always aligned to a 16 byte (or higher) boundary will now only be aligned to an 8
  byte boundary.
  Some programs that use assembly instructions that require memory addresses to be
  more than 8-byte aligned and rely on the memory allocator's previous alignment behavior
  may break, but we expect such programs to be rare.
  Such programs may be built with <code>GOEXPERIMENT=noallocheaders</code> to revert

may be implemented as a write of each individual sub-value,
in any order.
</p>

<p>
A read <i>r</i> of a memory location <i>x</i>
holding a value
that is not larger than a machine word must observe
some write <i>w</i> such that <i>r</i> does not happen before <i>w</i>
and there is no write <i>w'</i> such that <i>w</i> happens before <i>w'</i>
and <i>w'</i> happens before <i>r</i>.

</p>

<h4 id="Type_switches">Type switches</h4>

<p>
A type switch compares types rather than values. It is otherwise similar
to an expression switch. It is marked by a special switch expression that
has the form of a <a href="#Type_assertions">type assertion</a>
using the keyword <code>type</code> rather than an actual type:
</p>

<pre>
switch x.(type) {
// cases
}
</pre>

<p>

except it uses <code>MOVQ</code> rather than <code>MOVL</code>:
</p>

<pre>
get_tls(CX)
MOVQ	g(CX), AX     // Move g into AX.
MOVQ	g_m(AX), BX   // Move g.m into BX.
</pre>

<p>
Register <code>BP</code> is callee-save.
The assembler automatically inserts <code>BP</code> save/restore when frame size is larger than zero.
Using <code>BP</code> as a general purpose register is allowed,

<pre>
   x        y    min(x, y)    max(x, y)

  -0.0    0.0         -0.0          0.0    // negative zero is smaller than (non-negative) zero
  -Inf      y         -Inf            y    // negative infinity is smaller than any other number
  +Inf      y            y         +Inf    // positive infinity is larger than any other number
   NaN      y          NaN          NaN    // if any argument is a NaN, the result is a NaN
</pre>