Allow inlining Integer#-@ and #~

```
$ benchmark-driver -v --rbenv 'before --jit;after --jit' benchmark/mjit_integer.yml --filter '(comp|uminus)'
before --jit: ruby 3.0.0dev (2020-12-23T05:41:44Z master 0dd4896175) +JIT [x86_64-linux]
after --jit: ruby 3.0.0dev (2020-12-23T06:25:41Z master 8887d78992) +JIT [x86_64-linux]
last_commit=Allow inlining Integer#-@ and #~
Calculating -------------------------------------
                     before --jit  after --jit
        mjit_comp(1)      44.006M      70.417M i/s -     40.000M times in 0.908967s 0.568042s
      mjit_uminus(1)      44.333M      68.422M i/s -     40.000M times in 0.902255s 0.584603s

Comparison:
                     mjit_comp(1)
         after --jit:  70417331.4 i/s
        before --jit:  44005980.4 i/s - 1.60x  slower

                   mjit_uminus(1)
         after --jit:  68422468.8 i/s
        before --jit:  44333371.0 i/s - 1.54x  slower
```

4 files changed, 35 insertions, 31 deletions

diff --git a/benchmark/mjit_integer.yml b/benchmark/mjit_integer.yml
index cd3288978b..edc3556479 100644
--- a/benchmark/mjit_integer.yml
+++ b/benchmark/mjit_integer.yml
@@ -2,6 +2,7 @@ type: lib/benchmark_driver/runner/mjit
 prelude: |
   def mjit_abs(int)        int.abs        end
   def mjit_bit_length(int) int.bit_length end
+  def mjit_comp(int)       ~int           end
   def mjit_even?(int)      int.even?      end
   def mjit_integer?(int)   int.integer?   end
   def mjit_magnitude(int)  int.magnitude  end
@@ -9,11 +10,13 @@ prelude: |
   def mjit_ord(int)        int.ord        end
   def mjit_to_i(int)       int.to_i       end
   def mjit_to_int(int)     int.to_int     end
+  def mjit_uminus(int)     -int           end
   def mjit_zero?(int)      int.zero?      end
 
 benchmark:
   - mjit_abs(-1)
   - mjit_bit_length(100)
+  - mjit_comp(1)
   - mjit_even?(2)
   - mjit_integer?(0)
   - mjit_magnitude(-1)
@@ -21,6 +24,7 @@ benchmark:
   - mjit_ord(1)
   - mjit_to_i(1)
   - mjit_to_int(1)
+  - mjit_uminus(1)
   - mjit_zero?(0)
 
 loop_count: 40000000
diff --git a/integer.rb b/integer.rb
index b9cde8f390..d18494f42f 100644
--- a/integer.rb
+++ b/integer.rb
@@ -1,4 +1,29 @@
 class Integer
+  # call-seq:
+  #    -int  ->  integer
+  #
+  # Returns +int+, negated.
+  def -@
+    Primitive.attr! 'inline'
+    Primitive.cexpr! 'rb_int_uminus(self)'
+  end
+
+  # call-seq:
+  #   ~int  ->  integer
+  #
+  # One's complement: returns a number where each bit is flipped.
+  #
+  # Inverts the bits in an Integer. As integers are conceptually of
+  # infinite length, the result acts as if it had an infinite number of
+  # one bits to the left. In hex representations, this is displayed
+  # as two periods to the left of the digits.
+  #
+  #   sprintf("%X", ~0x1122334455)    #=> "..FEEDDCCBBAA"
+  def ~
+    Primitive.attr! 'inline'
+    Primitive.cexpr! 'rb_int_comp(self)'
+  end
+
   def abs
     Primitive.attr! 'inline'
     Primitive.cexpr! 'rb_int_abs(self)'
diff --git a/internal/numeric.h b/internal/numeric.h
index 3dc72d22f5..32d5bd27fa 100644
--- a/internal/numeric.h
+++ b/internal/numeric.h
@@ -50,7 +50,6 @@ double ruby_float_step_size(double beg, double end, double unit, int excl);
 int ruby_float_step(VALUE from, VALUE to, VALUE step, int excl, int allow_endless);
 int rb_num_negative_p(VALUE);
 VALUE rb_int_succ(VALUE num);
-VALUE rb_int_uminus(VALUE num);
 VALUE rb_float_uminus(VALUE num);
 VALUE rb_int_plus(VALUE x, VALUE y);
 VALUE rb_float_plus(VALUE x, VALUE y);
@@ -112,6 +111,8 @@ VALUE rb_int_even_p(VALUE num);
 VALUE rb_int_odd_p(VALUE num);
 VALUE rb_int_abs(VALUE num);
 VALUE rb_int_bit_length(VALUE num);
+VALUE rb_int_uminus(VALUE num);
+VALUE rb_int_comp(VALUE num);
 MJIT_SYMBOL_EXPORT_END
 
