diff mbox series

[v3,45/81] target/arm: Implement SVE2 HISTCNT, HISTSEG

Message ID 20200918183751.2787647-46-richard.henderson@linaro.org
State New
Headers show
Series target/arm: Implement SVE2 | expand

Commit Message

Richard Henderson Sept. 18, 2020, 6:37 p.m. UTC
From: Stephen Long <steplong@quicinc.com>

Signed-off-by: Stephen Long <steplong@quicinc.com>
Message-Id: <20200416173109.8856-1-steplong@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Fix overlap between output and input vectors.
---
 target/arm/helper-sve.h    |   7 +++
 target/arm/sve.decode      |   6 ++
 target/arm/sve_helper.c    | 124 +++++++++++++++++++++++++++++++++++++
 target/arm/translate-sve.c |  19 ++++++
 4 files changed, 156 insertions(+)

Comments

LIU Zhiwei Oct. 9, 2020, 6:13 a.m. UTC | #1
On 2020/9/19 2:37, Richard Henderson wrote:
> From: Stephen Long <steplong@quicinc.com>
>
> Signed-off-by: Stephen Long <steplong@quicinc.com>
> Message-Id: <20200416173109.8856-1-steplong@quicinc.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> v2: Fix overlap between output and input vectors.
> ---
>   target/arm/helper-sve.h    |   7 +++
>   target/arm/sve.decode      |   6 ++
>   target/arm/sve_helper.c    | 124 +++++++++++++++++++++++++++++++++++++
>   target/arm/translate-sve.c |  19 ++++++
>   4 files changed, 156 insertions(+)
>
> diff --git a/target/arm/helper-sve.h b/target/arm/helper-sve.h
> index 9e8641e1c0..34bbb767ef 100644
> --- a/target/arm/helper-sve.h
> +++ b/target/arm/helper-sve.h
> @@ -2551,6 +2551,13 @@ DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_b, TCG_CALL_NO_RWG,
>   DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_h, TCG_CALL_NO_RWG,
>                      i32, ptr, ptr, ptr, ptr, i32)
>   
> +DEF_HELPER_FLAGS_5(sve2_histcnt_s, TCG_CALL_NO_RWG,
> +                   void, ptr, ptr, ptr, ptr, i32)
> +DEF_HELPER_FLAGS_5(sve2_histcnt_d, TCG_CALL_NO_RWG,
> +                   void, ptr, ptr, ptr, ptr, i32)
> +
> +DEF_HELPER_FLAGS_4(sve2_histseg, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
> +
>   DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_h, TCG_CALL_NO_RWG,
>                      void, ptr, ptr, ptr, ptr, ptr, i32)
>   DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_s, TCG_CALL_NO_RWG,
> diff --git a/target/arm/sve.decode b/target/arm/sve.decode
> index 3121eabbf8..0edb72d4fb 100644
> --- a/target/arm/sve.decode
> +++ b/target/arm/sve.decode
> @@ -146,6 +146,7 @@
>                   &rprrr_esz rn=%reg_movprfx
>   @rdn_pg_rm_ra   ........ esz:2 . ra:5  ... pg:3 rm:5 rd:5 \
>                   &rprrr_esz rn=%reg_movprfx
> +@rd_pg_rn_rm   ........ esz:2 . rm:5 ... pg:3 rn:5 rd:5       &rprr_esz
>   
>   # One register operand, with governing predicate, vector element size
>   @rd_pg_rn       ........ esz:2 ... ... ... pg:3 rn:5 rd:5       &rpr_esz
> @@ -1336,6 +1337,11 @@ RSUBHNT         01000101 .. 1 ..... 011 111 ..... .....  @rd_rn_rm
>   MATCH           01000101 .. 1 ..... 100 ... ..... 0 .... @pd_pg_rn_rm
>   NMATCH          01000101 .. 1 ..... 100 ... ..... 1 .... @pd_pg_rn_rm
>   
> +### SVE2 Histogram Computation
> +
> +HISTCNT         01000101 .. 1 ..... 110 ... ..... .....  @rd_pg_rn_rm
> +HISTSEG         01000101 .. 1 ..... 101 000 ..... .....  @rd_rn_rm
