Hi!
| On 7/16/21 11:42 AM, Thomas Schwinge wrote:
|> On 2021-07-09T17:11:25-0600, Martin Sebor via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
|>> The attached tweak avoids the new -Warray-bounds instances when
|>> building libatomic for arm. Christophe confirms it resolves
|>> the problem (thank you!)
|>
|> As Abid has just reported in
|> <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101374#c16>, similar
|> problem with GCN target libgomp build:
|>
|> In function ‘gcn_thrs’,
|> inlined from ‘gomp_thread’ at
[...]/source-gcc/libgomp/libgomp.h:803:10,
|> inlined from ‘GOMP_barrier’ at
[...]/source-gcc/libgomp/barrier.c:34:29:
|> [...]/source-gcc/libgomp/libgomp.h:792:10: error: array subscript 0 is
outside array bounds of ‘__lds struct gomp_thread * __lds[0]’
[-Werror=array-bounds]
|> 792 | return *thrs;
|> | ^~~~~
|>
|> gcc/config/gcn/gcn.h: c_register_addr_space ("__lds", ADDR_SPACE_LDS);
\
|>
|> libgomp/libgomp.h-static inline struct gomp_thread *gcn_thrs (void)
|> libgomp/libgomp.h-{
|> libgomp/libgomp.h- /* The value is at the bottom of LDS. */
|> libgomp/libgomp.h: struct gomp_thread * __lds *thrs = (struct
gomp_thread * __lds *)4;
|> libgomp/libgomp.h- return *thrs;
|> libgomp/libgomp.h-}
|>
|> ..., plus a few more. Work-around:
|>
|> struct gomp_thread * __lds *thrs = (struct gomp_thread * __lds *)4;
|> +# pragma GCC diagnostic push
|> +# pragma GCC diagnostic ignored "-Warray-bounds"
|> return *thrs;
|> +# pragma GCC diagnostic pop
|>
|> ..., but it's a bit tedious to add that in all that the other places,
|> too.
Wasn't so bad after all; a lot of duplicates due to 'libgomp.h'. I've
thus pushed "[gcn] Work-around libgomp 'error: array subscript 0 is
outside array bounds of ‘__lds struct gomp_thread * __lds[0]’
[-Werror=array-bounds]' [PR101484]" to master branch in commit
9f2bc5077debef2b046b6c10d38591ac324ad8b5, see attached.
|> (So I'll consider some GCN-specific '-Wno-array-bounds' if we don't
|> get to resolve this otherwise, soon.)
Now: "Awaiting a different solution, of course." ;-)
On 2021-07-17T23:28:45+0100, Andrew Stubbs <a...@codesourcery.com> wrote:
> On 16/07/2021 18:42, Thomas Schwinge wrote:
>> Of course, we may simply re-work the libgomp/GCN code -- but don't we
>> first need to answer the question whether the current code is actually
>> "bad"? Aren't we going to get a lot of similar reports from
>> kernel/embedded/other low-level software developers, once this is out in
>> the wild? I mean:
>
> GCN already uses address 4 for this value because address 0 caused
> problems with null-pointer checks.
Ugh. How much wasted bytes per what is that? (I haven't looked yet;
hopefully not per GPU thread?) Because:
> It really ought not be this hard. :-(
I'm sure we can avoid that.
Grüße
Thomas
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>From 9f2bc5077debef2b046b6c10d38591ac324ad8b5 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tho...@codesourcery.com>
Date: Fri, 16 Jul 2021 19:12:02 +0200
Subject: [PATCH] =?UTF-8?q?[gcn]=20Work-around=20libgomp=20'error:=20array?=
=?UTF-8?q?=20subscript=200=20is=20outside=20array=20bounds=20of=20?=
=?UTF-8?q?=E2=80=98=5F=5Flds=20struct=20gomp=5Fthread=20*=20=5F=5Flds[0]?=
=?UTF-8?q?=E2=80=99=20[-Werror=3Darray-bounds]'=20[PR101484]?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
... seen as of commit a110855667782dac7b674d3e328b253b3b3c919b "Correct
handling of variable offset minus constant in -Warray-bounds [PR100137]".
Awaiting a different solution, of course.
libgomp/
PR target/101484
* config/gcn/team.c: Apply '-Werror=array-bounds' work-around.
* libgomp.h [__AMDGCN__]: Likewise.
---
libgomp/config/gcn/team.c | 3 +++
libgomp/libgomp.h | 12 ++++++++++++
2 files changed, 15 insertions(+)
diff --git a/libgomp/config/gcn/team.c b/libgomp/config/gcn/team.c
index 627210ea407..94ce2f2dfeb 100644
--- a/libgomp/config/gcn/team.c
+++ b/libgomp/config/gcn/team.c
@@ -65,9 +65,12 @@ gomp_gcn_enter_kernel (void)
void * __lds *arena_start = (void * __lds *)TEAM_ARENA_START;
void * __lds *arena_free = (void * __lds *)TEAM_ARENA_FREE;
void * __lds *arena_end = (void * __lds *)TEAM_ARENA_END;
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Warray-bounds" /*TODO PR101484 */
*arena_start = team_arena;
*arena_free = team_arena;
*arena_end = team_arena + TEAM_ARENA_SIZE;
+# pragma GCC diagnostic pop
/* Allocate and initialize the team-local-storage data. */
struct gomp_thread *thrs = team_malloc_cleared (sizeof (*thrs)
diff --git a/libgomp/libgomp.h b/libgomp/libgomp.h
index 8d25dc8e2a8..4159cbe3334 100644
--- a/libgomp/libgomp.h
+++ b/libgomp/libgomp.h
@@ -128,7 +128,10 @@ team_malloc (size_t size)
: "=v"(result) : "v"(TEAM_ARENA_FREE), "v"(size), "e"(1L) : "memory");
/* Handle OOM. */
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Warray-bounds" /*TODO PR101484 */
if (result + size > *(void * __lds *)TEAM_ARENA_END)
+# pragma GCC diagnostic pop
{
/* While this is experimental, let's make sure we know when OOM
happens. */
@@ -159,8 +162,11 @@ team_free (void *ptr)
However, if we fell back to using heap then we should free it.
It would be better if this function could be a no-op, but at least
LDS loads are cheap. */
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Warray-bounds" /*TODO PR101484 */
if (ptr < *(void * __lds *)TEAM_ARENA_START
|| ptr >= *(void * __lds *)TEAM_ARENA_END)
+# pragma GCC diagnostic pop
free (ptr);
}
#else
@@ -789,13 +795,19 @@ static inline struct gomp_thread *gcn_thrs (void)
{
/* The value is at the bottom of LDS. */
struct gomp_thread * __lds *thrs = (struct gomp_thread * __lds *)4;
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Warray-bounds" /*TODO PR101484 */
return *thrs;
+# pragma GCC diagnostic pop
}
static inline void set_gcn_thrs (struct gomp_thread *val)
{
/* The value is at the bottom of LDS. */
struct gomp_thread * __lds *thrs = (struct gomp_thread * __lds *)4;
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Warray-bounds" /*TODO PR101484 */
*thrs = val;
+# pragma GCC diagnostic pop
}
static inline struct gomp_thread *gomp_thread (void)
{
--
2.30.2
