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Fix calculation of mask for constant values #7507

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Fix calculation of mask for constant values #7507

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14 changes: 8 additions & 6 deletions rust/src/low_level_il/operation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1754,12 +1754,14 @@ where
}
}

let mut mask = -1i64 as u64;

if self.op.size < mem::size_of::<u64>() {
mask <<= self.op.size * 8;
mask = !mask;
}
let mask: u64 = if self.op.size == 0 {
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Copilot AI Oct 28, 2025

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A mask of 1 will only preserve the least significant bit, not the lowest byte. To correctly mask the lowest byte as described in the PR description, the mask should be 0xFF (255) instead of 1.

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1
0xFF

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Nice catch. That is a bug in the wording of my MR message though and not the actual code.

} else if self.op.size < mem::size_of::<u64>() {
let m = -1i64 << (self.op.size * 8);
!m as u64
} else {
(-1i64) as u64
};

self.op.operands[0] & mask
}
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