Fix GCC 7 -Wimplicit-fallthrough warnings.

src/lj_asm.c

@@ -1725,6 +1725,7 @@ static void asm_setup_regsp(ASMState *as)
     case IR_SNEW: case IR_XSNEW: case IR_NEWREF:
       if (REGARG_NUMGPR < 3 && as->evenspill < 3)
 	as->evenspill = 3;  /* lj_str_new and lj_tab_newkey need 3 args. */
+      /* fallthrough */
     case IR_TNEW: case IR_TDUP: case IR_CNEW: case IR_CNEWI: case IR_TOSTR:
       ir->prev = REGSP_HINT(RID_RET);
       if (inloop)
@@ -1750,7 +1751,7 @@ static void asm_setup_regsp(ASMState *as)
 #endif
 	continue;
       }
-      /* fallthrough for integer POW */
+      /* fallthrough */ /* for integer POW */
     case IR_DIV: case IR_MOD:
       if (!irt_isnum(ir->t)) {
 	ir->prev = REGSP_HINT(RID_RET);

src/lj_cparse.c

@@ -590,28 +590,34 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	k->id = k2.id > k3.id ? k2.id : k3.id;
 	continue;
       }
+      /* fallthrough */
     case 1:
       if (cp_opt(cp, CTOK_OROR)) {
 	cp_expr_sub(cp, &k2, 2); k->i32 = k->u32 || k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 2:
       if (cp_opt(cp, CTOK_ANDAND)) {
 	cp_expr_sub(cp, &k2, 3); k->i32 = k->u32 && k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 3:
       if (cp_opt(cp, '|')) {
 	cp_expr_sub(cp, &k2, 4); k->u32 = k->u32 | k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 4:
       if (cp_opt(cp, '^')) {
 	cp_expr_sub(cp, &k2, 5); k->u32 = k->u32 ^ k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 5:
       if (cp_opt(cp, '&')) {
 	cp_expr_sub(cp, &k2, 6); k->u32 = k->u32 & k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 6:
       if (cp_opt(cp, CTOK_EQ)) {
 	cp_expr_sub(cp, &k2, 7); k->i32 = k->u32 == k2.u32; k->id = CTID_INT32;
@@ -620,6 +626,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	cp_expr_sub(cp, &k2, 7); k->i32 = k->u32 != k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 7:
       if (cp_opt(cp, '<')) {
 	cp_expr_sub(cp, &k2, 8);
@@ -654,6 +661,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 8:
       if (cp_opt(cp, CTOK_SHL)) {
 	cp_expr_sub(cp, &k2, 9); k->u32 = k->u32 << k2.u32;
@@ -666,6 +674,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	  k->u32 = k->u32 >> k2.u32;
 	continue;
       }
+      /* fallthrough */
     case 9:
       if (cp_opt(cp, '+')) {
 	cp_expr_sub(cp, &k2, 10); k->u32 = k->u32 + k2.u32;
@@ -675,6 +684,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
       } else if (cp_opt(cp, '-')) {
 	cp_expr_sub(cp, &k2, 10); k->u32 = k->u32 - k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 10:
       if (cp_opt(cp, '*')) {
 	cp_expr_unary(cp, &k2); k->u32 = k->u32 * k2.u32; goto arith_result;

src/lj_err.c

@@ -153,6 +153,7 @@ static void *err_unwind(lua_State *L, void *stopcf, int errcode)
       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 	goto unwind_c;
 #endif
+      /* fallthrough */
     case FRAME_VARG:  /* Vararg frame. */
       frame = frame_prevd(frame);
       break;

src/lj_opt_sink.c

@@ -100,8 +100,8 @@ static void sink_mark_ins(jit_State *J)
 	   (LJ_32 && ir+1 < irlast && (ir+1)->o == IR_HIOP &&
 	    !sink_checkphi(J, ir, (ir+1)->op2))))
 	irt_setmark(ir->t);  /* Mark ineligible allocation. */
-      /* fallthrough */
 #endif
+      /* fallthrough */
     case IR_USTORE:
       irt_setmark(IR(ir->op2)->t);  /* Mark stored value. */
       break;

src/lj_parse.c

@@ -2696,7 +2696,8 @@ static int parse_stmt(LexState *ls)
       lj_lex_next(ls);
       parse_goto(ls);
       break;
-    }  /* else: fallthrough */
+    }
+    /* fallthrough */
   default:
     parse_call_assign(ls);
     break;

src/luajit.c

@@ -419,6 +419,7 @@ static int collectargs(char **argv, int *flags)
       break;
     case 'e':
       *flags |= FLAGS_EXEC;
+      /* fallthrough */
     case 'j':  /* LuaJIT extension */
     case 'l':
       *flags |= FLAGS_OPTION;