[PATCH] pcnet_cs.c: IRQ handler optimization

During some performance diagnostics I stumbled on this slightly wasteful
code in pcnet_cs.c which I made the patch included at the bottom for (two
minor comment fixes included).

Improvement:
instead of *always* calculating
lea 0x2c0(%edx),%ebx
and then additionally doing the
mov %edx,0xc0(%ebx)
addition *if we need it*,

we now do the *whole* calculation of
mov %edx,0x380(%ebx)
*only* if we need it.
This even manages to save us a whole 16-byte alignment buffer loss
in this compilation case.

Result: slightly improves IRQ handler performance in both shared and
non-shared IRQ case, which should make my rusty P3/700 a slight bit happier.

Thank you for your support,

Andreas Mohr

old asm result (using gcc 3.3.5):

000015a0 <ei_irq_wrapper>:
15a0: 55 push %ebp
15a1: 89 e5 mov %esp,%ebp
15a3: 53 push %ebx
15a4: 8d 9a c0 02 00 00 lea 0x2c0(%edx),%ebx
15aa: e8 fc ff ff ff call 15ab <ei_irq_wrapper+0xb>
15af: 83 f8 01 cmp $0x1,%eax
15b2: 74 03 je 15b7 <ei_irq_wrapper+0x17>
15b4: 5b pop %ebx
15b5: 5d pop %ebp
15b6: c3 ret
15b7: 31 d2 xor %edx,%edx
15b9: 89 93 c0 00 00 00 mov %edx,0xc0(%ebx)
15bf: eb f3 jmp 15b4 <ei_irq_wrapper+0x14>
15c1: eb 0d jmp 15d0 <ei_watchdog>
15c3: 90 nop
15c4: 90 nop
15c5: 90 nop
15c6: 90 nop
15c7: 90 nop
15c8: 90 nop
15c9: 90 nop
15ca: 90 nop
15cb: 90 nop
15cc: 90 nop
15cd: 90 nop
15ce: 90 nop
15cf: 90 nop

000015d0 <ei_watchdog>:

new asm result:

000015a0 <ei_irq_wrapper>:
15a0: 55 push %ebp
15a1: 89 e5 mov %esp,%ebp
15a3: 53 push %ebx
15a4: 89 d3 mov %edx,%ebx
15a6: e8 fc ff ff ff call 15a7 <ei_irq_wrapper+0x7>
15ab: 83 f8 01 cmp $0x1,%eax
15ae: 74 03 je 15b3 <ei_irq_wrapper+0x13>
15b0: 5b pop %ebx
15b1: 5d pop %ebp
15b2: c3 ret
15b3: 31 d2 xor %edx,%edx
15b5: 89 93 80 03 00 00 mov %edx,0x380(%ebx)
15bb: eb f3 jmp 15b0 <ei_irq_wrapper+0x10>
15bd: 8d 76 00 lea 0x0(%esi),%esi

000015c0 <ei_watchdog>:

Signed-off-by: Andrew Morton <[e-mail]>

drivers/net/pcmcia/pcnet_cs.c

···
 static irqreturn_t ei_irq_wrapper(int irq, void *dev_id, struct pt_regs *regs)
 {
     struct net_device *dev = dev_id;
-    pcnet_dev_t *info = PRIV(dev);
+    pcnet_dev_t *info;
     irqreturn_t ret = ei_interrupt(irq, dev_id, regs);
 
-    if (ret == IRQ_HANDLED)
+    if (ret == IRQ_HANDLED) {
+	    info = PRIV(dev);
 	    info->stale = 0;
+    }
     return ret;
 }
 
···
     if (count & 0x01)
 	buf[count-1] = inb(nic_base + PCNET_DATAPORT), xfer_count++;
 
-    /* This was for the ALPHA version only, but enough people have
+    /* This was for the ALPHA version only, but enough people have been
        encountering problems that it is still here. */
 #ifdef PCMCIA_DEBUG
     if (ei_debug > 4) {		/* DMA termination address check... */
···
     dma_start = jiffies;
 
 #ifdef PCMCIA_DEBUG
-    /* This was for the ALPHA version only, but enough people have
+    /* This was for the ALPHA version only, but enough people have been
        encountering problems that it is still here. */
     if (ei_debug > 4) {	/* DMA termination address check... */
 	int addr, tries = 20;