VideoCommon: Add ability for backends to override bugs

1 files changed, 100 insertions, 26 deletions

diff --git a/Source/Core/VideoBackends/Metal/MTLUtil.mm b/Source/Core/VideoBackends/Metal/MTLUtil.mm
index 987d36cbfc..5870cc5ad5 100644
--- a/Source/Core/VideoBackends/Metal/MTLUtil.mm
+++ b/Source/Core/VideoBackends/Metal/MTLUtil.mm
@@ -89,36 +89,19 @@ void Metal::Util::PopulateBackendInfoAdapters(VideoConfig* config,
   }
 }
 
-static bool DetectIntelGPUFBFetch(id<MTLDevice> dev)
+/// For testing driver brokenness
+static bool RenderSinglePixel(id<MTLDevice> dev, id<MTLFunction> vs, id<MTLFunction> fs,  //
+                              u32 px_in, u32* px_out)
 {
-  // Even though it's nowhere in the feature set tables, some Intel GPUs support fbfetch!
-  // Annoyingly, the Haswell compiler successfully makes a pipeline but actually miscompiles it and
-  // doesn't insert any fbfetch instructions.
-  // The Broadwell compiler inserts the Skylake fbfetch instruction,
-  // but Broadwell doesn't support that.  It seems to make the shader not do anything.
-  // So we actually have to test the thing
-
-  static constexpr const char* shader = R"(
-vertex float4 fs_triangle(uint vid [[vertex_id]]) {
-  return float4(vid & 1 ? 3 : -1, vid & 2 ? 3 : -1, 0, 1);
-}
-fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
-  return in * 2;
-}
-)";
-  auto lib = MRCTransfer([dev newLibraryWithSource:[NSString stringWithUTF8String:shader]
-                                           options:nil
-                                             error:nil]);
-  if (!lib)
-    return false;
   auto pdesc = MRCTransfer([MTLRenderPipelineDescriptor new]);
-  [pdesc setVertexFunction:MRCTransfer([lib newFunctionWithName:@"fs_triangle"])];
-  [pdesc setFragmentFunction:MRCTransfer([lib newFunctionWithName:@"fbfetch_test"])];
+  [pdesc setVertexFunction:vs];
+  [pdesc setFragmentFunction:fs];
   [[pdesc colorAttachments][0] setPixelFormat:MTLPixelFormatRGBA8Unorm];
   auto pipe = MRCTransfer([dev newRenderPipelineStateWithDescriptor:pdesc error:nil]);
   if (!pipe)
     return false;
   auto buf = MRCTransfer([dev newBufferWithLength:4 options:MTLResourceStorageModeShared]);
+  memcpy([buf contents], &px_in, sizeof(px_in));
   auto tdesc = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatRGBA8Unorm
                                                                   width:1
                                                                  height:1
@@ -126,9 +109,8 @@ fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
   [tdesc setUsage:MTLTextureUsageRenderTarget];
   auto tex = MRCTransfer([dev newTextureWithDescriptor:tdesc]);
   auto q = MRCTransfer([dev newCommandQueue]);
-  u32 px = 0x11223344;
-  memcpy([buf contents], &px, 4);
   id<MTLCommandBuffer> cmdbuf = [q commandBuffer];
+
   id<MTLBlitCommandEncoder> upload_encoder = [cmdbuf blitCommandEncoder];
   [upload_encoder copyFromBuffer:buf
                     sourceOffset:0
@@ -140,6 +122,7 @@ fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
                 destinationLevel:0
                destinationOrigin:MTLOriginMake(0, 0, 0)];
   [upload_encoder endEncoding];
+
   auto rpdesc = MRCTransfer([MTLRenderPassDescriptor new]);
   [[rpdesc colorAttachments][0] setTexture:tex];
   [[rpdesc colorAttachments][0] setLoadAction:MTLLoadActionLoad];
@@ -148,6 +131,7 @@ fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
   [renc setRenderPipelineState:pipe];
   [renc drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];
   [renc endEncoding];
+
   id<MTLBlitCommandEncoder> download_encoder = [cmdbuf blitCommandEncoder];
   [download_encoder copyFromTexture:tex
                         sourceSlice:0
@@ -159,10 +143,44 @@ fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
              destinationBytesPerRow:4
            destinationBytesPerImage:4];
   [download_encoder endEncoding];
+
   [cmdbuf commit];
   [cmdbuf waitUntilCompleted];
+
+  memcpy(px_out, [buf contents], sizeof(*px_out));
+  return [cmdbuf status] == MTLCommandBufferStatusCompleted;
+}
+
+static bool DetectIntelGPUFBFetch(id<MTLDevice> dev)
+{
+  // Even though it's nowhere in the feature set tables, some Intel GPUs support fbfetch!
+  // Annoyingly, the Haswell compiler successfully makes a pipeline but actually miscompiles it and
+  // doesn't insert any fbfetch instructions.
+  // The Broadwell compiler inserts the Skylake fbfetch instruction,
+  // but Broadwell doesn't support that.  It seems to make the shader not do anything.
+  // So we actually have to test the thing
+
+  static constexpr const char* shader = R"(
+vertex float4 fs_triangle(uint vid [[vertex_id]]) {
+  return float4(vid & 1 ? 3 : -1, vid & 2 ? 3 : -1, 0, 1);
+}
+fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
+  return in * 2;
+}
+)";
+  auto lib = MRCTransfer([dev newLibraryWithSource:[NSString stringWithUTF8String:shader]
+                                           options:nil
+                                             error:nil]);
+  if (!lib)
+    return false;
   u32 outpx;
-  memcpy(&outpx, [buf contents], 4);
+  bool ok = RenderSinglePixel(dev,                                                     //
+                              MRCTransfer([lib newFunctionWithName:@"fs_triangle"]),   //
+                              MRCTransfer([lib newFunctionWithName:@"fbfetch_test"]),  //
+                              0x11223344, &outpx);
+  if (!ok)
+    return false;
+
   // Proper fbfetch will double contents, Haswell will return black, and Broadwell will do nothing
   if (outpx == 0x22446688)
     return true;  // Skylake+
@@ -172,6 +190,52 @@ fragment float4 fbfetch_test(float4 in [[color(0), raster_order_group(0)]]) {
     return false;  // Haswell
 }
 
