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authorSverker Eriksson <[email protected]>2017-04-28 14:43:45 +0200
committerGitHub <[email protected]>2017-04-28 14:43:45 +0200
commit2e2526b58f74c6c3209b3feca34866772be65335 (patch)
treedae03bda8fe8418cb874ae2074916f74087b7758
parent28d64608d9f9e1d86d34323d1d1646ab17278d64 (diff)
parent282a7cab9989abb7a1b2daca7aec907d53163ff4 (diff)
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Merge PR-1431 from richcarl/mseg-debruijn-usage
Rename macro and add clarifying comment
-rw-r--r--erts/emulator/sys/common/erl_mseg.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/erts/emulator/sys/common/erl_mseg.c b/erts/emulator/sys/common/erl_mseg.c
index d1895f3793..1e99078906 100644
--- a/erts/emulator/sys/common/erl_mseg.c
+++ b/erts/emulator/sys/common/erl_mseg.c
@@ -83,12 +83,13 @@ static const int debruijn[32] = {
31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
};
-#define LOG2(X) (debruijn[((Uint32)(((X) & -(X)) * 0x077CB531U)) >> 27])
+#define LSB(X) (debruijn[((Uint32)(((X) & -(X)) * 0x077CB531U)) >> 27])
#define CACHE_AREAS (32 - MSEG_ALIGN_BITS)
/* FIXME: segment sizes > 2 GB result in bogus negative indices */
-#define SIZE_TO_CACHE_AREA_IDX(S) (LOG2((S)) - MSEG_ALIGN_BITS)
+/* NOTE: using LSB instead of proper log2 only works if S is a power of 2 */
+#define SIZE_TO_CACHE_AREA_IDX(S) (LSB((S)) - MSEG_ALIGN_BITS)
#define MAX_CACHE_SIZE (30)
#define MSEG_FLG_IS_2POW(X) ((X) & ERTS_MSEG_FLG_2POW)