Re: [PATCH v2 09/22] target/loongarch: Add fixed point bit instruction translation

[Song Gao]

Hi, Philippe

On 07/22/2021 01:46 AM, Philippe Mathieu-Daudé wrote:
> On 7/21/21 11:53 AM, Song Gao wrote:
>> This patch implement fixed point bit instruction translation.
>>
>> This includes:
>> - EXT.W.{B/H}
>> - CL{O/Z}.{W/D}, CT{O/Z}.{W/D}
>> - BYTEPICK.{W/D}
>> - REVB.{2H/4H/2W/D}
>> - REVH.{2W/D}
>> - BITREV.{4B/8B}, BITREV.{W/D}
>> - BSTRINS.{W/D}, BSTRPICK.{W/D}
>> - MASKEQZ, MASKNEZ
>>
>> Signed-off-by: Song Gao <gaosong@loongson.cn>
>> ---
>>  target/loongarch/helper.h     |  10 +
>>  target/loongarch/insns.decode |  45 +++
>>  target/loongarch/op_helper.c  | 119 ++++++++
>>  target/loongarch/trans.inc.c  | 665 
>> ++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 839 insertions(+)
> 
>> diff --git a/target/loongarch/op_helper.c b/target/loongarch/op_helper.c
>> index b2cbdd7..07c3d52 100644
>> --- a/target/loongarch/op_helper.c
>> +++ b/target/loongarch/op_helper.c
>> @@ -25,3 +25,122 @@ void helper_raise_exception(CPULoongArchState *env, 
>> uint32_t exception)
>>  {
>>      do_raise_exception(env, exception, GETPC());
>>  }
>> +
>> +target_ulong helper_cto_w(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    uint32_t v = (uint32_t)rj;
>> +    int temp = 0;
>> +
>> +    while ((v & 0x1) == 1) {
>> +        temp++;
>> +        v = v >> 1;
>> +    }
> 
> Why not use cto32() from "qemu/host-utils.h"
>>> +
>> +    return (target_ulong)temp;
>> +}
>> +
>> +target_ulong helper_ctz_w(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    uint32_t v = (uint32_t)rj;
>> +
>> +    if (v == 0) {
>> +        return 32;
>> +    }
>> +
>> +    int temp = 0;
>> +    while ((v & 0x1) == 0) {
>> +        temp++;
>> +        v = v >> 1;
>> +    }
> 
> ctz32
> 
>> +
>> +    return (target_ulong)temp;
>> +}
>> +
>> +target_ulong helper_cto_d(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    uint64_t v = rj;
>> +    int temp = 0;
>> +
>> +    while ((v & 0x1) == 1) {
>> +        temp++;
>> +        v = v >> 1;
>> +    }
> 
> cto64
> 
>> +
>> +    return (target_ulong)temp;
>> +}
>> +
>> +target_ulong helper_ctz_d(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    uint64_t v = rj;
>> +
>> +    if (v == 0) {
>> +        return 64;
>> +    }
>> +
>> +    int temp = 0;
>> +    while ((v & 0x1) == 0) {
>> +        temp++;
>> +        v = v >> 1;
>> +    }
> 
> and ctz64?
> 

Yes,  I didn't notice the file "qemu/host-utils.h" before,  thanks for kindly 
help! 

>> +
>> +    return (target_ulong)temp;
>> +}
>> +
>> +target_ulong helper_bitrev_w(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    int32_t v = (int32_t)rj;
>> +    const int SIZE = 32;
>> +    uint8_t bytes[SIZE];
>> +
>> +    int i;
>> +    for (i = 0; i < SIZE; i++) {
>> +        bytes[i] = v & 0x1;
>> +        v = v >> 1;
>> +    }
>> +    /* v == 0 */
>> +    for (i = 0; i < SIZE; i++) {
>> +        v = v | ((uint32_t)bytes[i] << (SIZE - 1 - i));
>> +    }
>> +
>> +    return (target_ulong)(int32_t)v;
>> +}
>> +
>> +target_ulong helper_bitrev_d(CPULoongArchState *env, target_ulong rj)
>> +{
>> +    uint64_t v = rj;
>> +    const int SIZE = 64;
>> +    uint8_t bytes[SIZE];
>> +
>> +    int i;
>> +    for (i = 0; i < SIZE; i++) {
>> +        bytes[i] = v & 0x1;
>> +        v = v >> 1;
>> +    }
>> +    /* v == 0 */
>> +    for (i = 0; i < SIZE; i++) {
>> +        v = v | ((uint64_t)bytes[i] << (SIZE - 1 - i));
>> +    }
>> +
>> +    return (target_ulong)v;
>> +}
>> +
>> +static inline target_ulong bitswap(target_ulong v)
>> +{
>> +    v = ((v >> 1) & (target_ulong)0x5555555555555555ULL) |
>> +        ((v & (target_ulong)0x5555555555555555ULL) << 1);
>> +    v = ((v >> 2) & (target_ulong)0x3333333333333333ULL) |
>> +        ((v & (target_ulong)0x3333333333333333ULL) << 2);
>> +    v = ((v >> 4) & (target_ulong)0x0F0F0F0F0F0F0F0FULL) |
>> +        ((v & (target_ulong)0x0F0F0F0F0F0F0F0FULL) << 4);
>> +    return v;
> 
> Is this revbit64?
> 

No, helper_bitrev_d is revbit64(LoongArch insn is 'bitrev.d rd, rj').

bitswap function for 'bitrev.4b/8b rd, rj' instruction.

    BITREV.4B:
      bstr32[31:24] = BITREV(GR[rj][31:24])
      bstr32[23:16] = BITREV(GR[rj][23:16])
      bstr32[15: 8] = BITREV(GR[rj][15: 8])
      bstr32[ 7: 0] = BITREV(GR[rj][ 7: 0])
      GR[rd] = SignExtend(bstr32, GRLEN)
     
    BITREV.8B:
      GR[rd][63:56] = BITREV(GR[rj][63:56])
      GR[rd][55:48] = BITREV(GR[rj][55:48])
      GR[rd][47:40] = BITREV(GR[rj][47:40])
      GR[rd][39:32] = BITREV(GR[rj][39:32])
      GR[rd][31:24] = BITREV(GR[rj][31:24])
      GR[rd][23:16] = BITREV(GR[rj][23:16])
      GR[rd][15: 8] = BITREV(GR[rj][15: 8])
      GR[rd][ 7: 0] = BITREV(GR[rj][ 7: 0])

We can see a detailed introduction in [1]  2.2.3.6.

[1] : 
https://github.com/loongson/LoongArch-Documentation/releases/download/LoongArch-Vol1-v3/LoongArch-Vol1-v1.00-EN.pdf

Thanks
Song Gao