1. results

BEFORE interpreted:
                                          user     system      total        real
control, 1 and :to_ary                0.070000   0.000000   0.070000 (  0.068000)
1m 1.respond_to?(:to_ary)             0.130000   0.000000   0.130000 (  0.126000)
1m 1.respond_to?(:to_ary,true)        0.120000   0.000000   0.120000 (  0.122000)
1m 1.respond_to?(:next)               0.100000   0.000000   0.100000 (  0.093000)
1m redefined obj.respond_to?          0.130000   0.000000   0.130000 (  0.135000)
1m varying name respond_to?           0.280000   0.010000   0.290000 (  0.272000)

BEFORE compiled:
                                          user     system      total        real
control, 1 and :to_ary                0.040000   0.000000   0.040000 (  0.037000)
1m 1.respond_to?(:to_ary)             0.110000   0.000000   0.110000 (  0.108000)
1m 1.respond_to?(:to_ary,true)        0.110000   0.000000   0.110000 (  0.109000)
1m 1.respond_to?(:next)               0.070000   0.000000   0.070000 (  0.072000)
1m redefined obj.respond_to?          0.060000   0.000000   0.060000 (  0.059000)
1m varying name respond_to?           0.060000   0.000000   0.060000 (  0.059000)

AFTER interpreted:
                                          user     system      total        real
control, 1 and :to_ary                0.070000   0.000000   0.070000 (  0.069000)
1m 1.respond_to?(:to_ary)             0.060000   0.000000   0.060000 (  0.063000)
1m 1.respond_to?(:to_ary,true)        0.070000   0.000000   0.070000 (  0.061000)
1m 1.respond_to?(:next)               0.060000   0.000000   0.060000 (  0.065000)
1m redefined obj.respond_to?          0.130000   0.000000   0.130000 (  0.131000)
1m varying name respond_to?           0.250000   0.000000   0.250000 (  0.250000)

AFTER compiled:
                                          user     system      total        real
control, 1 and :to_ary                0.040000   0.000000   0.040000 (  0.035000)
1m 1.respond_to?(:to_ary)             0.050000   0.000000   0.050000 (  0.050000)
1m 1.respond_to?(:to_ary,true)        0.050000   0.000000   0.050000 (  0.050000)
1m 1.respond_to?(:next)               0.050000   0.000000   0.050000 (  0.045000)
1m redefined obj.respond_to?          0.060000   0.000000   0.060000 (  0.063000)
1m varying name respond_to?           0.070000   0.000000   0.070000 (  0.071000)
1m varying name respond_to?           0.060000   0.000000   0.060000 (  0.058000)

2.diff

diff --git a/core/src/main/java/org/jruby/Ruby.java b/core/src/main/java/org/jruby/Ruby.java
index f780f2c..3f5a16b 100644
--- a/core/src/main/java/org/jruby/Ruby.java
+++ b/core/src/main/java/org/jruby/Ruby.java
@@ -1849,6 +1849,14 @@ public final class Ruby {
     public void setRespondToMethod(DynamicMethod rtm) {
         this.respondTo = rtm;
     }
+
+    public DynamicMethod getRespondToMissingMethod() {
+        return respondToMissing;
+    }
+
+    public void setRespondToMissingMethod(DynamicMethod rtmm) {
+        this.respondToMissing = rtmm;
+    }
     
     public RubyClass getDummy() {
         return dummyClass;
@@ -4695,7 +4703,7 @@ public final class Ruby {
             procSysModule, precisionModule, errnoModule;
 
     private DynamicMethod privateMethodMissing, protectedMethodMissing, variableMethodMissing,
-            superMethodMissing, normalMethodMissing, defaultMethodMissing, respondTo;
+            superMethodMissing, normalMethodMissing, defaultMethodMissing, respondTo, respondToMissing;
     
     // record separator var, to speed up io ops that use it
     private GlobalVariable recordSeparatorVar;
diff --git a/core/src/main/java/org/jruby/RubyKernel.java b/core/src/main/java/org/jruby/RubyKernel.java
index 31bf0b8..0c4f15b 100644
--- a/core/src/main/java/org/jruby/RubyKernel.java
+++ b/core/src/main/java/org/jruby/RubyKernel.java
@@ -164,6 +164,7 @@ public class RubyKernel {
         RubyModule module = runtime.getKernel();
 
         runtime.setRespondToMethod(module.searchMethod("respond_to?"));
+        runtime.setRespondToMissingMethod(module.searchMethod("respond_to_missing?"));
     }
 
