[Qemu-devel] [PATCH v2] Use ffs in favor of ffsll

[Jan Kiszka]

Jan Kiszka wrote:
> Blue Swirl wrote:
>> On 7/1/09, Jan Kiszka <address@hidden> wrote:
>>> Not all host platforms support the ll variant. This is not a critical
>>>  path, so go the easy way.
>>>  -    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++) {
>>>  +        bit = ffs(((int *)env->interrupt_bitmap)[i]);
>>>          if (bit) {
>>>  -            pending_irq = i * 64 + bit - 1;
>>>  +            pending_irq = i * 8 * sizeof(int) + bit - 1;
>> I think this will not work on a big endian host.
> 
> Right, may theoretically bite us once we are able to migrate between kvm
> and tcg. Will send a better version nevertheless.
> 

I decided that a comment should suffice.

-----

Not all host platforms support the ll variant. This is not a critical
path, so go the easy way.

Signed-off-by: Jan Kiszka <address@hidden>
---

 target-i386/machine.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/target-i386/machine.c b/target-i386/machine.c
index 259302c..1a56b3d 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -147,10 +147,12 @@ void cpu_save(QEMUFile *f, void *opaque)
     /* There can only be one pending IRQ set in the bitmap at a time, so try
        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]);
+    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]);
         if (bit) {
-            pending_irq = i * 64 + bit - 1;
+            pending_irq = i * 8 * sizeof(int) + bit - 1;
             break;
         }
     }