Hi, by folding a constant prepend followed by an argument prepend into a single prepender with the constant bound in, we significantly reduce the amount of possible MH shapes that the String concat bootstrap method can generate by sharing the stem of the combinator tree between similar concatenations like '"foo" + obj + obj' and 'obj + "foo" + obj'.
See bug for details and the outline of a proof that this turns an exponential growth factor into a constant one. Bug: https://bugs.openjdk.java.net/browse/JDK-8222852 Webrev: http://cr.openjdk.java.net/~redestad/8222852/open.00/ Testing: tier1-3, verified retained throughput performance in microbenchmarks, verified significant startup and footprint improvements for both realistic and synthetically complex combinations of argument shapes. Thanks! /Claes
