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RE: ARM gcc generates incorrect code?
- From: "Dave Korn" <dave dot korn at artimi dot com>
- To: "'Krzysztof Halasa'" <khc at pm dot waw dot pl>, <gcc at gcc dot gnu dot org>
- Date: Wed, 27 Feb 2008 12:40:37 -0000
- Subject: RE: ARM gcc generates incorrect code?
- References: <m3wsoqmxhk.fsf@maximus.localdomain>
On 27 February 2008 11:48, Krzysztof Halasa wrote:
> Hi,
>
> not sure where the bug is - gcc 4.2.4pre (CVS), binutils 2.17,
> cross compiler X86_64 -> ARM BE.
That asm looks a bit odd to me (but I haven't had much coffee today so I
could be reading it wrong):-
> #define get_user(x,p) \
> ({ \
> register const u8 __user *__p asm("r0") = (p); \
> register unsigned long __r2 asm("r2"); \
> register int __e asm("r0"); \
> __asm__ __volatile__ ( \
> __asmeq("%0", "r0") __asmeq("%1", "r2") \
> "bl __get_user_1" \
> : "=&r" (__e), "=r" (__r2) \
^^^^^ '&' means output operand (zero)
is early-clobber, so cannot share
a register with any input operand.
> : "0" (__p) \
^^^^^^ '0' means forcibly share an input
operand with operand zero.
> : "lr", "cc"); \
> x = (u8) __r2; \
> __e; \
> })
That's quite likely to do reload's head in, isn't it?
> Gcc bug? get_user() bug? Should I file a bug entry?
I think the macro could well be wrong. Do you know why those constraints
were chosen?
cheers,
DaveK
--
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