> +
>   ## SVE2 floating-point pairwise operations
>   
>   FADDP           01100100 .. 010 00 0 100 ... ..... ..... @rdn_pg_rm
> diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
> index 19fbf94189..fa4848bc5c 100644
> --- a/target/arm/sve_helper.c
> +++ b/target/arm/sve_helper.c
> @@ -7095,3 +7095,127 @@ DO_PPZZ_MATCH(sve2_nmatch_ppzz_b, MO_8, true)
>   DO_PPZZ_MATCH(sve2_nmatch_ppzz_h, MO_16, true)
>   
>   #undef DO_PPZZ_MATCH
> +
> +void HELPER(sve2_histcnt_s)(void *vd, void *vn, void *vm, void *vg,
> +                            uint32_t desc)
> +{
> +    ARMVectorReg scratch;
> +    intptr_t i, j;
> +    intptr_t opr_sz = simd_oprsz(desc);
> +    uint32_t *d = vd, *n = vn, *m = vm;
> +    uint8_t *pg = vg;
> +
> +    if (d == n) {
> +        n = memcpy(&scratch, n, opr_sz);
> +        if (d == m) {
> +            m = n;
> +        }
> +    } else if (d == m) {
> +        m = memcpy(&scratch, m, opr_sz);
> +    }
> +
> +    for (i = 0; i < opr_sz; i += 4) {
> +        uint64_t count = 0;
> +        uint8_t pred;
> +
> +        pred = pg[H1(i >> 3)] >> (i & 7);
> +        if (pred & 1) {
> +            uint32_t nn = n[H4(i >> 2)];
> +
> +            for (j = 0; j <= i; j += 4) {
> +                pred = pg[H1(j >> 3)] >> (j & 7);
> +                if ((pred & 1) && nn == m[H4(j >> 2)]) {
> +                    ++count;
> +                }
> +            }
> +        }
> +        d[H4(i >> 2)] = count;
> +    }
> +}
> +
> +void HELPER(sve2_histcnt_d)(void *vd, void *vn, void *vm, void *vg,
> +                            uint32_t desc)
> +{
> +    ARMVectorReg scratch;
> +    intptr_t i, j;
> +    intptr_t opr_sz = simd_oprsz(desc);
> +    uint64_t *d = vd, *n = vn, *m = vm;
> +    uint8_t *pg = vg;
> +
> +    if (d == n) {
> +        n = memcpy(&scratch, n, opr_sz);
> +        if (d == m) {
> +            m = n;
> +        }
> +    } else if (d == m) {
> +        m = memcpy(&scratch, m, opr_sz);
> +    }
> +
> +    for (i = 0; i < opr_sz / 8; ++i) {
> +        uint64_t count = 0;
> +        if (pg[H1(i)] & 1) {
> +            uint64_t nn = n[i];
> +            for (j = 0; j <= i; ++j) {
> +                if ((pg[H1(j)] & 1) && nn == m[j]) {
> +                    ++count;
> +                }
> +            }
> +        }
> +        d[i] = count;
> +    }
> +}
> +
> +/*
> + * Returns the number of bytes in m0 and m1 that match n.
> + * See comment for do_match2().
> + * */
> +static inline uint64_t do_histseg_cnt(uint8_t n, uint64_t m0, uint64_t m1)
> +{
> +    int esz = MO_8;
> +    int bits = 8 << esz;
> +    uint64_t ones = dup_const(esz, 1);
> +    uint64_t signs = ones << (bits - 1);
> +    uint64_t cmp0, cmp1;
> +
> +    cmp1 = dup_const(esz, n);
> +    cmp0 = cmp1 ^ m0;
> +    cmp1 = cmp1 ^ m1;
> +    cmp0 = (cmp0 - ones) & ~cmp0 & signs;
> +    cmp1 = (cmp1 - ones) & ~cmp1 & signs;
> +
Hi Richard,

Although we can detect zero byte with this method, we can't use it to 
count the zero bytes.

For example,
IF
     cmp1 =  0x0100010001000100 , ones = 0x101010101010101, signs = 
0x8080808080808080,
THEN
     cmp1 = (cmp1 - ones) & ~cmp1 & signs = 0x8080808080808080
So
     cmp1 will have 6 zeros by this method. In fact, cmp1 only have 4 
zeros instead of 6 zeros.

