Created attachment 52950 [details]
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