Date: Sun, 02 Jul 2000 15:01:04 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: hackers@freebsd.org Subject: GCC extended asm experts please look at this Message-ID: <XFMail.000702150104.jdp@polstra.com>
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I _thought_ I was an expert in gcc's extended asm feature, but I
can't figure out why this won't compile when optmization is
disabled:
===============================================================================
#define xchgl(v, m) ({ \
int __result; \
__asm __volatile ("xchgl %0, %1" \
: "=r"(__result), "=m"(m) \
: "0"(v), "1"(m)); \
(__result); })
void
lock80386_acquire(volatile int *lock)
{
while (xchgl(1, *lock) != 0)
while (*lock != 0)
;
}
===============================================================================
It compiles and works fine with -O or higher; but without -O gcc
says:
locktest.c: In function `lock80386_acquire':
locktest.c:11: inconsistent operand constraints in an `asm'
This happens with both gcc-2.95.2 (the version in -current) and with
the much older gcc-2.7.2.3.
I believe the code is correct according to the documentation in the
gcc info pages. I tried changing several things anyway to make it
more conservative, but I haven't been able to make it compile
without optimization.
Can any of you see an error in the code?
John
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