RE: [PATCH] x86: rte_mov256 was missing for AVX2

[Morten Brørup]

> From: Thomas Monjalon [mailto:tho...@monjalon.net]
> Sent: Monday, 29 August 2022 12.56
> 
> 20/08/2022 12:30, Morten Brørup:
> > The rte_mov256 function was missing for AVX2.
> > Does nobody build test for AVX2 and check the compiler output?
> 
> Please could you specify the context/setup to reproduce the issue?
I stumbled upon it while working on the new non-temporal memcpy function.

Reproduction described below.

> 
> An error message would be nice to paste here as well.
> Thanks

The rte_memcpy declarations are in the lib/eal/generic/rte_memcpy.h header 
file, so add this declaration header file to the implementation file. (I wonder 
why it is not already there?)

lib/eal/x86/rte_memcpy.h:

  #include <rte_common.h>
  #include <rte_config.h>
  #include <rte_debug.h>
+ #include "generic/rte_memcpy.h"

  #ifdef __cplusplus
  extern "C" {
  #endif


The error messages from ninja look like this:

[46/2597] Compiling C object lib/acl/libavx2_tmp.a.p/acl_run_avx2.c.o
In file included from ../lib/eal/x86/include/rte_memcpy.h:24,
                 from ../lib/acl/rte_acl_osdep.h:40,
                 from ../lib/acl/rte_acl.h:14,
                 from ../lib/acl/acl_run.h:8,
                 from ../lib/acl/acl_run_sse.h:5,
                 from ../lib/acl/acl_run_avx2.h:5,
                 from ../lib/acl/acl_run_avx2.c:6:
../lib/eal/include/generic/rte_memcpy.h:89:1: warning: 'rte_mov256' declared 
'static' but never defined [-Wunused-function]
   89 | rte_mov256(uint8_t *dst, const uint8_t *src);
      | ^~~~~~~~~~
[52/2597] Compiling C object lib/acl/libavx512_tmp.a.p/acl_run_avx512.c.o
In file included from ../lib/eal/x86/include/rte_memcpy.h:24,
                 from ../lib/acl/rte_acl_osdep.h:40,
                 from ../lib/acl/rte_acl.h:14,
                 from ../lib/acl/acl_run.h:8,
                 from ../lib/acl/acl_run_sse.h:5,
                 from ../lib/acl/acl_run_avx512.c:5:
../lib/eal/include/generic/rte_memcpy.h:89:1: warning: 'rte_mov256' declared 
'static' but never defined [-Wunused-function]
   89 | rte_mov256(uint8_t *dst, const uint8_t *src);
      | ^~~~~~~~~~


At SmartShare Systems we follow a coding convention of including the 
declaration header file at the absolute top of the file implementing it. This 
reveals at build time if anything is missing in the declaration header file. 
The DPDK Project could do the same, and find bugs like this.

Here's an example:

foo.h:
------
// Declaration
static inline uint32_t bar(uint32_t x);

foo.c:
------
#include <foo.h> // <-- Note: At the absolute top!
#include <stdint.h>

// Implementation
static inline uint32_t bar(uint32_t x)
{
        return x * 2;
}

Following our coding convention will reveal that <stdint.h> is required for 
using <foo.h>, and thus should be included in foo.h (not in foo.c) - because 
someone else might include <foo.h>, and then <stdint.h> could be missing there.

-Morten