Date: Mon, 24 Jun 2002 15:30:51 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: current@freebsd.org Cc: ak03@gte.com Subject: Re: Bootstrap problems for asm Message-ID: <200206242230.g5OMUpw31505@vashon.polstra.com> In-Reply-To: <20020624175612.7abe6e52.ak03@gte.com> References: <Pine.NEB.3.96L.1020624111138.32271E-100000@fledge.watson.org> <200206241524.g5OFO6p30824@vashon.polstra.com> <20020624112151.A55057@dragon.nuxi.com> <20020624175612.7abe6e52.ak03@gte.com>
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In article <20020624175612.7abe6e52.ak03@gte.com>,
Alexander Kabaev <ak03@gte.com> wrote:
> I am not an inline assembler guru, but here is the patch I think get the
> job done. If I understannd things correcly, GCC accepts matching
> constraints only for parameters for which registers are allowed.
>
> Any constructive critique is appreciated.
Your patch isn't quite right. It's true that matching constraints
are allowed only for registers. But read-modify-write operands can
still be specified in other ways, specifically using the "+"
modifier. Here's the patch which I'm testing at the moment. I'll
commit it later today unless I find something wrong with it.
John
Index: i386/lockdflt.c
===================================================================
RCS file: /home/ncvs/src/libexec/rtld-elf/i386/lockdflt.c,v
retrieving revision 1.6
diff -u -r1.6 lockdflt.c
--- i386/lockdflt.c 17 Jul 2000 17:18:13 -0000 1.6
+++ i386/lockdflt.c 24 Jun 2002 20:46:05 -0000
@@ -80,8 +80,8 @@
int result;
__asm __volatile ("lock; cmpxchgl %2, %0"
- : "=m"(*m), "=a"(result)
- : "r"(new), "0"(*m), "1"(old)
+ : "+m"(*m), "=a"(result)
+ : "r"(new), "1"(old)
: "cc");
return result;
@@ -93,8 +93,8 @@
int result;
__asm __volatile ("xchgl %0, %1"
- : "=r"(result), "=m"(*m)
- : "0"(v), "1"(*m));
+ : "=r"(result), "+m"(*m)
+ : "0"(v));
return result;
}
Index: i386/rtld_machdep.h
===================================================================
RCS file: /home/ncvs/src/libexec/rtld-elf/i386/rtld_machdep.h,v
retrieving revision 1.6
diff -u -r1.6 rtld_machdep.h
--- i386/rtld_machdep.h 29 Oct 2001 10:10:10 -0000 1.6
+++ i386/rtld_machdep.h 24 Jun 2002 20:44:30 -0000
@@ -55,21 +55,21 @@
static inline void
atomic_decr_int(volatile int *p)
{
- __asm __volatile ("lock; decl %0" : "=m"(*p) : "0"(*p) : "cc");
+ __asm __volatile ("lock; decl %0" : "+m"(*p) : : "cc");
}
static inline void
atomic_incr_int(volatile int *p)
{
- __asm __volatile ("lock; incl %0" : "=m"(*p) : "0"(*p) : "cc");
+ __asm __volatile ("lock; incl %0" : "+m"(*p) : : "cc");
}
static inline void
atomic_add_int(volatile int *p, int val)
{
__asm __volatile ("lock; addl %1, %0"
- : "=m"(*p)
- : "ri"(val), "0"(*p)
+ : "+m"(*p)
+ : "ri"(val)
: "cc");
}
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