compiler: open code string slice expressions

    
    Currently a string slice expression is implemented with a runtime
    call __go_string_slice. Change it to open code it, which is more
    efficient, and allows the backend to further optimize it.
    
    Also omit the write barrier for length-only update (i.e.
    s = s[:n]).
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/182540

From-SVN: r272549

1 files changed, 0 insertions, 30 deletions

diff --git a/libgo/runtime/go-strslice.c b/libgo/runtime/go-strslice.c
deleted file mode 100644
index d51c249..0000000
--- a/libgo/runtime/go-strslice.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/* go-strslice.c -- the go string slice function.
-
-   Copyright 2009 The Go Authors. All rights reserved.
-   Use of this source code is governed by a BSD-style
-   license that can be found in the LICENSE file.  */
-
-#include "runtime.h"
-
-String
-__go_string_slice (String s, intgo start, intgo end)
-{
-  intgo len;
-  String ret;
-
-  len = s.len;
-  if (end == -1)
-    end = len;
-  if (start > len || end < start || end > len)
-    runtime_panicstring ("string index out of bounds");
-  ret.len = end - start;
-  // If the length of the new string is zero, the str field doesn't
-  // matter, so just set it to nil.  This avoids the problem of
-  // s.str + start pointing just past the end of the string,
-  // which may keep the next memory block alive unnecessarily.
-  if (ret.len == 0)
-    ret.str = nil;
-  else
-    ret.str = s.str + start;
-  return ret;
-}