Re: [PATCH v2 02/13] target/arm: Fix SQDMULH (by element) with Q=0

[Michael Tokarev]

25.06.2024 21:35, Richard Henderson wrote:
> The inner loop, bounded by eltspersegment, must not be
> larger than the outer loop, bounded by elements.
>
> Cc: qemu-stable@nongnu.org
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/arm/tcg/vec_helper.c | 24 ++++++++++++++++--------
>   1 file changed, 16 insertions(+), 8 deletions(-)

If my understanding is correct, this one

Fixes: f80701cb44d3 ("target/arm: Convert SQDMULH, SQRDMULH to decodetree")

and before this commit, there was no issue.

Is my understanding correct?

Thanks,

/mjt

> diff --git a/target/arm/tcg/vec_helper.c b/target/arm/tcg/vec_helper.c
> index 7b34cc98af..d477479bb1 100644
> --- a/target/arm/tcg/vec_helper.c
> +++ b/target/arm/tcg/vec_helper.c
> @@ -317,10 +317,12 @@ void HELPER(neon_sqdmulh_idx_h)(void *vd, void *vn, void 
> *vm,
>       intptr_t i, j, opr_sz = simd_oprsz(desc);
>       int idx = simd_data(desc);
>       int16_t *d = vd, *n = vn, *m = (int16_t *)vm + H2(idx);
> +    intptr_t elements = opr_sz / 2;
> +    intptr_t eltspersegment = MIN(16 / 2, elements);
>   
> -    for (i = 0; i < opr_sz / 2; i += 16 / 2) {
> +    for (i = 0; i < elements; i += 16 / 2) {
>           int16_t mm = m[i];
> -        for (j = 0; j < 16 / 2; ++j) {
> +        for (j = 0; j < eltspersegment; ++j) {
>               d[i + j] = do_sqrdmlah_h(n[i + j], mm, 0, false, false, vq);
>           }
>       }
> @@ -333,10 +335,12 @@ void HELPER(neon_sqrdmulh_idx_h)(void *vd, void *vn, void 
> *vm,
>       intptr_t i, j, opr_sz = simd_oprsz(desc);
>       int idx = simd_data(desc);
>       int16_t *d = vd, *n = vn, *m = (int16_t *)vm + H2(idx);
> +    intptr_t elements = opr_sz / 2;
> +    intptr_t eltspersegment = MIN(16 / 2, elements);
>   
> -    for (i = 0; i < opr_sz / 2; i += 16 / 2) {
> +    for (i = 0; i < elements; i += 16 / 2) {
>           int16_t mm = m[i];
> -        for (j = 0; j < 16 / 2; ++j) {
> +        for (j = 0; j < eltspersegment; ++j) {
>               d[i + j] = do_sqrdmlah_h(n[i + j], mm, 0, false, true, vq);
>           }
>       }
> @@ -512,10 +516,12 @@ void HELPER(neon_sqdmulh_idx_s)(void *vd, void *vn, void 
> *vm,
>       intptr_t i, j, opr_sz = simd_oprsz(desc);
>       int idx = simd_data(desc);
>       int32_t *d = vd, *n = vn, *m = (int32_t *)vm + H4(idx);
> +    intptr_t elements = opr_sz / 4;
> +    intptr_t eltspersegment = MIN(16 / 4, elements);
>   
> -    for (i = 0; i < opr_sz / 4; i += 16 / 4) {
> +    for (i = 0; i < elements; i += 16 / 4) {
>           int32_t mm = m[i];
> -        for (j = 0; j < 16 / 4; ++j) {
> +        for (j = 0; j < eltspersegment; ++j) {
>               d[i + j] = do_sqrdmlah_s(n[i + j], mm, 0, false, false, vq);
>           }
>       }
> @@ -528,10 +534,12 @@ void HELPER(neon_sqrdmulh_idx_s)(void *vd, void *vn, void 
> *vm,
>       intptr_t i, j, opr_sz = simd_oprsz(desc);
>       int idx = simd_data(desc);
>       int32_t *d = vd, *n = vn, *m = (int32_t *)vm + H4(idx);
> +    intptr_t elements = opr_sz / 4;
> +    intptr_t eltspersegment = MIN(16 / 4, elements);
>   
> -    for (i = 0; i < opr_sz / 4; i += 16 / 4) {
> +    for (i = 0; i < elements; i += 16 / 4) {
>           int32_t mm = m[i];
> -        for (j = 0; j < 16 / 4; ++j) {
> +        for (j = 0; j < eltspersegment; ++j) {
>               d[i + j] = do_sqrdmlah_s(n[i + j], mm, 0, false, true, vq);
>           }
>       }

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