From 3adc77d2bbb7ab35375659a658052fa1831f2745 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Fri, 26 May 2017 13:44:00 -0700
Subject: [PATCH] Optimize instance variable access if $VERBOSE is not true
 when compiling

This patch optimizes instance variable lookup in the case the $VERBOSE
is not true when compiling.  If $VERBOSE is not true when compiling
code, it makes the instance variable access use an optimized VM
instruction that does not check $VERBOSE at runtime.

This does not change the behavior if $VERBOSE is not changed at runtime,
only when $VERBOSE is not true when compiling the code, but is true when
running it.  In the case where $VERBOSE is not true when compiling and
true at runtime, this patch makes ruby no longer emit the warning
message.
---
 compile.c                   |  8 +++++++-
 insns.def                   | 14 ++++++++++++++
 test/ruby/test_exception.rb |  2 +-
 test/ruby/test_module.rb    |  4 +---
 vm_insnhelper.c             | 46 +++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/compile.c b/compile.c
index 3939ea0360..84d29b38de 100644
--- a/compile.c
+++ b/compile.c
@@ -5685,9 +5685,15 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, NODE *node, int popp
       case NODE_IVAR:{
 	debugi("nd_vid", node->nd_vid);
 	if (!popped) {
-	    ADD_INSN2(ret, line, getinstancevariable,
+            if (RTEST(ruby_verbose)) {
+		ADD_INSN2(ret, line, getinstancevariable,
 		      ID2SYM(node->nd_vid),
 		      get_ivar_ic_value(iseq,node->nd_vid));
+	    } else {
+		ADD_INSN2(ret, line, getinstancevariablefast,
+		      ID2SYM(node->nd_vid),
+		      get_ivar_ic_value(iseq,node->nd_vid));
+	    }
 	}
 	break;
       }
diff --git a/insns.def b/insns.def
index fa82d80850..b83febe792 100644
--- a/insns.def
+++ b/insns.def
@@ -121,6 +121,20 @@ getinstancevariable
 
 /**
   @c variable
+  @e Get value of instance variable id of self (optimized version
+     used when $VERBOSE is not true).
+ */
+DEFINE_INSN
+getinstancevariablefast
+(ID id, IC ic)
+()
+(VALUE val)
+{
+    val = vm_getinstancevariablefast(GET_SELF(), id, ic);
+}
+
+/**
+  @c variable
   @e Set value of instance variable id of self to val.
      If is_local is not 0, set value of class local variable.
   @j self のインスタンス変数 id を val にする。
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index 6955118de7..6566a65e7c 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -995,7 +995,7 @@ def capture_warning_warn
   end
 
   def test_warning_warn
-    warning = capture_warning_warn {@a}
+    warning = capture_warning_warn {eval '@a'}
     assert_match(/instance variable @a not initialized/, warning[0])
 
     assert_equal(["a\nz\n"], capture_warning_warn {warn "a\n", "z"})
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index d1c5d53822..debdf581f4 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -1970,14 +1970,12 @@ class << self
       attr_accessor :cattr
     end
     attr_accessor :iattr
-    def ivar
-      @ivar
-    end
   end
 
   def test_uninitialized_instance_variable
     a = AttrTest.new
     assert_warning(/instance variable @ivar not initialized/) do
+      eval 'def a.ivar; @ivar end'
       assert_nil(a.ivar)
     end
     a.instance_variable_set(:@ivar, 42)
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 4c25ba6e8d..fcf41dda90 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1010,6 +1010,52 @@ vm_setivar(VALUE obj, ID id, VALUE val, IC ic, struct rb_call_cache *cc, int is_
 }
 
 static inline VALUE
+vm_getinstancevariablefast(VALUE obj, ID id, IC ic)
+{
+#if USE_IC_FOR_IVAR
+    if (LIKELY(RB_TYPE_P(obj, T_OBJECT))) {
+	VALUE val = Qnil;
+	if (RB_DEBUG_COUNTER_INC_UNLESS(ivar_get_ic_miss_serial,
+					       ic->ic_serial == RCLASS_SERIAL(RBASIC(obj)->klass))) {
+	    st_index_t index = ic->ic_value.index;
+	    if (LIKELY(index < ROBJECT_NUMIV(obj))) {
+		val = ROBJECT_IVPTR(obj)[index];
+		if (UNLIKELY(val == Qundef)) {
+		    val = Qnil;
+		}
+	    }
+	    RB_DEBUG_COUNTER_INC(ivar_get_ic_hit);
+	    return val;
+	}
+	else {
+	    st_data_t index;
+	    struct st_table *iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
+
+	    if (iv_index_tbl) {
+		if (st_lookup(iv_index_tbl, id, &index)) {
+		    if (index < ROBJECT_NUMIV(obj)) {
+			val = ROBJECT_IVPTR(obj)[index];
+			if (UNLIKELY(val == Qundef)) {
+			    val = Qnil;
+			}
+		    }
+		    ic->ic_value.index = index;
+		    ic->ic_serial = RCLASS_SERIAL(RBASIC(obj)->klass);
+		}
+	    }
+	    RB_DEBUG_COUNTER_INC(ivar_get_ic_hit);
+	    return val;
+	}
+    }
+    else {
+	RB_DEBUG_COUNTER_INC(ivar_get_ic_miss_noobject);
+    }
+#endif
+    RB_DEBUG_COUNTER_INC(ivar_get_ic_miss);
+    return rb_attr_get(obj, id);
+}
+
+static inline VALUE
 vm_getinstancevariable(VALUE obj, ID id, IC ic)
 {
     return vm_getivar(obj, id, ic, 0, 0);
-- 
2.11.0