https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105558
Bug ID: 105558
Summary: simple 8-byte integer calculation fails with -O3 /
march=core-avx2 on some gfortran 8/9/10 versions
Product: gcc
Version: 10.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: federico.perini at gmail dot com
Target Milestone: ---
Created attachment 52950
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52950&action=edit
integer(1) test program
Hi gcc/gfortran team,
I have two routines that encode and decode two integer(1) IDs (in [1:6] and
[1:32] respectively) to a unique 8-byte integer(1), for 192 possible cases.
The example that fails should behave like
encode(1, 32) returns 77
decode(77) returns [1, 32]
but returns either [-5, 33] or sometimes [3,71]
With -O3, there are both versions and architectures of gfortran that either
work or not. On godbolt (https://godbolt.org/z/5GboahWs1), this is what I see:
gfortran | -O3 -mtune=generic | -O3 -march=core-avx2 |
12.1 | OK | OK |
11.3 | OK | OK |
11.2 | OK | OK |
11.1 | OK | OK |
10.3 | OK | ERROR |
10.2 | OK | ERROR |
10.1 | OK | ERROR |
9.4 | OK | ERROR |
9.3 | OK | ERROR |
9.2 | OK | ERROR |
9.1 | OK | ERROR |
8.5 | ERROR | ERROR |
8.4 | ERROR | ERROR |
8.3 | ERROR | ERROR |
8.2 | ERROR | ERROR |
8.1 | ERROR | ERROR |
7.3 | OK | OK |
7.2 | OK | OK |
7.1 | OK | OK |
6.3 | OK | OK |
5.5 | OK | OK |
Also note that:
- problem is with int8 only; all is OK with int16,int32,int64
- no problems with -O2.
I'm attaching the code here as well,
thank you,
Federico
