Add --drop-edges

base/options.jl

@@ -63,6 +63,7 @@ struct JLOptions
     task_metrics::Int8
     timeout_for_safepoint_straggler_s::Int16
     serialize_machine_code_only::Int8
+    drop_edges::Int8
 end
 
 # This runs early in the sysimage != is not defined yet

src/gc.c

@@ -1014,6 +1014,7 @@ STATIC_INLINE jl_value_t *jl_gc_big_alloc_inner(jl_ptls_t ptls, size_t sz)
     memset(v, 0xee, allocsz);
 #endif
     v->sz = allocsz;
+    v->header = 0;
     gc_big_object_link(ptls->gc_tls.heap.young_generation_of_bigvals, v);
     return jl_valueof(&v->header);
 }

src/jloptions.c

@@ -96,6 +96,7 @@ JL_DLLEXPORT void jl_init_options(void)
                         0, // task_metrics
                         25, // timeout_for_safepoint_straggler_s
                         0, // serialize_machine_code_only
+                        0, // drop_edges
     };
     jl_options_initialized = 1;
 }
@@ -247,6 +248,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
            opt_inline,
            opt_polly,
            opt_serialize_machine_code_only,
+           opt_drop_edges,
            opt_timeout_for_safepoint_straggler,
            opt_trace_compile,
            opt_trace_compile_timing,
@@ -328,6 +330,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         { "inline",          required_argument, 0, opt_inline },
         { "polly",           required_argument, 0, opt_polly },
         { "serialize-machine-code-only", no_argument, 0, opt_serialize_machine_code_only },
+        { "drop-edges", no_argument, 0, opt_drop_edges },
         { "timeout-for-safepoint-straggler", required_argument, 0, opt_timeout_for_safepoint_straggler },
         { "trace-compile",   required_argument, 0, opt_trace_compile },
         { "trace-compile-timing",  no_argument, 0, opt_trace_compile_timing },
@@ -899,6 +902,9 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         case opt_serialize_machine_code_only:
             jl_options.serialize_machine_code_only = 1;
             break;
+        case opt_drop_edges:
+            jl_options.drop_edges = 1;
+            break;
         case opt_task_metrics:
             if (!strcmp(optarg, "no"))
                 jl_options.task_metrics = JL_OPTIONS_TASK_METRICS_OFF;

src/jloptions.h

@@ -67,6 +67,7 @@ typedef struct {
     int8_t task_metrics;
     int16_t timeout_for_safepoint_straggler_s;
     int8_t serialize_machine_code_only;
+    int8_t drop_edges;
 } jl_options_t;
 
 #endif

src/staticdata.c

@@ -2244,9 +2244,11 @@ static void strip_specializations_(jl_method_instance_t *mi)
         }
         codeinst = jl_atomic_load_relaxed(&codeinst->next);
     }
+    if (jl_options.strip_ir || jl_options.drop_edges) {
+        record_field_change((jl_value_t**)&mi->backedges, NULL);
+    }
     if (jl_options.strip_ir) {
         record_field_change((jl_value_t**)&mi->uninferred, NULL);
-        record_field_change((jl_value_t**)&mi->backedges, NULL);
         record_field_change((jl_value_t**)&mi->callbacks, NULL);
     }
 }
@@ -2300,7 +2302,7 @@ static int strip_all_codeinfos__(jl_typemap_entry_t *def, void *_env)
 
 static int strip_all_codeinfos_(jl_methtable_t *mt, void *_env)
 {
-    if (jl_options.strip_ir && mt->backedges)
+    if ((jl_options.strip_ir || jl_options.drop_edges) && mt->backedges)
         record_field_change((jl_value_t**)&mt->backedges, NULL);
     return jl_typemap_visitor(mt->defs, strip_all_codeinfos__, NULL);
 }
@@ -2411,7 +2413,7 @@ static void jl_save_system_image_to_stream(ios_t *f, jl_array_t *mod_array,
 {
     htable_new(&field_replace, 0);
     // strip metadata and IR when requested
-    if (jl_options.strip_metadata || jl_options.strip_ir)
+    if (jl_options.strip_metadata || jl_options.strip_ir || jl_options.drop_edges)
         jl_strip_all_codeinfos();
 
     int en = jl_gc_enable(0);
@@ -2525,6 +2527,17 @@ static void jl_save_system_image_to_stream(ios_t *f, jl_array_t *mod_array,
             // Queue the new roots
             jl_queue_for_serialization(&s, method_roots_list);
             // Queue the edges
+            if (jl_options.drop_edges) {
+                // Empty ext_targets
+                ext_targets = jl_alloc_vec_any(0);
+                // The caller field in `edges` is used in loading so we only empty the
+                // callees array when we drop edges.
+                size_t i, l = jl_array_len(edges) / 2;
+                for (i = 0; i < l; i++) {
+                    jl_array_t *cids = jl_alloc_array_1d(jl_array_int32_type, 0);
+                    jl_array_ptr_set(edges, 2 * i + 1, cids);
+                }
+            }
             jl_queue_for_serialization(&s, ext_targets);
             jl_queue_for_serialization(&s, edges);
         }

test/cmdlineargs.jl

@@ -1137,3 +1137,8 @@ end
     exename = `$(Base.julia_cmd())`
     @test parse(Int,read(`$exename --serialize-machine-code-only -E "Base.JLOptions().serialize_machine_code_only"`, String)) == 1
 end
+
+@testset "--drop-edges" begin
+    exename = `$(Base.julia_cmd())`
+    @test parse(Int,read(`$exename --drop-edges -E "Base.JLOptions().drop_edges`, String)) == 1
+end