--- a/toolkit/recordreplay/ProcessRedirect.cpp
+++ b/toolkit/recordreplay/ProcessRedirect.cpp
@@ -10,24 +10,33 @@
 #include "MiddlemanCall.h"
 #include "ipc/ChildInternal.h"
 #include "ipc/ParentInternal.h"
 #include "mozilla/Sprintf.h"
 
 #include <dlfcn.h>
 #include <string.h>
 
+#if defined(__clang__)
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wimplicit-fallthrough"
+#endif
+
 namespace {
 
 #include "udis86/udis86.c"
 #include "udis86/decode.c"
 #include "udis86/itab.c"
 
 }  // anonymous namespace
 
+#if defined(__clang__)
+#  pragma clang diagnostic pop
+#endif
+
 namespace mozilla {
 namespace recordreplay {
 
 ///////////////////////////////////////////////////////////////////////////////
 // Redirection Skeleton
 ///////////////////////////////////////////////////////////////////////////////
 
 static bool CallPreambleHook(PreambleFn aPreamble, size_t aCallId,

--- a/toolkit/recordreplay/udis86/decode.c
+++ b/toolkit/recordreplay/udis86/decode.c
@@ -643,22 +643,22 @@ decode_operand(struct ud           *u,
       break;
     case OP_MR:
       decode_modrm_rm(u, operand, REGCLASS_GPR, 
                       MODRM_MOD(modrm(u)) == 3 ? 
                         Mx_reg_size(size) : Mx_mem_size(size));
       break;
     case OP_F:
       u->br_far  = 1;
-      MOZ_FALLTHROUGH;
+      /* intended fall through */
     case OP_M:
       if (MODRM_MOD(modrm(u)) == 3) {
         UDERR(u, "expected modrm.mod != 3\n");
       }
-      MOZ_FALLTHROUGH;
+      /* intended fall through */
     case OP_E:
       decode_modrm_rm(u, operand, REGCLASS_GPR, size);
       break;
     case OP_G:
       decode_modrm_reg(u, operand, REGCLASS_GPR, size);
       break;
     case OP_sI:
     case OP_I:
@@ -667,28 +667,28 @@ decode_operand(struct ud           *u,
     case OP_I1:
       operand->type = UD_OP_CONST;
       operand->lval.udword = 1;
       break;
     case OP_N:
       if (MODRM_MOD(modrm(u)) != 3) {
         UDERR(u, "expected modrm.mod == 3\n");
       }
-      MOZ_FALLTHROUGH;
+      /* intended fall through */
     case OP_Q:
       decode_modrm_rm(u, operand, REGCLASS_MMX, size);
       break;
     case OP_P:
       decode_modrm_reg(u, operand, REGCLASS_MMX, size);
       break;
     case OP_U:
       if (MODRM_MOD(modrm(u)) != 3) {
         UDERR(u, "expected modrm.mod == 3\n");
       }
-      MOZ_FALLTHROUGH;
+      /* intended fall through */
     case OP_W:
       decode_modrm_rm(u, operand, REGCLASS_XMM, size);
       break;
     case OP_V:
       decode_modrm_reg(u, operand, REGCLASS_XMM, size);
       break;
     case OP_MU:
       decode_modrm_rm(u, operand, REGCLASS_XMM,