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Improve usage of sf_assume

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Make the sf_assume also have an effect with clang and help the compiler
proof it's side effect free by comparing against a variable.

https://tests.stockfishchess.org/tests/view/6979d14fa2c75f923be1e681
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 63488 W: 16530 L: 16188 D: 30770
Ptnml(0-2): 167, 6904, 17277, 7212, 184

closes https://github.com/official-stockfish/Stockfish/pull/6573

No functional change
This commit is contained in:
disservin
2026-02-04 17:46:47 +01:00
committed by Joost VandeVondele
parent 542c30c292
commit 9f968446cb
2 changed files with 39 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/misc.h
+9 -1
View File
@@ -444,7 +444,9 @@ void move_to_front(std::vector<T>& vec, Predicate pred) {
#define sf_always_inline
#endif
#if defined(__GNUC__) && !defined(__clang__)
#if defined(__clang__)
#define sf_assume(cond) __builtin_assume(cond)
#elif defined(__GNUC__)
#if __GNUC__ >= 13
#define sf_assume(cond) __attribute__((assume(cond)))
#else
@@ -460,6 +462,12 @@ void move_to_front(std::vector<T>& vec, Predicate pred) {
#define sf_assume(cond)
#endif
#ifdef __GNUC__
#define sf_unreachable() __builtin_unreachable()
#else
#define sf_unreachable()
#endif
} // namespace Stockfish
template<std::size_t N>
src/nnue/nnue_accumulator.cpp
+30 -20
View File
@@ -507,19 +507,23 @@ void double_inc_update(Color p
assert(added.size() < 2);
PSQFeatureSet::append_changed_indices(perspective, ksq, target_state.diff, removed, added);
assert(added.size() == 1);
assert(removed.size() == 2 || removed.size() == 3);
[[maybe_unused]] const int addedSize = added.ssize();
[[maybe_unused]] const int removedSize = removed.ssize();
assert(addedSize == 1);
assert(removedSize == 2 || removedSize == 3);
// Workaround compiler warning for uninitialized variables, replicated on
// profile builds on windows with gcc 14.2.0.
// TODO remove once unneeded
sf_assume(added.size() == 1);
sf_assume(removed.size() == 2 || removed.size() == 3);
// Also helps with optimizations on some compilers.
sf_assume(addedSize == 1);
sf_assume(removedSize == 2 || removedSize == 3);
auto updateContext =
make_accumulator_update_context(perspective, featureTransformer, computed, target_state);
if (removed.size() == 2)
if (removedSize == 2)
{
updateContext.template apply<Add, Sub, Sub>(added[0], removed[0], removed[1]);
}
@@ -593,35 +597,41 @@ void update_accumulator_incremental(
updateContext.apply(added, removed);
else
{
assert(added.size() == 1 || added.size() == 2);
assert(removed.size() == 1 || removed.size() == 2);
assert((Forward && added.size() <= removed.size())
|| (!Forward && added.size() >= removed.size()));
[[maybe_unused]] const int addedSize = added.ssize();
[[maybe_unused]] const int removedSize = removed.ssize();
assert(addedSize == 1 || addedSize == 2);
assert(removedSize == 1 || removedSize == 2);
assert((Forward && addedSize <= removedSize) || (!Forward && addedSize >= removedSize));
// Workaround compiler warning for uninitialized variables, replicated
// on profile builds on windows with gcc 14.2.0.
// TODO remove once unneeded
sf_assume(added.size() == 1 || added.size() == 2);
sf_assume(removed.size() == 1 || removed.size() == 2);
// Also helps with optimizations on some compilers.
if ((Forward && removed.size() == 1) || (!Forward && added.size() == 1))
sf_assume(addedSize == 1 || addedSize == 2);
sf_assume(removedSize == 1 || removedSize == 2);
if (!(removedSize == 1 || removedSize == 2) || !(addedSize == 1 || addedSize == 2))
sf_unreachable();
if ((Forward && removedSize == 1) || (!Forward && addedSize == 1))
{
assert(added.size() == 1 && removed.size() == 1);
assert(addedSize == 1 && removedSize == 1);
updateContext.template apply<Add, Sub>(added[0], removed[0]);
}
else if (Forward && added.size() == 1)
else if (Forward && addedSize == 1)
{
assert(removed.size() == 2);
assert(removedSize == 2);
updateContext.template apply<Add, Sub, Sub>(added[0], removed[0], removed[1]);
}
else if (!Forward && removed.size() == 1)
else if (!Forward && removedSize == 1)
{
assert(added.size() == 2);
assert(addedSize == 2);
updateContext.template apply<Add, Add, Sub>(added[0], added[1], removed[0]);
}
else
{
assert(added.size() == 2 && removed.size() == 2);
assert(addedSize == 2 && removedSize == 2);
updateContext.template apply<Add, Add, Sub, Sub>(added[0], added[1], removed[0],
removed[1]);
}