On Wed, 21 Oct 2015, Jakub Jelinek wrote:
> > At the moment the attribute setting logic in omp-low.c is such that if a
> > function that should be present in target code does not already have 'omp
> > declare target' attribute, it receives 'omp target entrypoint'. That is
> > wasteful: clearly not all user-declared target functions will be target
> > region
> > entry points in OpenMP.
> >
> > The motivating example for this change is OpenMP parallel target regions.
> > The
> > 'parallel' part is outlined into its own function. We don't want that
> > function be an 'entrypoint' on PTX (but only as a matter of optimality
> > rather
> > than correctness).
> >
> > * omp-low.c (create_omp_child_function): Set "omp target entrypoint"
> > or "omp declare target" attribute based on is_gimple_omp_offloaded.
>
> This is principally ok, but you want to change it for 01/14.
> After that I think it is ready for trunk.
As you suggested in patch 01/14, I'll want to use different attributes to
distinguish between OpenACC and OpenMP entrypoints. I've tried your
suggestion "acc target entrypoint", and unfortunately it doesn't work because
ipa-icf does:
sem_function::parse (cgraph_node *node, bitmap_obstack *stack)
{
...
if (lookup_attribute_by_prefix ("omp ", DECL_ATTRIBUTES (node->decl)) != NULL)
return NULL;
...
}
so changing the prefix affects code generation. I don't see why IPA-ICF needs
that (it's there from when the file was added to trunk, and there's no comment).
I went with "omp acc target entrypoint" instead, as below.
OK? (for trunk?)
Thanks.
Alexander
omp-low: set more precise attributes on offloaded functions
At the moment the attribute setting logic in omp-low.c is such that if a
function that should be present in target code does not already have 'omp
declare target' attribute, it receives 'omp target entrypoint'. However, that
is inaccurate for OpenMP: functions outlined for e.g. omp-parallel regions do
not have 'omp declare target' attribute, but they cannot be entrypoints either.
Detect entrypoints using 'is_gimple_omp_offloaded'. Additionally, distinguish
between OpenACC and OpenMP entrypoints, and use 'omp acc target entrypoint'
for the former.
* omp-low.c (create_omp_child_function): Set "omp target entrypoint",
"omp acc target entrypoint" or "omp declare target" attribute based on
is_gimple_omp_offloaded and is_gimple_omp_oacc.
* config/nvptx/nvptx.c (write_as_kernel): Test OpenACC-specific
attribute "omp acc target entrypoint". Add a comment about the OpenMP
attribute handling.
diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index 21c59ef..ac021fc 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -402,7 +402,10 @@ static bool
write_as_kernel (tree attrs)
{
return (lookup_attribute ("kernel", attrs) != NULL_TREE
- || lookup_attribute ("omp target entrypoint", attrs) != NULL_TREE);
+ || lookup_attribute ("omp acc target entrypoint", attrs) !=
NULL_TREE);
+ /* Ignore "omp target entrypoint" here: OpenMP target region functions are
+ called from gomp_nvptx_main. The corresponding kernel entry is emitted
+ from write_omp_entry. */
}
/* Write a function decl for DECL to S, where NAME is the name to be used.
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 06b4a5e..696889d 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -2245,9 +2245,16 @@ create_omp_child_function (omp_context *ctx, bool
task_copy)
if (cgraph_node::get_create (decl)->offloadable
&& !lookup_attribute ("omp declare target",
DECL_ATTRIBUTES (current_function_decl)))
- DECL_ATTRIBUTES (decl)
- = tree_cons (get_identifier ("omp target entrypoint"),
- NULL_TREE, DECL_ATTRIBUTES (decl));
+ {
+ const char *target_attr = (is_gimple_omp_offloaded (ctx->stmt)
+ ? (is_gimple_omp_oacc (ctx->stmt)
+ ? "omp acc target entrypoint"
+ : "omp target entrypoint")
+ : "omp declare target");
+ DECL_ATTRIBUTES (decl)
+ = tree_cons (get_identifier (target_attr),
+ NULL_TREE, DECL_ATTRIBUTES (decl));
+ }
t = build_decl (DECL_SOURCE_LOCATION (decl),
RESULT_DECL, NULL_TREE, void_type_node);
