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