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From: Richard Henderson <rth@redhat.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: optimization/5366: asm code produces an error without -O but is ok with -O Date: Mon, 14 Jan 2002 18:26:00 -0000 [thread overview] Message-ID: <20020115022601.1330.qmail@sources.redhat.com> (raw) The following reply was made to PR optimization/5366; it has been noted by GNATS. From: Richard Henderson <rth@redhat.com> To: erl-dev@altus.qc.ca Cc: gcc-gnats@gcc.gnu.org Subject: Re: optimization/5366: asm code produces an error without -O but is ok with -O Date: Mon, 14 Jan 2002 18:18:39 -0800 On Sat, Jan 12, 2002 at 07:29:09PM -0500, erl-dev@altus.qc.ca wrote: > __asm __volatile ("" : "=m" (lock->__status) : "0" (lock->__status)); You needn't bother with the matching constraint, and that is in fact what leads to your troubles. The memory address is fully specified by lock->__status. Since the same value is used on both sides, you know it is the same address, and thus using "=m" and "m" is sufficient. At -O0, the address calculations for the two structure references are not subject to common subexpression elimination, so the register allocator cannot easily prove that the two addresses are the same, so it aborts. r~
next reply other threads:[~2002-01-15 2:26 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-01-14 18:26 Richard Henderson [this message] -- strict thread matches above, loose matches on Subject: below -- 2002-01-12 17:17 rodrigc 2002-01-12 16:36 erl-dev
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