[bigint] fix detection of negative numbers from binary ops

This should fix RT #109740

Author: moritz

src/ops/nqp_bigint.ops

@@ -89,6 +89,7 @@ static void grow_and_negate(mp_int *a, int size, mp_int *b) {
     mp_add_d(b, 1, b);
 }
 
+
 static void two_complement_bitop(mp_int *a, mp_int *b, mp_int *c,
         int (*mp_bitop)(mp_int *, mp_int *, mp_int *)) {
     mp_int d;
@@ -104,7 +105,7 @@ static void two_complement_bitop(mp_int *a, mp_int *b, mp_int *c,
             grow_and_negate(b, USED(a), &d);
             mp_bitop(a, &d, c);
         }
-        if (DIGIT(c, USED(c) - 1) & (MP_MASK > 1)) {
+        if (DIGIT(c, USED(c) - 1) & ((mp_digit)1<<(mp_digit)(DIGIT_BIT - 1))) {
             grow_and_negate(c, c->used, &d);
             mp_copy(&d, c);
             mp_neg(c, c);

t/nqp/60-bigint.t

@@ -1,7 +1,7 @@
 #! nqp
 use nqpmo;
 
-plan(31);
+plan(32);
 
 my $knowhow := pir::get_knowhow__P();
 my $bi_type := $knowhow.new_type(:name('TestBigInt'), :repr('P6bigint'));
@@ -35,6 +35,8 @@ ok(iseq(nqp::bitxor_I(box(0xdead), box(0xbeef), $one), 0x6042), 'bit xor');
 
 ok(iseq(nqp::bitneg_I(box(-123), $one), 122), 'bit negation');
 
+ok(iseq(nqp::bitand_I(pir::nqp_bigint_from_str__PSP('-1073741825', $one), $one, $one), 1),
+    'Bit ops (RT 109740)');
 
 # Now we'll create a type that boxes a P6bigint.
 my $bi_boxer := $knowhow.new_type(:name('TestPerl6Int'), :repr('P6opaque'));