     @JRubyMethod(module = true, visibility = PRIVATE)
diff --git a/core/src/main/java/org/jruby/compiler/impl/InvokeDynamicInvocationCompiler.java b/core/src/main/java/org/jruby/compiler/impl/InvokeDynamicInvocationCompiler.java
index 15f0bd9..51762ba 100644
--- a/core/src/main/java/org/jruby/compiler/impl/InvokeDynamicInvocationCompiler.java
+++ b/core/src/main/java/org/jruby/compiler/impl/InvokeDynamicInvocationCompiler.java
@@ -98,10 +98,17 @@ public class InvokeDynamicInvocationCompiler extends StandardInvocationCompiler
 
     @Override
     public void invokeDynamic(String name, CompilerCallback receiverCallback, ArgumentsCallback argsCallback, CallType callType, CompilerCallback closureArg, boolean iterator) {
+        // super calls do not optimize in indy right now
         if (callType == CallType.SUPER) {
             super.invokeDynamic(name, receiverCallback, argsCallback, callType, closureArg, iterator);
             return;
         }
+
+        // respond_to? calls do not optimize in indy right now
+        if (name.equals("respond_to?")) {
+            super.invokeDynamic(name, receiverCallback, argsCallback, callType, closureArg, iterator);
+            return;
+        }
         
         methodCompiler.loadThreadContext(); // [adapter, tc]
         
diff --git a/core/src/main/java/org/jruby/runtime/callsite/RespondToCallSite.java b/core/src/main/java/org/jruby/runtime/callsite/RespondToCallSite.java
index 202a6ac..ba61e75 100644
--- a/core/src/main/java/org/jruby/runtime/callsite/RespondToCallSite.java
+++ b/core/src/main/java/org/jruby/runtime/callsite/RespondToCallSite.java
@@ -68,13 +68,16 @@ public class RespondToCallSite extends NormalCachingCallSite {
         }
 
         // alternate logic to cache the result of respond_to if it's the standard one
-        // FIXME: 1.9's respond_to_missing breaks this, so we have to bail out
-        if (false &&
-                entry.method.equals(context.runtime.getRespondToMethod())) {
+        if (entry.method.equals(context.runtime.getRespondToMethod())) {
             String name = arg.asJavaString();
             RespondToTuple tuple = recacheRespondsTo(entry, name, selfType, true, context);
-            respondToTuple = tuple;
-            return tuple.respondsTo;
+
+            // only cache if it does respond_to? or there's no custom respond_to_missing? logic
+            if (tuple.respondsTo.isTrue() ||
+                    selfType.searchWithCache("respond_to_missing?").method == context.runtime.getRespondToMissingMethod()) {
+                respondToTuple = tuple;
+                return tuple.respondsTo;
+            }
         }
 
         // normal logic if it's not the builtin respond_to? method
@@ -91,14 +94,16 @@ public class RespondToCallSite extends NormalCachingCallSite {
         }
 
         // alternate logic to cache the result of respond_to if it's the standard one
-        // FIXME: 1.9's respond_to_missing breaks this, so we have to bail out
-        // FIXME: 1.9's respond_to_missing breaks this, so we have to bail out
-        if (false &&
-                entry.method.equals(context.runtime.getRespondToMethod())) {
+        if (entry.method.equals(context.runtime.getRespondToMethod())) {
             String name = arg0.asJavaString();
             RespondToTuple tuple = recacheRespondsTo(entry, name, selfType, !arg1.isTrue(), context);
-            respondToTuple = tuple;
-            return tuple.respondsTo;
+
+            // only cache if it does respond_to? or there's no custom respond_to_missing? logic
+            if (tuple.respondsTo.isTrue() ||
+                    selfType.searchWithCache("respond_to_missing?").method == context.runtime.getRespondToMissingMethod()) {
+                respondToTuple = tuple;
+                return tuple.respondsTo;
+            }
         }
 
         // normal logic if it's not the builtin respond_to? method