[RFC v3 5/5] eal: provide option to use compiler memcpy instead of RTE

[Morten Brørup]

> From: Mattias Rönnblom [mailto:mattias.ronnblom at ericsson.com]
> Sent: Sunday, 2 June 2024 14.39
> 
> Provide build option to have functions in <rte_memcpy.h> delegate to
> the standard compiler/libc memcpy(), instead of using the various
> custom DPDK, handcrafted, per-architecture rte_memcpy()
> implementations.
> 
> A new meson build option 'use_cc_memcpy' is added. By default,
> the compiler/libc memcpy() is used.
> 
> The performance benefits of the custom DPDK rte_memcpy()
> implementations have been diminishing with every compiler release, and
> with current toolchains the usage of a custom memcpy() implementation
> may even be a liability.
> 
> An additional benefit of this change is that compilers and static
> analysis tools have an easier time detecting incorrect usage of
> memcpy() (e.g., buffer overruns, or overlapping source and destination
> buffers).
> 
> This patch makes DPDK and DPDK applications using <rte_memcpy.h> use
> compiler/libc memcpy() by default, but leaves an option to stay on the
> custom DPDK implementations, would that prove beneficial for certain
> applications or architectures.
> 
> RFC v3:
>  o Fix missing #endif on loongarch.
>  o PPC and RISCV now implemented, meaning all architectures are
> supported.
>  o Unnecessary <rte_vect.h> include is removed from <rte_memcpy.h>.
> 
> RFC v2:
>  * Fix bug where rte_memcpy.h was not installed on x86.
>  * Made attempt to make Loongarch compile.
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> ---

We should keep pushing DPDK forward and cleaning up old cruft along the way.

The memcpy discussion has convinced me that:
1. This change is a good idea, and
2. Mainstream compilers are sufficiently mature to do it now.

So, for the series,
Acked-by: Morten Brørup <mb at smartsharesystems.com>

>  static inline void
>  rte_mov32(uint8_t *dst, const uint8_t *src);

While at it, would it be somehow beneficial to change these from uint8_t* to void* or char* (keeping const where relevant)?