Re: [RFC v2 2/5] cputlb: Replace switches in load/store_helper with callback

[David Hildenbrand <david@redhat.com>]

On 18.09.19 20:02, Richard Henderson wrote:
> Add a function parameter to perform the actual load/store to ram.
> With optimization, this results in identical code.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  accel/tcg/cputlb.c | 159 +++++++++++++++++++++++----------------------
>  1 file changed, 83 insertions(+), 76 deletions(-)

I would have guessed the compiler propagates the constant and eliminates
the switch completely for the variants. After all, we now have more LOC ...

I would have moved the actual read/write to a separate function
containing the switch statement instead.

But I am pretty sure you know what you're doing here :)

> 
> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index 2222b87764..b4a63d3928 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -1280,11 +1280,38 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
>  
>  typedef uint64_t FullLoadHelper(CPUArchState *env, target_ulong addr,
>                                  TCGMemOpIdx oi, uintptr_t retaddr);
> +typedef uint64_t LoadHelper(const void *);
> +
> +/* Wrap the unaligned load helpers to that they have a common signature.  */
> +static inline uint64_t wrap_ldub(const void *haddr)
> +{
> +    return ldub_p(haddr);

I wonder if you should just add proper type cast to all of the <
uint64_t accessors (e.g., here (uint8_t) ). Shouldn't hurt and makes
people wonder less how the conversion from the int these accessors
return to uint64_t will turn out.

But yeah, you're simply moving code here.

> +}
> +
> +static inline uint64_t wrap_lduw_be(const void *haddr)
> +{
> +    return lduw_be_p(haddr);
> +}
> +
> +static inline uint64_t wrap_lduw_le(const void *haddr)
> +{
> +    return lduw_le_p(haddr);
> +}
> +
> +static inline uint64_t wrap_ldul_be(const void *haddr)
> +{
> +    return (uint32_t)ldl_be_p(haddr);
> +}
> +
> +static inline uint64_t wrap_ldul_le(const void *haddr)
> +{
> +    return (uint32_t)ldl_le_p(haddr);
> +}

Looks sane to me!


-- 

Thanks,

David / dhildenb