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8178352: BitMap::get_next_zero_offset may give wrong result on Mac

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Invert and search initial word for trailing ones.

Reviewed-by: stefank, cjplummer
This commit is contained in:
Kim Barrett 2017-05-03 14:13:48 -04:00
parent c386cec7b1
commit a896bf909c
1 changed files with 5 additions and 5 deletions
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10
hotspot/src/share/vm/utilities/bitMap.inline.hpp
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@ -222,12 +222,12 @@ BitMap::get_next_zero_offset(idx_t l_offset, idx_t r_offset) const {
idx_t res_offset = l_offset; idx_t res_offset = l_offset;
// check bits including and to the _left_ of offset's position // check bits including and to the _left_ of offset's position
idx_t pos = res_offset & (BitsPerWord - 1); idx_t pos = bit_in_word(res_offset);
bm_word_t res = (map(index) >> pos) | left_n_bits((int)pos); bm_word_t res = ~map(index) >> pos; // flip bits and shift for l_offset
if (res != ~(bm_word_t)0) { if (res != 0) {
// find the position of the 0-bit // find the position of the 1-bit
for (; res & 1; res_offset++) { for (; !(res & 1); res_offset++) {
res = res >> 1; res = res >> 1;
} }
assert(res_offset >= l_offset, "just checking"); assert(res_offset >= l_offset, "just checking");