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Diffstat (limited to 'doc/asm.html')
| -rw-r--r-- | doc/asm.html | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/doc/asm.html b/doc/asm.html index 2af2005143..392af174c2 100644 --- a/doc/asm.html +++ b/doc/asm.html @@ -12,7 +12,7 @@ The document is not comprehensive. <p> The assembler is based on the input style of the Plan 9 assemblers, which is documented in detail -<a href="http://plan9.bell-labs.com/sys/doc/asm.html">elsewhere</a>. +<a href="https://9p.io/sys/doc/asm.html">elsewhere</a>. If you plan to write assembly language, you should read that document although much of it is Plan 9-specific. The current document provides a summary of the syntax and the differences with what is explained in that document, and @@ -23,7 +23,7 @@ describes the peculiarities that apply when writing assembly code to interact wi The most important thing to know about Go's assembler is that it is not a direct representation of the underlying machine. Some of the details map precisely to the machine, but some do not. This is because the compiler suite (see -<a href="http://plan9.bell-labs.com/sys/doc/compiler.html">this description</a>) +<a href="https://9p.io/sys/doc/compiler.html">this description</a>) needs no assembler pass in the usual pipeline. Instead, the compiler operates on a kind of semi-abstract instruction set, and instruction selection occurs partly after code generation. @@ -621,6 +621,15 @@ These modes accept only 1, 2, 4, and 8 as scale factors. </ul> +<p> +When using the compiler and assembler's +<code>-dynlink</code> or <code>-shared</code> modes, +any load or store of a fixed memory location such as a global variable +must be assumed to overwrite <code>CX</code>. +Therefore, to be safe for use with these modes, +assembly sources should typically avoid CX except between memory references. +</p> + <h3 id="amd64">64-bit Intel 386 (a.k.a. amd64)</h3> <p> |