Add tracing of specializations/new methods

This adds a new API that allows code to register two callbacks to be informed of new
specializations/methods in the system:
- jl_register_tracer, which will call the passed callback on any newly added specialization
  of a lambda info that has the `traced` flag set.
- jl_register_newmeth_tracer, which will call the passed callback on any newly created method
  in the system.

Author: Keno

src/alloc.c

@@ -373,6 +373,7 @@ jl_lambda_info_t *jl_new_lambda_info(jl_value_t *ast, jl_svec_t *tvars, jl_svec_
     li->pure = 0;
     li->called = 0xff;
     li->needs_sparam_vals_ducttape = 2;
+    li->traced = 0;
     if (ast != NULL) {
         JL_GC_PUSH1(&li);
         jl_lambda_info_set_ast(li, ast);

src/dump.c

@@ -1475,6 +1475,7 @@ static jl_value_t *jl_deserialize_value_(ios_t *s, jl_value_t *vtag, jl_value_t
         jl_delayed_fptrs(li, func_llvm, cfunc_llvm);
         li->jlcall_api = func_llvm ? read_int8(s) : 0;
         li->needs_sparam_vals_ducttape = read_int8(s);
+        li->traced = 0;
         return (jl_value_t*)li;
     }
     else if (vtag == (jl_value_t*)jl_module_type) {

src/gf.c

@@ -465,6 +465,8 @@ static int is_kind(jl_value_t *v)
 static jl_value_t *ml_matches(jl_methlist_t *ml, jl_value_t *type,
                               jl_sym_t *name, int lim);
 
+extern void (*jl_linfo_tracer)(jl_lambda_info_t *tracee);
+
 static jl_lambda_info_t *cache_method(jl_methtable_t *mt, jl_tupletype_t *type,
                                       jl_lambda_info_t *method, jl_methlist_t *m,
                                       jl_svec_t *sparams)
@@ -839,6 +841,8 @@ static jl_lambda_info_t *cache_method(jl_methtable_t *mt, jl_tupletype_t *type,
     }
     JL_GC_POP();
     JL_UNLOCK(codegen);
+    if (method->traced)
+        jl_linfo_tracer(newmeth);
     return newmeth;
 }
 
@@ -2020,6 +2024,8 @@ JL_DLLEXPORT jl_function_t *jl_new_generic_function(jl_sym_t *name, jl_module_t
     return jl_new_generic_function_with_supertype(name, module, jl_function_type, 0);
 }
 
+
+extern void (*jl_newmeth_tracer)(jl_methlist_t *tracee);
 void jl_add_method_to_table(jl_methtable_t *mt, jl_tupletype_t *types, jl_lambda_info_t *meth,
                             jl_svec_t *tvars, int8_t isstaged)
 {
@@ -2035,7 +2041,9 @@ void jl_add_method_to_table(jl_methtable_t *mt, jl_tupletype_t *types, jl_lambda
         meth->unspecialized = NULL;
     }
     meth->name = n;
-    (void)jl_method_table_insert(mt, types, meth, tvars, isstaged);
+    jl_methlist_t *newmeth = jl_method_table_insert(mt, types, meth, tvars, isstaged);
+    if (jl_newmeth_tracer)
+        jl_newmeth_tracer(newmeth);
     JL_GC_POP();
 }
 

src/jlapi.c

@@ -308,6 +308,31 @@ JL_DLLEXPORT const char *jl_git_commit(void)
     return commit;
 }
 
+JL_DLLEXPORT void jl_trace_linfo(jl_lambda_info_t *li)
+{
+    assert(jl_is_lambda_info(li));
+    li->traced = 1;
+}
+
+JL_DLLEXPORT void jl_untrace_linfo(jl_lambda_info_t *li)
+{
+    assert(jl_is_lambda_info(li));
+    li->traced = 0;
+}
+
+void (*jl_linfo_tracer)(jl_lambda_info_t *tracee) = 0;
+JL_DLLEXPORT void jl_register_tracer(void (*callback)(jl_lambda_info_t *tracee))
+{
+    jl_linfo_tracer = callback;
+}
+
+void (*jl_newmeth_tracer)(jl_methlist_t *tracee) = 0;
+JL_DLLEXPORT void jl_register_newmeth_tracer(void (*callback)(jl_methlist_t *tracee))
+{
+    jl_newmeth_tracer = callback;
+}
+
+
 // Create function versions of some useful macros
 JL_DLLEXPORT jl_taggedvalue_t *(jl_astaggedvalue)(jl_value_t *v)
 {

src/julia.h

@@ -210,6 +210,9 @@ typedef struct _jl_lambda_info_t {
     // and so unspecialized will be created for each linfo instead of once in linfo->def.
     // 0 = no, 1 = yes, 2 = not yet known
     uint8_t needs_sparam_vals_ducttape : 2;
+    // If this flag is set, the system will call a callback if a specialization
+    // is added to this lambda info. See jl_register_tracer below.
+    uint8_t traced : 1;
     jl_fptr_t fptr;             // jlcall entry point
 
     // On the old JIT, handles to all Functions generated for this linfo
@@ -1243,6 +1246,12 @@ JL_DLLEXPORT jl_value_t *jl_interpret_toplevel_expr_in(jl_module_t *m, jl_value_
                                                        jl_lambda_info_t *lam);
 JL_DLLEXPORT jl_module_t *jl_base_relative_to(jl_module_t *m);
 
+// tracing
+JL_DLLEXPORT void jl_trace_linfo(jl_lambda_info_t *li);
+JL_DLLEXPORT void jl_untrace_linfo(jl_lambda_info_t *li);
+JL_DLLEXPORT void jl_register_tracer(void (*callback)(jl_lambda_info_t *tracee));
+JL_DLLEXPORT void jl_register_newmeth_tracer(void (*callback)(jl_methlist_t *tracee));
+
 // AST access
 JL_DLLEXPORT int jl_is_rest_arg(jl_value_t *ex);