[Qemu-devel] [PATCH v2 2/4] openpic: IRQ_check: search the queue a word at a time

[Scott Wood]

Search the queue more efficiently by first looking for a non-zero word,
and then using the common bit-searching function to find the bit within
the word.  It would be even nicer if bitops_ffsl() could be hooked up
to the compiler intrinsic so that bit-searching instructions could be
used, but that's another matter.

Signed-off-by: Scott Wood <address@hidden>
---
v2: use find_next_bit

 hw/openpic.c |   28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/hw/openpic.c b/hw/openpic.c
index 66179c2..7645d67 100644
--- a/hw/openpic.c
+++ b/hw/openpic.c
@@ -277,21 +277,25 @@ static inline int IRQ_testbit(IRQQueue *q, int n_IRQ)
 
 static void IRQ_check(OpenPICState *opp, IRQQueue *q)
 {
-    int next, i;
-    int priority;
+    int irq = -1;
+    int next = -1;
+    int priority = -1;
 
-    next = -1;
-    priority = -1;
-    for (i = 0; i < opp->max_irq; i++) {
-        if (IRQ_testbit(q, i)) {
-            DPRINTF("IRQ_check: irq %d set ivpr_pr=%d pr=%d\n",
-                    i, IVPR_PRIORITY(opp->src[i].ivpr), priority);
-            if (IVPR_PRIORITY(opp->src[i].ivpr) > priority) {
-                next = i;
-                priority = IVPR_PRIORITY(opp->src[i].ivpr);
-            }
+    for (;;) {
+        irq = find_next_bit(q->queue, opp->max_irq, irq + 1);
+        if (irq == opp->max_irq) {
+            break;
+        }
+
+        DPRINTF("IRQ_check: irq %d set ivpr_pr=%d pr=%d\n",
+                irq, IVPR_PRIORITY(opp->src[irq].ivpr), priority);
+
+        if (IVPR_PRIORITY(opp->src[irq].ivpr) > priority) {
+            next = irq;
+            priority = IVPR_PRIORITY(opp->src[irq].ivpr);
         }
     }
+
     q->next = next;
     q->priority = priority;
 }
-- 
1.7.9.5