proper regw and regrw16?

[Kevin B. Hendricks]

Hi Ani and Ben,

I asked about the "correct" form for regr and regw to the list a while back
(and it generated a big discussion!) and I put in the "best" suggested form
but it obviously impacts something.

So exactly what in the generated code is different about these two cases
that makes such a big difference in performance?  I need to understand why
the "output constraint" approach has such a bad performance impact?


--- r128_reg.h.orig	Thu Mar 23 18:10:17 2000
+++ r128_reg.h	Thu Mar 23 18:15:43 2000
@@ -50,9 +50,7 @@

 static inline void regw(volatile unsigned long base_addr, unsigned long
regindex, unsigned long regdata)
 {
- asm volatile ("stwbrx %1,%2,%3; eieio"
-          : "=m" (*(volatile unsigned *)(base_addr+regindex))
-          : "r" (regdata), "b" (regindex), "r" (base_addr));
+	asm volatile ("stwbrx %0,%1,%2; eieio" : : "r"(regdata), "b"
(regindex), "r"(base_addr) : "memory");
 }

Could you post the assembler (.S) file that each of these makes?

Thanks,

Kevin


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