From d00dd5a2bc0bd361e8b0f1b67d9ac790dc750a36 Mon Sep 17 00:00:00 2001
From: Triang3l <triang3l@yandex.ru>
Date: Wed, 9 Jun 2021 20:22:24 +0300
Subject: [PATCH] [GPU] Disable primitive reset for non-list types in primitive
 processor

---
 src/xenia/gpu/d3d12/pipeline_cache.cc |  1 -
 src/xenia/gpu/primitive_processor.cc  | 38 ++++++++++++++++++++-------
 src/xenia/gpu/primitive_processor.h   |  3 ++-
 3 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/src/xenia/gpu/d3d12/pipeline_cache.cc b/src/xenia/gpu/d3d12/pipeline_cache.cc
index 97606a3cf..b28369d54 100644
--- a/src/xenia/gpu/d3d12/pipeline_cache.cc
+++ b/src/xenia/gpu/d3d12/pipeline_cache.cc
@@ -1340,7 +1340,6 @@ bool PipelineCache::GetCurrentStateDescription(
         break;
       case xenos::PrimitiveType::kLineList:
       case xenos::PrimitiveType::kLineStrip:
-      case xenos::PrimitiveType::kLineLoop:
       // Quads are emulated as line lists with adjacency.
       case xenos::PrimitiveType::kQuadList:
       case xenos::PrimitiveType::k2DLineStrip:
diff --git a/src/xenia/gpu/primitive_processor.cc b/src/xenia/gpu/primitive_processor.cc
index 62864a256..b00e4ce50 100644
--- a/src/xenia/gpu/primitive_processor.cc
+++ b/src/xenia/gpu/primitive_processor.cc
@@ -458,16 +458,34 @@ bool PrimitiveProcessor::Process(ProcessingResult& result_out) {
       }
     } else {
       if (regs.Get<reg::PA_SU_SC_MODE_CNTL>().multi_prim_ib_ena) {
-        guest_primitive_reset_index_guest_endian = xenos::GpuSwap(
-            regs.Get<reg::VGT_MULTI_PRIM_IB_RESET_INDX>().reset_indx,
-            guest_index_endian);
-        // - VGT, what does the guest say about its primitive reset index?
-        // - It's over 0xFFFF!!!
-        // - What!? 0xFFFF!? There's no way that can be stored in 16 bits!
-        guest_primitive_reset_enabled =
-            guest_index_format == xenos::IndexFormat::kInt16
-                ? guest_primitive_reset_index_guest_endian <= UINT16_MAX
-                : true;
+        switch (guest_primitive_type) {
+          case xenos::PrimitiveType::kLineStrip:
+          case xenos::PrimitiveType::kTriangleFan:
+          case xenos::PrimitiveType::kTriangleStrip:
+          case xenos::PrimitiveType::kLineLoop:
+          case xenos::PrimitiveType::kQuadStrip:
+          case xenos::PrimitiveType::kPolygon:
+          case xenos::PrimitiveType::k2DLineStrip:
+          case xenos::PrimitiveType::k2DTriStrip:
+            guest_primitive_reset_index_guest_endian = xenos::GpuSwap(
+                regs.Get<reg::VGT_MULTI_PRIM_IB_RESET_INDX>().reset_indx,
+                guest_index_endian);
+            // - VGT, what does the guest say about its primitive reset index?
+            // - It's over 0xFFFF!!!
+            // - What!? 0xFFFF!? There's no way that can be stored in 16 bits!
+            guest_primitive_reset_enabled =
+                guest_index_format == xenos::IndexFormat::kInt16
+                    ? guest_primitive_reset_index_guest_endian <= UINT16_MAX
+                    : true;
+            break;
+          default:
+            // Vulkan explicitly disallows primitive restart index for "list"
+            // topologies. In Direct3D 12, it's valid for non-strips, but has
+            // implementation-defined behavior. Make backend usage simpler by
+            // explicitly filtering lists out, and hope the guest never uses
+            // primitive reset for lists.
+            break;
+        }
       }
     }
 
diff --git a/src/xenia/gpu/primitive_processor.h b/src/xenia/gpu/primitive_processor.h
index 762b7f1f9..046928738 100644
--- a/src/xenia/gpu/primitive_processor.h
+++ b/src/xenia/gpu/primitive_processor.h
@@ -138,7 +138,8 @@ class PrimitiveProcessor {
     xenos::IndexFormat host_index_format;
     xenos::Endian host_index_endian;
     // The reset index, if enabled, is always 0xFFFF for host_index_format
-    // kInt16 and 0xFFFFFFFF for kInt32.
+    // kInt16 and 0xFFFFFFFF for kInt32. Never enabled for "list" primitive
+    // types, thus safe for direct usage on Vulkan.
     bool host_primitive_reset_enabled;
     // Backend-specific handle for the index buffer valid for the current draw,
     // only valid for index_buffer_type kHostConverted and kHostBuiltin.