remove low-level subroutines

passes/lang0.md

@@ -59,7 +59,7 @@ cont_name ::= <int>
 
 goto ::= (Continue <cont_name>)
 err_goto ::= (Unwind)
-          |  (List (Continue <cont_name>)* (Unwind)?)
+          |  (Continue <cont_name>)
 
 choice ::= (Choice <intVal> <goto>)
         |  (Choice <floatVal> <goto>)
@@ -91,7 +91,6 @@ stmt ::= (Asgn <local> <value>)
 
 continuation ::= (Continuation (Params) stack:<int> <stmt>* <exit>)
               |  (Continuation (Params <type_id>?)) # return continuation
-              |  (Subroutine (Params) stack:<int> <stmt>* <exit>)
               |  (Except <local> stack:<int> <stmt>* <exit>)
 
 procdef ::= (ProcDef <type_id> (Locals <type_id>*) (Continuations <continuation>+))

passes/lang1.md

@@ -27,11 +27,9 @@ Each continuation names the locals alive for the duration of it:
 
 ```grammar
 continuation -= (Continuation (Params) stack:<int> <stmt>* <exit>)
-              | (Subroutine (Params) stack:<int> <stmt>* <exit>)
               | (Except <local> stack:<int> <stmt>* <exit>)
 
 continuation += (Continuation (Params) (Locals <local>*) <stmt>* <exit>)
-              | (Subroutine (Params) (Locals <local>*) <stmt>* <exit>)
               | (Except <local> (Locals <local>*) <stmt>* <exit>)
 ```
 

passes/pass0.nim

@@ -21,8 +21,7 @@ type
     code: seq[Instr]
     locals: seq[ValueType]
     constants: seq[TypedValue]
-    ehCode: seq[EhInstr]
-    ehTable: seq[HandlerTableEntry]
+    ehTable: seq[EhMapping]
 
     # per-procedure temporary state:
     current: int
@@ -47,8 +46,7 @@ type
     ## needed for the procedure.
     code: seq[Instr]
     locals: seq[ValueType]
-    ehTable: seq[HandlerTableEntry]
-    ehCode: seq[EhInstr]
+    ehTable: seq[EhMapping]
     constants: seq[TypedValue]
 
 # shorten some common parameter definitions:
@@ -430,25 +428,14 @@ proc genChoice(c; tree; typ: Type0, val, choice: NodeIndex) =
     c.join(x)
 
 proc genEh(c; tree; exit: NodeIndex) =
-  ## Generates the EH code for the `exit` and registers an EH mapping entry.
+  ## Registers an EH table entry corresponding to `exit`, if necessary.
   case tree[exit].kind
   of Unwind:
     discard "attach nothing"
-  of List:
+  of Continue:
     # register an EH mapping:
-    c.ehTable.add (c.code.high.uint32, c.ehCode.len.uint32)
-
-    let L = tree.len(exit)
-    for i, it in tree.pairs(exit):
-      case tree[it].kind
-      of Continue:
-        c.ehCode.add ((if i == L-1: ehoExcept else: ehoSubroutine), 0'u16)
-        # the jump destination is filled in later:
-        c.ehPatch.add (tree[it, 0].imm.int, c.ehCode.high)
-      of Unwind:
-        c.ehCode.add (ehoEnd, 0'u16)
-      else:
-        unreachable()
+    c.ehTable.add (c.code.high.uint32, 0'u32) # patched later
+    c.ehPatch.add (tree[exit, 0].imm.int, c.ehTable.high)
   else:
     unreachable()
 
