https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106445
Bug ID: 106445
Summary: nvptx offloading: C++ constructor symbol alias getting
lost
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Keywords: openmp, wrong-code
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: tschwinge at gcc dot gnu.org
CC: vries at gcc dot gnu.org
Target Milestone: ---
Target: nvptx
I found this during my "GPU support for minimal C++ library" investigations,
PR101544. You're not currently able to reproduce this, as it depends on a
number of WIP patches, but I'm filing it for later reference. (Or, I suppose
could maybe come up with a non-C++ reproducer.) I've not yet looked through
the existing nvptx symbol alias issues in detail. I've also not yet tried
reproducing the issue without offloading, with a nvptx target toolchain.
Simple 'std::vector<int> v;' in OpenMP 'target', '-O0', host-side
'-fno-exceptions', '-foffload-options=nvptx-none=-malias\ -mptx=6.3' works for
GCN, but fails to compile for nvptx:
ptxas ./a.xnvptx-none.mkoffload.o, line 243; error : Label expected for
argument 0 of instruction 'call'
ptxas ./a.xnvptx-none.mkoffload.o, line 243; error : Function
'_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev' not declared in this scope
$ c++filt _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev
std::_Vector_base<int, std::allocator<int> >::_Vector_impl::_Vector_impl()
Looking for '_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev':
For all host/device '-fdump-tree-all-raw-asmname', we only ever see:
gimple_call <_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev, NULL, _1>
Correspondingly, for all device '-fdump-rtl-all-raw-asmname':
(call (mem:QI (symbol_ref:DI
("_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev") [flags 0x3] <function_decl
0x7f08a2fe0d00 __ct_comp >) [0 _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev S1
A8])
In 'a.xnvptx-none.mkoffload.s' only ever:
call _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev, (%out_arg1);
In 'a.xamdgcn-amdhsa.mkoffload.1.s' however:
s_add_u32 s2, s2,
_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev@rel32@lo+4
s_addc_u32 s3, s3,
_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev@rel32@hi+4
..., but also:
.set
_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev,_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev
..., that is, a symbol alias (C++ constructors) -- that's missing for nvptx.
Looking for '_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev':
There is no (relevant) difference in device '-fdump-tree-all-raw-asmname'
'*.094t.fixup_cfg3' and still not '*.253t.optimized'.
There is no (relevant) difference in device '-fdump-rtl-all-raw-asmname'
'*.254r.expand' and still not (approximately) '*.333r.final'.
That is, '_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev' is still present in
nvptx '*.333r.final'.
In 'a.xamdgcn-amdhsa.mkoffload.1.s':
.type _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev,@function
_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev:
[...]
.size _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev,
.-_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev
.set
_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev,_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev
In 'a.xnvptx-none.mkoffload.s':
// BEGIN FUNCTION DECL: _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev
.func _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev (.param.u64 %in_ar0);
// BEGIN FUNCTION DEF: _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev
.func _ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev (.param.u64 %in_ar0)
{
[...]
}
..., but not followed by a '.alias'.
In case that's relevant (... for nvptx...): the difference for a very similar
'_ZNSt6vectorIiSaIiEEC1Ev' -> '_ZNSt6vectorIiSaIiEEC2Ev' symbol alias (which
does get defined for both GCN and nvptx) is that the use of
'_ZNSt6vectorIiSaIiEEC1Ev' appears after definition of
'_ZNSt6vectorIiSaIiEEC2Ev' and its '_ZNSt6vectorIiSaIiEEC1Ev' alias, but for
the '_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev' reported above, the use
appears before the '_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev' function and
'_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC1Ev' ->
'_ZNSt12_Vector_baseIiSaIiEE12_Vector_implC2Ev' symbol alias definitions (the
latter missing for nvptx).
---
Similar issue (but different constructor) for 'std::vector<int> v(100);'.
