make Task smaller by rearranging fields (#41351)

This makes jl_task_t 8 bytes smaller, moving it into the next-smallest
pool, which drops the effective size from 400 to 368 bytes.

(cherry picked from commit af4bbfd)

Author: JeffBezanson

src/jltypes.c

@@ -2539,13 +2539,13 @@ void jl_init_types(void) JL_GC_DISABLED
                                         "result",
                                         "logstate",
                                         "code",
-                                        "_state",
-                                        "sticky",
-                                        "_isexception",
                                         "rngState0",
                                         "rngState1",
                                         "rngState2",
-                                        "rngState3"),
+                                        "rngState3",
+                                        "_state",
+                                        "sticky",
+                                        "_isexception"),
                         jl_svec(14,
                                 jl_any_type,
                                 jl_any_type,
@@ -2554,13 +2554,13 @@ void jl_init_types(void) JL_GC_DISABLED
                                 jl_any_type,
                                 jl_any_type,
                                 jl_any_type,
-                                jl_uint8_type,
-                                jl_bool_type,
-                                jl_bool_type,
                                 jl_uint64_type,
                                 jl_uint64_type,
                                 jl_uint64_type,
-                                jl_uint64_type),
+                                jl_uint64_type,
+                                jl_uint8_type,
+                                jl_bool_type,
+                                jl_bool_type),
                         jl_emptysvec,
                         0, 1, 6);
     jl_value_t *listt = jl_new_struct(jl_uniontype_type, jl_task_type, jl_nothing_type);

src/julia.h

@@ -1829,24 +1829,24 @@ typedef struct _jl_task_t {
     jl_value_t *result;
     jl_value_t *logstate;
     jl_function_t *start;
-    uint8_t _state;
-    uint8_t sticky; // record whether this Task can be migrated to a new thread
-    uint8_t _isexception; // set if `result` is an exception to throw or that we exited with
     uint64_t rngState0; // really rngState[4], but more convenient to split
     uint64_t rngState1;
     uint64_t rngState2;
     uint64_t rngState3;
+    uint8_t _state;
+    uint8_t sticky; // record whether this Task can be migrated to a new thread
+    uint8_t _isexception; // set if `result` is an exception to throw or that we exited with
 
 // hidden state:
+    // id of owning thread - does not need to be defined until the task runs
+    int16_t tid;
+    // multiqueue priority
+    int16_t prio;
     // saved gc stack top for context switches
     jl_gcframe_t *gcstack;
     size_t world_age;
     // quick lookup for current ptls
     jl_tls_states_t *ptls; // == jl_all_tls_states[tid]
-    // id of owning thread - does not need to be defined until the task runs
-    int16_t tid;
-    // multiqueue priority
-    int16_t prio;
     // saved exception stack
     jl_excstack_t *excstack;
     // current exception handler