find_new_bit bloat from x86 tree...

David Miller
2008-04-27T05:07:38Z

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.