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Convert ffs() != 0 callers to ctz32()

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There are a number of ffs(3) callers that do roughly:

  bit = ffs(val);
  if (bit) {
      do_something(bit - 1);
  }

This pattern can be converted to ctz32() like this:

  zeroes = ctz32(val);
  if (zeroes != 32) {
      do_something(zeroes);
  }

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1427124571-28598-6-git-send-email-stefanha@redhat.com
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2015-03-23 15:29:27 +00:00 • committed by Kevin Wolf
parent 786a4ea82e
commit bd2a88840e
6 changed files with 26 additions and 27 deletions
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8
kvm-all.c
View file

@ -1141,18 +1141,18 @@ static int kvm_irqchip_get_virq(KVMState *s)
{
uint32_t *word = s->used_gsi_bitmap;
int max_words = ALIGN(s->gsi_count, 32) / 32;
int i, bit;
int i, zeroes;
bool retry = true;
again:
/* Return the lowest unused GSI in the bitmap */
for (i = 0; i < max_words; i++) {
bit = ffs(~word[i]);
if (!bit) {
zeroes = ctz32(~word[i]);
if (zeroes == 32) {
continue;
}
return bit - 1 + i * 32;
return zeroes + i * 32;
}
if (!s->direct_msi && retry) {
retry = false;