ? DxbcDest::X(0, 1)
+                               : DxbcDest::R(1));
+          for (uint32_t i = 0; i < 3; ++i) {
+            DxbcOpMov(
+                r1_dest.Mask(1 << i),
+                DxbcSrc::VICP(1 + i,
+                              uint32_t(InOutRegister::kDSInControlPointIndex),
+                              DxbcSrc::kXXXX));
+          }
+        }
+      }
+      break;
+
     case Shader::HostVertexShaderType::kQuadDomainAdaptive:
       assert_true(register_count() >= 2);
       if (register_count() >= 1) {