[LLVMbugs] [Bug 6931] New: Substandard performance of fibonacci example code

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Apr 25 02:21:19 PDT 2010


           Summary: Substandard performance of fibonacci example code
           Product: new-bugs
           Version: 2.6
          Platform: PC
        OS/Version: FreeBSD
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: yuri at tsoft.com
                CC: llvmbugs at cs.uiuc.edu

I compiled this simple example:

#include <stdlib.h>
#include <stdio.h>

int fib(int AnArg) {
 if (AnArg <= 2) return (1);
 return (fib(AnArg-1)+fib(AnArg-2));

int main(int argc, char* argv[]) {
 int n = atoi(argv[1]);
 printf("fib(%i)=%i\n", n, fib(n));

with llvm-2.6 with gcc frontend.

Runtime with argument 45 is ~4.3sec.
Runtime of mainstream gcc compiled code is always below 4 sec (3.4-3.9sec).

This is a very basic example and should produce a very optimal code.

Intel(R) Core(TM) i7 CPU       @ 9200 @ 2.67GHz

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