Re: [Qemu-devel] [PATCH] ppc: Convert op_440_dlmzb to TCG

["Laurent Desnogues" <laurent.desnogues@gmail.com>]

On Sun, Nov 30, 2008 at 6:25 PM, Andreas Färber <andreas.faerber@web.de> wrote:
>
> Am 30.11.2008 um 17:31 schrieb Aurélien Jarno:
>>
>> Doing loops with TCG is a bad idea as it is very inefficient.
>
> Did you read the code? There is no loop in TCG here, that's exactly what I
> was saying.
> The labels are for conditionals only and for exiting the non-loop.
>
> If you have a better suggestion, please say so as this is one of the dyngen
> ops that keep me from working on the conversion on my own system.

Going for a helper might be better for larger sequences of TCG ops;
Fabrice mentions a threshold of about 20 ops.  And your replacement
is certainly larger than 20 ops :-)  Plus given it uses brcond, it would
prevent TCG liveness analysis from doing its job in the basic block
containing that instruction.


Laurent


> Andreas
>
>>
>>
>>> ---
>>> Compile-tested on Linux/amd64.
>>>
>>> diff --git a/target-ppc/op.c b/target-ppc/op.c
>>> index 5d2cfa1..a26b1da 100644
>>> --- a/target-ppc/op.c
>>> +++ b/target-ppc/op.c
>>> @@ -839,25 +839,6 @@ void OPPROTO op_4xx_tlbwe_hi (void)
>>> }
>>> #endif
>>>
>>> -/* SPR micro-ops */
>>> -/* 440 specific */
>>> -void OPPROTO op_440_dlmzb (void)
>>> -{
>>> -    do_440_dlmzb();
>>> -    RETURN();
>>> -}
>>> -
>>> -void OPPROTO op_440_dlmzb_update_Rc (void)
>>> -{
>>> -    if (T0 == 8)
>>> -        T0 = 0x2;
>>> -    else if (T0 < 4)
>>> -        T0 = 0x4;
>>> -    else
>>> -        T0 = 0x8;
>>> -    RETURN();
>>> -}
>>> -
>>> #if !defined(CONFIG_USER_ONLY)
>>> void OPPROTO op_store_pir (void)
>>> {
>>> diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
>>> index 6addc74..a055ee6 100644
>>> --- a/target-ppc/op_helper.c
>>> +++ b/target-ppc/op_helper.c
>>> @@ -1754,27 +1754,6 @@ void do_store_403_pb (int num)
>>> }
>>> #endif
>>>
>>> -/* 440 specific */
>>> -void do_440_dlmzb (void)
>>> -{
>>> -    target_ulong mask;
>>> -    int i;
>>> -
>>> -    i = 1;
>>> -    for (mask = 0xFF000000; mask != 0; mask = mask >> 8) {
>>> -        if ((T0 & mask) == 0)
>>> -            goto done;
>>> -        i++;
>>> -    }
>>> -    for (mask = 0xFF000000; mask != 0; mask = mask >> 8) {
>>> -        if ((T1 & mask) == 0)
>>> -            break;
>>> -        i++;
>>> -    }
>>> - done:
>>> -    T0 = i;
>>> -}
>>> -
>>> /
>>>
>>> *****************************************************************************/
>>> /* SPE extension helpers */
>>> /* Use a table to make this quicker */
>>> diff --git a/target-ppc/op_helper.h b/target-ppc/op_helper.h
>>> index 1c046d8..aaaba5c 100644
>>> --- a/target-ppc/op_helper.h
>>> +++ b/target-ppc/op_helper.h
>>> @@ -112,9 +112,6 @@ void do_4xx_tlbwe_lo (void);
>>> void do_4xx_tlbwe_hi (void);
>>> #endif
