RFR: 8061472 String.format in DeferredAttr.DeferredTypeMap constructor leads to excessive object creation

[Joel Borggrén-Franck]

Hi,

Claes in the performance team noticed that we spend a lot of time in String.format() in the constructor in DeferredTypeMap. For an sjavac compile of the jdk a profile could show as high as 2% time spent in that method, excluding the cost of garbage collection.

This simple fix results in up to a 5% performance enhancement compiling the Jdk in a micro benchmark setup.

Bug: https://bugs.openjdk.java.net/browse/JDK-8061472

Patch is really small:

cheers
/Joel

diff -r 46105e2a56c7 src/jdk.compiler/share/classes/com/sun/tools/javac/comp/DeferredAttr.java
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/DeferredAttr.java	Wed Dec 17 16:47:56 2014 +0000
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/DeferredAttr.java	Wed Dec 17 17:58:33 2014 +0100
@@ -352,11 +352,26 @@
          * type are reversed after the speculative round finishes. This means the
          * expression tree will be left in a blank state.
          */
-        SPECULATIVE,
+        SPECULATIVE {
+             @Override
+             public String getDescriptiveName() {
+                 return "deferredTypeMap[SPECULATIVE]";
+             }
+         },
         /**
          * This is the plain type-checking mode. Produces side-effects on the underlying AST node
          */
-        CHECK
+        CHECK {
+             @Override
+             public String getDescriptiveName() {
+                 return "deferredTypeMap[CHECK]";
+             }
+         };
+
+         /**
+          * @return a descriptive name of this mode
+          */
+         public abstract String getDescriptiveName();
     }

     /**
@@ -849,7 +864,7 @@
         DeferredAttrContext deferredAttrContext;

         protected DeferredTypeMap(AttrMode mode, Symbol msym, MethodResolutionPhase phase) {
-            super(String.format("deferredTypeMap[%s]", mode));
+            super(mode.getDescriptiveName());
             this.deferredAttrContext = new DeferredAttrContext(mode, msym, phase,
                     infer.emptyContext, emptyDeferredAttrContext, types.noWarnings);
         }