Speed up hash literals by duping

This commit replaces the `newhashfromarray` instruction with a `duphash`
instruction.  Instead of allocating a new hash from an array stored in
the Instruction Sequences, store a hash directly in the instruction
sequences and dup it on execution.

== Instruction sequence changes ==

```ruby
code = <<-eorby
  { "foo" => "bar", "baz" => "lol" }
eorby

insns = RubyVM::InstructionSequence.compile(code, __FILE__, nil, 0, frozen_string_literal: true)
puts insns.disasm
```

On Ruby 2.5:

```
== disasm: #<ISeq:<compiled>@test.rb:0 (0,0)-(0,36)>====================
0000 putobject        "foo"
0002 putobject        "bar"
0004 putobject        "baz"
0006 putobject        "lol"
0008 newhash          4
0010 leave
```

Ruby 2.6@r66174 3b6321083a2e3525da3b34d08a0b68bac094bd7f:

```
$ ./ruby test.rb
== disasm: #<ISeq:<compiled>@test.rb:0 (0,0)-(0,36)> (catch: FALSE)
0000 newhashfromarray             2, ["foo", "bar", "baz", "lol"]
0003 leave
```

Ruby 2.6 + This commit:

```
$ ./ruby test.rb
== disasm: #<ISeq:<compiled>@test.rb:0 (0,0)-(0,36)> (catch: FALSE)
0000 duphash                      {"foo"=>"bar", "baz"=>"lol"}
0002 leave
```

== Benchmark Results ==

Compared to 2.5.3:

```
$ make benchmark ITEM=hash_literal_small COMPARE_RUBY=/Users/aaron/.rbenv/versions/2.5.3/bin/ruby
generating known_errors.inc
known_errors.inc unchanged
./revision.h unchanged
/Users/aaron/.rbenv/shims/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver \
	            --executables="compare-ruby::/Users/aaron/.rbenv/versions/2.5.3/bin/ruby -I.ext/common --disable-gem" \
	            --executables="built-ruby::./miniruby -I./lib -I. -I.ext/common  -r./prelude --disable-gem" \
	            $(find ./benchmark -maxdepth 1 -name '*hash_literal_small*.yml' -o -name '*hash_literal_small*.rb' | sort)
Calculating -------------------------------------
                     compare-ruby  built-ruby
 hash_literal_small2        1.498       1.877 i/s -       1.000 times in 0.667581s 0.532656s
 hash_literal_small4        1.197       1.642 i/s -       1.000 times in 0.835375s 0.609160s
 hash_literal_small8        0.620       1.215 i/s -       1.000 times in 1.611638s 0.823090s

Comparison:
              hash_literal_small2
          built-ruby:         1.9 i/s
        compare-ruby:         1.5 i/s - 1.25x  slower

              hash_literal_small4
          built-ruby:         1.6 i/s
        compare-ruby:         1.2 i/s - 1.37x  slower

              hash_literal_small8
          built-ruby:         1.2 i/s
        compare-ruby:         0.6 i/s - 1.96x  slower
```

Compared to r66255

```
$ make benchmark ITEM=hash_literal_small COMPARE_RUBY=/Users/aaron/.rbenv/versions/ruby-trunk/bin/ruby
generating known_errors.inc
known_errors.inc unchanged
./revision.h unchanged
/Users/aaron/.rbenv/shims/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver \
	            --executables="compare-ruby::/Users/aaron/.rbenv/versions/ruby-trunk/bin/ruby -I.ext/common --disable-gem" \
	            --executables="built-ruby::./miniruby -I./lib -I. -I.ext/common  -r./prelude --disable-gem" \
	            $(find ./benchmark -maxdepth 1 -name '*hash_literal_small*.yml' -o -name '*hash_literal_small*.rb' | sort)
Calculating -------------------------------------
                     compare-ruby  built-ruby
 hash_literal_small2        1.567       1.831 i/s -       1.000 times in 0.638056s 0.546039s
 hash_literal_small4        1.298       1.652 i/s -       1.000 times in 0.770214s 0.605182s
 hash_literal_small8        0.873       1.216 i/s -       1.000 times in 1.145304s 0.822047s

Comparison:
              hash_literal_small2
          built-ruby:         1.8 i/s
        compare-ruby:         1.6 i/s - 1.17x  slower

              hash_literal_small4
          built-ruby:         1.7 i/s
        compare-ruby:         1.3 i/s - 1.27x  slower

              hash_literal_small8
          built-ruby:         1.2 i/s
        compare-ruby:         0.9 i/s - 1.39x  slower
```

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66258 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -3984,7 +3984,12 @@ compile_array(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node_ro
 			    ADD_INSN1(ret, line, duparray, ary);
 			}
 			else { /* COMPILE_ARRAY_TYPE_HASH */
-                            ADD_INSN2(ret, line, newhashfromarray, INT2FIX(RARRAY_LEN(ary)/2), ary);
+			    VALUE hash;
+
+			    hash = rb_hash_new_with_size(RARRAY_LEN(ary) / 2);
+			    rb_hash_bulk_insert(RARRAY_LEN(ary), RARRAY_CONST_PTR_TRANSIENT(ary), hash);
+			    iseq_add_mark_object_compile_time(iseq, hash);
+			    ADD_INSN1(ret, line, duphash, hash);
 			}
 		    }
 		    else {

insns.def

@@ -454,6 +454,16 @@ duparray
     val = rb_ary_resurrect(ary);
 }
 
+/* dup hash */
+DEFINE_INSN
+duphash
+(VALUE hash)
+()
+(VALUE val)
+{
+    val = rb_hash_dup(hash);
+}
+
 /* if TOS is an array expand, expand it to num objects.
      if the number of the array is less than num, push nils to fill.
      if it is greater than num, exceeding elements are dropped.
@@ -514,19 +524,6 @@ newhash
     }
 }
 
-/* make new Hash object from (frozen) Array object */
-DEFINE_INSN
-newhashfromarray
-(rb_num_t num, VALUE ary)
-()
-(VALUE hash)
-// attr bool leaf = false; /* rb_hash_bulk_insert() can call methods. */
-{
-    VM_ASSERT(num * 2 == (rb_num_t)RARRAY_LEN(ary));
-    hash = rb_hash_new_with_size(num);
-    rb_hash_bulk_insert(num * 2, RARRAY_CONST_PTR_TRANSIENT(ary), hash);
-}
-
 /* put new Range object.(Range.new(low, high, flag)) */
 DEFINE_INSN
 newrange

test/ruby/test_jit.rb

@@ -239,8 +239,8 @@ class TestJIT < Test::Unit::TestCase
     assert_compile_once('a = 1; { a: a }', result_inspect: '{:a=>1}', insns: %i[newhash])
   end
 
-  def test_compile_insn_newhashfromarray
+  def test_compile_insn_duphash
-    assert_compile_once('{ a: 1 }', result_inspect: '{:a=>1}', insns: %i[newhashfromarray])
+    assert_compile_once('{ a: 1 }', result_inspect: '{:a=>1}', insns: %i[duphash])
   end
 
   def test_compile_insn_newrange