rsx/fp: Reimplement GLSL code generation from CFG

rpcs3/Emu/RSX/Program/FragmentProgramDecompiler.cpp

@@ -1319,72 +1319,83 @@ std::string FragmentProgramDecompiler::Decompile()
 	m_is_valid_ucode = true;
 	m_constant_offsets.clear();
 
-	enum
+	// For GLSL scope wind/unwind. We store the min scope depth and loop count for each block and "unwind" to it.
-	{
+	// This should recover information lost when multiple nodes converge on a single merge node or even skip a merge node as is the case with "ELSE" nodes.
-		FORCE_NONE,
+	std::unordered_map<const BasicBlock*, std::pair<int, u32>> block_data;
-		FORCE_SCT,
-		FORCE_SCB,
-	};
 
-	int forced_unit = FORCE_NONE;
+	auto push_block_info = [&](const BasicBlock* block)
+	{
+		u32 loop = m_loop_count;
+		int level = m_code_level;
+
+		auto found = block_data.find(block);
+		if (found != block_data.end())
+		{
+			level = std::min(level, found->second.first);
+			loop = std::min(loop, found->second.second);
+		}
+
+		block_data[block] = { level, loop };
+	};
 
 	for (const auto &block : graph.blocks)
 	{
-		// TODO: Handle block prologue if any
+		auto found = block_data.find(&block);
+		if (found != block_data.end())
+		{
+			const auto [level, loop] = found->second;
+			for (int i = m_code_level; i > level; i--)
+			{
+				m_code_level--;
+				AddCode("}");
+			}
+
+			m_loop_count = loop;
+		}
+
 		if (!block.pred.empty())
 		{
-			// CFG guarantees predecessors are sorted, closest one first
+			// Predecessors are always sorted closest last.
-			for (const auto& pred : block.pred)
+			// This gives some adjacency info and tells us how the previous block connects to this one.
-			{
+			const auto& pred = block.pred.back();
 			switch (pred.type)
 			{
-				case EdgeType::ENDLOOP:
-					// Because of succession rules, endloop is seen twice.
-					// Once from the the for statement at the end of the parent
-					// and again at the end of the child block.
-					if (pred.from->is_of_type(EdgeType::LOOP))
-					{
-						m_loop_count--;
-						m_code_level--;
-						AddCode("}");
-					}
-					break;
-				case EdgeType::ENDIF:
-				{
-					// Same thing happens with ENDIF
-					// Once for the IF statement itself
-					// And again for the child blocks with code for the IF and ELSE paths.
-					const bool is_else_end = pred.from->is_of_type(EdgeType::ELSE);
-					const bool is_if_end = pred.from->is_of_type(EdgeType::IF) &&
-						!pred.from->has_sibling_of_type(EdgeType::ELSE); // Avoid double-counting if the IF has an ELSE sibling
-					if (is_else_end || is_if_end)
-					{
-						m_code_level--;
-						AddCode("}");
-					}
-					break;
-				}
 			case EdgeType::LOOP:
 				m_loop_count++;
 				[[ fallthrough ]];
 			case EdgeType::IF:
-					// Instruction will be inserted by the SIP decoder
 				AddCode("{");
 				m_code_level++;
 				break;
 			case EdgeType::ELSE:
-					// This one needs more testing
-					m_code_level--;
-					AddCode("}");
 				AddCode("else");
 				AddCode("{");
 				m_code_level++;
 				break;
+			case EdgeType::ENDIF:
+			case EdgeType::ENDLOOP:
+				// Pure merge block?
+				break;
 			default:
-					// Start a new block anyway
+				fmt::throw_exception("Unhandled edge type %d", static_cast<int>(pred.type));
-					fmt::throw_exception("Unexpected block found");
+				break;
 			}
 		}
+
+		if (!block.prologue.empty())
+		{
+			AddCode("// Prologue");
+
+			for (auto& inst : block.prologue)
+			{
+				m_instruction = &inst;
+				dst.HEX = inst.bytecode[0];
+				src0.HEX = inst.bytecode[1];
+				src1.HEX = inst.bytecode[2];
+				src2.HEX = inst.bytecode[3];
+
+				ensure(handle_tex_srb(inst.opcode) || handle_sct_scb(inst.opcode), "Unsupported operation");
+			}
 		}
 
 		for (const auto& inst : block.instructions)
@@ -1398,11 +1409,9 @@ std::string FragmentProgramDecompiler::Decompile()
 
 			opflags = 0;
 
-			const u32 opcode = dst.opcode | (src1.opcode_is_branch << 6);
-
 			auto SIP = [&]()
 			{
-				switch (opcode)
+				switch (m_instruction->opcode)
 				{
 				case RSX_FP_OPCODE_BRK:
 					if (m_loop_count) AddFlowOp("break");
@@ -1413,11 +1422,9 @@ std::string FragmentProgramDecompiler::Decompile()
 					break;
 				case RSX_FP_OPCODE_FENCT:
 					AddCode("// FENCT");
-					forced_unit = FORCE_SCT;
 					break;
 				case RSX_FP_OPCODE_FENCB:
 					AddCode("// FENCB");
-					forced_unit = FORCE_SCB;
 					break;
 				case RSX_FP_OPCODE_IFE:
 					AddCode("if($cond)");
@@ -1441,7 +1448,7 @@ std::string FragmentProgramDecompiler::Decompile()
 				return true;
 			};
 
-			switch (opcode)
+			switch (m_instruction->opcode)
 			{
 			case RSX_FP_OPCODE_NOP:
 				break;
@@ -1450,19 +1457,10 @@ std::string FragmentProgramDecompiler::Decompile()
 				AddFlowOp("_kill()");
 				break;
 			default:
-				int prev_force_unit = forced_unit;
-
-				// Some instructions do not respect forced unit
-				// Tested with Tales of Vesperia
 				if (SIP()) break;
-				if (handle_tex_srb(opcode)) break;
+				if (handle_tex_srb(m_instruction->opcode)) break;
-
+				if (handle_sct_scb(m_instruction->opcode)) break;
-				// FENCT/FENCB do not actually reject instructions if they dont match the forced unit
+				rsx_log.error("Unknown/illegal instruction: 0x%x", m_instruction->opcode);
-				// Looks like they are optimization hints and not hard-coded forced paths
-				if (handle_sct_scb(opcode)) break;
-				forced_unit = FORCE_NONE;
-
-				rsx_log.error("Unknown/illegal instruction: 0x%x (forced unit %d)", opcode, prev_force_unit);
 				break;
 			}
 
@@ -1470,11 +1468,8 @@ std::string FragmentProgramDecompiler::Decompile()
 			if (dst.end) break;
 		}
 
-		if (block.epilogue.empty())
+		if (!block.epilogue.empty())
 		{
-			continue;
-		}
-
 			AddCode("// Epilogue");
 
 			for (auto& inst : block.epilogue)
@@ -1489,13 +1484,22 @@ std::string FragmentProgramDecompiler::Decompile()
 			}
 		}
 
-	while (m_code_level > 1)
+		for (auto& succ : block.succ)
 		{
-		// Happens if the last block was hanging (no merge)
+			switch (succ.type)
-		// FIXME: We must always have a merge block on exit to resolve dependencies on outputs
+			{
-		m_code_level--;
+			case EdgeType::ENDIF:
-		AddCode("}");
+			case EdgeType::ENDLOOP:
+			case EdgeType::ELSE:
+				push_block_info(succ.to);
+				break;
+			default:
+				break;
 			}
+		}
+	}
+
+	ensure(m_code_level == 1);
 
 	// flush m_code_level
 	m_code_level = 1;