[Patch, Fortran] PRs 60283/60543: Fix two wrong-code bugs related for implicit pure

[Tobias Burnus]

Early *ping*  - I think this wrong-code GCC 4.7/4.8/4.9 issue is pretty 
severe.

Tobias Burnus wrote:
> This patch fixes two issues, where gfortran claims that a function is 
> implicit pure, but it is not. That will cause a wrong-code 
> optimization in the middle end.
>
> First problem, cf. PR60543, is that implicit pure was not set to 0 for 
> calls to impure intrinsic subroutines. (BTW: There are no impure 
> intrinsic functions.) Example:
>
>   module m
>   contains
>     REAL(8) FUNCTION random()
>       CALL RANDOM_NUMBER(random)
>     END FUNCTION random
>   end module m
>
>
> The second problem pops up if one adds a BLOCK ... END BLOCK around 
> the random_number call after applying the patch of the PR, which just 
> does: gfc_current_ns->proc_name->attr.implicit_pure = 0.
>
> The problem is that one sets only the implicit_pure of the block to 0 
> and not of the function. That's the reason that the patch became much 
> longer and that I added gfc_unset_implicit_pure as new function.
>
> Thus, the suspicion I had when reviewing the OpenACC patches turned 
> out to be founded. Cf. PR60283.
>
> Build and regtested on x86-64-gnu-linux.
> OK for the trunk and for the 4.7 and 4.8 branches?
>
> Note: I failed to create a test case.
>
> Tobias