I don't  find  a "bit twiddling" way,  if you find it, please let me know.

Best Regards,
Zhiwei
> +    /*
> +     * Combine the two compares in a way that the bits do
> +     * not overlap, and so preserves the count of set bits.
> +     * If the host has an efficient instruction for ctpop,
> +     * then ctpop(x) + ctpop(y) has the same number of
> +     * operations as ctpop(x | (y >> 1)).  If the host does
> +     * not have an efficient ctpop, then we only want to
> +     * use it once.
> +     */
> +    return ctpop64(cmp0 | (cmp1 >> 1));
> +}
> +
> +void HELPER(sve2_histseg)(void *vd, void *vn, void *vm, uint32_t desc)
> +{
> +    intptr_t i, j;
> +    intptr_t opr_sz = simd_oprsz(desc);
> +
> +    for (i = 0; i < opr_sz; i += 16) {
> +        uint64_t n0 = *(uint64_t *)(vn + i);
> +        uint64_t m0 = *(uint64_t *)(vm + i);
> +        uint64_t n1 = *(uint64_t *)(vn + i + 8);
> +        uint64_t m1 = *(uint64_t *)(vm + i + 8);
> +        uint64_t out0 = 0;
> +        uint64_t out1 = 0;
> +
> +        for (j = 0; j < 64; j += 8) {
> +            uint64_t cnt0 = do_histseg_cnt(n0 >> j, m0, m1);
> +            uint64_t cnt1 = do_histseg_cnt(n1 >> j, m0, m1);
> +            out0 |= cnt0 << j;
> +            out1 |= cnt1 << j;
> +        }
> +
> +        *(uint64_t *)(vd + i) = out0;
> +        *(uint64_t *)(vd + i + 8) = out1;
> +    }
> +}
> diff --git a/target/arm/translate-sve.c b/target/arm/translate-sve.c
> index e947a0ff25..4e792c9b9a 100644
> --- a/target/arm/translate-sve.c
> +++ b/target/arm/translate-sve.c
> @@ -7509,6 +7509,25 @@ static bool trans_##NAME(DisasContext *s, arg_rprr_esz *a)                  \
>   DO_SVE2_PPZZ_MATCH(MATCH, match)
>   DO_SVE2_PPZZ_MATCH(NMATCH, nmatch)
>   
> +static bool trans_HISTCNT(DisasContext *s, arg_rprr_esz *a)
> +{
> +    static gen_helper_gvec_4 * const fns[2] = {
> +        gen_helper_sve2_histcnt_s, gen_helper_sve2_histcnt_d
> +    };
> +    if (a->esz < 2) {
> +        return false;
> +    }
> +    return do_sve2_zpzz_ool(s, a, fns[a->esz - 2]);
> +}
> +
> +static bool trans_HISTSEG(DisasContext *s, arg_rrr_esz *a)
> +{
> +    if (a->esz != 0) {
> +        return false;
> +    }
> +    return do_sve2_zzz_ool(s, a, gen_helper_sve2_histseg);
> +}
> +
>   static bool do_sve2_zpzz_fp(DisasContext *s, arg_rprr_esz *a,
>                               gen_helper_gvec_4_ptr *fn)
>   {
Richard Henderson Oct. 9, 2020, 12:35 p.m. UTC | #2
On 10/9/20 1:13 AM, LIU Zhiwei wrote:
> 
> 
> On 2020/9/19 2:37, Richard Henderson wrote:
>> From: Stephen Long <steplong@quicinc.com>
>>
>> Signed-off-by: Stephen Long <steplong@quicinc.com>
>> Message-Id: <20200416173109.8856-1-steplong@quicinc.com>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>> v2: Fix overlap between output and input vectors.
>> ---
