Don't compile subroutine threaded docol if the word is never called.

Author: Molorius

pkg/forth/flag.go

@@ -24,4 +24,6 @@ type Flag struct {
 	// not dependent on current state.
 	isPure          bool
 	usesReturnStack bool // This primitive word uses the return stack.
+
+	calls int // The number of times that this is called, not including tail calls.
 }

pkg/forth/ulpBuild.go

@@ -171,6 +171,8 @@ func (u *Ulp) buildAssemblyHelper(vm *VirtualMachine, header string) (string, er
 	if err != nil {
 		return "", err
 	}
+	// count the number of calls
+	u.countCalls()
 	// create the different assemblies
 	asm, err := u.buildAssemblyWords()
 	if err != nil {
@@ -327,6 +329,32 @@ func (u *Ulp) replaceOtherChars(str string) string {
 	return sb.String()
 }
 
+// Count the number of times that each word is called,
+// not including tail calls.
+func (u *Ulp) countCalls() {
+	u.resetCalls()
+	for _, w := range u.forthWords {
+		for _, c := range w.Cells {
+			switch cell := c.(type) {
+			case CellAddress:
+				cell.Entry.Flag.calls += 1
+			}
+		}
+	}
+}
+
+// Reset the number of times that each word is called.
+func (u *Ulp) resetCalls() {
+	for _, w := range u.forthWords {
+		for _, c := range w.Cells {
+			switch cell := c.(type) {
+			case CellAddress:
+				cell.Entry.Flag.calls = 0
+			}
+		}
+	}
+}
+
 func (u *Ulp) buildInterpreter() string {
 	i := []string{
 		// required data, will be placed at the start of .data
@@ -342,8 +370,8 @@ func (u *Ulp) buildInterpreter() string {
 		"HOST_FUNC:   .int 0",
 		"HOST_PARAM0: .int 0",
 		".data",
-		"__ip:  .int __forth_VM.INIT", // instruction pointer starts at word VM.INIT
-		"__rsp: .int __stack_start",   // return stack pointer starts at the beginning of the stack section
+		"__ip:  .int __body__forth_VM.INIT", // instruction pointer starts at word VM.INIT
+		"__rsp: .int __stack_start",         // return stack pointer starts at the beginning of the stack section
 
 		// boot labels
 		".boot",

pkg/forth/word.go

@@ -132,7 +132,7 @@ func (w *WordForth) BuildAssembly(u *Ulp) (string, error) {
 		}
 	} else { // executable forth word
 		if u.compileTarget == UlpCompileTargetSubroutine {
-			if w.Entry.Name != "VM.INIT" { // the init word shouldn't docol
+			if w.Entry.Flag.calls != 0 { // if this word is directly called
 				output = append(output, "jump __docol")
 			}
 		}