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Ensure next_values(StateRead*) returns an empty set in the rare case where no next's are associated with a read #3469

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Merged
copybara-service merged 1 commit into from
Dec 12, 2025
Merged

Ensure next_values(StateRead*) returns an empty set in the rare case where no next's are associated with a read #3469

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1 change: 1 addition & 0 deletions xls/ir/BUILD
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Original file line number Diff line number Diff line change
Expand Up @@ -647,6 +647,7 @@ cc_library(
"//xls/data_structures:leaf_type_tree",
"@com_google_absl//absl/algorithm:container",
"@com_google_absl//absl/base",
"@com_google_absl//absl/base:no_destructor",
"@com_google_absl//absl/container:btree",
"@com_google_absl//absl/container:fixed_array",
"@com_google_absl//absl/container:flat_hash_map",
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19 changes: 19 additions & 0 deletions xls/ir/function_base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@
#include <utility>
#include <vector>

#include "absl/algorithm/container.h"
#include "absl/base/no_destructor.h"
#include "absl/container/btree_set.h"
#include "absl/container/flat_hash_map.h"
#include "absl/log/check.h"
Expand Down Expand Up @@ -228,6 +230,23 @@ class FunctionBase {

const absl::btree_set<Next*, Node::NodeIdLessThan>& next_values(
StateRead* state_read) const {
if (!next_values_by_state_read_.contains(state_read)) {
// This should be pretty rare. Basically this should only happen in the
// short time before the non-updated state element is replaced. Just
// returning what is actually there is nicer than crashing however. Do
// check that this is not just some sort of weird corruption however.
static const absl::NoDestructor<
absl::btree_set<Next*, Node::NodeIdLessThan>>
kEmptySet;
CHECK(absl::c_none_of(nodes(),
[state_read](Node* n) {
return n->Is<Next>() &&
n->As<Next>()->state_read() == state_read;
}))
<< "Invalid side table for next values. Missing " << state_read
<< " in " << this;
return *kEmptySet;
}
return next_values_by_state_read_.at(state_read);
}

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