https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104879
Bug ID: 104879
Summary: [nvptx] Use .common directive (available starting ptx
isa version 5.0)
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
We currently have in the nvptx port in nvptx_option_override:
...
/* Set flag_no_common, unless explicitly disabled. We fake common
using .weak, and that's not entirely accurate, so avoid it
unless forced. */
if (!OPTION_SET_P (flag_no_common))
flag_no_common = 1;
...
and in nvptx_output_aligned_decl:
...
/* If this is public, it is common. The nearest thing we have to
common is weak. */
fprintf (file, "\t%s", TREE_PUBLIC (decl) ? ".weak " : "");
...
[ There's also some optimisation note related to .common:
...
/* Buffer needed to broadcast across workers and vectors. This is
used for both worker-neutering and worker broadcasting, and
vector-neutering and boardcasting when vector_length > 32. It is
shared by all functions emitted. The buffer is placed in shared
memory. It'd be nice if PTX supported common blocks, because then
this could be shared across TUs (taking the largest size). */
...
but I'm not sure whether this is safe, perhaps this would require a mutex to
make it safe. ]
Starting with ptx isa 5.0, we have the .common directive available in ptx.
However, it "can be used only on variables with .global storage", so it's
somewhat limited.
