There's three cases: 1) the program does not contain an instruction that touches s3_5_c15_c10_1 2) the program contains an instruction that touches s3_5_c15_c

There's three cases: 1) the program does not contain an instruction that touches s3_5_c15_c10_1 2) the program contains an instruction that touches s3_5_c15_c10_1, but never executes that instruction 3) the program contains an instruction that touches s3_5_c15_c10_1, and uses it Rice's theorem means we cannot tell whether a program will touch the register at runtime (as that's a dynamic property of the program). But that's because we cannot tell case 2 from case 3. It's perfectly decidable whether a program is in case 1 (as that's a static property of the program). Any sound static analysis must have false positives -- but those are exactly the programs in case 2. It doesn't mean we end up blocking other kinds of instructions.