[PATCH] 8147527: Non-optimal code generated for postfix unary operators

[bsrbnd]

Hi,

Next is a probably better patch (derived from issue 8143388 changeset)
that handles also "this, this$0, ..." in addition to the existing
"super" handling. It optimizes the both cases ("this" and "super")
described in issue 8147527.
Notice that "thisDollar" could be part of the "Names" class if necessary.

Bernard

diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
@@ -2218,8 +2218,10 @@
                 return builder.build(rval);
         }
         Name name = TreeInfo.name(rval);
-        if (name == names._super)
+        Name thisDollar = names.fromString(names._this + "$");
+        if (name != null && (name == names._super || name ==
names._this || name.startsWith(thisDollar))) {
             return builder.build(rval);
+        }
         VarSymbol var =
             new VarSymbol(FINAL|SYNTHETIC,
                           names.fromString(


2016-10-10 13:45 GMT+02:00 bsrbnd <bsrbnd at gmail.com>:
> Hi,
>
> Consider the following example slightly modified from issue 8147527
> description to incorporate an assignment operator and an inner class
> which are both of them involved in the optimization process:
>
> class Issue8147527 {
>     Integer i=0;
>     private Integer test() {
>         this.i += 3;
>         for (; i<5; this.i++);
>         return this.i++;
>     }
>
>     Integer j=10;
>     class Inner {
>         private Integer test() {
>             return Issue8147527.this.j++;
>         }
>     }
>
>     public static void main(String[] args) {
>         Issue8147527 self = new Issue8147527();
>         System.out.println(self.test());
>         System.out.println(self.i);
>
>         Inner in = self.new Inner();
>         System.out.println(in.test());
>         System.out.println(self.j);
>     }
> }
>
> The following patch omits "this" for the special case of a
> select-expression used as an lvalue.
> Thus we had before optimization:
>
>   private java.lang.Integer test();
>     Code:
>        0: aload_0
>        1: astore_1
>        2: aload_1
>        3: aload_1
>        4: getfield      #3                  // Field i:Ljava/lang/Integer;
>        7: invokevirtual #5                  // Method
> java/lang/Integer.intValue:()I
>       10: iconst_3
>       11: iadd
>       12: invokestatic  #2                  // Method
> java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
>       15: dup_x1
>       16: putfield      #3                  // Field i:Ljava/lang/Integer;
>
> And after optimization, we have:
>
>   private java.lang.Integer test();
>     Code:
>        0: aload_0
>        1: aload_0
>        2: getfield      #3                  // Field i:Ljava/lang/Integer;
>        5: invokevirtual #5                  // Method
> java/lang/Integer.intValue:()I
>        8: iconst_3
>        9: iadd
>       10: invokestatic  #2                  // Method
> java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
>       13: putfield      #3                  // Field i:Ljava/lang/Integer;
>
> I've run all javac tests and it seems quite good.
> Notice that I haven't checked the "super" case yet, waiting for any
> feedback about the first optimization.
>
> Regards,
> Bernard
>
> diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
> b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
> --- a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
> +++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java
> @@ -2253,6 +2253,7 @@
>          case SELECT: {
>              final JCFieldAccess s = (JCFieldAccess)lval;
>              Symbol lid = TreeInfo.symbol(s.selected);
> +            if (lid != null && lid.name.equals(names._this)) return
> builder.build(make.Ident(s.sym));
>              if (lid != null && lid.kind == TYP) return builder.build(lval);
>              return abstractRval(s.selected, new TreeBuilder() {
>                      public JCExpression build(final JCExpression selected) {