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doc/go1.17: add release notes for register ABI

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Also delete the TODO for the linker section.

Updates #44513.
Updates #40724.

Change-Id: I4d62a907e8c3070831a052cdfe1e21648698df12
Reviewed-on: https://go-review.googlesource.com/c/go/+/323289
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Cherry Mui 2021-05-27 10:13:00 -04:00
parent 2e59cc5fb4
commit 2bec019fb5
1 changed files with 39 additions and 13 deletions
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doc/go1.17.html
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@ -226,31 +226,57 @@ Do not send CLs removing the interior tags from such phrases.
<h2 id="runtime">Runtime</h2>
<p><!-- CL 304470 -->
TODO: <a href="https://golang.org/cl/304470">https://golang.org/cl/304470</a>: cmd/compile, runtime: add metadata for argument printing in traceback
</p>
<p>
TODO: complete the Runtime section
</p>
<h2 id="compiler">Compiler</h2>
<p><!-- CL 283112, golang.org/issue/28727 -->
<p><!-- golang.org/issue/40724 -->
Go 1.17 implements a new way of passing function arguments and results using
registers instead of the stack. This work is enabled for Linux, MacOS, and
Windows on the 64-bit x86 architecture (the <code>linux/amd64</code>,
<code>darwin/amd64</code>, <code>windows/amd64</code> ports). For a
representative set of Go packages and programs, benchmarking has shown
performance improvements of about 5%, and a typical reduction in binary size
of about 2%.
</p>
<p>
This change does not affect the functionality of any safe Go code. It can affect
code outside the <a href="/doc/go1compat">compatibility guidelines</a> with
minimal impact. To maintain compatibility with existing assembly functions,
adapter functions converting between the new register-based calling convention
and the previous stack-based calling convention (also known as ABI wrappers)
are sometimes used. This is mostly invisible to users, except for assembly
functions that have their addresses taken in Go. Using <code>reflect.ValueOf(fn).Pointer()</code>
(or similar approaches such as via <code>unsafe.Pointer</code>) to get the address
of an assembly function will now return the address of the ABI wrapper. This is
mostly harmless, except for special-purpose assembly code (such as accessing
thread-local storage or requiring a special stack alignment). Assembly functions
called indirectly from Go via <code>func</code> values will now be made through
ABI wrappers, which may cause a very small performance overhead. Also, calling
Go functions from assembly may now go through ABI wrappers, with a very small
performance overhead.
</p>
<p><!-- CL 304470 -->
The format of stack traces from the runtime (printed when an uncaught panic
occurs, or when <code>runtime.Stack</code> is called) is improved. Previously,
the function arguments were printed as hexadecimal words based on the memory
layout. Now each argument in the source code is printed separately, separated
by commas. Aggregate-typed (struct, array, string, slice, interface, and complex)
arguments are delimited by curly braces. A caveat is that the value of an
argument that only lives in a register and is not stored to memory may be
inaccurate. Results (which were usually inaccurate) are no longer printed.
</p>
<p><!-- CL 283112, golang.org/issue/28727 -->
Functions containing closures can now be inlined. One effect of this change is
that a function with a closure may actually produce a distinct closure function
for each place that the function is inlined. Hence, this change could reveal
bugs where Go functions are compared (incorrectly) by pointer value. Go
functions are by definition not comparable.
TODO: complete the Compiler section, or delete if not needed
</p>
<h2 id="linker">Linker</h2>
<p>
TODO: complete the Linker section, or delete if not needed
</p>
<h2 id="library">Core library</h2>