Re: [Qemu-devel] [PATCH v2] target/i386: Fix BLSR and BLSI

[Ricardo Ribalda Delgado]

Hi

For completion. This is my poor man tbm test. It has run for 5 minutes
with no errors

gcc tbm.c -O3 -march=native  -o pc
gcc tbm.c -mtbm -O3

 for a in $(seq 0 65535); do /tmp/qemu/x86_64-linux-user/qemu-x86_64
-cpu qemu64,+tbm ./a.out $a >/tmp/res.qemu ; ./pc $a  > /tmp/res.pc ;
if !  diff  /tmp/res.pc /tmp/res.qemu; then echo $a ; fi ; done



#include <stdio.h>
#include <stdlib.h>
#include <x86intrin.h>


long test_bextr(long src) {
unsigned char start =1, len=3;
return (src >> start) & ((1 << len)-1);
}

long test_blcfill(long val){

return val & (val + 1);
}

long test_blci(long val){

return val | ~(val + 1);
}

long test_blcic(long val){

return ~val & (val + 1);
}

long test_blcmsk(long val){

return val ^ (val + 1);
}

long test_blcs(long val){

return val | (val + 1);
}

long test_blsfill(long val){

return val | (val - 1);
}

long test_blsic(long val){

return ~val | (val - 1);
}

long test_t1mskc(long val){

return ~val | (val + 1);
}

long test_tzmsk(long val){

return ~val & (val - 1);
}

int main(int argc, char *argv[]) {
long op1;
long ret;

if (argc < 2) {
fprintf(stderr, "use %s op1 \n", argv[0]);
return -1;
}
op1 = strtoul(argv[1], NULL, 0);

fprintf(stdout, "op 1 %ld (0x%lx)\n", op1, op1);

ret = test_bextr(op1);
fprintf(stdout, "bextr %ld (0x%lx)\n",ret, ret);

ret = test_blcfill(op1);
fprintf(stdout, "blcfill %ld (0x%lx)\n",ret, ret);

ret = test_blci(op1);
fprintf(stdout, "blci %ld (0x%lx)\n",ret, ret);

ret = test_blcic(op1);
fprintf(stdout, "blcic %ld (0x%lx)\n",ret, ret);

ret = test_blcmsk(op1);
fprintf(stdout, "blcmsk %ld (0x%lx)\n",ret, ret);

ret = test_blcs(op1);
fprintf(stdout, "blcs %ld (0x%lx)\n",ret, ret);

ret = test_blsfill(op1);
fprintf(stdout, "blsfill %ld (0x%lx)\n",ret, ret);

ret = test_blsic(op1);
fprintf(stdout, "blsic %ld (0x%lx)\n",ret, ret);

ret = test_t1mskc(op1);
fprintf(stdout, "t1mskc %ld (0x%lx)\n",ret, ret);

ret = test_tzmsk(op1);
fprintf(stdout, "tzmsk %ld (0x%lx)\n",ret, ret);



