https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100235
Bug ID: 100235
Summary: 10.3.0 Performance regressions for compile-time math
intrinsics computation on arrays
Product: gcc
Version: 10.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: molah at ucar dot edu
Target Milestone: ---
I am observing a significant compile time increase for gfortran-10.3.0, when
computing math intrinsic operations over arrays constructed at compile-time.
======= Test case =========
#define N 8000
PROGRAM TEST
REAL :: V(0:N)
V = ACOS( (/ (I, I=0,N) /)/100000.0 )
END PROGRAM
==========================
Performance:
gfortran-9.3.0: 0.05s
gfortran-10.2.0: 0.05s
gfortran-10.3.0: 27.0s !!
The runtime is increasing exponentially, so that N=1600 takes a few minutes for
10.3.0.
The optimization flags appear to have no effect on the runtime.