>>   target/arm/helper-sve.h    |   7 +++
>>   target/arm/sve.decode      |   6 ++
>>   target/arm/sve_helper.c    | 124 +++++++++++++++++++++++++++++++++++++
>>   target/arm/translate-sve.c |  19 ++++++
>>   4 files changed, 156 insertions(+)
>>
>> diff --git a/target/arm/helper-sve.h b/target/arm/helper-sve.h
>> index 9e8641e1c0..34bbb767ef 100644
>> --- a/target/arm/helper-sve.h
>> +++ b/target/arm/helper-sve.h
>> @@ -2551,6 +2551,13 @@ DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_b, TCG_CALL_NO_RWG,
>>   DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_h, TCG_CALL_NO_RWG,
>>                      i32, ptr, ptr, ptr, ptr, i32)
>>   +DEF_HELPER_FLAGS_5(sve2_histcnt_s, TCG_CALL_NO_RWG,
>> +                   void, ptr, ptr, ptr, ptr, i32)
>> +DEF_HELPER_FLAGS_5(sve2_histcnt_d, TCG_CALL_NO_RWG,
>> +                   void, ptr, ptr, ptr, ptr, i32)
>> +
>> +DEF_HELPER_FLAGS_4(sve2_histseg, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
>> +
>>   DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_h, TCG_CALL_NO_RWG,
>>                      void, ptr, ptr, ptr, ptr, ptr, i32)
>>   DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_s, TCG_CALL_NO_RWG,
>> diff --git a/target/arm/sve.decode b/target/arm/sve.decode
>> index 3121eabbf8..0edb72d4fb 100644
>> --- a/target/arm/sve.decode
>> +++ b/target/arm/sve.decode
>> @@ -146,6 +146,7 @@
>>                   &rprrr_esz rn=%reg_movprfx
>>   @rdn_pg_rm_ra   ........ esz:2 . ra:5  ... pg:3 rm:5 rd:5 \
>>                   &rprrr_esz rn=%reg_movprfx
>> +@rd_pg_rn_rm   ........ esz:2 . rm:5 ... pg:3 rn:5 rd:5       &rprr_esz
>>     # One register operand, with governing predicate, vector element size
>>   @rd_pg_rn       ........ esz:2 ... ... ... pg:3 rn:5 rd:5       &rpr_esz
>> @@ -1336,6 +1337,11 @@ RSUBHNT         01000101 .. 1 ..... 011 111 .....
>> .....  @rd_rn_rm
>>   MATCH           01000101 .. 1 ..... 100 ... ..... 0 .... @pd_pg_rn_rm
>>   NMATCH          01000101 .. 1 ..... 100 ... ..... 1 .... @pd_pg_rn_rm
>>   +### SVE2 Histogram Computation
>> +
>> +HISTCNT         01000101 .. 1 ..... 110 ... ..... .....  @rd_pg_rn_rm
>> +HISTSEG         01000101 .. 1 ..... 101 000 ..... .....  @rd_rn_rm
>> +
>>   ## SVE2 floating-point pairwise operations
>>     FADDP           01100100 .. 010 00 0 100 ... ..... ..... @rdn_pg_rm
>> diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
>> index 19fbf94189..fa4848bc5c 100644
>> --- a/target/arm/sve_helper.c
>> +++ b/target/arm/sve_helper.c
>> @@ -7095,3 +7095,127 @@ DO_PPZZ_MATCH(sve2_nmatch_ppzz_b, MO_8, true)
>>   DO_PPZZ_MATCH(sve2_nmatch_ppzz_h, MO_16, true)
>>     #undef DO_PPZZ_MATCH
>> +
>> +void HELPER(sve2_histcnt_s)(void *vd, void *vn, void *vm, void *vg,
>> +                            uint32_t desc)
>> +{
>> +    ARMVectorReg scratch;
>> +    intptr_t i, j;
