Re: [Qemu-devel] [PATCH v3 03/32] s390x/tcg: Utilities for vector instruction helpers

[Thomas Huth <thuth@redhat.com>]

On 07/03/2019 13.15, David Hildenbrand wrote:
> We'll have to read/write vector elements quite frequently from helpers.
> The tricky bit is properly taking care of endianess. Handle it similar
> to aarch64.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/vec.h | 101 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 101 insertions(+)
>  create mode 100644 target/s390x/vec.h
> 
> diff --git a/target/s390x/vec.h b/target/s390x/vec.h
> new file mode 100644
> index 0000000000..3313fb43ee
> --- /dev/null
> +++ b/target/s390x/vec.h
> @@ -0,0 +1,101 @@
> +/*
> + * QEMU TCG support -- s390x vector utilitites
> + *
> + * Copyright (C) 2019 Red Hat Inc
> + *
> + * Authors:
> + *   David Hildenbrand <david@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#ifndef S390X_VEC_H
> +#define S390X_VEC_H
> +
> +typedef union S390Vector {
> +    uint64_t doubleword[2];
> +    uint32_t word[4];
> +    uint16_t halfword[8];
> +    uint8_t byte[16];
> +} S390Vector;
> +
> +/*
> + * Each vector is stored as two 64bit host values. So when talking about
> + * byte/halfword/word numbers, we have to take care of proper translation
> + * between element numbers.
> + *
> + * Big Endian (target/possible host)
> + * B:  [ 0][ 1][ 2][ 3][ 4][ 5][ 6][ 7] - [ 8][ 9][10][11][12][13][14][15]
> + * HW: [     0][     1][     2][     3] - [     4][     5][     6][     7]
> + * W:  [             0][             1] - [             2][             3]
> + * DW: [                             0] - [                             1]
> + *
> + * Little Endian (possible host)
> + * B:  [ 7][ 6][ 5][ 4][ 3][ 2][ 1][ 0] - [15][14][13][12][11][10][ 9][ 8]
> + * HW: [     3][     2][     1][     0] - [     7][     6][     5][     4]
> + * W:  [             1][             0] - [             3][             2]
> + * DW: [                             0] - [                             1]
> + */
> +#ifndef HOST_WORDS_BIGENDIAN
> +#define H1(x)  ((x) ^ 7)
> +#define H2(x)  ((x) ^ 3)
> +#define H4(x)  ((x) ^ 1)
> +#else
> +#define H1(x)  (x)
> +#define H2(x)  (x)
> +#define H4(x)  (x)
> +#endif
> +
> +static inline uint8_t s390_vec_read_element8(const S390Vector *v, uint8_t enr)
> +{
> +    g_assert(enr < 16);
> +    return v->byte[H1(enr)];
> +}
> +
> +static inline uint16_t s390_vec_read_element16(const S390Vector *v, uint8_t enr)
> +{
> +    g_assert(enr < 8);
> +    return v->halfword[H2(enr)];
> +}
> +
> +static inline uint32_t s390_vec_read_element32(const S390Vector *v, uint8_t enr)
> +{
> +    g_assert(enr < 4);
> +    return v->word[H4(enr)];
> +}
> +
> +static inline uint64_t s390_vec_read_element64(const S390Vector *v, uint8_t enr)
> +{
> +    g_assert(enr < 2);
> +    return v->doubleword[enr];
> +}
> +
> +static inline void s390_vec_write_element8(S390Vector *v, uint8_t enr,
> +                                           uint8_t data)
> +{
> +    g_assert(enr < 16);
> +    v->byte[H1(enr)] = data;
> +}
> +
> +static inline void s390_vec_write_element16(S390Vector *v, uint8_t enr,
> +                                            uint16_t data)
> +{
> +    g_assert(enr < 8);
> +    v->halfword[H2(enr)] = data;
> +}
> +
> +static inline void s390_vec_write_element32(S390Vector *v, uint8_t enr,
> +                                            uint32_t data)
> +{
> +    g_assert(enr < 4);
> +    v->word[H4(enr)] = data;
> +}
> +
> +static inline void s390_vec_write_element64(S390Vector *v, uint8_t enr,
> +                                            uint64_t data)
> +{
> +    g_assert(enr < 2);
> +    v->doubleword[enr] = data;
> +}
> +
> +#endif /* S390X_VEC_H */
> 

Pretty brain-twisting, but it looks right to me.

Reviewed-by: Thomas Huth <thuth@redhat.com>