Re: [PATCH for-10.1 08/10] target/arm: Don't nest H() macro calls in SVE DO_REDUCE

[Richard Henderson <richard.henderson@linaro.org>]

On 7/18/25 10:30, Peter Maydell wrote:
> In the part of the SVE DO_REDUCE macro used by the SVE2p1 FMAXQV,
> FMINQV, etc insns, we incorrectly applied the H() macro twice when
> calculating an offset to add to the vn pointer.  This has no effect
> on little-endian hosts but on big-endian hosts the two invocations
> will cancel each other out and we will access the wrong part of the
> array.
> 
> The "s * 16" part of the expression is already aligned, so we only
> need to use the H macro on the "e". Correct the macro usage.
> 
> Fixes: 1de7ecfc12d05 ("target/arm: Implement FADDQV, F{MIN, MAX}{NM}QV for SVE2p1")
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/arm/tcg/sve_helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/arm/tcg/sve_helper.c b/target/arm/tcg/sve_helper.c
> index 105cc5dd122..bf894f0bf13 100644
> --- a/target/arm/tcg/sve_helper.c
> +++ b/target/arm/tcg/sve_helper.c
> @@ -4509,7 +4509,7 @@ void helper_sve2p1_##NAME##qv_##SUF(void *vd, void *vn, void *vg,     \
>           TYPE data[ARM_MAX_VQ];                                        \
>           for (unsigned s = 0; s < segments; s++) {                     \
>               uint16_t pg = *(uint16_t *)(vg + H1_2(s * 2));            \
> -            TYPE nn = *(TYPE *)(vn + H(s * 16 + H(e)));               \
> +            TYPE nn = *(TYPE *)(vn + (s * 16 + H(e)));                \
>               data[s] = (pg >> e) & 1 ? nn : IDENT;                     \
>           }                                                             \
>           *(TYPE *)(vd + H(e)) = FUNC##_reduce(data, status, segments); \

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~