On 05/04/2016 17:41, Richard Henderson wrote:
>
>> +static inline
>> +uint32_t tb_hash_func(tb_page_addr_t phys_pc, target_ulong pc,
>> uint64_t flags)
>> {
>> - return (pc >> 2) & (CODE_GEN_PHYS_HASH_SIZE - 1);
>> + struct key {
>> + tb_page_addr_t phys_pc;
>> + target_ulong pc;
>> + uint64_t flags;
>
> The flags field should be uint32_t, not uint64_t.
> See its definition in TranslationBlock.
>
>> + } QEMU_PACKED k;
>> + unsigned int hash;
>> +
>> + k.phys_pc = phys_pc;
>> + k.pc = pc;
>> + k.flags = flags;
>> + hash = qemu_xxh32((uint32_t *)&k, sizeof(k) / sizeof(uint32_t), 1);
>
> I'm less than happy about putting data into a struct and hashing that
> memory. Why don't you just take the ideas from xxh32/xxh64 and perform
> the hash directly right here?
>
> In particular, you've 3 data elements here, a maximum of 5 32-bit words,
> thus the loop within xxh32 will never roll, so it's mostly dead code.
I think it's fine to use the struct. The exact size of the struct
varies from 3 to 5 32-bit words, so it's hard to write nice
size-dependent code for the hash.
Paolo
