On 7/23/20 7:47 PM, LIU Zhiwei wrote:
>
>
> On 2020/7/24 8:28, Richard Henderson wrote:
>> If a 32-bit input is not properly nanboxed, then the input is
>> replaced with the default qnan.
>>
>> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
>> ---
>> target/riscv/internals.h | 11 +++++++
>> target/riscv/fpu_helper.c | 64 ++++++++++++++++++++++++++++-----------
>> 2 files changed, 57 insertions(+), 18 deletions(-)
>>
>> diff --git a/target/riscv/internals.h b/target/riscv/internals.h
>> index 9f4ba7d617..f1a546dba6 100644
>> --- a/target/riscv/internals.h
>> +++ b/target/riscv/internals.h
>> @@ -43,4 +43,15 @@ static inline uint64_t nanbox_s(float32 f)
>> return f | MAKE_64BIT_MASK(32, 32);
>> }
>> +static inline float32 check_nanbox_s(uint64_t f)
>> +{
>> + uint64_t mask = MAKE_64BIT_MASK(32, 32);
>> +
>> + if (likely((f & mask) == mask)) {
>> + return (uint32_t)f;
>> + } else {
>> + return 0x7fc00000u; /* default qnan */
>> + }
>> +}
>> +
> If possible,
>
> +static inline float32 check_nanbox(uint64_t f, uint32_t flen)
> +{
> + uint64_t mask = MAKE_64BIT_MASK(flen, 64 - flen);
> +
> + if (likely((f & mask) == mask)) {
> + return (uint32_t)f;
> + } else {
> + return (flen == 32) ? 0x7fc00000u : 0x7e00u; /* default qnan */
> + }
> +}
The difficulty of choosing the proper default qnan is an example of why we
should *not* attempt to make this function fully general, but should instead
define separate functions for each type. E.g.
static inline float16 check_nanbox_h(uint64_t f);
static inline bfloat16 check_nanbox_b(uint64_t f);
r~
