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[Qemu-devel] [PATCH] Use ctz64 in favor of ffsll
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] [PATCH] Use ctz64 in favor of ffsll |
Date: |
Thu, 02 Jul 2009 09:04:46 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Stuart Brady wrote:
> On Wed, Jul 01, 2009 at 01:58:02PM -0700, Nathan Froyd wrote:
>> On Wed, Jul 01, 2009 at 10:55:02PM +0200, Jan Kiszka wrote:
>>> - for (i = 0; i < ARRAY_SIZE(env->interrupt_bitmap); i++) {
>>> - bit = ffsll(env->interrupt_bitmap[i]);
>>> + for (i = 0; i < sizeof(env->interrupt_bitmap) / sizeof(int); i++) {
>>> + /* Note: This assumes little endian host, which is true in KVM
>>> mode.
>>> + In TCG mode it must be zero anyway. */
>>> + bit = ffs(((int *)env->interrupt_bitmap)[i]);
>> ISTR that some PPC hosts support KVM...
>
> FWIW, I notice we currently have a qemu_fls() defined in cutils.c, which
> uses the clz32() defined in host-utils.h.
>
> qemu_ffsll() could be implemented fairly easily in terms of ctz64(),
> although note that ffsll(n) == (ctz64(n) + 1) % 65.
ctz64 - that's what I wanted! (No need to introduce qemu_ffsll, at least
not for this use case.)
Jan
--------->
Not all host platforms support ffsll.
Signed-off-by: Jan Kiszka <address@hidden>
---
target-i386/machine.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/target-i386/machine.c b/target-i386/machine.c
index 259302c..e4099ca 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -148,9 +148,9 @@ void cpu_save(QEMUFile *f, void *opaque)
to find it and save its number instead (-1 for none). */
pending_irq = -1;
for (i = 0; i < ARRAY_SIZE(env->interrupt_bitmap); i++) {
- bit = ffsll(env->interrupt_bitmap[i]);
- if (bit) {
- pending_irq = i * 64 + bit - 1;
+ if (env->interrupt_bitmap[i]) {
+ bit = ctz64(env->interrupt_bitmap[i]);
+ pending_irq = i * 64 + bit;
break;
}
}
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- [Qemu-devel] [PATCH] Use ffs in favor of ffsll, Jan Kiszka, 2009/07/01
- [Qemu-devel] Re: [PATCH] Use ffs in favor of ffsll, Blue Swirl, 2009/07/01
- [Qemu-devel] Re: [PATCH] Use ffs in favor of ffsll, Jan Kiszka, 2009/07/01
- [Qemu-devel] [PATCH v2] Use ffs in favor of ffsll, Jan Kiszka, 2009/07/01
- Re: [Qemu-devel] [PATCH v2] Use ffs in favor of ffsll, Nathan Froyd, 2009/07/01
- [Qemu-devel] Re: [PATCH v2] Use ffs in favor of ffsll, Jan Kiszka, 2009/07/01
- Re: [Qemu-devel] [PATCH v2] Use ffs in favor of ffsll, Stuart Brady, 2009/07/01
- [Qemu-devel] [PATCH] Use ctz64 in favor of ffsll,
Jan Kiszka <=
- [Qemu-devel] [PATCH v2] Use ctz64 in favor of ffsll, Jan Kiszka, 2009/07/02
- Re: [Qemu-devel] [PATCH v2] Use ctz64 in favor of ffsll, Paul Brook, 2009/07/03
- Re: [Qemu-devel] [PATCH v2] Use ctz64 in favor of ffsll, Jan Kiszka, 2009/07/04
Re: [Qemu-devel] Re: [PATCH] Use ffs in favor of ffsll, Christoph Egger, 2009/07/02