On 08/11/2014 09:23 AM, Tom Musta wrote:
> Fix the code to properly detect overflow; the 128 bit signed
> product must have all zeroes or all ones in the first 65 bits
> otherwise OV should be set.
>
> Signed-off-by: Tom Musta <tommu...@gmail.com>
> ---
> target-ppc/int_helper.c | 14 ++++++++++++--
> 1 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/target-ppc/int_helper.c b/target-ppc/int_helper.c
> index f6e8846..e83a25d 100644
> --- a/target-ppc/int_helper.c
> +++ b/target-ppc/int_helper.c
> @@ -32,12 +32,22 @@ uint64_t helper_mulldo(CPUPPCState *env, uint64_t arg1,
> uint64_t arg2)
> uint64_t tl;
>
> muls64(&tl, (uint64_t *)&th, arg1, arg2);
> - /* If th != 0 && th != -1, then we had an overflow */
> - if (likely((uint64_t)(th + 1) <= 1)) {
> +
> + /* th should either contain all 1 bits or all 0 bits and should
> + * match the sign bit of tl; otherwise we have overflowed. */
> +
> + if ((int64_t)tl < 0) {
> + if (likely(th == -1LL)) {
> + env->ov = 0;
> + } else {
> + env->so = env->ov = 1;
> + }
> + } else if (likely(th == 0LL)) {
> env->ov = 0;
> } else {
> env->so = env->ov = 1;
> }
> +
As far as it goes,
Reviewed-by: Richard Henderson <r...@twiddle.net>
But we can just as easily implement this inline, as we do for mullwo. We've
added a tcg_gen_muls2_i64 since this code was written.
r~
