Refactor interpreter slightly in preparation for resume-at-any-point

Previously things were hardcoded to only allow a single entry point to
the interpreter (since that is how the unwinder determines if the frame
is an interpreter frame).

Instead of having astInterpretFunction be the interpreter frame, make
execute() the frame.  Have to make it a static class function so we can
take its address.

src/codegen/ast_interpreter.cpp

@@ -61,12 +61,11 @@ class ASTInterpreter {
 public:
     typedef llvm::StringMap<Box*> SymMap;
 
-    ASTInterpreter(CompiledFunction* compiled_function, void* frame_addr);
-    ~ASTInterpreter();
+    ASTInterpreter(CompiledFunction* compiled_function);
 
     void initArguments(int nargs, BoxedClosure* closure, BoxedGenerator* generator, Box* arg1, Box* arg2, Box* arg3,
                        Box** args);
-    Value execute(CFGBlock* block = 0);
+    static Value execute(ASTInterpreter& interpreter, AST* start_at = NULL);
 
 private:
     Box* createFunction(AST* node, AST_arguments* args, const std::vector<AST_stmt*>& body);
@@ -117,7 +116,6 @@ private:
     Value visit_jump(AST_Jump* node);
     Value visit_langPrimitive(AST_LangPrimitive* node);
 
-    void* frame_addr;
     CompiledFunction* compiled_func;
     SourceInfo* source_info;
     ScopeInfo* scope_info;
@@ -136,18 +134,13 @@ public:
     const SymMap& getSymbolTable() { return sym_table; }
 };
 
+const void* interpreter_instr_addr = (void*)&ASTInterpreter::execute;
+
 static_assert(THREADING_USE_GIL, "have to make the interpreter map thread safe!");
 static std::unordered_map<void*, ASTInterpreter*> s_interpreterMap;
 
 Box* astInterpretFunction(CompiledFunction* cf, int nargs, Box* closure, Box* generator, Box* arg1, Box* arg2,
                           Box* arg3, Box** args) {
-    // The ASTInterpreter ctor registers this frame so that we can introspect it.
-    // Currently we have to do that even if we are about to immediately reopt
-    // and we won't actually end up interpreting anything.
-    // TODO don't make "astInterpretFunction() == interpreter-is-running"?
-    void* frame_addr = __builtin_frame_address(0);
-    ASTInterpreter interpreter(cf, frame_addr);
-
     if (unlikely(cf->times_called > REOPT_THRESHOLD)) {
         CompiledFunction* optimized = reoptCompiledFuncInternal(cf);
         if (closure && generator)
@@ -161,9 +154,10 @@ Box* astInterpretFunction(CompiledFunction* cf, int nargs, Box* closure, Box* ge
     }
 
     ++cf->times_called;
+    ASTInterpreter interpreter(cf);
 
     interpreter.initArguments(nargs, (BoxedClosure*)closure, (BoxedGenerator*)generator, arg1, arg2, arg3, args);
-    Value v = interpreter.execute();
+    Value v = ASTInterpreter::execute(interpreter);
 
     return v.o ? v.o : None;
 }
@@ -211,12 +205,10 @@ void gatherInterpreterRoots(GCVisitor* visitor) {
 }
 
 
-ASTInterpreter::ASTInterpreter(CompiledFunction* compiled_function, void* frame_addr)
-    : frame_addr(frame_addr), compiled_func(compiled_function), source_info(compiled_function->clfunc->source),
-      scope_info(0), next_block(0), current_block(0), current_inst(0), last_exception(0), passed_closure(0),
-      created_closure(0), generator(0), edgecount(0) {
-
-    s_interpreterMap[frame_addr] = this;
+ASTInterpreter::ASTInterpreter(CompiledFunction* compiled_function)
+    : compiled_func(compiled_function), source_info(compiled_function->clfunc->source), scope_info(0), next_block(0),
+      current_block(0), current_inst(0), last_exception(0), passed_closure(0), created_closure(0), generator(0),
+      edgecount(0) {
 
     CLFunction* f = compiled_function->clfunc;
     if (!source_info->cfg)
@@ -225,11 +217,6 @@ ASTInterpreter::ASTInterpreter(CompiledFunction* compiled_function, void* frame_
     scope_info = source_info->getScopeInfo();
 }
 
-ASTInterpreter::~ASTInterpreter() {
-    assert(s_interpreterMap[frame_addr] == this);
-    s_interpreterMap.erase(frame_addr);
-}
-
 void ASTInterpreter::initArguments(int nargs, BoxedClosure* _closure, BoxedGenerator* _generator, Box* arg1, Box* arg2,
                                    Box* arg3, Box** args) {
     passed_closure = _closure;
@@ -260,19 +247,37 @@ void ASTInterpreter::initArguments(int nargs, BoxedClosure* _closure, BoxedGener
     }
 }
 
-Value ASTInterpreter::execute(CFGBlock* block) {
-    if (!block)
-        block = source_info->cfg->getStartingBlock();
+namespace {
+class RegisterHelper {
+private:
+    void* frame_addr;
+
+public:
+    RegisterHelper(ASTInterpreter* interpreter, void* frame_addr) : frame_addr(frame_addr) {
+        s_interpreterMap[frame_addr] = interpreter;
+    }
+    ~RegisterHelper() {
+        assert(s_interpreterMap.count(frame_addr));
+        s_interpreterMap.erase(frame_addr);
+    }
+};
+}
+
+Value ASTInterpreter::execute(ASTInterpreter& interpreter, AST* start_at) {
+    assert(start_at == NULL);
+
+    void* frame_addr = __builtin_frame_address(0);
+    RegisterHelper frame_registerer(&interpreter, frame_addr);
 
     Value v;
-    next_block = block;
-    while (next_block) {
-        current_block = next_block;
-        next_block = 0;
-
-        for (AST_stmt* s : current_block->body) {
-            current_inst = s;
-            v = visit_stmt(s);
+    interpreter.next_block = interpreter.source_info->cfg->getStartingBlock();
+    while (interpreter.next_block) {
+        interpreter.current_block = interpreter.next_block;
+        interpreter.next_block = 0;
+
+        for (AST_stmt* s : interpreter.current_block->body) {
+            interpreter.current_inst = s;
+            v = interpreter.visit_stmt(s);
         }
     }
     return v;

src/codegen/ast_interpreter.h

@@ -21,12 +21,15 @@ namespace gc {
 class GCVisitor;
 }
 
+class AST;
 class Box;
 class BoxedDict;
 class BoxedModule;
 struct CompiledFunction;
 struct LineInfo;
 
+extern const void* interpreter_instr_addr;
+
 Box* astInterpretFunction(CompiledFunction* f, int nargs, Box* closure, Box* generator, Box* arg1, Box* arg2, Box* arg3,
                           Box** args);
 

src/codegen/unwinding.cpp

@@ -307,7 +307,7 @@ public:
             int code = unw_get_proc_info(&this->cursor, &pip);
             RELEASE_ASSERT(code == 0, "%d", code);
 
-            if (pip.start_ip == (intptr_t)astInterpretFunction) {
+            if (pip.start_ip == (intptr_t)interpreter_instr_addr) {
                 unw_word_t bp;
                 unw_get_reg(&this->cursor, UNW_TDEP_BP, &bp);