Graph simplification generates invalid IR when block capture uses other value from same chain

[hansihe]

When a block capture is part of a chain, and the captured block uses any other value from the same chain, the graph simplification pass may generate invalid IR.

Invalid IR is caught by the graph validation pass.

This issue presents itself when compiling Elixir.Enum. It is high priority.

[hansihe]

This triggers when blocks are used in static value chains.

Workaround

In a case like this

-module(init).
-export([start/0]).
-import(erlang, [print/1]).
start() ->
    Name = <<"Paul">>,
    Callback = 
        fun(Greeting) ->
            print(Greeting),
            print(Name)
        end,
    greet(Callback).

greet(Greeter) -> 
    Greeter(<<"Hello">>).

Workaround:

• Make sure any values captured by a block becomes argument values (map through void_map)
• Insert a dummy function call after the values and before the function (void)

-module(init).
-export([start/0]).
-import(erlang, [print/1]).
start() ->
    Name = void_map(<<"Name">>),
    void(),
    Callback = 
        fun(Greeting) ->
            print(Greeting),
            print(Name)
        end,
    greet(Callback).

greet(Greeter) ->
    Greeter(<<"Hello">>).

void() -> ok.
void_map(A) -> A.

[hansihe]

This was fixed by the graph simplification pass rewrite.