From 086ffe72c711179c30a773027e0b4113e908d399 Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Fri, 2 Aug 2019 23:25:38 +0900
Subject: [PATCH] Revert "Revert "Add a specialized instruction for `.nil?`
 calls""

This reverts commit a0980f2446c0db735b8ffeb37e241370c458a626.

Retry for macOS Mojave.
---
 benchmark/nil_p.yml |  9 +++++++++
 compile.c           |  1 +
 defs/id.def         |  1 +
 insns.def           | 14 ++++++++++++++
 object.c            |  2 +-
 vm.c                |  1 +
 vm_core.h           |  1 +
 vm_insnhelper.c     | 20 ++++++++++++++++++++
 8 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 benchmark/nil_p.yml

diff --git a/benchmark/nil_p.yml b/benchmark/nil_p.yml
new file mode 100644
index 0000000000..79ba4f2177
--- /dev/null
+++ b/benchmark/nil_p.yml
@@ -0,0 +1,9 @@
+prelude: |
+  class Niller; def nil?; true; end; end
+  xnil, notnil = nil, Object.new
+  niller = Niller.new
+benchmark:
+  - xnil.nil?
+  - notnil.nil?
+  - niller.nil?
+loop_count: 10000000
diff --git a/compile.c b/compile.c
index 774dadfc79..0dbefd3155 100644
--- a/compile.c
+++ b/compile.c
@@ -3255,6 +3255,7 @@ iseq_specialized_instruction(rb_iseq_t *iseq, INSN *iobj)
 		  case idLength: SP_INSN(length); return COMPILE_OK;
 		  case idSize:	 SP_INSN(size);	  return COMPILE_OK;
 		  case idEmptyP: SP_INSN(empty_p);return COMPILE_OK;
+                  case idNilP:   SP_INSN(nil_p);  return COMPILE_OK;
 		  case idSucc:	 SP_INSN(succ);	  return COMPILE_OK;
 		  case idNot:	 SP_INSN(not);	  return COMPILE_OK;
 		}
diff --git a/defs/id.def b/defs/id.def
index 66dfdf915a..25677ffdc2 100644
--- a/defs/id.def
+++ b/defs/id.def
@@ -3,6 +3,7 @@ firstline, predefined = __LINE__+1, %[\
   max
   min
   freeze
+  nil?
   inspect
   intern
   object_id
diff --git a/insns.def b/insns.def
index c971026cf6..7c93af6e4d 100644
--- a/insns.def
+++ b/insns.def
@@ -808,6 +808,20 @@ opt_str_freeze
     }
 }
 
+/* optimized nil? */
+DEFINE_INSN
+opt_nil_p
+(CALL_INFO ci, CALL_CACHE cc)
+(VALUE recv)
+(VALUE val)
+{
+    val = vm_opt_nil_p(ci, cc, recv);
+
+    if (val == Qundef) {
+        CALL_SIMPLE_METHOD();
+    }
+}
+
 DEFINE_INSN
 opt_str_uminus
 (VALUE str, CALL_INFO ci, CALL_CACHE cc)
diff --git a/object.c b/object.c
index 3aa7cd20d2..16dce71671 100644
--- a/object.c
+++ b/object.c
@@ -1687,7 +1687,7 @@ rb_true(VALUE obj)
  */
 
 
-static VALUE
+MJIT_FUNC_EXPORTED VALUE
 rb_false(VALUE obj)
 {
     return Qfalse;
diff --git a/vm.c b/vm.c
index 115bdca503..b4e2e3c5e6 100644
--- a/vm.c
+++ b/vm.c
@@ -1656,6 +1656,7 @@ vm_init_redefined_flag(void)
     OP(Call, CALL), (C(Proc));
     OP(And, AND), (C(Integer));
     OP(Or, OR), (C(Integer));
+    OP(NilP, NIL_P), (C(NilClass));
 #undef C
 #undef OP
 }
diff --git a/vm_core.h b/vm_core.h
index 0120f21831..d5e18ba489 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -550,6 +550,7 @@ enum ruby_basic_operators {
     BOP_LENGTH,
     BOP_SIZE,
     BOP_EMPTY_P,
+    BOP_NIL_P,
     BOP_SUCC,
     BOP_GT,
     BOP_GE,
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 57f6d91e88..1875d35de1 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -4228,6 +4228,26 @@ vm_opt_empty_p(VALUE recv)
     }
 }
 
+VALUE rb_false(VALUE obj);
+
+static VALUE
+vm_opt_nil_p(CALL_INFO ci, CALL_CACHE cc, VALUE recv)
+{
+    if (recv == Qnil) {
+        if (BASIC_OP_UNREDEFINED_P(BOP_NIL_P, NIL_REDEFINED_OP_FLAG)) {
+            return Qtrue;
+        } else {
+            return Qundef;
+        }
+    } else {
+        if (vm_method_cfunc_is(ci, cc, recv, rb_false)) {
+            return Qfalse;
+        } else {
+            return Qundef;
+        }
+    }
+}
+
 static VALUE
 fix_succ(VALUE x)
 {