From 568f8adfc884d1897eca56c8b6c0ec0018cf3816 Mon Sep 17 00:00:00 2001
From: normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 10 Mar 2017 20:09:06 +0000
Subject: [PATCH] compile.c: apply opt_str_freeze to String#-@ (uminus)

The same optimization used for "literal string".freeze
can easily apply to uminus without introducing any
compatibility problems.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57828 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 bootstraptest/test_insns.rb | 1 +
 compile.c                   | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/bootstraptest/test_insns.rb b/bootstraptest/test_insns.rb
index 2001e2c0ef..3a6e677885 100644
--- a/bootstraptest/test_insns.rb
+++ b/bootstraptest/test_insns.rb
@@ -178,6 +178,7 @@ tests = [
   },
 
   [ 'opt_str_freeze', %q{ 'true'.freeze }, ],
+  [ 'opt_str_freeze', %q{ -'true' }, ],
   [ 'opt_str_freeze', <<~'},', ], # {
     class String
       def freeze
diff --git a/compile.c b/compile.c
index f1ba0946b3..be38c63dea 100644
--- a/compile.c
+++ b/compile.c
@@ -5188,7 +5188,8 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *const ret, NODE *node, int poppe
 	 *   "literal".freeze -> opt_str_freeze("literal")
 	 */
 	if (node->nd_recv && nd_type(node->nd_recv) == NODE_STR &&
-	    node->nd_mid == idFreeze && node->nd_args == NULL &&
+	    (node->nd_mid == idFreeze || node->nd_mid == idUMinus) &&
+	    node->nd_args == NULL &&
 	    ISEQ_COMPILE_DATA(iseq)->current_block == NULL &&
 	    ISEQ_COMPILE_DATA(iseq)->option->specialized_instruction) {
 	    VALUE str = rb_fstring(node->nd_recv->nd_lit);