https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117010
Thomas Schwinge <tschwinge at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |tschwinge at gcc dot
gnu.org
Status|NEW |ASSIGNED
CC| |jakub at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
Last reconfirmed|2024-10-08 00:00:00 |2025-3-25
--- Comment #4 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
Jakub, Richi, C++/offloading question. For the small test case posted here,
for 'V<0>::V()' I see in the '-O0' x86_64 host code:
.section
.text._ZN1VILi0EEC2Ev,"axG",@progbits,_ZN1VILi0EEC5Ev,comdat
.align 2
.weak _ZN1VILi0EEC2Ev
.type _ZN1VILi0EEC2Ev, @function
_ZN1VILi0EEC2Ev:
[...]
.size _ZN1VILi0EEC2Ev, .-_ZN1VILi0EEC2Ev
.weak _ZN1VILi0EEC1Ev
.set _ZN1VILi0EEC1Ev,_ZN1VILi0EEC2Ev
That is, weak definitions of '_ZN1VILi0EEC2Ev' and its alias '_ZN1VILi0EEC1Ev'
(which gets called from 'foo').
Likewise, I see weak definitions, if compiling such code for GCN target:
.section
.text._ZN1VILi0EEC2Ev,"axG",@progbits,_ZN1VILi0EEC5Ev,comdat
.align 4
.weak _ZN1VILi0EEC2Ev
.type _ZN1VILi0EEC2Ev,@function
_ZN1VILi0EEC2Ev:
[...]
.size _ZN1VILi0EEC2Ev, .-_ZN1VILi0EEC2Ev
.weak _ZN1VILi0EEC1Ev
.set _ZN1VILi0EEC1Ev,_ZN1VILi0EEC2Ev
..., so that appears consistent.
For nvptx target (with '-malias'), I see:
.weak .func _ZN1VILi0EEC1Ev (.param.u64 %in_ar0)
{
[...]
}
That is, it directly emits the (used) '_ZN1VILi0EEC1Ev' constructor, instead of
emitting '_ZN1VILi0EEC2Ev' and then aliasing the former to the latter. (I'll
look into that, to understand why that's happening; maybe it does it this way,
because PTX doesn't support weak aliases.)
Now, the observation/question: compiling this code for offloading (as
originally reported), I see for GCN offloading:
.text
[...]
.type _ZN1VILi0EEC2Ev,@function
_ZN1VILi0EEC2Ev:
[...]
.size _ZN1VILi0EEC2Ev, .-_ZN1VILi0EEC2Ev
.set _ZN1VILi0EEC1Ev,_ZN1VILi0EEC2Ev
That is, '_ZN1VILi0EEC2Ev' and its alias '_ZN1VILi0EEC1Ev' are now strong
instead of weak definitions. Is this expected, or unexpected, and potentially
problematic?
