[Oberon] New Oberon to Lua Transpiler

[rochus.keller at bluewin.ch]

@ Luca Boasso:

Meanwhile I found some time to further analyze the generated IR and machine code using the -jdump option of LuaJIT. 

If you have this Lua code "increment(function(set,val) if set then x =  val else return x end end)" as in LuaDemo2 of my article then LuaJIT indeed finds the following trace into increment() and the thunk but then aborts because it cannot handle traces including the FNEW opcode as it seems:

---- TRACE 2 start 1/0 VarDemo1.lua:10
0001  ISF          0
0002  JMP      2 => 0005
0005  UGET     2   0      ; x
0006  RET1     2   2
0005  ADDVN    3   3   0  ; 1
0006  CALL     1   1   3
0000  . JFUNCF   3   1         ; VarDemo1.lua:10
0001  . ISF          0
0002  . JMP      2 => 0005
0003  . USETV    0   1      ; x
0004  . JMP      2 => 0007
0007  . RET0     0   1
0007  RET0     0   1
0014  FORL     3 => 0011
0011  MOV      7   1
0012  FNEW     8   3      ; VarDemo1.lua:10
---- TRACE 2 abort VarDemo1.lua:10 -- NYI: bytecode 49 ; FNEW

If I don't define the thunk inline but use a local variable for the thunk instead, full inlining works and the runtime is as fast as corresponding C code.

I therefore need to redesign my Lua code generator to no longer inline the thunk definitions and to even take the thunk declarations out of loops. To do that I likely need a separate optimization pass to rewrite the AST which is not feasible with my current, syntax directed approach. I will come back with results.

Best
R.