shader_decode: Implement HADD2 and HMUL2

src/video_core/shader/decode/arithmetic_half.cpp

@@ -16,7 +16,54 @@ u32 ShaderIR::DecodeArithmeticHalf(BasicBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);
 
-    UNIMPLEMENTED();
+    if (opcode->get().GetId() == OpCode::Id::HADD2_C ||
+        opcode->get().GetId() == OpCode::Id::HADD2_R) {
+        UNIMPLEMENTED_IF(instr.alu_half.ftz != 0);
+    }
+    UNIMPLEMENTED_IF_MSG(instr.alu_half.saturate != 0,
+                         "Half float saturation not implemented");
+
+    const bool negate_a =
+        opcode->get().GetId() != OpCode::Id::HMUL2_R && instr.alu_half.negate_a != 0;
+    const bool negate_b =
+        opcode->get().GetId() != OpCode::Id::HMUL2_C && instr.alu_half.negate_b != 0;
+
+    const Node op_a = GetOperandAbsNegHalf(GetRegister(instr.gpr8), instr.alu_half.abs_a, negate_a);
+
+    // instr.alu_half.type_a
+
+    Node op_b = [&]() {
+        switch (opcode->get().GetId()) {
+        case OpCode::Id::HADD2_C:
+        case OpCode::Id::HMUL2_C:
+            return GetConstBuffer(instr.cbuf34.index, instr.cbuf34.offset);
+        case OpCode::Id::HADD2_R:
+        case OpCode::Id::HMUL2_R:
+            return GetRegister(instr.gpr20);
+        default:
+            UNREACHABLE();
+            return Immediate(0);
+        }
+    }();
+    op_b = GetOperandAbsNegHalf(op_b, instr.alu_half.abs_b, negate_b);
+
+    Node value = [&]() {
+        MetaHalfArithmetic meta{true, {instr.alu_half_imm.type_a, instr.alu_half.type_b}};
+        switch (opcode->get().GetId()) {
+        case OpCode::Id::HADD2_C:
+        case OpCode::Id::HADD2_R:
+            return Operation(OperationCode::HAdd, meta, op_a, op_b);
+        case OpCode::Id::HMUL2_C:
+        case OpCode::Id::HMUL2_R:
+            return Operation(OperationCode::HMul, meta, op_a, op_b);
+        default:
+            UNIMPLEMENTED_MSG("Unhandled half float instruction: {}", opcode->get().GetName());
+            return Immediate(0);
+        }
+    }();
+    value = HalfMerge(GetRegister(instr.gpr0), value, instr.alu_half.merge);
+
+    SetRegister(bb, instr.gpr0, value);
 
     return pc;
 }