feat: support mpz in the shareCommon APIs (#7838)

This PR adds support for mpz objects (i.e., big nums) to the
`shareCommon` functions.

src/runtime/sharecommon.cpp

@@ -17,22 +17,32 @@ extern "C" LEAN_EXPORT uint8 lean_sharecommon_eq(b_obj_arg o1, b_obj_arg o2) {
     size_t sz2 = lean_object_data_byte_size(o2);
     if (sz1 != sz2) return false;
     // compare relevant parts of the header
-    if (lean_ptr_tag(o1) != lean_ptr_tag(o2)) return false;
+    uint8_t tag = lean_ptr_tag(o1);
+    if (tag != lean_ptr_tag(o2)) return false;
     if (lean_ptr_other(o1) != lean_ptr_other(o2)) return false;
-    size_t header_sz = sizeof(lean_object);
-    lean_assert(sz1 >= header_sz);
-    // compare objects' bodies
-    return memcmp(reinterpret_cast<char*>(o1) + header_sz, reinterpret_cast<char*>(o2) + header_sz, sz1 - header_sz) == 0;
+    if (tag == LeanMPZ) {
+        return mpz_value(o1) == mpz_value(o2);
+    } else {
+        size_t header_sz = sizeof(lean_object);
+        lean_assert(sz1 >= header_sz);
+        // compare objects' bodies
+        return memcmp(reinterpret_cast<char*>(o1) + header_sz, reinterpret_cast<char*>(o2) + header_sz, sz1 - header_sz) == 0;
+    }
 }
 
 extern "C" LEAN_EXPORT uint64_t lean_sharecommon_hash(b_obj_arg o) {
     lean_assert(!lean_is_scalar(o));
     size_t sz = lean_object_data_byte_size(o);
     size_t header_sz = sizeof(lean_object);
-    // hash relevant parts of the header
-    unsigned init = hash(lean_ptr_tag(o), lean_ptr_other(o));
-    // hash body
-    return hash_str(sz - header_sz, reinterpret_cast<unsigned char const *>(o) + header_sz, init);
+    uint8_t tag = lean_ptr_tag(o);
+    if (tag == LeanMPZ) {
+        return hash(tag, mpz_value(o).hash());
+    } else {
+        // hash relevant parts of the header
+        unsigned init = hash(tag, lean_ptr_other(o));
+        // hash body
+        return hash_str(sz - header_sz, reinterpret_cast<unsigned char const *>(o) + header_sz, init);
+    }
 }
 
 static obj_res mk_pair(obj_arg a, obj_arg b) {
@@ -114,7 +124,7 @@ class sharecommon_fn {
         case LeanReserved:
             lean_unreachable();
         // We do not maximize sharing for the following kinds of objects
-        case LeanMPZ:      case LeanThunk:
+        case LeanThunk:
         case LeanTask:     case LeanRef:
         case LeanExternal: case LeanClosure:
         case LeanPromise:
@@ -201,6 +211,11 @@ class sharecommon_fn {
         save(a, (lean_object*)new_a);
     }
 
+    void visit_mpz(b_obj_arg a) {
+        object * new_a = alloc_mpz(mpz_value(a));
+        save(a, new_a);
+    }
+
     void visit_ctor(b_obj_arg a) {
         clear_children();
         unsigned num_objs  = lean_ctor_num_objs(a);
@@ -247,7 +262,7 @@ public:
             case LeanArray:           visit_array(curr); break;
             case LeanScalarArray:     visit_sarray(curr); break;
             case LeanString:          visit_string(curr); break;
-            case LeanMPZ:             lean_unreachable();
+            case LeanMPZ:             visit_mpz(curr); break;
             case LeanThunk:           lean_unreachable();
             case LeanTask:            lean_unreachable();
             case LeanPromise:         lean_unreachable();
@@ -409,7 +424,6 @@ lean_object * sharecommon_quick_fn::visit(lean_object * a) {
       Similarly to `sharecommon_fn`, we only maximally share arrays, scalar arrays, strings, and
       constructor objects.
     */
-    case LeanMPZ:             lean_inc_ref(a); return a;
     case LeanClosure:         lean_inc_ref(a); return a;
     case LeanThunk:           lean_inc_ref(a); return a;
     case LeanTask:            lean_inc_ref(a); return a;
@@ -417,6 +431,7 @@ lean_object * sharecommon_quick_fn::visit(lean_object * a) {
     case LeanRef:             lean_inc_ref(a); return a;
     case LeanExternal:        lean_inc_ref(a); return a;
     case LeanReserved:        lean_inc_ref(a); return a;
+    case LeanMPZ:             return visit_terminal(a);
     case LeanScalarArray:     return visit_terminal(a);
     case LeanString:          return visit_terminal(a);
     case LeanArray:           return visit_array(a);

tests/lean/run/sharecommon_mpz.lean

@@ -0,0 +1,54 @@
+import Lean
+
+open Lean Meta Tactic Grind
+
+def runGrind (x : GrindM α) : MetaM α := do
+  GrindM.run x `dummy (← mkParams {}) (pure ())
+
+@[noinline] def mkA (x : Nat) := x + 1
+
+def tst (a b : Nat) : GrindM Unit := do
+  IO.println a
+  IO.println b
+  let a ← shareCommon (mkNatLit a)
+  let b ← shareCommon (mkNatLit b)
+  IO.println (isSameExpr a b)
+
+/--
+info: 1000000000000000000000000001
+1000000000000000000000000001
+true
+-/
+#guard_msgs (info) in
+run_meta do
+  let a := mkA 1000000000000000000000000000
+  let b := 1000000000000000000000000001
+  runGrind (tst a b)
+
+/--
+info: 1001
+1001
+true
+-/
+#guard_msgs (info) in
+run_meta do
+  let a := mkA 1000
+  let b := 1001
+  runGrind (tst a b)
+
+def tst2 (a b : Nat) : IO Unit := do
+  IO.println a
+  IO.println b
+  let (a, b) := ShareCommon.shareCommon' (mkNatLit a, mkNatLit b)
+  IO.println (isSameExpr a b)
+
+/--
+info: 1000000000000000000000000001
+1000000000000000000000000001
+true
+-/
+#guard_msgs (info) in
+run_meta do
+  let a := mkA 1000000000000000000000000000
+  let b := 1000000000000000000000000001
+  tst2 a b