return 0;
}

On Thu, Jul 13, 2017 at 11:55 PM, Ricardo Ribalda Delgado
<address@hidden> wrote:
> Hi again
>
> Some progress here, I think that I have found a bug in andn, I have
> already send a patch.
>
> I have made a rudimentary testcase for bmi. I will try tomorrow o
> build something similar for tbm.
>
> For reference, I am using this script:
>
> for a in $(seq 0 255); do for b in $(seq 0 255); do for c in $(seq 0
> 255); do /tmp/qemu/x86_64-linux-user/qemu-x86_64 -cpu qemu64,+bmi1
> ./a.out $a $b $c >/tmp/res.qemu; ./pc $a $b $c > /tmp/res.pc; if !
> diff  /tmp/res.pc /tmp/res.qemu; then echo $a $b $c; fi ; done ; done
> ; done
>
> with this build options
> gcc kk.c -mbmi -O3 -Wall
> gcc kk.c -march=native -O3 -Wall -o pc
>
> and this code:
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <x86intrin.h>
>
>
> long test_blsr(long val){
>
> return (val & (val - 1));
> }
>
> long test_blsi(long val){
>
> return (val & (-val));
> }
>
> long test_blmsk(long val){
>
> return (val ^ (val -1));
> }
>
> long test_andn(long v1, long v2){
>
> return (~v1 & v2);
> }
>
> long test_tzcnt(long val) {
> #ifdef PC
> return val ? __builtin_ctz(val) : 32;
> #else
> return __tzcnt_u32(val);
> #endif
> }
>
> long test_bextr(long src, unsigned char start, unsigned char len) {
> #ifdef PC
> return (src >> start) & ((1 << len)-1);
> #else
> return __bextr_u32(src, start | len <<8);
> #endif
> }
>
> int main(int argc, char *argv[]) {
> long op1, op2, op3;
> long ret;
>
> if (argc < 4) {
> fprintf(stderr, "use %s op1 op2 op3\n", argv[0]);
> return -1;
> }
> op1 = strtoul(argv[1], NULL, 0);
> op2 = strtoul(argv[2], NULL, 0);
> op3 = strtoul(argv[3], NULL, 0);
>
> fprintf(stdout, "op 1 %ld (0x%lx)\n", op1, op1);
> fprintf(stdout, "op 2 %ld (0x%lx)\n", op2, op2);
>
> ret = test_blsr(op1);
> fprintf(stdout, "blsr %ld (0x%lx)\n",ret, ret);
>
> ret = test_blsi(op1);
> fprintf(stdout, "blsi %ld (0x%lx)\n",ret, ret);
>
> ret = test_blmsk(op1);
> fprintf(stdout, "blmsk %ld (0x%lx)\n",ret, ret);
>
> ret = test_andn(op1,op2);
> fprintf(stdout, "andn %ld (0x%lx)\n",ret, ret);
>
> ret = test_tzcnt(op1);
> fprintf(stdout, "tzcnt %ld (0x%lx)\n",ret, ret);
>
> ret = test_bextr(op1, op2, op3);
> fprintf(stdout, "bextr %ld (0x%lx)\n",ret, ret);
>
> return 0;
> }
>
> On Thu, Jul 13, 2017 at 10:42 PM, Ricardo Ribalda Delgado
> <address@hidden> wrote:
>> Hi Richard
>>
>> The simple example works as expected, but my big application
>> (gobject-introspection) still crashes with sigsegv :(.
>>
>> it seems to be something related to the bmi and tbm instructions. If I
>> disable them in gcc ( -mno-bmi -mno-tbm), the application
>> runs ok.
>>
>> A look at qemu's code does not show anything obvious, but I am not
>> that familiar with qemu source yet to find something like this through
>> static analysis.
>>
>> My plan (as soon as I have some time) is to create a small set of apps
>> to validate bmi/tbm/ (Are you aware of something already existing for
>> this?)
>> My stupid guess is that maybe the ops are switched, or the flags are
>> not properly modified.
>>
>> If you want, I can share the application that crashes with you, just
>> be aware that the number of dependencies is considerable.
>>
>> BTW I can only run the gdb stub on version 2.8.0. On git HEAD I am getting 
>> only:
>>
>> Quit
>> (gdb) c
>> Continuing.
>> warning: Remote failure reply: E22
>>
>> Program stopped.
>> 0x00000040017bac07 in ?? ()
>> (gdb) c
>> Continuing.
>>
>>
>>
>> Thanks for your help, it is greatly appreciated!
>>
>> On Wed, Jul 12, 2017 at 9:29 PM, Richard Henderson <address@hidden> wrote:
>>> The implementation of these two instructions was swapped.
>>> At the same time, unify the setup of eflags for the insn group.
>>>
>>> Reported-by: Ricardo Ribalda Delgado <address@hidden>
>>> Signed-off-by: Richard Henderson <address@hidden>
>>> ---
>>>  target/i386/translate.c | 26 +++++++++-----------------
>>>  1 file changed, 9 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/target/i386/translate.c b/target/i386/translate.c
>>> index 9d5f1c3..69d3787 100644
>>> --- a/target/i386/translate.c
>>> +++ b/target/i386/translate.c
>>> @@ -4031,34 +4031,26 @@ static void gen_sse(CPUX86State *env, DisasContext 
>>> *s, int b,
>>>                  ot = mo_64_32(s->dflag);
>>>                  gen_ldst_modrm(env, s, modrm, ot, OR_TMP0, 0);
>>>
>>> +                tcg_gen_mov_tl(cpu_cc_src, cpu_T0);
>>>                  switch (reg & 7) {
>>>                  case 1: /* blsr By,Ey */
>>> -                    tcg_gen_neg_tl(cpu_T1, cpu_T0);
>>> +                    tcg_gen_subi_tl(cpu_T1, cpu_T0, 1);
>>>                      tcg_gen_and_tl(cpu_T0, cpu_T0, cpu_T1);
>>> -                    gen_op_mov_reg_v(ot, s->vex_v, cpu_T0);
>>> -                    gen_op_update2_cc();
>>> -                    set_cc_op(s, CC_OP_BMILGB + ot);
>>>                      break;
>>> -
>>>                  case 2: /* blsmsk By,Ey */
>>> -                    tcg_gen_mov_tl(cpu_cc_src, cpu_T0);
>>> -                    tcg_gen_subi_tl(cpu_T0, cpu_T0, 1);
>>> -                    tcg_gen_xor_tl(cpu_T0, cpu_T0, cpu_cc_src);
>>> -                    tcg_gen_mov_tl(cpu_cc_dst, cpu_T0);
>>> -                    set_cc_op(s, CC_OP_BMILGB + ot);
>>> +                    tcg_gen_subi_tl(cpu_T1, cpu_T0, 1);
>>> +                    tcg_gen_xor_tl(cpu_T0, cpu_T0, cpu_T1);
>>>                      break;
>>> -
>>>                  case 3: /* blsi By, Ey */
>>> -                    tcg_gen_mov_tl(cpu_cc_src, cpu_T0);
>>> -                    tcg_gen_subi_tl(cpu_T0, cpu_T0, 1);
>>> -                    tcg_gen_and_tl(cpu_T0, cpu_T0, cpu_cc_src);
>>> -                    tcg_gen_mov_tl(cpu_cc_dst, cpu_T0);
>>> -                    set_cc_op(s, CC_OP_BMILGB + ot);
>>> +                    tcg_gen_neg_tl(cpu_T1, cpu_T0);
>>> +                    tcg_gen_and_tl(cpu_T0, cpu_T0, cpu_T1);
>>>                      break;
>>> -
>>>                  default:
>>>                      goto unknown_op;
>>>                  }
>>> +                tcg_gen_mov_tl(cpu_cc_dst, cpu_T0);
>>> +                gen_op_mov_reg_v(ot, s->vex_v, cpu_T0);
>>> +                set_cc_op(s, CC_OP_BMILGB + ot);
>>>                  break;
>>>
>>>              default:
>>> --
>>> 2.9.4
>>>
>>
>>
>>
>> --
>> Ricardo Ribalda
>
>
>
> --
> Ricardo Ribalda



-- 
Ricardo Ribalda