Hello all,
I noticed the very "non-nice" asymmetry of i8259A_irq_real(),
so I decided to fix the weirdly aligned branches.
While doing this, I noticed that it could be streamlined much more,
resulting in an astonishing 208 byte object code saving for such a tiny code
fragment! (gcc 3.2.3)
Review appreciated, I believe it's correct but I've only tested it shortly
and it's slowpath anyway.
Patch against 2.6.17-rc2-mm1.
Thanks!
Signed-off-by: Andreas Mohr <[email protected]>
--- linux-2.6.17-rc2-mm1.orig/arch/i386/kernel/i8259.c 2006-04-18 11:45:21.000000000 +0200
+++ linux-2.6.17-rc2-mm1/arch/i386/kernel/i8259.c 2006-04-27 23:57:34.000000000 +0200
@@ -145,17 +145,20 @@
static inline int i8259A_irq_real(unsigned int irq)
{
int value;
- int irqmask = 1<<irq;
+ int irqmask;
+ int reg;
if (irq < 8) {
- outb(0x0B,PIC_MASTER_CMD); /* ISR register */
- value = inb(PIC_MASTER_CMD) & irqmask;
- outb(0x0A,PIC_MASTER_CMD); /* back to the IRR register */
- return value;
+ reg = PIC_MASTER_CMD;
+ irqmask = 1 << irq;
+ } else {
+ reg = PIC_SLAVE_CMD;
+ irqmask = 1 << (irq - 8);
}
- outb(0x0B,PIC_SLAVE_CMD); /* ISR register */
- value = inb(PIC_SLAVE_CMD) & (irqmask >> 8);
- outb(0x0A,PIC_SLAVE_CMD); /* back to the IRR register */
+
+ outb(0x0B, reg); /* ISR register */
+ value = inb(reg) & irqmask;
+ outb(0x0A, reg); /* back to the IRR register */
return value;
}
-
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