shader/bfi: Implement register-constant buffer variant

It's the same as the variant that was implemented, but it takes the
operands from another source.

src/video_core/engines/shader_bytecode.h

@@ -1675,6 +1675,7 @@ public:
         BFE_C,
         BFE_R,
         BFE_IMM,
+        BFI_RC,
         BFI_IMM_R,
         BRA,
         BRX,
@@ -2098,6 +2099,7 @@ private:
             INST("0100110000000---", Id::BFE_C, Type::Bfe, "BFE_C"),
             INST("0101110000000---", Id::BFE_R, Type::Bfe, "BFE_R"),
             INST("0011100-00000---", Id::BFE_IMM, Type::Bfe, "BFE_IMM"),
+            INST("0101001111110---", Id::BFI_RC, Type::Bfi, "BFI_RC"),
             INST("0011011-11110---", Id::BFI_IMM_R, Type::Bfi, "BFI_IMM_R"),
             INST("0100110001000---", Id::LOP_C, Type::ArithmeticInteger, "LOP_C"),
             INST("0101110001000---", Id::LOP_R, Type::ArithmeticInteger, "LOP_R"),

src/video_core/shader/decode/bfi.cpp

@@ -17,10 +17,13 @@ u32 ShaderIR::DecodeBfi(NodeBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);
 
-    const auto [base, packed_shift] = [&]() -> std::tuple<Node, Node> {
+    const auto [packed_shift, base] = [&]() -> std::pair<Node, Node> {
         switch (opcode->get().GetId()) {
+        case OpCode::Id::BFI_RC:
+            return {GetRegister(instr.gpr39),
+                    GetConstBuffer(instr.cbuf34.index, instr.cbuf34.offset)};
         case OpCode::Id::BFI_IMM_R:
-            return {GetRegister(instr.gpr39), Immediate(instr.alu.GetSignedImm20_20())};
+            return {Immediate(instr.alu.GetSignedImm20_20()), GetRegister(instr.gpr39)};
         default:
             UNREACHABLE();
             return {Immediate(0), Immediate(0)};