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Sema: fix comptime-known union initialization with OPV field

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The previous commit uncovered this existing OPV bug by triggering this
logic more frequently.
This commit is contained in:
mlugg 2025-07-29 10:36:31 +01:00
parent a8888afcc0
commit b1dcf2b149
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GPG Key ID: 3F5B7DCCBF4AF02E
1 changed files with 19 additions and 5 deletions
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24
src/Sema.zig
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@ -3922,7 +3922,7 @@ fn resolveComptimeKnownAllocPtr(sema: *Sema, block: *Block, alloc: Air.Inst.Ref,
const store_inst = sema.air_instructions.get(@intFromEnum(store_inst_idx));
const ptr_to_map = switch (store_inst.tag) {
.store, .store_safe => store_inst.data.bin_op.lhs.toIndex().?, // Map the pointer being stored to.
.set_union_tag => continue, // We can completely ignore these: we'll do it implicitly when we get the field pointer.
.set_union_tag => continue, // Ignore for now; handled after we map pointers
.optional_payload_ptr_set, .errunion_payload_ptr_set => store_inst_idx, // Map the generated pointer itself.
else => unreachable,
};
@ -4055,19 +4055,33 @@ fn resolveComptimeKnownAllocPtr(sema: *Sema, block: *Block, alloc: Air.Inst.Ref,
}
// We have a correlation between AIR pointers and decl pointers. Perform all stores at comptime.
// Any implicit stores performed by `optional_payload_ptr_set`, `errunion_payload_ptr_set`, or
// `set_union_tag` instructions were already done above.
// Any implicit stores performed by `optional_payload_ptr_set` or `errunion_payload_ptr_set`
// instructions were already done above.
for (stores) |store_inst_idx| {
const store_inst = sema.air_instructions.get(@intFromEnum(store_inst_idx));
switch (store_inst.tag) {
.set_union_tag => {}, // Handled implicitly by field pointers above
.optional_payload_ptr_set, .errunion_payload_ptr_set => {}, // Handled explicitly above
.set_union_tag => {
// Usually, we can ignore these, because the creation of the field pointer above
// already did it for us. However, if the field is OPV, this is relevant, because
// there is not going to be a store to the field. So we must initialize the union
// tag if the field is OPV.
const union_ptr_inst = store_inst.data.bin_op.lhs.toIndex().?;
const union_ptr_val: Value = .fromInterned(ptr_mapping.get(union_ptr_inst).?);
const tag_val: Value = .fromInterned(store_inst.data.bin_op.rhs.toInterned().?);
const union_ty = union_ptr_val.typeOf(zcu).childType(zcu);
const field_ty = union_ty.unionFieldType(tag_val, zcu).?;
if (try sema.typeHasOnePossibleValue(field_ty)) |payload_val| {
const new_union_val = try pt.unionValue(union_ty, tag_val, payload_val);
try sema.storePtrVal(block, .unneeded, union_ptr_val, new_union_val, union_ty);
}
},
.store, .store_safe => {
const air_ptr_inst = store_inst.data.bin_op.lhs.toIndex().?;
const store_val = (try sema.resolveValue(store_inst.data.bin_op.rhs)).?;
const new_ptr = ptr_mapping.get(air_ptr_inst).?;
try sema.storePtrVal(block, LazySrcLoc.unneeded, Value.fromInterned(new_ptr), store_val, .fromInterned(zcu.intern_pool.typeOf(store_val.toIntern())));
try sema.storePtrVal(block, .unneeded, .fromInterned(new_ptr), store_val, store_val.typeOf(zcu));
},
else => unreachable,
}