On 2/7/24 2:12 AM, Jose E. Marchesi wrote:
Some BPF tests use loop unrolling compiler pragmas that are clang
specific and not supported by GCC. These pragmas, along with their
GCC equivalences are:
#pragma clang loop unroll_count(N)
#pragma GCC unroll N
#pragma clang loop unroll(full)
#pragma GCC unroll 65534
#pragma clang loop unroll(disable)
#pragma GCC unroll 1
#pragma unroll [aka #pragma clang loop unroll(enable)]
There is no GCC equivalence, and it seems to me that this clang
pragma may be only useful when building without -funroll-loops to
enable the optimization in particular loops. In GCC -funroll-loops
is enabled with -O2 and higher. If this is also true in clang,
perhaps these pragmas in selftests are redundant?
You are right, at -O2 level, loop unrolling is enabled by default.
So I think '#pragma unroll' can be removed since gcc also has
loop unrolling enabled by default at -O2.
Your patch has a conflict with latest bpf-next. Please rebase it
on top of bpf-next, remove '#pragma unroll' support and resubmit.
Thanks!
This patch adds a new header progs/bpf_compiler.h that defines the
following macros, which correspond to each pair of compiler-specific
pragmas above:
__pragma_loop_unroll_count(N)
__pragma_loop_unroll_full
__pragma_loop_no_unroll
__pragma_loop_unroll
The selftests using loop unrolling pragmas are then changed to include
the header and use these macros in place of the explicit pragmas.
Tested in bpf-next master.
No regressions.
Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxxxx>
Cc: Eduard Zingerman <eddyz87@xxxxxxxxx>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: david.faust@xxxxxxxxxx
Cc: cupertino.miranda@xxxxxxxxxx
---
.../selftests/bpf/progs/bpf_compiler.h | 33 +++++++++++++++++++
tools/testing/selftests/bpf/progs/iters.c | 5 +--
tools/testing/selftests/bpf/progs/loop4.c | 4 ++-
.../selftests/bpf/progs/profiler.inc.h | 17 +++++-----
tools/testing/selftests/bpf/progs/pyperf.h | 7 ++--
.../testing/selftests/bpf/progs/strobemeta.h | 18 +++++-----
.../selftests/bpf/progs/test_cls_redirect.c | 5 +--
.../selftests/bpf/progs/test_lwt_seg6local.c | 6 ++--
.../selftests/bpf/progs/test_seg6_loop.c | 4 ++-
.../selftests/bpf/progs/test_skb_ctx.c | 4 ++-
.../selftests/bpf/progs/test_sysctl_loop1.c | 6 ++--
.../selftests/bpf/progs/test_sysctl_loop2.c | 6 ++--
.../selftests/bpf/progs/test_sysctl_prog.c | 6 ++--
.../selftests/bpf/progs/test_tc_tunnel.c | 4 ++-
tools/testing/selftests/bpf/progs/test_xdp.c | 3 +-
.../selftests/bpf/progs/test_xdp_loop.c | 3 +-
.../selftests/bpf/progs/test_xdp_noinline.c | 5 +--
.../selftests/bpf/progs/xdp_synproxy_kern.c | 6 ++--
.../testing/selftests/bpf/progs/xdping_kern.c | 3 +-
19 files changed, 103 insertions(+), 42 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_compiler.h
diff --git a/tools/testing/selftests/bpf/progs/bpf_compiler.h b/tools/testing/selftests/bpf/progs/bpf_compiler.h
new file mode 100644
index 000000000000..a7c343dc82e6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_compiler.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BPF_COMPILER_H__
+#define __BPF_COMPILER_H__
+
+#define DO_PRAGMA_(X) _Pragma(#X)
+
+#if __clang__
+#define __pragma_loop_unroll DO_PRAGMA_(clang loop unroll(enable))
+#else
+/* In GCC -funroll-loops, which is enabled with -O2, should have the
+ same impact than the loop-unroll-enable pragma above. */
+#define __pragma_loop_unroll
+#endif
+
+#if __clang__
+#define __pragma_loop_unroll_count(N) DO_PRAGMA_(clang loop unroll_count(N))
+#else
+#define __pragma_loop_unroll_count(N) DO_PRAGMA_(GCC unroll N)
+#endif
+
+#if __clang__
+#define __pragma_loop_unroll_full DO_PRAGMA_(clang loop unroll(full))
+#else
+#define __pragma_loop_unroll_full DO_PRAGMA_(GCC unroll 65534)
+#endif
+
+#if __clang__
+#define __pragma_loop_no_unroll DO_PRAGMA_(clang loop unroll(disable))
+#else
+#define __pragma_loop_no_unroll DO_PRAGMA_(GCC unroll 1)
+#endif
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/iters.c b/tools/testing/selftests/bpf/progs/iters.c
index 225f02dd66d0..3db416606f2f 100644
--- a/tools/testing/selftests/bpf/progs/iters.c
+++ b/tools/testing/selftests/bpf/progs/iters.c
@@ -5,6 +5,7 @@
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
+#include "bpf_compiler.h"
#define ARRAY_SIZE(x) (int)(sizeof(x) / sizeof((x)[0]))
@@ -183,7 +184,7 @@ int iter_pragma_unroll_loop(const void *ctx)
MY_PID_GUARD();
bpf_iter_num_new(&it, 0, 2);
-#pragma nounroll
+ __pragma_loop_no_unroll
for (i = 0; i < 3; i++) {
v = bpf_iter_num_next(&it);
bpf_printk("ITER_BASIC: E3 VAL: i=%d v=%d", i, v ? *v : -1);
@@ -238,7 +239,7 @@ int iter_multiple_sequential_loops(const void *ctx)
bpf_iter_num_destroy(&it);
bpf_iter_num_new(&it, 0, 2);
-#pragma nounroll
+ __pragma_loop_no_unroll
for (i = 0; i < 3; i++) {
v = bpf_iter_num_next(&it);
bpf_printk("ITER_BASIC: E3 VAL: i=%d v=%d", i, v ? *v : -1);
[...]
