* [PATCH 1/1] [gdb/reverse] Fix failing test: i386-avx-reverse
@ 2025-07-19 20:00 Shiven Kashyap
2025-07-20 2:48 ` Tom de Vries
0 siblings, 1 reply; 3+ messages in thread
From: Shiven Kashyap @ 2025-07-19 20:00 UTC (permalink / raw)
To: gdb-patches; +Cc: guinevere, Shiven Kashyap
Running the standalone test `gdb.reverse` leads to the following failure:
'''
FAIL: gdb.reverse/i386-avx-reverse.exp: verify ymm15 before vbroadcastsd
'''
This happens because the AVX broadcast instructions expect an actual value, but instead
it cast memory address of a buffer like so (see 'vpbroadcast_test' in 'i386-avx-reverse.c'):
'''
asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
'''
which lead to the test failing for the next instruction (`vbroadcastsd`), which depended on the correct value being broadcast to the register.
Also, updated the corresponding expected output (gdb.reverse/i386-avx-reverse.exp) to match.
Tested on x86-64 Linux.
Signed-off-by: Shiven Kashyap <shivenkashyap24@gmail.com>
---
gdb/testsuite/gdb.reverse/i386-avx-reverse.c | 4 ++--
gdb/testsuite/gdb.reverse/i386-avx-reverse.exp | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
index a3d64272f24..bf6cb77f313 100644
--- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
+++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
@@ -299,10 +299,10 @@ vpbroadcast_test ()
asm volatile ("vbroadcastss %xmm1, %xmm0");
asm volatile ("vbroadcastss %xmm1, %ymm15");
asm volatile ("vbroadcastss %0, %%ymm0" : : "m" (global_buf0));
- asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
+ asm volatile ("vbroadcastss %0, %%xmm15": : "m" (*dyn_buf0));
asm volatile ("vbroadcastsd %xmm1, %ymm0");
asm volatile ("vbroadcastsd %0, %%ymm15": : "m" (global_buf0));
- asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (dyn_buf0));
+ asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (*dyn_buf0));
/* We have a return statement to deal with
epilogue in different compilers. */
diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
index 7e75542720c..fb04260766e 100644
--- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
+++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
@@ -395,7 +395,7 @@ if {[record_full_function "vpbroadcast"] == true} {
test_one_register "vbroadcastf128" "ymm0" \
"0x17161514131211101716151413121110, 0x17161514131211101716151413121110"
test_one_register "vbroadcastsd" "ymm15" \
- "0x404060004040600040406000404060, 0x0"
+ "0x23222120232221202322212023222120, 0x0"
test_one_register "vbroadcastsd" "ymm0" \
"0x13121110131211101312111013121110, 0x13121110131211101312111013121110"
--
2.50.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/1] [gdb/reverse] Fix failing test: i386-avx-reverse
2025-07-19 20:00 [PATCH 1/1] [gdb/reverse] Fix failing test: i386-avx-reverse Shiven Kashyap
@ 2025-07-20 2:48 ` Tom de Vries
2025-07-21 19:14 ` Guinevere Larsen
0 siblings, 1 reply; 3+ messages in thread
From: Tom de Vries @ 2025-07-20 2:48 UTC (permalink / raw)
To: Shiven Kashyap, gdb-patches; +Cc: guinevere
On 7/19/25 22:00, Shiven Kashyap wrote:
> Running the standalone test `gdb.reverse` leads to the following failure:
> '''
> FAIL: gdb.reverse/i386-avx-reverse.exp: verify ymm15 before vbroadcastsd
> '''
>
Hi,
thanks for the patch.
I first couldn't reproduce this, but then I managed using target board
unix/-fPIE/-pie.
> This happens because the AVX broadcast instructions expect an actual value, but instead
> it cast memory address of a buffer like so (see 'vpbroadcast_test' in 'i386-avx-reverse.c'):
> '''
> asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
> '''
>
This is a bit misleading, because vbroadcastss can handle memory
operands, not just "actual values".
After your fix (which looks correct to me), the generated instruction
still accesses a memory address:
...
400abd: 48 8b 05 04 26 00 00 mov 0x2604(%rip),%rax
# 4030c8 <dyn_buf0>
400ac4: c4 62 79 18 38 vbroadcastss (%rax),%xmm15
...
but this time, the correct one.
Thanks,
- Tom
> which lead to the test failing for the next instruction (`vbroadcastsd`), which depended on the correct value being broadcast to the register.
> Also, updated the corresponding expected output (gdb.reverse/i386-avx-reverse.exp) to match.
>
> Tested on x86-64 Linux.
