infernap12/jdk
1
0
Fork 0
mirror of https://github.com/openjdk/jdk.git synced 2026-02-16 05:15:22 +00:00
Code Issues Packages Projects Releases Wiki Activity

8368307: Shenandoah: get_next_bit_impl should special case weak and strong mark bits

Browse Source 
Reviewed-by: wkemper
This commit is contained in:
Kelvin Nilsen 2025-09-27 04:07:29 +00:00
parent 9093d3a04c
commit af8fb20ac0
1 changed files with 6 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/hotspot/share/gc/shenandoah/shenandoahMarkBitMap.inline.hpp
View File

@ -135,14 +135,12 @@ inline ShenandoahMarkBitMap::idx_t ShenandoahMarkBitMap::get_next_bit_impl(idx_t
// Get the word containing l_index, and shift out low bits.
idx_t index = to_words_align_down(l_index);
bm_word_t cword = (map(index) ^ flip) >> bit_in_word(l_index);
if ((cword & 1) != 0) {
// The first bit is similarly often interesting. When it matters
// (density or features of the calling algorithm make it likely
// the first bit is set), going straight to the next clause compares
// poorly with doing this check first; count_trailing_zeros can be
// relatively expensive, plus there is the additional range check.
// But when the first bit isn't set, the cost of having tested for
// it is relatively small compared to the rest of the search.
if ((cword & 0x03) != 0) {
// The first bits (representing weak mark or strong mark) are similarly often interesting. When it matters
// (density or features of the calling algorithm make it likely the first bits are set), going straight to
// the next clause compares poorly with doing this check first; count_trailing_zeros can be relatively expensive,
// plus there is the additional range check. But when the first bits are not set, the cost of having tested for
// them is relatively small compared to the rest of the search.
return l_index;
} else if (cword != 0) {
// Flipped and shifted first word is non-zero.