>> +    intptr_t opr_sz = simd_oprsz(desc);
>> +    uint32_t *d = vd, *n = vn, *m = vm;
>> +    uint8_t *pg = vg;
>> +
>> +    if (d == n) {
>> +        n = memcpy(&scratch, n, opr_sz);
>> +        if (d == m) {
>> +            m = n;
>> +        }
>> +    } else if (d == m) {
>> +        m = memcpy(&scratch, m, opr_sz);
>> +    }
>> +
>> +    for (i = 0; i < opr_sz; i += 4) {
>> +        uint64_t count = 0;
>> +        uint8_t pred;
>> +
>> +        pred = pg[H1(i >> 3)] >> (i & 7);
>> +        if (pred & 1) {
>> +            uint32_t nn = n[H4(i >> 2)];
>> +
>> +            for (j = 0; j <= i; j += 4) {
>> +                pred = pg[H1(j >> 3)] >> (j & 7);
>> +                if ((pred & 1) && nn == m[H4(j >> 2)]) {
>> +                    ++count;
>> +                }
>> +            }
>> +        }
>> +        d[H4(i >> 2)] = count;
>> +    }
>> +}
>> +
>> +void HELPER(sve2_histcnt_d)(void *vd, void *vn, void *vm, void *vg,
>> +                            uint32_t desc)
>> +{
>> +    ARMVectorReg scratch;
>> +    intptr_t i, j;
>> +    intptr_t opr_sz = simd_oprsz(desc);
>> +    uint64_t *d = vd, *n = vn, *m = vm;
>> +    uint8_t *pg = vg;
>> +
>> +    if (d == n) {
>> +        n = memcpy(&scratch, n, opr_sz);
>> +        if (d == m) {
>> +            m = n;
>> +        }
>> +    } else if (d == m) {
>> +        m = memcpy(&scratch, m, opr_sz);
>> +    }
>> +
>> +    for (i = 0; i < opr_sz / 8; ++i) {
>> +        uint64_t count = 0;
>> +        if (pg[H1(i)] & 1) {
>> +            uint64_t nn = n[i];
>> +            for (j = 0; j <= i; ++j) {
>> +                if ((pg[H1(j)] & 1) && nn == m[j]) {
>> +                    ++count;
>> +                }
>> +            }
>> +        }
>> +        d[i] = count;
>> +    }
>> +}
>> +
>> +/*
>> + * Returns the number of bytes in m0 and m1 that match n.
>> + * See comment for do_match2().
>> + * */
>> +static inline uint64_t do_histseg_cnt(uint8_t n, uint64_t m0, uint64_t m1)
>> +{
>> +    int esz = MO_8;
>> +    int bits = 8 << esz;
>> +    uint64_t ones = dup_const(esz, 1);
>> +    uint64_t signs = ones << (bits - 1);
>> +    uint64_t cmp0, cmp1;
>> +
>> +    cmp1 = dup_const(esz, n);
>> +    cmp0 = cmp1 ^ m0;
>> +    cmp1 = cmp1 ^ m1;
>> +    cmp0 = (cmp0 - ones) & ~cmp0 & signs;
>> +    cmp1 = (cmp1 - ones) & ~cmp1 & signs;
>> +
> Hi Richard,
> 
> Although we can detect zero byte with this method, we can't use it to count the
> zero bytes.
> 
> For example,
> IF
>     cmp1 =  0x0100010001000100 , ones = 0x101010101010101, signs =
> 0x8080808080808080,
> THEN
>     cmp1 = (cmp1 - ones) & ~cmp1 & signs = 0x8080808080808080
> So
>     cmp1 will have 6 zeros by this method. In fact, cmp1 only have 4 zeros
> instead of 6 zeros.
> 
> I don't  find  a "bit twiddling" way,  if you find it, please let me know.

