For a given program execution, the mapping <i>W</i>, when limited to synchronizing operations,
must be explainable by some implicit total order of the synchronizing operations
that is consistent with sequencing and the values read and written by those operations.
</p>

<p>
The <i>synchronized before</i> relation is a partial order on synchronizing memory operations,
derived from <i>W</i>.
If a synchronizing read-like memory operation <i>r</i>

unless the operation involves shifts or untyped <a href="#Constants">constants</a>.
For operations involving constants only, see the section on
<a href="#Constant_expressions">constant expressions</a>.
</p>

<p>
Except for shift operations, if one operand is an untyped <a href="#Constants">constant</a>

what the toolchain actually generates for that operation might
not be a move instruction at all, perhaps a clear or load.
Or it might correspond exactly to the machine instruction with that name.
In general, machine-specific operations tend to appear as themselves, while more general concepts like
memory move and subroutine call and return are more abstract.
The details vary with architecture, and we apologize for the imprecision; the situation is not well-defined.

unless the operation involves shifts or untyped <a href="#Constants">constants</a>.
For operations involving constants only, see the section on
<a href="#Constant_expressions">constant expressions</a>.
</p>

<p>
Except for shift operations, if one operand is an untyped <a href="#Constants">constant</a>