# HG changeset patch
# User kbarrett
# Date 1493835228 14400
# Node ID d577822ca75cc22f90285ef7ca914ea0457c524f
# Parent  54713555867ee2c7cac1954fd40f284240af8d51
8178352: BitMap::get_next_zero_offset may give wrong result on Mac
Summary: Invert and search initial word for trailing ones.
Reviewed-by: stefank, cjplummer

diff -r 54713555867e -r d577822ca75c hotspot/src/share/vm/utilities/bitMap.inline.hpp
--- a/hotspot/src/share/vm/utilities/bitMap.inline.hpp	Fri Mar 03 23:08:35 2017 -0800
+++ b/hotspot/src/share/vm/utilities/bitMap.inline.hpp	Wed May 03 14:13:48 2017 -0400
@@ -222,12 +222,12 @@
   idx_t res_offset = l_offset;
 
   // check bits including and to the _left_ of offset's position
-  idx_t pos = res_offset & (BitsPerWord - 1);
-  bm_word_t res = (map(index) >> pos) | left_n_bits((int)pos);
+  idx_t pos = bit_in_word(res_offset);
+  bm_word_t res = ~map(index) >> pos; // flip bits and shift for l_offset
 
-  if (res != ~(bm_word_t)0) {
-    // find the position of the 0-bit
-    for (; res & 1; res_offset++) {
+  if (res != 0) {
+    // find the position of the 1-bit
+    for (; !(res & 1); res_offset++) {
       res = res >> 1;
     }
     assert(res_offset >= l_offset, "just checking");