 static inline bool
diff --git a/numeric.c b/numeric.c
index d599e123f5..e4bb4817bb 100644
--- a/numeric.c
+++ b/numeric.c
@@ -3456,15 +3456,6 @@ int_chr(int argc, VALUE *argv, VALUE num)
  * Fixnum
  */
 
-
-/*
- * Document-method: Integer#-@
- * call-seq:
- *    -int  ->  integer
- *
- * Returns +int+, negated.
- */
-
 static VALUE
 fix_uminus(VALUE num)
 {
@@ -3477,10 +3468,10 @@ rb_int_uminus(VALUE num)
     if (FIXNUM_P(num)) {
 	return fix_uminus(num);
     }
-    else if (RB_TYPE_P(num, T_BIGNUM)) {
+    else {
+        assert(RB_TYPE_P(num, T_BIGNUM));
 	return rb_big_uminus(num);
     }
-    return num_funcall0(num, idUMinus);
 }
 
 /*
@@ -4371,29 +4362,14 @@ int_le(VALUE x, VALUE y)
     return Qnil;
 }
 
-/*
- * Document-method: Integer#~
- * call-seq:
- *   ~int  ->  integer
- *
- * One's complement: returns a number where each bit is flipped.
- *
- * Inverts the bits in an Integer. As integers are conceptually of
- * infinite length, the result acts as if it had an infinite number of
- * one bits to the left. In hex representations, this is displayed
- * as two periods to the left of the digits.
- *
- *   sprintf("%X", ~0x1122334455)    #=> "..FEEDDCCBBAA"
- */
-
 static VALUE
 fix_comp(VALUE num)
 {
     return ~num | FIXNUM_FLAG;
 }
 
-static VALUE
-int_comp(VALUE num)
+VALUE
+rb_int_comp(VALUE num)
 {
     if (FIXNUM_P(num)) {
 	return fix_comp(num);
@@ -5576,7 +5552,6 @@ Init_Numeric(void)
     rb_define_method(rb_cInteger, "round", int_round, -1);
     rb_define_method(rb_cInteger, "<=>", rb_int_cmp, 1);
 
-    rb_define_method(rb_cInteger, "-@", rb_int_uminus, 0);
     rb_define_method(rb_cInteger, "+", rb_int_plus, 1);
     rb_define_method(rb_cInteger, "-", rb_int_minus, 1);
     rb_define_method(rb_cInteger, "*", rb_int_mul, 1);
@@ -5598,7 +5573,6 @@ Init_Numeric(void)
     rb_define_method(rb_cInteger, "<", int_lt, 1);
     rb_define_method(rb_cInteger, "<=", int_le, 1);
 
-    rb_define_method(rb_cInteger, "~", int_comp, 0);
     rb_define_method(rb_cInteger, "&", rb_int_and, 1);
     rb_define_method(rb_cInteger, "|", int_or,  1);
     rb_define_method(rb_cInteger, "^", int_xor, 1);