>
> Signed-off-by: Shiven Kashyap <shivenkashyap24@gmail.com>
> ---
> gdb/testsuite/gdb.reverse/i386-avx-reverse.c | 4 ++--
> gdb/testsuite/gdb.reverse/i386-avx-reverse.exp | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
> index a3d64272f24..bf6cb77f313 100644
> --- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
> +++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
> @@ -299,10 +299,10 @@ vpbroadcast_test ()
> asm volatile ("vbroadcastss %xmm1, %xmm0");
> asm volatile ("vbroadcastss %xmm1, %ymm15");
> asm volatile ("vbroadcastss %0, %%ymm0" : : "m" (global_buf0));
> - asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
> + asm volatile ("vbroadcastss %0, %%xmm15": : "m" (*dyn_buf0));
> asm volatile ("vbroadcastsd %xmm1, %ymm0");
> asm volatile ("vbroadcastsd %0, %%ymm15": : "m" (global_buf0));
> - asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (dyn_buf0));
> + asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (*dyn_buf0));
>
> /* We have a return statement to deal with
> epilogue in different compilers. */
> diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
> index 7e75542720c..fb04260766e 100644
> --- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
> +++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
> @@ -395,7 +395,7 @@ if {[record_full_function "vpbroadcast"] == true} {
> test_one_register "vbroadcastf128" "ymm0" \
> "0x17161514131211101716151413121110, 0x17161514131211101716151413121110"
> test_one_register "vbroadcastsd" "ymm15" \
> - "0x404060004040600040406000404060, 0x0"
> + "0x23222120232221202322212023222120, 0x0"
> test_one_register "vbroadcastsd" "ymm0" \
> "0x13121110131211101312111013121110, 0x13121110131211101312111013121110"
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/1] [gdb/reverse] Fix failing test: i386-avx-reverse
2025-07-20 2:48 ` Tom de Vries
@ 2025-07-21 19:14 ` Guinevere Larsen
0 siblings, 0 replies; 3+ messages in thread
From: Guinevere Larsen @ 2025-07-21 19:14 UTC (permalink / raw)
To: Tom de Vries, Shiven Kashyap, gdb-patches
Hi! Thank you for this patch!
I have a comments, slightly expanding Tom's reply. A v2 with updated
commit wording should be ready to push :)
On 7/19/25 11:48 PM, Tom de Vries wrote:
> On 7/19/25 22:00, Shiven Kashyap wrote:
>> Running the standalone test `gdb.reverse` leads to the following
>> failure:
>> '''
>> FAIL: gdb.reverse/i386-avx-reverse.exp: verify ymm15 before vbroadcastsd
>> '''
>>
>
> Hi,
>
> thanks for the patch.
>
> I first couldn't reproduce this, but then I managed using target board
> unix/-fPIE/-pie.
>
>> This happens because the AVX broadcast instructions expect an actual
>> value, but instead
>> it cast memory address of a buffer like so (see 'vpbroadcast_test' in
>> 'i386-avx-reverse.c'):
>> '''
>> asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
>> '''
>>
>
> This is a bit misleading, because vbroadcastss can handle memory
> operands, not just "actual values".
I second this, the instruction doesn't expect anything, but the test
itself expects to have the contents in the address, not the address. I
think the issue is better described as the test expecting the stored
value, as those are fully under our control.
--
Cheers,
Guinevere Larsen
She/Her/Hers
>
> After your fix (which looks correct to me), the generated instruction
> still accesses a memory address:
> ...
> 400abd: 48 8b 05 04 26 00 00 mov 0x2604(%rip),%rax
> # 4030c8 <dyn_buf0>
> 400ac4: c4 62 79 18 38 vbroadcastss (%rax),%xmm15
> ...
> but this time, the correct one.
>
> Thanks,
> - Tom
>
>> which lead to the test failing for the next instruction
>> (`vbroadcastsd`), which depended on the correct value being broadcast
>> to the register.
>> Also, updated the corresponding expected output
>> (gdb.reverse/i386-avx-reverse.exp) to match.
>>
>> Tested on x86-64 Linux.
>>
>> Signed-off-by: Shiven Kashyap <shivenkashyap24@gmail.com>
>> ---
>> gdb/testsuite/gdb.reverse/i386-avx-reverse.c | 4 ++--
>> gdb/testsuite/gdb.reverse/i386-avx-reverse.exp | 2 +-
>> 2 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
>> b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
>> index a3d64272f24..bf6cb77f313 100644
>> --- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
>> +++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.c
>> @@ -299,10 +299,10 @@ vpbroadcast_test ()
>> asm volatile ("vbroadcastss %xmm1, %xmm0");
>> asm volatile ("vbroadcastss %xmm1, %ymm15");
>> asm volatile ("vbroadcastss %0, %%ymm0" : : "m" (global_buf0));
>> - asm volatile ("vbroadcastss %0, %%xmm15": : "m" (dyn_buf0));
>> + asm volatile ("vbroadcastss %0, %%xmm15": : "m" (*dyn_buf0));
>> asm volatile ("vbroadcastsd %xmm1, %ymm0");
>> asm volatile ("vbroadcastsd %0, %%ymm15": : "m" (global_buf0));
>> - asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (dyn_buf0));
>> + asm volatile ("vbroadcastf128 %0, %%ymm0" : : "m" (*dyn_buf0));
>> /* We have a return statement to deal with
>> epilogue in different compilers. */
>> diff --git a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
>> b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
>> index 7e75542720c..fb04260766e 100644
>> --- a/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
>> +++ b/gdb/testsuite/gdb.reverse/i386-avx-reverse.exp
>> @@ -395,7 +395,7 @@ if {[record_full_function "vpbroadcast"] == true} {
>> test_one_register "vbroadcastf128" "ymm0" \
>> "0x17161514131211101716151413121110,
>> 0x17161514131211101716151413121110"
>> test_one_register "vbroadcastsd" "ymm15" \
>> - "0x404060004040600040406000404060, 0x0"
>> + "0x23222120232221202322212023222120, 0x0"
>> test_one_register "vbroadcastsd" "ymm0" \
>> "0x13121110131211101312111013121110,
>> 0x13121110131211101312111013121110"
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-07-21 19:15 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2025-07-19 20:00 [PATCH 1/1] [gdb/reverse] Fix failing test: i386-avx-reverse Shiven Kashyap
2025-07-20 2:48 ` Tom de Vries
2025-07-21 19:14 ` Guinevere Larsen
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox