From: David Miller <davem@davemloft.net>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, torvalds@linux-foundation.org,
akpm@linux-foundation.org, viro@ZenIV.linux.org.uk
Subject: find_new_bit bloat from x86 tree...
Date: Sat, 26 Apr 2008 22:07:26 -0700 (PDT) [thread overview]
Message-ID: <20080426.220726.13692428.davem@davemloft.net> (raw)
Ingo, what the heck is this?
commit 64970b68d2b3ed32b964b0b30b1b98518fde388e
Author: Alexander van Heukelum <heukelum@mailshack.com>
Date: Tue Mar 11 16:17:19 2008 +0100
x86, generic: optimize find_next_(zero_)bit for small constant-size bitmaps
Thanks for bloating up the inline expansion of this thing on every
architecture that doesn't do __ffs() in a simple sequence of a few
instructions like x86 does.
Now every call that matches your tests gets this turd inline:
static inline unsigned long __ffs(unsigned long word)
{
int num = 0;
#if BITS_PER_LONG == 64
if ((word & 0xffffffff) == 0) {
num += 32;
word >>= 32;
}
#endif
if ((word & 0xffff) == 0) {
num += 16;
word >>= 16;
}
if ((word & 0xff) == 0) {
num += 8;
word >>= 8;
}
if ((word & 0xf) == 0) {
num += 4;
word >>= 4;
}
if ((word & 0x3) == 0) {
num += 2;
word >>= 2;
}
if ((word & 0x1) == 0)
num += 1;
return num;
}
as well as all of that address formation, bit shifting, and masking.
Please revert or make this conditional on something architectures can
opt-in for.
The version actually applied was posted only on linux-kernel, instead
of also CC:'ing linux-arch as previous versions had been. Nobody
commented on this version other than you Ingo.
next reply other threads:[~2008-04-27 5:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-27 5:07 David Miller [this message]
2008-04-27 20:41 ` Ingo Molnar
2008-04-28 11:41 ` Alexander van Heukelum
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