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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug rtl-optimization/53190] CSE (?) CSEs asms
Date: Thu, 03 May 2012 08:39:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53190

--- Comment #7 from Uros Bizjak <ubizjak at gmail dot com> 2012-05-03 08:39:19 UTC ---
(In reply to comment #6)

> Well, the asm in glibc is simply
> 
> extern __inline __attribute__ ((__always_inline__)) long int
> __attribute__ ((__nothrow__ )) lrintf (float __x)
> {
>   long int __res;
>   __asm ("cvtss2si %1, %0" : "=r" (__res) : "xm" (__x));
>   return __res;
> }
> 
> thus the CLOBBERs somehow magically appear anyways it seems.

Yes, this is done in ix86_md_asm_clobbers. The reasoning is the same as for
flags reg, most asms "probably" touch both status regs anyway. This prevents
asms from being scheduled in between CC-like producer/consumer chain.