[a64] Implement OPCODE_DID_SATURATE

This directly maps to the QC bit in the FPSR. Just have to make sure
that the saturated instruction is the very last instruction(which is
currently the case for stuff like VECTOR_ADD and such).

Author: Wunkolo

src/xenia/cpu/backend/a64/a64_sequences.cc

@@ -1107,8 +1107,9 @@ EMITTER_ASSOCIATIVE_COMPARE_FLT_XX(UGE, Cond::HS);  // setae
 struct DID_SATURATE
     : Sequence<DID_SATURATE, I<OPCODE_DID_SATURATE, I8Op, V128Op>> {
   static void Emit(A64Emitter& e, const EmitArgType& i) {
-    // TODO(benvanik): implement saturation check (VECTOR_ADD, etc).
-    e.EOR(i.dest, i.dest, i.dest);
+    // Bit 27 in the FPSR is the QC bit
+    e.MRS(X0, SystemReg::FPSR);
+    e.UBFX(i.dest, W0, 27, 1);
   }
 };
 EMITTER_OPCODE_TABLE(OPCODE_DID_SATURATE, DID_SATURATE);