Make build_id.lo more random (#58258)

This does not fix the underlying issue that can occur here which is a
collision of build_ids.lo between modules in IR decompression. Fixing
that requires a somewhat significant overhaul to the serialization of IR
(probably using the module identity as a key). This does mean we use a
lot more of the bits available here so it makes collisions a lot less
likely( they were already extremely rare) but hrtime does tend to only
use the lower bits of a 64 bit integer and this will hopefully add some
more randomness and make this even less likely

(cherry picked from commit 7157407)

Author: gbaraldi

src/module.c

@@ -24,7 +24,8 @@ JL_DLLEXPORT jl_module_t *jl_new_module_(jl_sym_t *name, jl_module_t *parent, ui
     m->istopmod = 0;
     m->uuid = uuid_zero;
     static unsigned int mcounter; // simple counter backup, in case hrtime is not incrementing
-    m->build_id.lo = jl_hrtime() + (++mcounter);
+    // TODO: this is used for ir decompression and is liable to hash collisions so use more of the bits
+    m->build_id.lo = bitmix(jl_hrtime() + (++mcounter), jl_rand());
     if (!m->build_id.lo)
         m->build_id.lo++; // build id 0 is invalid
     m->build_id.hi = ~(uint64_t)0;

src/staticdata.c

@@ -3475,7 +3475,11 @@ static jl_value_t *jl_restore_package_image_from_stream(void* pkgimage_handle, i
             jl_insert_methods(extext_methods);
             // No special processing of `new_specializations` is required because recaching handled it
             // Add roots to methods
-            jl_copy_roots(method_roots_list, jl_worklist_key((jl_array_t*)restored));
+            int failed = jl_copy_roots(method_roots_list, jl_worklist_key((jl_array_t*)restored));
+            if (failed != 0) {
+                jl_printf(JL_STDERR, "Error copying roots to methods from Module: %s\n", pkgname);
+                abort();
+            }
             // Handle edges
             size_t world = jl_atomic_load_acquire(&jl_world_counter);
             jl_insert_backedges((jl_array_t*)edges, (jl_array_t*)ext_targets, (jl_array_t*)new_specializations, world); // restore external backedges (needs to be last)

src/staticdata_utils.c

@@ -847,17 +847,31 @@ static void jl_insert_methods(jl_array_t *list)
     }
 }
 
-static void jl_copy_roots(jl_array_t *method_roots_list, uint64_t key)
+static int jl_copy_roots(jl_array_t *method_roots_list, uint64_t key)
 {
     size_t i, l = jl_array_len(method_roots_list);
+    int failed = 0;
     for (i = 0; i < l; i+=2) {
         jl_method_t *m = (jl_method_t*)jl_array_ptr_ref(method_roots_list, i);
         jl_array_t *roots = (jl_array_t*)jl_array_ptr_ref(method_roots_list, i+1);
         if (roots) {
             assert(jl_is_array(roots));
+            if (m->root_blocks) {
+                // check for key collision
+                uint64_t *blocks = (uint64_t*)jl_array_data(m->root_blocks);
+                size_t nx2 = jl_array_nrows(m->root_blocks);
+                for (size_t i = 0; i < nx2; i+=2) {
+                    if (blocks[i] == key) {
+                        // found duplicate block
+                        failed = -1;
+                    }
+                }
+            }
+
             jl_append_method_roots(m, key, roots);
         }
     }
+    return failed;
 }