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Re: optimization/8220: return value of a function is forgotten/inlining assembler code
- From: ebotcazou at gcc dot gnu dot org
- To: ck189400 at zodiac dot mimuw dot edu dot pl, gcc-bugs at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org, nobody at gcc dot gnu dot org
- Date: 18 Feb 2003 15:28:20 -0000
- Subject: Re: optimization/8220: return value of a function is forgotten/inlining assembler code
- Reply-to: ebotcazou at gcc dot gnu dot org, ck189400 at zodiac dot mimuw dot edu dot pl, gcc-bugs at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org, nobody at gcc dot gnu dot org, gcc-gnats at gcc dot gnu dot org
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