Add jumps support in do while loops

[RRozak]

Previously do while loops were parsed as normal while loops with a copy of body inserted before a loop. If there was break statement inside a body, the error was thrown: break isn't underneath a loop. Similar situation was with continue statement. So I created separate node for that kind of loop and I added converting it into while loop in V3LinkJump, when break and continue statements are handled.

Now I explain the change in addPrev implementation. Without it, the statement
whilep->addPrev(bodyp->cloneTree(false));
moved whilep node at the end of statements in a block.
Here is an example:

      while (1) begin
         do
            ++incr;
         while (incr < 9);
         incr++;
         break;

In the example, the inner while is put after postincrementation and break stataments.
Here is the AST (without the change, PREADD and POSTADD subtrees are shortened):

    1:2:3: JUMPBLOCK 0x555556d20000 <e122#> {c4ah}
    1:2:3:1: WHILE 0x555556d16370 <e120#> {c4ah}
    1:2:3:1:2: CONST 0x555556cc2300 <e66> {c4ao} @dt=0x555556cd61a0@(G/swu32/1)  ?32?sh1
    1:2:3:1:3: BEGIN 0x555556cee380 <e25> {c4ar} [UNNAMED]
    1:2:3:1:3:1: PREADD 0x555556d16630 <e116#> {c6an} @dt=0@
    1:2:3:1:3:1: POSTADD 0x555556d16210 <e62> {c8ao} @dt=0@
    1:2:3:1:3:1: JUMPGO 0x555556d20180 <e124#> {c9ak} -> JUMPLABEL 0x555556d200c0 <e119#> {c4ah} -> JUMPBLOCK 0x555556d20000 <e122#> {c4ah}
    1:2:3:1:3:1: WHILE 0x555556d16580 <e117#> {c5ak}
    1:2:3:1:3:1:2: LT 0x555556d160b0 <e110#> {c7aw} @dt=0x555556cd6820@(G/w1)
    1:2:3:1:3:1:2:1: VARREF 0x555556cd0360 <e80#> {c7ar} @dt=0@  incr [RV] <- VAR 0x555556cce180 <e16> {c3al} @dt=0@  incr [FUNC] [VAUTOM]  VAR
    1:2:3:1:3:1:2:2: CONST 0x555556cc2500 <e44> {c7ay} @dt=0x555556cd6750@(G/swu32/4)  ?32?sh9
    1:2:3:1:3:1:3: PREADD 0x555556d16000 <e108#> {c6an} @dt=0@
    1:2:3:2: JUMPLABEL 0x555556d200c0 <e119#> {c4ah} -> JUMPBLOCK 0x555556d20000 <e122#> {c4ah}

And the one after the change (correct one):

    1:2:3: JUMPBLOCK 0x555556d20000 <e122#> {c4ah}
    1:2:3:1: WHILE 0x555556d16370 <e120#> {c4ah}
    1:2:3:1:2: CONST 0x555556cc2300 <e66> {c4ao} @dt=0x555556cd61a0@(G/swu32/1)  ?32?sh1
    1:2:3:1:3: BEGIN 0x555556cee380 <e25> {c4ar} [UNNAMED]
    1:2:3:1:3:1: PREADD 0x555556d16630 <e116#> {c6an} @dt=0@
    1:2:3:1:3:1: WHILE 0x555556d16580 <e117#> {c5ak}
    1:2:3:1:3:1:2: LT 0x555556d160b0 <e110#> {c7aw} @dt=0x555556cd6820@(G/w1)
    1:2:3:1:3:1:2:1: VARREF 0x555556cd0360 <e80#> {c7ar} @dt=0@  incr [RV] <- VAR 0x555556cce180 <e16> {c3al} @dt=0@  incr [FUNC] [VAUTOM]  VAR
    1:2:3:1:3:1:2:2: CONST 0x555556cc2500 <e44> {c7ay} @dt=0x555556cd6750@(G/swu32/4)  ?32?sh9
    1:2:3:1:3:1:3: PREADD 0x555556d16000 <e108#> {c6an} @dt=0@
    1:2:3:1:3:1: POSTADD 0x555556d16210 <e62> {c8ao} @dt=0@
    1:2:3:1:3:1: JUMPGO 0x555556d20180 <e124#> {c9ak} -> JUMPLABEL 0x555556d200c0 <e119#> {c4ah} -> JUMPBLOCK 0x555556d20000 <e122#> {c4ah}
    1:2:3:2: JUMPLABEL 0x555556d200c0 <e119#> {c4ah} -> JUMPBLOCK 0x555556d20000 <e122#> {c4ah}

So old addPrev implementation breaks the order of other nodes, which sometimes may cause a different behavior.

[rkapuscik]

Looks OK, just one minor suggestion.

[RRozak]

Created PR to mainline: verilator#3731