+enum class DetectionResult
+{
+  Yes,
+  No,
+  Unsure
+};
+
+static DetectionResult DetectInvertedIsHelper(id<MTLDevice> dev)
+{
+  static constexpr const char* shader = R"(
+vertex float4 fs_triangle(uint vid [[vertex_id]]) {
+  return float4(vid & 1 ? 3 : -1, vid & 2 ? 3 : -1, 0, 1);
+}
+fragment float4 is_helper_test() {
+  float val = metal::simd_is_helper_thread() ? 1 : 0.5;
+  return float4(val, metal::dfdx(val) + 0.5, metal::dfdy(val) + 0.5, 0);
+}
+)";
+
+  auto lib = MRCTransfer([dev newLibraryWithSource:[NSString stringWithUTF8String:shader]
+                                           options:nil
+                                             error:nil]);
+  if (!lib)
+    return DetectionResult::Unsure;
+
+  u32 outpx;
+  bool ok = RenderSinglePixel(dev,                                                       //
+                              MRCTransfer([lib newFunctionWithName:@"fs_triangle"]),     //
+                              MRCTransfer([lib newFunctionWithName:@"is_helper_test"]),  //
+                              0, &outpx);
+
+  // The pixel itself should not be a helper thread (0.5)
+  // The pixels to its right and below should be helper threads (1.0)
+  // Correctly working would therefore be 0.5 for the pixel and (0.5 + 0.5) for the derivatives
+  // Inverted would be 1.0 for the pixel and (-0.5 + 0.5) for the derivatives
+  if (!ok)
+    return DetectionResult::Unsure;
+  if (outpx == 0xffff80)
+    return DetectionResult::No;  // Working correctly
+  if (outpx == 0x0000ff)
+    return DetectionResult::Yes;  // Inverted
+  WARN_LOG_FMT(VIDEO, "metal::simd_is_helper_thread might be broken! Test shader returned {:06x}!",
+               outpx);
+  return DetectionResult::Unsure;
+}
+
 void Metal::Util::PopulateBackendInfoFeatures(VideoConfig* config, id<MTLDevice> device)
 {
   // Initialize DriverDetails first so we can use it later
@@ -245,6 +309,16 @@ void Metal::Util::PopulateBackendInfoFeatures(VideoConfig* config, id<MTLDevice>
         [device supportsFamily:MTLGPUFamilyMac2] || [device supportsFamily:MTLGPUFamilyApple6];
     config->backend_info.bSupportsFramebufferFetch = [device supportsFamily:MTLGPUFamilyApple1];
   }
+  if (g_features.subgroup_ops)
+  {
+    DetectionResult result = DetectInvertedIsHelper(device);
+    if (result != DetectionResult::Unsure)
+    {
+      bool is_helper_inverted = result == DetectionResult::Yes;
+      if (is_helper_inverted != DriverDetails::HasBug(DriverDetails::BUG_INVERTED_IS_HELPER))
+        DriverDetails::OverrideBug(DriverDetails::BUG_INVERTED_IS_HELPER, is_helper_inverted);
+    }
+  }
 #if TARGET_OS_OSX
   if (@available(macOS 11, *))
     if (vendor == DriverDetails::VENDOR_INTEL)