@@ -457,8 +444,6 @@ proc genExit(c; tree; exit: NodeIndex) =
   case tree[exit].kind
   of Continue:
     case tree.len(exit)
-    of 0:
-      c.instr(opcEnd) # end the subroutine
     of 1:
       c.jump(opcJmp, tree[exit, 0].imm)
     of 2:
@@ -473,13 +458,6 @@ proc genExit(c; tree; exit: NodeIndex) =
     c.genExpr(tree, tree.child(exit, 0))
     c.instr(opcRaise)
     c.genEh(tree, tree.child(exit, 1))
-  of Enter:
-    c.jump(opcEnter, tree[exit, 0].imm)
-    c.jump(opcJmp, tree[exit, 1].imm)
-  of Leave:
-    # TODO: merge subsequent leaves into a single instruction
-    let target = c.prepareJump(tree[exit, 0].imm)
-    c.instr(opcLeave, target, int16 1)
   of SelectBool:
     let (sel, a, b) = triplet(tree, exit)
     c.genExpr(tree, sel)
@@ -518,10 +496,10 @@ proc start(c; idx: int) =
       inc i
 
   i = 0
-  # patch EH instructions:
+  # patch EH mappings:
   while i < c.ehPatch.len:
     if c.ehPatch[i][0] == idx:
-      c.ehCode[c.ehPatch[i][1]].a = c.code.len.uint16
+      c.ehTable[c.ehPatch[i][1]].dst = c.code.len.uint16
       c.ehPatch.del(i)
     else:
       inc i
@@ -582,8 +560,6 @@ proc gen(c; tree; n: NodeIndex) =
     c.instr(opcExcept)
     # assign the passed-along value to the provided local
     c.instr(opcPopLocal, tree[n, 0].id)
-  of Subroutine:
-    c.instr(opcBegin)
   of Continuation:
     discard "no special instruction needed"
   else:
@@ -642,8 +618,8 @@ proc translate(tree; types, def: NodeIndex): ProcResult =
         c.start(i)
         c.instr(opcRet)
 
-  result = ProcResult(code: c.code, locals: c.locals, ehCode: c.ehCode,
-                      ehTable: c.ehTable, constants: c.constants)
+  result = ProcResult(code: c.code, locals: c.locals, ehTable: c.ehTable,
+                      constants: c.constants)
 
 proc slice[T](old, with: seq[T]): Slice[uint32] =
   old.len.uint32 .. uint32(old.len + with.len - 1)
@@ -717,10 +693,5 @@ proc translate*(module: PackedTree[NodeKind], env: var VmEnv) =
     env.procs[i].locals = hoSlice(env.locals, prc.locals)
     env.locals.add prc.locals
 
-    # patch the EH table:
-    for it in prc.ehTable.mitems:
-      it.offset += env.ehCode.len.uint32
-
     env.procs[i].eh = hoSlice(env.ehTable, prc.ehTable)
     env.ehTable.add prc.ehTable
-    env.ehCode.add prc.ehCode

passes/spec.nim

@@ -29,10 +29,10 @@ type
     Conv, Reinterp
 
     Continue, Loop, Enter, Leave, Raise, Unreachable, Select, SelectBool
-    CheckedCall, CheckedCallAsgn, Unwind, Choice, List
+    CheckedCall, CheckedCallAsgn, Unwind, Choice
 
     Module, TypeDefs, ProcDefs, ProcDef, Locals, Continuations, Continuation,
-    Subroutine, Except, Params, GlobalDefs, GlobalDef
+    Except, Params, GlobalDefs, GlobalDef
 
 template isAtom*(x: NodeKind): bool =
   ord(x) <= ord(Global)

tests/pass0/t04_except.expected

@@ -4,7 +4,7 @@
 .local lo0 int
   LdImmInt 10
   Raise
-.eh ((Except L2))
+.eh L2
 .label L2
   Except
   PopLocal lo0

tests/pass0/t04_except.test

@@ -11,7 +11,7 @@ discard """
     (Locals (Type 0))
     (Continuations
       (Continuation (Params) 0
-        (Raise (IntVal 10) (List (Continue 1)))
+        (Raise (IntVal 10) (Continue 1))
       )
       (Except (Local 0) 0
         (Continue 2 (Copy (Local 0)))