On 29 June 2018 at 01:15, Richard Henderson <richard.hender...@linaro.org> wrote: > We already check for the same condition within the normal integer > sdiv and sdiv64 helpers. Use a slightly different formation that > does not require deducing the expression type. > > Fixes: f97cfd596ed > Signed-off-by: Richard Henderson <richard.hender...@linaro.org> > --- > target/arm/sve_helper.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c > index 790cbacd14..7d7fc90566 100644 > --- a/target/arm/sve_helper.c > +++ b/target/arm/sve_helper.c > @@ -369,7 +369,13 @@ void HELPER(NAME)(void *vd, void *vn, void *vm, void > *vg, uint32_t desc) \ > #define DO_MIN(N, M) ((N) >= (M) ? (M) : (N)) > #define DO_ABD(N, M) ((N) >= (M) ? (N) - (M) : (M) - (N)) > #define DO_MUL(N, M) (N * M) > -#define DO_DIV(N, M) (M ? N / M : 0) > + > +/* The zero divisor case is architectural; the -1 divisor case works > + * around the x86 INT_MIN / -1 overflow exception without having to > + * deduce the minimum integer for the type of the expression. > + */
It works around INT_MIN / -1 being C undefined behaviour: the need to special-case this is not x86-specific... The required answer for Arm is just as architectural as the required answer for division-by-zero (which is also C UB). > +#define DO_SDIV(N, M) (unlikely(M == 0) ? 0 : unlikely(M == -1) ? -N : N / M) > +#define DO_UDIV(N, M) (unlikely(M == 0) ? 0 : N / M) > > DO_ZPZZ(sve_and_zpzz_b, uint8_t, H1, DO_AND) > DO_ZPZZ(sve_and_zpzz_h, uint16_t, H1_2, DO_AND) > @@ -477,11 +483,11 @@ DO_ZPZZ(sve_umulh_zpzz_h, uint16_t, H1_2, do_mulh_h) > DO_ZPZZ(sve_umulh_zpzz_s, uint32_t, H1_4, do_mulh_s) > DO_ZPZZ_D(sve_umulh_zpzz_d, uint64_t, do_umulh_d) > > -DO_ZPZZ(sve_sdiv_zpzz_s, int32_t, H1_4, DO_DIV) > -DO_ZPZZ_D(sve_sdiv_zpzz_d, int64_t, DO_DIV) > +DO_ZPZZ(sve_sdiv_zpzz_s, int32_t, H1_4, DO_SDIV) > +DO_ZPZZ_D(sve_sdiv_zpzz_d, int64_t, DO_SDIV) > > -DO_ZPZZ(sve_udiv_zpzz_s, uint32_t, H1_4, DO_DIV) > -DO_ZPZZ_D(sve_udiv_zpzz_d, uint64_t, DO_DIV) > +DO_ZPZZ(sve_udiv_zpzz_s, uint32_t, H1_4, DO_UDIV) > +DO_ZPZZ_D(sve_udiv_zpzz_d, uint64_t, DO_UDIV) > > /* Note that all bits of the shift are significant > and not modulo the element size. */ Other than quibbling about the comment, Reviewed-by: Peter Maydell <peter.mayd...@linaro.org> thanks -- PMM
