[PATCH] [gdb/testsuite] Fix gdb.arch/i386-avx.exp with clang

Tom de Vries via Gdb-patches
2021-11-04T13:56:21Z

When running test-case gdb.arch/i386-avx.exp with clang I ran into:
...
(gdb) PASS: gdb.arch/i386-avx.exp: set first breakpoint in main
continue^M
Continuing.^M
^M
Program received signal SIGSEGV, Segmentation fault.^M
0x000000000040052b in main (argc=1, argv=0x7fffffffd3c8) at i386-avx.c:54^M
54 asm ("vmovaps 0(%0), %%ymm0\n\t"^M
(gdb) FAIL: gdb.arch/i386-avx.exp: continue to breakpoint: \
continue to first breakpoint in main
...

The problem is that the vmovaps insn requires an 256-bit (or 32-byte aligned
address), and it's only 16-byte aligned:
...
(gdb) p /x $rax
$1 = 0x601030
...

Fix this by copying to a sufficiently aligned address.

Tested on x86_64-linux, with both gcc and clang.
---
gdb/testsuite/gdb.arch/i386-avx.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.arch/i386-avx.c b/gdb/testsuite/gdb.arch/i386-avx.c
index 4e938399a24..9b5323f9f76 100644
--- a/gdb/testsuite/gdb.arch/i386-avx.c
+++ b/gdb/testsuite/gdb.arch/i386-avx.c
@@ -18,6 +18,9 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */

#include <stdio.h>
+#include <stdint.h>
+#include <assert.h>
+#include <string.h>
#include "nat/x86-cpuid.h"

typedef struct {
@@ -25,7 +28,7 @@ typedef struct {
} v8sf_t;

-v8sf_t data[] =
+v8sf_t data_orig[] =
{
{ { 0.0, 0.125, 0.25, 0.375, 0.50, 0.625, 0.75, 0.875 } },
{ { 1.0, 1.125, 1.25, 1.375, 1.50, 1.625, 1.75, 1.875 } },
@@ -47,10 +50,33 @@ v8sf_t data[] =
#endif
};

+float data_buf[sizeof (data_orig) * 2 / sizeof (float)];

int
main (int argc, char **argv)
{
+ v8sf_t *data;
+
+ /* Initialize data pointer. */
+ {
+ float *p = data_buf;
+ float *data_buf_end = &data_buf[sizeof (data_buf) / sizeof (*data_buf)];
+ while (((uintptr_t)p & 0x1f) != 0
+ && p < data_buf_end)
+ p++;
+ data = (v8sf_t *)p;
+ }
+
+ /* Check that data pointer is sufficiently aligned to use vmovaps. */
+ assert (((uintptr_t)data & 0x1f) == 0);
+
+ /* Check that memcpy does not write out of bounds. */
+ assert ((void *)data + sizeof (data_orig)
+ <= (void *)data_buf + sizeof (data_buf));
+
+ /* Initialize data contents. */
+ memcpy (data, data_orig, sizeof (data_orig));
+
asm ("vmovaps 0(%0), %%ymm0\n\t"
"vmovaps 32(%0), %%ymm1\n\t"
"vmovaps 64(%0), %%ymm2\n\t"

base-commit: edc77c591add0a9c7740a9ed9f7e40358bf65dbf
--
2.26.2