[Bug middle-end/78918] missing -Wrestrict on memcpy copying over self

[dimhen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78918

--- Comment #7 from Dmitry G. Dyachenko <dimhen at gmail dot com> ---
I'm a bit confused:
-- warning about `static inline bar()' inlined into `foo()'
-- and no warning about `baz()'

What is the difference?
May be no warnings will be more consistent?

$ cat x.c
#include <string.h>
static inline void bar(void *d, void *s, unsigned N)
{
    if(s != d)
        memcpy(d, s, N);
}

void baz(void *d, void *s, unsigned N)
{
    if(s != d)
        memcpy(d, s, N);
}

void foo(void* src)
{
    bar(src, src, 1);
}

$ gcc -O2 -S -Wall -Wextra -Wpedantic -Wrestrict x.c
x.c: In function ‘foo’:
x.c:5:2: warning: ‘memcpy’ source argument is the same as destination
[-Wrestrict]
  memcpy(d, s, N);
  ^~~~~~~~~~~~~~~

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc_current/libexec/gcc/x86_64-pc-linux-gnu/8.0.0/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
Target: x86_64-pc-linux-gnu
Configured with: /home/dimhen/src/gcc_current/configure
--prefix=/usr/local/gcc_current --enable-checking=yes,df,fold,rtl,extra
--enable-languages=c,c++,lto --disable-multilib --enable-shared
--enable-threads=posix --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl
--enable-libmpx --enable-offload-targets=nvptx-none --without-cuda-driver
--enable-gnu-indirect-function --with-tune=native
Thread model: posix
gcc version 8.0.0 20171217 (experimental) [trunk revision 255759] (GCC) 

$ gcc -O2 -S -Wall -Wextra -Wpedantic -Wrestrict
-fdump-tree-optimized=/dev/stdout x.c
x.c: In function ‘foo’:
x.c:5:2: warning: ‘memcpy’ source argument is the same as destination
[-Wrestrict]
  memcpy(d, s, N);
  ^~~~~~~~~~~~~~~

;; Function baz (baz, funcdef_no=1, decl_uid=2076, cgraph_uid=1,
symbol_order=1)

baz (void * d, void * s, unsigned int N)
{
  long unsigned int _1;

  <bb 2> [local count: 1073741825]:
  if (s_3(D) != d_4(D))
    goto <bb 3>; [53.47%]
  else
    goto <bb 4>; [46.53%]

  <bb 3> [local count: 574129753]:
  _1 = (long unsigned int) N_6(D);
  memcpy (d_4(D), s_3(D), _1); [tail call]

  <bb 4> [local count: 1073741825]:
  return;

}



;; Function foo (foo, funcdef_no=2, decl_uid=2079, cgraph_uid=2,
symbol_order=2)

foo (void * src)
{
  <bb 2> [local count: 1073741825]:
  return;

}