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From: ebotcazou@gcc.gnu.org
To: ck189400@zodiac.mimuw.edu.pl, gcc-bugs@gcc.gnu.org,
	gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org
Subject: Re: optimization/8220: return value of a function is forgotten/inlining assembler code
Date: Tue, 18 Feb 2003 15:28:00 -0000	[thread overview]
Message-ID: <20030218152820.21552.qmail@sources.redhat.com> (raw)

Synopsis: return value of a function is forgotten/inlining assembler code

State-Changed-From-To: open->closed
State-Changed-By: ebotcazou
State-Changed-When: Tue Feb 18 15:28:20 2003
State-Changed-Why:
    Not a bug. Output operands in extended asm must be placed
    after the _first_ colon and must use the "=" symbol.
    Moreover the extended asm has no side-effect so you must
    explicit declare it as "volatile".
    
    inline int getcputime(void) {
      int i;
      __asm__ __volatile__(
        "rdtsc ;"
        "movl %%eax, %0"
        : "=g" (i) : :"eax", "edx");
      return i;
    }
    
    int main(void) {
      int x = getcputime();
      int y = getcputime();
      printf ("Time measure resolution: %i\n", y - x);
      return 0;
    }

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8220


                 reply	other threads:[~2003-02-18 15:28 UTC|newest]

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