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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.




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