On 17 September 2022 21:33:22 CEST, Mikael Morin <morin-mik...@orange.fr> wrote: >Le 17/09/2022 à 19:03, Thomas Koenig via Fortran a écrit : >> >> Hi Mikael, >> >>> This adds support for clobbering of partial variable references, when >>> they are passed as actual argument and the associated dummy has the >>> INTENT(OUT) attribute. >>> Support includes array elements, derived type component references, >>> and complex real or imaginary parts. >>> >>> This is done by removing the check for lack of subreferences, which is >>> basically a revert of r9-4911-gbd810d637041dba49a5aca3d085504575374ac6f. >>> This removal allows more expressions than just array elements, >>> components and complex parts, but the other expressions are excluded by >>> other conditions: substrings are excluded by the check on expression >>> type (CHARACTER is excluded), KIND and LEN references are rejected by >>> the compiler as not valid in a variable definition context. >>> >>> The check for scalarness is also updated as it was only valid when there >>> was no subreference. >> >> First, thanks a lot for digging into this subject. I have looked through >> the patch series, and it looks very good so far.
I second that! The series looks plausible IMO. >> >> I have a concern about this part, though. My understanding at the >> time was that it is not possible to clobber an individual array >> element, but that this clobbers anything off the pointer that this >> is based on. >> >Well, we need the middle-end guys to give a definitive answer on this topic, >but I think it would be a very penalizing limitation if that was the case. I >have assumed that the clobber spanned the value it was applied on, neither >more nor less, so just the array element in case of array elements. I would assume the same, fwiw. Let's blame the ME iff something goes amiss then, but I doubt it will. >> So, >> >> integer, dimension(3) :: a >> >> a(1) = 1 >> a(3) = 3 >> call foo(a(1)) >> >> would also invalidate the store to a(3). Is my understanding correct? > >I think it was the case before patch 2 in in the series, because the clobber >was applied to the symbol decl, so in the case of the expression A(1), it was >applied to A which is the full array. After patch 2, the clobber is applied >to the expression A(1), so the element alone. Yep. >> If so, I think this we cannot revert that patch (which was introduced >> because of a regression). >> >The testcase from the patch was not specifically checking lack of side-effect >clobbers, so I have double-checked with the following testcase, which should >lift your concerns. >I propose to keep the patch with the testcase added to it. What do you think? I cannot approve it but the series looks good to me. Thanks!