>>>
>>> -/* PowerPC 440 specific helpers */
>>> -void do_440_dlmzb (void);
>>> -
>>> /* PowerPC 403 specific helpers */
>>> #if !defined(CONFIG_USER_ONLY)
>>> void do_load_403_pb (int num);
>>> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
>>> index 95cb482..59533ac 100644
>>> --- a/target-ppc/translate.c
>>> +++ b/target-ppc/translate.c
>>> @@ -5872,12 +5872,49 @@ GEN_HANDLER(dlmzb, 0x1F, 0x0E, 0x02,
>>> 0x00000000, PPC_440_SPEC)
>>> {
>>>    tcg_gen_mov_tl(cpu_T[0], cpu_gpr[rS(ctx->opcode)]);
>>>    tcg_gen_mov_tl(cpu_T[1], cpu_gpr[rB(ctx->opcode)]);
>>> -    gen_op_440_dlmzb();
>>> +    TCGv t0 = tcg_temp_new();
>>> +    int endLabel = gen_new_label();
>>> +    int i = 1;
>>> +    target_ulong mask;
>>> +    for (mask = 0xFF000000; mask != 0; mask = mask >> 8) {
>>> +        tcg_gen_andi_tl(t0, cpu_T[0], mask);
>>> +        int nextLabel = gen_new_label();
>>> +        tcg_gen_brcondi_tl(TCG_COND_NE, t0, 0, nextLabel);
>>> +        tcg_gen_movi_tl(cpu_T[0], i++);
>>> +        tcg_gen_br(endLabel);
>>> +        gen_set_label(nextLabel);
>>> +    }
>>> +    for (mask = 0xFF000000; mask != 0; mask = mask >> 8) {
>>> +        tcg_gen_andi_tl(t0, cpu_T[1], mask);
>>> +        int nextLabel = gen_new_label();
>>> +        tcg_gen_brcondi_tl(TCG_COND_NE, t0, 0, nextLabel);
>>> +        tcg_gen_movi_tl(cpu_T[0], i++);
>>> +        tcg_gen_br(endLabel);
>>> +        gen_set_label(nextLabel);
>>> +    }
>>> +    tcg_gen_movi_tl(cpu_T[0], i);
>>> +    gen_set_label(endLabel);
>>> +    tcg_temp_free(t0);
>>>    tcg_gen_mov_tl(cpu_gpr[rA(ctx->opcode)], cpu_T[0]);
>>>    tcg_gen_andi_tl(cpu_xer, cpu_xer, ~0x7F);
>>>    tcg_gen_or_tl(cpu_xer, cpu_xer, cpu_T[0]);
>>>    if (Rc(ctx->opcode)) {
>>> -        gen_op_440_dlmzb_update_Rc();
>>> +        endLabel = gen_new_label();
>>> +        int nextLabel = gen_new_label();
>>> +        tcg_gen_brcondi_tl(TCG_COND_NE, cpu_T[0], 8, nextLabel);
>>> +        tcg_gen_movi_tl(cpu_T[0], 0x2);
>>> +        tcg_gen_br(endLabel);
>>> +
>>> +        gen_set_label(nextLabel);
>>> +        nextLabel = gen_new_label();
>>> +        tcg_gen_brcondi_tl(TCG_COND_GE, cpu_T[0], 4, nextLabel);
>>> +        tcg_gen_movi_tl(cpu_T[0], 0x4);
>>> +        tcg_gen_br(endLabel);
>>> +
>>> +        gen_set_label(nextLabel);
>>> +        tcg_gen_movi_tl(cpu_T[0], 0x8);
>>> +
>>> +        gen_set_label(endLabel);
>>>        tcg_gen_trunc_tl_i32(cpu_crf[0], cpu_T[0]);
>>>        tcg_gen_andi_i32(cpu_crf[0], cpu_crf[0], 0xf);
>>>    }
>>>
>>
>>
>>>
>>
>>
>> --
>>  .''`.  Aurelien Jarno              | GPG: 1024D/F1BCDB73
>> : :' :  Debian developer           | Electrical Engineer
>> `. `'   aurel32@debian.org         | aurelien@aurel32.net
>>  `-    people.debian.org/~aurel32 | www.aurel32.net
>>
>>
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