From 27c74d89746d582829c1038ca84dd5d22f089e38 Mon Sep 17 00:00:00 2001
From: Samuliak <samuliak77@gmail.com>
Date: Wed, 3 Jul 2024 20:52:05 +0200
Subject: [PATCH] emulate logic op in the shader

---
 src/core/renderer_mtl/renderer_mtl.cpp |  6 +++-
 src/host_shaders/metal_shaders.metal   | 48 ++++++++++++++++++++++++--
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/core/renderer_mtl/renderer_mtl.cpp b/src/core/renderer_mtl/renderer_mtl.cpp
index e42689de..98ba3cbf 100644
--- a/src/core/renderer_mtl/renderer_mtl.cpp
+++ b/src/core/renderer_mtl/renderer_mtl.cpp
@@ -353,9 +353,10 @@ void RendererMTL::drawVertices(PICA::PrimType primType, std::span<const PICA::Ve
         pipelineHash.depthFmt = depthStencilRenderTarget->format;
     }
 
-	// Blending
+	// Blending and logic op
 	pipelineHash.blendEnabled = (regs[PICA::InternalRegs::ColourOperation] & (1 << 8)) != 0;
 
+	u8 logicOp = 3; // Copy, which doesn't do anything
 	if (pipelineHash.blendEnabled) {
     	pipelineHash.blendControl = regs[PICA::InternalRegs::BlendFunc];
         // TODO: constant color
@@ -364,6 +365,8 @@ void RendererMTL::drawVertices(PICA::PrimType primType, std::span<const PICA::Ve
     	//const u8 g = Helpers::getBits<8, 8>(pipelineHash.constantColor);
     	//const u8 b = Helpers::getBits<16, 8>(pipelineHash.constantColor);
     	//const u8 a = Helpers::getBits<24, 8>(pipelineHash.constantColor);
+	} else {
+	    logicOp = Helpers::getBits<0, 4>(regs[PICA::InternalRegs::LogicOp]);
 	}
 
 	MTL::RenderPipelineState* pipeline = drawPipelineCache.get(pipelineHash);
@@ -406,6 +409,7 @@ void RendererMTL::drawVertices(PICA::PrimType primType, std::span<const PICA::Ve
 	bindTexturesToSlots(renderCommandEncoder);
 	renderCommandEncoder->setVertexBytes(&regs[0x48], 0x200 - 0x48, 0);
 	renderCommandEncoder->setFragmentBytes(&regs[0x48], 0x200 - 0x48, 0);
+	renderCommandEncoder->setFragmentBytes(&logicOp, sizeof(logicOp), 2);
 
 	renderCommandEncoder->drawPrimitives(toMTLPrimitiveType(primType), NS::UInteger(0), NS::UInteger(vertices.size()));
 }
diff --git a/src/host_shaders/metal_shaders.metal b/src/host_shaders/metal_shaders.metal
index 2947e827..abf26948 100644
--- a/src/host_shaders/metal_shaders.metal
+++ b/src/host_shaders/metal_shaders.metal
@@ -247,7 +247,51 @@ struct FragTEV {
     }
 };
 
-fragment float4 fragmentDraw(DrawVertexOut in [[stage_in]], constant PicaRegs& picaRegs [[buffer(0)]], constant FragTEV& tev [[buffer(1)]],
+enum class LogicOp : uint8_t {
+    Clear = 0,
+    And = 1,
+    AndReverse = 2,
+    Copy = 3,
+    Set = 4,
+    CopyInverted = 5,
+    NoOp = 6,
+    Invert = 7,
+    Nand = 8,
+    Or = 9,
+    Nor = 10,
+    Xor = 11,
+    Equiv = 12,
+    AndInverted = 13,
+    OrReverse = 14,
+    OrInverted = 15
+};
+
+uint4 performLogicOpU(LogicOp logicOp, uint4 s, uint4 d) {
+    switch (logicOp) {
+    case LogicOp::Clear: return as_type<uint4>(float4(0.0));
+    case LogicOp::And: return s & d;
+    case LogicOp::AndReverse: return s & ~d;
+    case LogicOp::Copy: return s;
+    case LogicOp::Set: return as_type<uint4>(float4(1.0));
+    case LogicOp::CopyInverted: return ~s;
+    case LogicOp::NoOp: return d;
+    case LogicOp::Invert: return ~d;
+    case LogicOp::Nand: return ~(s & d);
+    case LogicOp::Or: return s | d;
+    case LogicOp::Nor: return ~(s | d);
+    case LogicOp::Xor: return s ^ d;
+    case LogicOp::Equiv: return ~(s ^ d);
+    case LogicOp::AndInverted: return ~s & d;
+    case LogicOp::OrReverse: return s | ~d;
+    case LogicOp::OrInverted: return ~s | d;
+    }
+}
+
+float4 performLogicOp(LogicOp logicOp, float4 s, float4 d) {
+    return as_type<float4>(performLogicOpU(logicOp, as_type<uint4>(s), as_type<uint4>(d)));
+}
+
+fragment float4 fragmentDraw(DrawVertexOut in [[stage_in]], float4 prevColor [[color(0)]], constant PicaRegs& picaRegs [[buffer(0)]], constant FragTEV& tev [[buffer(1)]], constant LogicOp& logicOp [[buffer(2)]],
                              texture2d<float> tex0 [[texture(0)]], texture2d<float> tex1 [[texture(1)]], texture2d<float> tex2 [[texture(2)]],
                              sampler samplr0 [[sampler(0)]], sampler samplr1 [[sampler(1)]], sampler samplr2 [[sampler(2)]]) {
     Globals globals;
@@ -284,5 +328,5 @@ fragment float4 fragmentDraw(DrawVertexOut in [[stage_in]], constant PicaRegs& p
 		}
 	}
 
-	return globals.tevSources[15];
+	return performLogicOp(logicOp, globals.tevSources[15], prevColor);
 }