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[ADT] Use a C++17 fold expression in hash_combine (NFC) #159901

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kazutakahirata merged 2 commits into from
Sep 20, 2025
Merged

[ADT] Use a C++17 fold expression in hash_combine (NFC) #159901

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[ADT] Use a C++17 fold expression in hash_combine (NFC)
kazutakahirata Sep 15, 2025
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Address a comment.
kazutakahirata Sep 20, 2025
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22 changes: 8 additions & 14 deletions llvm/include/llvm/ADT/Hashing.h
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Original file line number Diff line number Diff line change
Expand Up @@ -503,7 +503,8 @@ struct hash_combine_recursive_helper {
/// hash_state, empties it, and then merges the new chunk in. This also
/// handles cases where the data straddles the end of the buffer.
template <typename T>
char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) {
char *combine_data(size_t &length, char *&buffer_ptr, char *buffer_end,
T data) {
if (!store_and_advance(buffer_ptr, buffer_end, data)) {
// Check for skew which prevents the buffer from being packed, and do
// a partial store into the buffer to fill it. This is only a concern
Expand Down Expand Up @@ -541,21 +542,14 @@ struct hash_combine_recursive_helper {
///
/// This function recurses through each argument, combining that argument
/// into a single hash.
template <typename T, typename ...Ts>
template <typename... Ts>
hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
const T &arg, const Ts &...args) {
buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg));
const Ts &...args) {
(combine_data(length, buffer_ptr, buffer_end, get_hashable_data(args)),
...);

// Recurse to the next argument.
return combine(length, buffer_ptr, buffer_end, args...);
}

/// Base case for recursive, variadic combining.
///
/// The base case when combining arguments recursively is reached when all
/// arguments have been handled. It flushes the remaining buffer and
/// constructs a hash_code.
hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) {
// Finalize the hash by flushing any remaining data in the buffer.
//
// Check whether the entire set of values fit in the buffer. If so, we'll
// use the optimized short hashing routine and skip state entirely.
if (length == 0)
Expand Down