Wasm GC: Fix is-null-or-i31ref checks #10221
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In the case where we need to check for either null or i31refs, we were attempting to fold the two checks together with a bitwise-and and a bitmask, but that was incorrect and buggy. We need to actually do the two separate checks and bitwise-or them together. Fixes bytecodealliance#10171
alexcrichton
approved these changes
Feb 12, 2025
| @@ -25,10 +25,6 @@ use core::alloc::Layout; | |||
| /// Discriminant to check whether GC reference is an `i31ref` or not. | |||
| pub const I31_DISCRIMINANT: u64 = 1; | |||
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Curiosity: why is this typed u64? This discriminant is technically only for 32-bit values right?
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I think it was useful at some point but might not be useful anymore, I’d have to look at uses again
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Looks like there's no issue changing it to a u32, so I'll do that in a follow up
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In the case where we need to check for either null or i31refs, we were attempting to fold the two checks together with a bitwise-and and a bitmask, but that was incorrect and buggy. We need to actually do the two separate checks and bitwise-or them together.
Fixes #10171