[Felix-language] flx now with stupid inner functions!

[Erick Tryzelaar]

It's been quite some time since I last posted, but I've been pretty busy. I 
only wasted 2 days this time wandering down the depths of the felix type system 
and name binding... *shudder*. A couple nice things this time around. flxc now 
partially uses the language independent frontend for symbol lowering. None of 
the optimizations yet though. Also managed to get trivial non-closured inner 
functions working, as demonstrated here:

    :::felix
    type int = "%i32";
    typedef bool = 2;
    fun add : int*int -> int = "%add";
    fun eq : int*int -> bool = "%eq";
    fun lnot : bool -> bool = "%lnot";
    proc exit : int = "exit";
 
    fun foo (x:int) = {
      val y = x + 1;
      fun bar (x:int) = {
        if x == 1 do
          return y;
        else
          return 3;
        done;
      }
      return bar y;
    }
    
    exit $ foo 2;

This now generates this code:

    :::llvm
    declare void @exit(i32)
    
    define i32 @foo(i32 %x) {
    entry:
      %foo.y = alloca i32                             ; <i32*> [#uses=2]
      %foo.x = alloca i32                             ; <i32*> [#uses=2]
      store i32 %x, i32* %foo.x
      %0 = load i32* %foo.x                           ; <i32> [#uses=1]
      %1 = add i32 %0, 1                              ; <i32> [#uses=1]
      store i32 %1, i32* %foo.y
      %2 = load i32* %foo.y                           ; <i32> [#uses=1]
      %3 = call i32 @foo.bar(i32 %2)                  ; <i32> [#uses=1]
      ret i32 %3
    }
    
    define i32 @foo.bar(i32 %x) {
    entry:
      %foo.bar.x = alloca i32                         ; <i32*> [#uses=2]
      store i32 %x, i32* %foo.bar.x
      %0 = load i32* %foo.bar.x                       ; <i32> [#uses=1]
      %1 = icmp eq i32 %0, 1                          ; <i1> [#uses=1]
      %2 = icmp eq i1 %1, false                       ; <i1> [#uses=1]
      br i1 %2, label %_ifdoend_1, label %else
    
    _ifdoend_1:                                       ; preds = %entry
      ret i32 3
    
    else:                                             ; preds = %entry
      ret i32 2
    }
    
    define void @0() {
    entry:
      %0 = call i32 @foo(i32 2)                       ; <i32> [#uses=1]
      call void @exit(i32 %0)
      ret void
    }

And if you optimize it with `flxc -O 1 ...`, then you'll get:

    :::llvm
    declare void @exit(i32)
    
    define i32 @foo(i32 %x) {
    entry:
      %0 = add i32 %x, 1                              ; <i32> [#uses=1]
      %1 = call i32 @foo.bar(i32 %0)                  ; <i32> [#uses=1]
      ret i32 %1
    }
    
    define i32 @foo.bar(i32 %x) {
    entry:
      %0 = icmp eq i32 %x, 1                          ; <i1> [#uses=1]
      %retval = select i1 %0, i32 2, i32 3            ; <i32> [#uses=1]
      ret i32 %retval
    }
    
    define void @0() {
    entry:
      %0 = call i32 @foo(i32 2)                       ; <i32> [#uses=1]
      call void @exit(i32 %0)
      ret void
    }
    
Which looks surprisingly readable. You'll also notice that we're prepending the 
parent's name in the llvm symbol name, so it should hopefully help with 
debugging.

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