From: Eric Lin <ericlinsechs@gmail.com>
Cc: Eric Lin <ericlinsechs@gmail.com>,
Jakub Jelinek <jakub@redhat.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH] ilog2: improve ilog2 for constant arguments
Date: Thu, 25 Apr 2024 09:59:28 +0800 [thread overview]
Message-ID: <20240425015936.41844-1-ericlinsechs@gmail.com> (raw)
Commit 2f78788b55ba ("ilog2: improve ilog2 for constant arguments")
used __builtin_clzll builtin to avoid generating a lot of code
which interferes badly with GCC inlining heuristics.
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eric Lin <ericlinsechs@gmail.com>
---
tools/include/linux/log2.h | 78 ++++----------------------------------
1 file changed, 8 insertions(+), 70 deletions(-)
diff --git a/tools/include/linux/log2.h b/tools/include/linux/log2.h
index e20a67d538b8..6180e8f879c4 100644
--- a/tools/include/linux/log2.h
+++ b/tools/include/linux/log2.h
@@ -68,76 +68,14 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
*
* selects the appropriately-sized optimised version depending on sizeof(n)
*/
-#define ilog2(n) \
-( \
- __builtin_constant_p(n) ? ( \
- (n) < 2 ? 0 : \
- (n) & (1ULL << 63) ? 63 : \
- (n) & (1ULL << 62) ? 62 : \
- (n) & (1ULL << 61) ? 61 : \
- (n) & (1ULL << 60) ? 60 : \
- (n) & (1ULL << 59) ? 59 : \
- (n) & (1ULL << 58) ? 58 : \
- (n) & (1ULL << 57) ? 57 : \
- (n) & (1ULL << 56) ? 56 : \
- (n) & (1ULL << 55) ? 55 : \
- (n) & (1ULL << 54) ? 54 : \
- (n) & (1ULL << 53) ? 53 : \
- (n) & (1ULL << 52) ? 52 : \
- (n) & (1ULL << 51) ? 51 : \
- (n) & (1ULL << 50) ? 50 : \
- (n) & (1ULL << 49) ? 49 : \
- (n) & (1ULL << 48) ? 48 : \
- (n) & (1ULL << 47) ? 47 : \
- (n) & (1ULL << 46) ? 46 : \
- (n) & (1ULL << 45) ? 45 : \
- (n) & (1ULL << 44) ? 44 : \
- (n) & (1ULL << 43) ? 43 : \
- (n) & (1ULL << 42) ? 42 : \
- (n) & (1ULL << 41) ? 41 : \
- (n) & (1ULL << 40) ? 40 : \
- (n) & (1ULL << 39) ? 39 : \
- (n) & (1ULL << 38) ? 38 : \
- (n) & (1ULL << 37) ? 37 : \
- (n) & (1ULL << 36) ? 36 : \
- (n) & (1ULL << 35) ? 35 : \
- (n) & (1ULL << 34) ? 34 : \
- (n) & (1ULL << 33) ? 33 : \
- (n) & (1ULL << 32) ? 32 : \
- (n) & (1ULL << 31) ? 31 : \
- (n) & (1ULL << 30) ? 30 : \
- (n) & (1ULL << 29) ? 29 : \
- (n) & (1ULL << 28) ? 28 : \
- (n) & (1ULL << 27) ? 27 : \
- (n) & (1ULL << 26) ? 26 : \
- (n) & (1ULL << 25) ? 25 : \
- (n) & (1ULL << 24) ? 24 : \
- (n) & (1ULL << 23) ? 23 : \
- (n) & (1ULL << 22) ? 22 : \
- (n) & (1ULL << 21) ? 21 : \
- (n) & (1ULL << 20) ? 20 : \
- (n) & (1ULL << 19) ? 19 : \
- (n) & (1ULL << 18) ? 18 : \
- (n) & (1ULL << 17) ? 17 : \
- (n) & (1ULL << 16) ? 16 : \
- (n) & (1ULL << 15) ? 15 : \
- (n) & (1ULL << 14) ? 14 : \
- (n) & (1ULL << 13) ? 13 : \
- (n) & (1ULL << 12) ? 12 : \
- (n) & (1ULL << 11) ? 11 : \
- (n) & (1ULL << 10) ? 10 : \
- (n) & (1ULL << 9) ? 9 : \
- (n) & (1ULL << 8) ? 8 : \
- (n) & (1ULL << 7) ? 7 : \
- (n) & (1ULL << 6) ? 6 : \
- (n) & (1ULL << 5) ? 5 : \
- (n) & (1ULL << 4) ? 4 : \
- (n) & (1ULL << 3) ? 3 : \
- (n) & (1ULL << 2) ? 2 : \
- 1 ) : \
- (sizeof(n) <= 4) ? \
- __ilog2_u32(n) : \
- __ilog2_u64(n) \
+#define ilog2(n) \
+( \
+ __builtin_constant_p(n) ? \
+ ((n) < 2 ? 0 : \
+ 63 - __builtin_clzll(n)) : \
+ (sizeof(n) <= 4) ? \
+ __ilog2_u32(n) : \
+ __ilog2_u64(n) \
)
/**
--
2.43.0
next reply other threads:[~2024-04-25 2:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 1:59 Eric Lin [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-11-20 12:51 [PATCH] ilog2: Improve ilog2 for constant arguments Peter Zijlstra
2020-11-21 20:23 ` Luc Van Oostenryck
2020-11-21 20:29 ` Jakub Jelinek
2020-11-21 20:46 ` Luc Van Oostenryck
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