Hi Richard, > On 3 Jun 2023, at 12:20, Richard Biener <richard.guent...@gmail.com> wrote: > >> Am 02.06.2023 um 21:12 schrieb Iain Sandoe via Gcc-patches >> <gcc-patches@gcc.gnu.org>: >>
>> --- 8< --- >> >> This bug was essentially that darwin_rs6000_special_round_type_align() >> was ignoring externally-imposed capping of field alignment. >> >> >> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc >> index 5b3b8b52e7e..42f49e4a56b 100644 >> --- a/gcc/config/rs6000/rs6000.cc >> +++ b/gcc/config/rs6000/rs6000.cc >> @@ -8209,7 +8209,8 @@ darwin_rs6000_special_round_type_align (tree type, >> unsigned int computed, >> type = TREE_TYPE (type); >> } while (AGGREGATE_TYPE_P (type)); >> >> - if (! AGGREGATE_TYPE_P (type) && type != error_mark_node) >> + if (type != error_mark_node && ! AGGREGATE_TYPE_P (type) >> + && ! TYPE_PACKED (type) && maximum_field_alignment == 0) > > Just noticed while browsing mail. ‚Maximum_field_alignment‘ sounds like > Something that should be factored in when > Computing align but as written there’s no adjustment done instead? Is there > a way to get that to more than BITS_PER_UNIT? I believe it is already correctly factored in (the values of ‘computed’ and ’specified’ supplied to the darwin_rs6000_special_round_type_align() take it into account). The point of this function is to override the supplied values under specific conditions (that the first element in the aggregate is a double or long long). However, [at least in the de facto Darwin PPC32 ABI] we should not do so if there is a packed pragma in effect (that takes priority) and omitting that check is the bug being fixed. It is a bit unfortunate to be looking at a global from deep in the machinery (although I did a quick grep and it seems that this would not be easily fixable - several targets and other places do inspect maximum_field_alignment). I suppose we could add a parm indicating the packed status and/or value. Part of the motivation for a self-contained and Darwin-local solution is to allow backport to 10.x before it closes (since that’s the last GCC branch that can be built with native tools on the earlier boxes). hopefully, I understood your point? cheers Iain
