r271044 - in /trunk/gcc: go/gofrontend/MERGE go...

[ian@gcc.gnu.org]

Author: ian
Date: Thu May  9 21:24:56 2019
New Revision: 271044

URL: https://gcc.gnu.org/viewcvs?rev=271044&root=gcc&view=rev
Log:
    compiler: avoid copy for string([]byte) conversion used in map keys
    
    If a string([]byte) conversion is used immediately as a key for a
    map read, we don't need to copy the backing store of the byte
    slice, as mapaccess does not keep a reference to it.
    
    The gc compiler does more than this: it also avoids the copy if
    the map key is a composite literal that contains the conversion
    as a field, like, T{ ... { ..., string(b), ... }, ... }. For now,
    we just optimize the simple case, which is probably most common.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/176197

	* go.dg/mapstring.go: New test.

Added:
    trunk/gcc/testsuite/go.dg/mapstring.go
Modified:
    trunk/gcc/go/gofrontend/MERGE
    trunk/gcc/go/gofrontend/expressions.cc
    trunk/gcc/go/gofrontend/statements.cc
    trunk/gcc/testsuite/ChangeLog