[PATCH 2/4] introduce region_overlap() function
Sascha Hauer
s.hauer at pengutronix.de
Fri Oct 5 17:33:02 EDT 2012
On Fri, Oct 05, 2012 at 09:55:04PM +0200, Robert Jarzmik wrote:
> Sascha Hauer <s.hauer at pengutronix.de> writes:
>
> > To check if two regions overlap
> >
> > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > ---
> > include/common.h | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> > diff --git a/include/common.h b/include/common.h
> > index c1f44b4..e30774a 100644
> > --- a/include/common.h
> > +++ b/include/common.h
> > @@ -256,4 +256,17 @@ static inline void barebox_banner(void) {}
> > (__x < 0) ? -__x : __x; \
> > })
> >
> > +/*
> > + * Check if two regions overlap. returns true if they do, false otherwise
> > + */
> > +static inline bool region_overlap(unsigned long starta, unsigned long lena,
> > + unsigned long startb, unsigned long lenb)
> > +{
> > + if (starta + lena <= startb)
> > + return 0;
> > + if (startb + lenb <= starta)
> > + return 0;
> > + return 1;
> > +}
> > +
> > #endif /* __COMMON_H_ */
>
> Or if you look for perfomance (I presume not in barebox) :
> static inline bool region_overlap(unsigned long starta, unsigned long lena,
> unsigned long startb, unsigned long lenb)
> {
> return starta <= startb + lenb && starta + lena >= startb;
> }
>
> It's a bit more obfuscated, but performance wise no branch prediction :)
You made me curious. I tried to compile both and here is the result on
ARM (I swapped the arguments left and right of the &&):
00025000 <_region_overlap>:
25000: e0811000 add r1, r1, r0
25004: e1510002 cmp r1, r2
25008: 9a000004 bls 25020 <_region_overlap+0x20>
2500c: e0832002 add r2, r3, r2
25010: e1520000 cmp r2, r0
25014: 93a00000 movls r0, #0
25018: 83a00001 movhi r0, #1
2501c: e12fff1e bx lr
25020: e3a00000 mov r0, #0
25024: e12fff1e bx lr
00025000 <__region_overlap>:
25000: e0811000 add r1, r1, r0
25004: e1510002 cmp r1, r2
25008: 3a000004 bcc 25020 <__region_overlap+0x20>
2500c: e0832002 add r2, r3, r2
25010: e1500002 cmp r0, r2
25014: 83a00000 movhi r0, #0
25018: 93a00001 movls r0, #1
2501c: e12fff1e bx lr
25020: e3a00000 mov r0, #0
25024: e12fff1e bx lr
Maybe gcc isn't so clever on other architectures, I don't know ;)
Sascha
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