[Bug middle-end/68649] [6 Regression] note: code may be misoptimized unless -fno-strict-aliasing is used

[Joost.VandeVondele at mat dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68649

Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |Joost.VandeVondele at mat dot ethz
                   |                            |.ch
            Summary|note: code may be           |[6 Regression] note: code
                   |misoptimized unless         |may be misoptimized unless
                   |-fno-strict-aliasing is     |-fno-strict-aliasing is
                   |used                        |used

--- Comment #1 from Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> ---
testcase

> cat foo.f90 
SUBROUTINE s8(a8,b8)
 REAL*8 :: a8(16),b8(4,4)
 a8=RESHAPE(b8,(/16/))
 b8=RESHAPE(a8,(/4,4/))
END SUBROUTINE
 REAL*8 :: a8(16),b8(4,4)
 CALL RANDOM_NUMBER(b8)
 CALL s8(a8,b8)
 WRITE(6,*) MAXVAL(a8),MAXVAL(b8)
END

> gfortran  -flto -O3 foo.f90 
foo.f90:3:0: warning: type of ‘_gfortran_reshape_r8’ does not match original
declaration [-Wlto-type-mismatch]
  a8=RESHAPE(b8,(/16/))


foo.f90:4:0: note: ‘_gfortran_reshape_r8’ was previously declared here
  b8=RESHAPE(a8,(/4,4/))


foo.f90:4:0: note: code may be misoptimized unless -fno-strict-aliasing is used