misc: Updates for gcc7.2 for x86

GCC 7.2 is much stricter than previous GCC versions. The following changes
are needed:

* There is now a warning if there is an implicit fallthrough between two
  case statments. C++17 adds the [[fallthrough]]; declaration. However,
  to support non C++17 standards (i.e., C++11), we use M5_FALLTHROUGH.
  M5_FALLTHROUGH checks for [[fallthrough]] compliant C++17 compiler and
  if that doesn't exist, it defaults to nothing (no older compilers
  generate warnings).
* The above resulted in a couple of bugs that were found. This is noted
  in the review request on gerrit.
* throw() for dynamic exception specification is deprecated
* There were a couple of new uninitialized variable warnings
* Can no longer perform bitwise operations on a bool.
* Must now include <functional> for std::function
* Compiler bug for void* lambda. Changed to auto as work around. See
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82878

Change-Id: I5d4c782a4e133fa4cdb119e35d9aff68c6e2958e
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/5802
Reviewed-by: Gabe Black <gabeblack@google.com>

1 files changed, 5 insertions, 39 deletions

diff --git a/ext/dnet/ip.h b/ext/dnet/ip.h
index 95b7718fb..d2f9ad1d8 100644
--- a/ext/dnet/ip.h
+++ b/ext/dnet/ip.h
@@ -428,47 +428,13 @@ inline int
 ip_cksum_add(const void *buf, size_t len, int cksum)
 {
         uint16_t *sp = (uint16_t *)buf;
-        int n, sn;
+        int sn;
 
         sn = len / 2;
-        n = (sn + 15) / 16;
-
-        /* XXX - unroll loop using Duff's device. */
-        switch (sn % 16) {
-        case 0:	do {
-                cksum += *sp++;
-        case 15:
-                cksum += *sp++;
-        case 14:
-                cksum += *sp++;
-        case 13:
-                cksum += *sp++;
-        case 12:
-                cksum += *sp++;
-        case 11:
-                cksum += *sp++;
-        case 10:
-                cksum += *sp++;
-        case 9:
-                cksum += *sp++;
-        case 8:
-                cksum += *sp++;
-        case 7:
-                cksum += *sp++;
-        case 6:
-                cksum += *sp++;
-        case 5:
-                cksum += *sp++;
-        case 4:
-                cksum += *sp++;
-        case 3:
-                cksum += *sp++;
-        case 2:
-                cksum += *sp++;
-        case 1:
-                cksum += *sp++;
-                } while (--n > 0);
-        }
+
+        do {
+            cksum += *sp++;
+        } while (--sn > 0);
         if (len & 1)
                 cksum += htons(*(u_char *)sp << 8);