Thanks for noticing the error.  We already have a bit twiddling example in qemu
for this in target/alpha:

uint64_t helper_cmpbe0(uint64_t a)
{
    uint64_t m = 0x7f7f7f7f7f7f7f7fULL;
    uint64_t c = ~(((a & m) + m) | a | m);
    ...

which produces the exact results that we need here.


r~
diff mbox series

Patch

diff --git a/target/arm/helper-sve.h b/target/arm/helper-sve.h
index 9e8641e1c0..34bbb767ef 100644
--- a/target/arm/helper-sve.h
+++ b/target/arm/helper-sve.h
@@ -2551,6 +2551,13 @@  DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_b, TCG_CALL_NO_RWG,
 DEF_HELPER_FLAGS_5(sve2_nmatch_ppzz_h, TCG_CALL_NO_RWG,
                    i32, ptr, ptr, ptr, ptr, i32)
 
+DEF_HELPER_FLAGS_5(sve2_histcnt_s, TCG_CALL_NO_RWG,
+                   void, ptr, ptr, ptr, ptr, i32)
+DEF_HELPER_FLAGS_5(sve2_histcnt_d, TCG_CALL_NO_RWG,
+                   void, ptr, ptr, ptr, ptr, i32)
+
+DEF_HELPER_FLAGS_4(sve2_histseg, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
+
 DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_h, TCG_CALL_NO_RWG,
                    void, ptr, ptr, ptr, ptr, ptr, i32)
 DEF_HELPER_FLAGS_6(sve2_faddp_zpzz_s, TCG_CALL_NO_RWG,
diff --git a/target/arm/sve.decode b/target/arm/sve.decode
index 3121eabbf8..0edb72d4fb 100644
--- a/target/arm/sve.decode
+++ b/target/arm/sve.decode
@@ -146,6 +146,7 @@ 
                 &rprrr_esz rn=%reg_movprfx
 @rdn_pg_rm_ra   ........ esz:2 . ra:5  ... pg:3 rm:5 rd:5 \
                 &rprrr_esz rn=%reg_movprfx
+@rd_pg_rn_rm   ........ esz:2 . rm:5 ... pg:3 rn:5 rd:5       &rprr_esz
 
 # One register operand, with governing predicate, vector element size
 @rd_pg_rn       ........ esz:2 ... ... ... pg:3 rn:5 rd:5       &rpr_esz
@@ -1336,6 +1337,11 @@  RSUBHNT         01000101 .. 1 ..... 011 111 ..... .....  @rd_rn_rm
 MATCH           01000101 .. 1 ..... 100 ... ..... 0 .... @pd_pg_rn_rm
 NMATCH          01000101 .. 1 ..... 100 ... ..... 1 .... @pd_pg_rn_rm
 
+### SVE2 Histogram Computation
+
+HISTCNT         01000101 .. 1 ..... 110 ... ..... .....  @rd_pg_rn_rm
+HISTSEG         01000101 .. 1 ..... 101 000 ..... .....  @rd_rn_rm
+
 ## SVE2 floating-point pairwise operations
 
 FADDP           01100100 .. 010 00 0 100 ... ..... ..... @rdn_pg_rm
diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
index 19fbf94189..fa4848bc5c 100644
--- a/target/arm/sve_helper.c
+++ b/target/arm/sve_helper.c
@@ -7095,3 +7095,127 @@  DO_PPZZ_MATCH(sve2_nmatch_ppzz_b, MO_8, true)
 DO_PPZZ_MATCH(sve2_nmatch_ppzz_h, MO_16, true)
 
