[DO NOT MERGE] Implement fast DFA's escape analysis

[rikkimax]

Escape analysis for the fast dfa engine based upon my previous DIP design work.

Two relationship strengths are implemented as well as an unknown state.
In outer cell of parameter @escape(var&) + via indirection @escape(var=)

No new attributes for users to use are implemented as that requires DIP.

There is a UDA recognized for specifically named test files, this does not affect the rest of the frontend. It is required for verifying inference.

Currently the engine is forced on for all code, except some specific test suite files, both of this will be disabled prior to merging. Have to verify what the CI as a whole does and that requires this behaviour. Same as previous PRs.

[rikkimax]

Ooo that is a fun little error, because in theory it should be true. But it requires assumptions in the AST.

src/dmd/glue/package.d(914): Error: Assert can be proven to be false
        assert(sthis);
               ^

[rikkimax]

I don't think this should be erroring:

src\core\internal\dassert.d(176): Error: Parameter is required to be scope but escapes
private string miniFormat(V)(const scope ref V v)
                                               ^
src\core\internal\dassert.d(521): Error: template instance `core.internal.dassert.miniFormat!(MonoTimeImpl!(ClockType.coarse))` error instantiating
    alias miniT = miniFormat!T;
                  ^

Ooo another fun one:

  compilable/test14781.d(13): Error: cannot rebind scope variables
              x = 1;      // accessing pure function context is just ok
                ^

I think that is because it's marking x as on stack.

[rikkimax]

Looks like the following code is not seeing the cell like it should.

                *(cast(void[]*)&ret) = _d_newarrayUTrace(__FILE__, __LINE__,
                __FUNCTION__, typeid(E[]), size);

It thinks that its a null deref on ret, which isn't correct.

[rikkimax]

For gcc iasm:

    scope tint32 = new TypeBasic(ASTCodegen.Tint32);
    tint32.merge();
    ASTCodegen.Type.tint32 = tint32;

Doesn't look right:

src/dmd/iasm/gcc.d(580): Error: Escape of unknown lifetime via global
    ASTCodegen.Type.tint32 = tint32;
                           ^
src/dmd/iasm/gcc.d(578):        Pointer stored in variable `tint32` has potentially escaped
    scope tint32 = new TypeBasic(ASTCodegen.Tint32);
          ^

Will need fixing.

That should be allowed due to it being @system but for some reason its not gated.

[rikkimax]

Aw after fixing bugs I've lost Ocean's null deref report that I was quite proud of.

Oh well, at least it was 0 + 0.

I don't think I can bring it back there is a rather large comment at this point showing why it can't be.

[rikkimax]

It looks like I may need to rebase.

compilable\dtoh_ignored.d is erroring out:

..\test\compilable\dtoh_ignored.d(103): Error: internal compiler error: type `ifloat` cannot be mapped to C++

    ifloat onReturn()
           ^

But only after I fix a segfault in dmd.mangle.cppwin:

    extern (D) this(VisualCPPMangler rvl) scope @safe
    {
        this.saved_idents[] = rvl.saved_idents[];
        this.saved_types[] = rvl.saved_types[];
        this.loc = rvl.loc;
        this.eSink = rvl.eSink;
    }

Missing eSink assignment.

I haven't figured out what commit I'm missing because clearly something is different between the two branches allowing this new untested pathway.