https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90567
Bug ID: 90567
Summary: GCC bad optimization on recursive functions
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msmaldi at hotmail dot com
Target Milestone: ---
consider code:
int fibo (int n)
{
if (n == 1 || n == 2)
return 1;
else
return fibo(n - 1) + fibo(n - 2);
}
int main()
{
printf ("%d\n", fibo (45));
return 0;
}
with flags: -m64 -flto -march=native -O3
GCC-7
real 0m3,066s
user 0m3,065s
sys 0m0,000s
GCC-8
real 0m4,868s
user 0m4,864s
sys 0m0,004s
GCC-9
real 0m5,015s
user 0m5,010s
sys 0m0,004s