 #undef DO_PPZZ_MATCH
+
+void HELPER(sve2_histcnt_s)(void *vd, void *vn, void *vm, void *vg,
+                            uint32_t desc)
+{
+    ARMVectorReg scratch;
+    intptr_t i, j;
+    intptr_t opr_sz = simd_oprsz(desc);
+    uint32_t *d = vd, *n = vn, *m = vm;
+    uint8_t *pg = vg;
+
+    if (d == n) {
+        n = memcpy(&scratch, n, opr_sz);
+        if (d == m) {
+            m = n;
+        }
+    } else if (d == m) {
+        m = memcpy(&scratch, m, opr_sz);
+    }
+
+    for (i = 0; i < opr_sz; i += 4) {
+        uint64_t count = 0;
+        uint8_t pred;
+
+        pred = pg[H1(i >> 3)] >> (i & 7);
+        if (pred & 1) {
+            uint32_t nn = n[H4(i >> 2)];
+
+            for (j = 0; j <= i; j += 4) {
+                pred = pg[H1(j >> 3)] >> (j & 7);
+                if ((pred & 1) && nn == m[H4(j >> 2)]) {
+                    ++count;
+                }
+            }
+        }
+        d[H4(i >> 2)] = count;
+    }
+}
+
+void HELPER(sve2_histcnt_d)(void *vd, void *vn, void *vm, void *vg,
+                            uint32_t desc)
+{
+    ARMVectorReg scratch;
+    intptr_t i, j;
+    intptr_t opr_sz = simd_oprsz(desc);
+    uint64_t *d = vd, *n = vn, *m = vm;
+    uint8_t *pg = vg;
+
+    if (d == n) {
+        n = memcpy(&scratch, n, opr_sz);
+        if (d == m) {
+            m = n;
+        }
+    } else if (d == m) {
+        m = memcpy(&scratch, m, opr_sz);
+    }
+
+    for (i = 0; i < opr_sz / 8; ++i) {
+        uint64_t count = 0;
+        if (pg[H1(i)] & 1) {
+            uint64_t nn = n[i];
+            for (j = 0; j <= i; ++j) {
+                if ((pg[H1(j)] & 1) && nn == m[j]) {
+                    ++count;
+                }
+            }
+        }
+        d[i] = count;
+    }
+}
+
+/*
+ * Returns the number of bytes in m0 and m1 that match n.
+ * See comment for do_match2().
+ * */
+static inline uint64_t do_histseg_cnt(uint8_t n, uint64_t m0, uint64_t m1)
+{
+    int esz = MO_8;
+    int bits = 8 << esz;
+    uint64_t ones = dup_const(esz, 1);
+    uint64_t signs = ones << (bits - 1);
+    uint64_t cmp0, cmp1;
+
+    cmp1 = dup_const(esz, n);
+    cmp0 = cmp1 ^ m0;
+    cmp1 = cmp1 ^ m1;
+    cmp0 = (cmp0 - ones) & ~cmp0 & signs;
+    cmp1 = (cmp1 - ones) & ~cmp1 & signs;
+
+    /*
+     * Combine the two compares in a way that the bits do
+     * not overlap, and so preserves the count of set bits.
+     * If the host has an efficient instruction for ctpop,
+     * then ctpop(x) + ctpop(y) has the same number of
+     * operations as ctpop(x | (y >> 1)).  If the host does
+     * not have an efficient ctpop, then we only want to
+     * use it once.
+     */
+    return ctpop64(cmp0 | (cmp1 >> 1));
+}
+
+void HELPER(sve2_histseg)(void *vd, void *vn, void *vm, uint32_t desc)
+{
+    intptr_t i, j;
+    intptr_t opr_sz = simd_oprsz(desc);
+
+    for (i = 0; i < opr_sz; i += 16) {
+        uint64_t n0 = *(uint64_t *)(vn + i);
+        uint64_t m0 = *(uint64_t *)(vm + i);
+        uint64_t n1 = *(uint64_t *)(vn + i + 8);
+        uint64_t m1 = *(uint64_t *)(vm + i + 8);
+        uint64_t out0 = 0;
+        uint64_t out1 = 0;
+
+        for (j = 0; j < 64; j += 8) {
+            uint64_t cnt0 = do_histseg_cnt(n0 >> j, m0, m1);
+            uint64_t cnt1 = do_histseg_cnt(n1 >> j, m0, m1);
+            out0 |= cnt0 << j;
+            out1 |= cnt1 << j;
+        }
+
+        *(uint64_t *)(vd + i) = out0;
+        *(uint64_t *)(vd + i + 8) = out1;
+    }
+}
diff --git a/target/arm/translate-sve.c b/target/arm/translate-sve.c
index e947a0ff25..4e792c9b9a 100644
--- a/target/arm/translate-sve.c
+++ b/target/arm/translate-sve.c
@@ -7509,6 +7509,25 @@  static bool trans_##NAME(DisasContext *s, arg_rprr_esz *a)                  \
 DO_SVE2_PPZZ_MATCH(MATCH, match)
 DO_SVE2_PPZZ_MATCH(NMATCH, nmatch)
 
+static bool trans_HISTCNT(DisasContext *s, arg_rprr_esz *a)
+{
+    static gen_helper_gvec_4 * const fns[2] = {
+        gen_helper_sve2_histcnt_s, gen_helper_sve2_histcnt_d
+    };
+    if (a->esz < 2) {
+        return false;
+    }
+    return do_sve2_zpzz_ool(s, a, fns[a->esz - 2]);
+}
+
+static bool trans_HISTSEG(DisasContext *s, arg_rrr_esz *a)
+{
+    if (a->esz != 0) {
+        return false;
+    }
+    return do_sve2_zzz_ool(s, a, gen_helper_sve2_histseg);
+}
+
 static bool do_sve2_zpzz_fp(DisasContext *s, arg_rprr_esz *a,
                             gen_helper_gvec_4_ptr *fn)
 {