Document -funbox-strict-primitive-fields

docs/users_guide/flags.xml

@@ -1739,6 +1739,14 @@
             <entry><option>-fno-unbox-strict-fields</option></entry>
           </row>
 
+          <row>
+            <entry><option>-funbox-strict-primitive-fields</option></entry>
+            <entry>Flatten strict constructor fields with a
+              pointer-sized representation</entry>
+            <entry>dynamic</entry>
+            <entry><option>-fno-unbox-strict-primitive-fields</option></entry>
+          </row>
+
           <row>
             <entry><option>-funfolding-creation-threshold</option></entry>
             <entry>Tweak unfolding settings</entry>

docs/users_guide/using.xml

@@ -1860,6 +1860,31 @@ f "2"    = 2
           </listitem>
         </varlistentry>
 
+        <varlistentry>
+          <term>
+            <option>-funbox-strict-primitive-fields</option>:
+            <indexterm><primary><option>-funbox-strict-primitive-fields</option></primary></indexterm>
+            <indexterm><primary>strict constructor fields</primary></indexterm>
+            <indexterm><primary>constructor fields, strict</primary></indexterm>
+          </term>
+          <listitem>
+            <para>This option causes all constructor fields which are marked
+            strict (i.e. &ldquo;!&rdquo;) and which representation is smaller or
+            equal to the size of a pointer to be unpacked if possible. It is
+            equivalent to adding an <literal>UNPACK</literal> pragma to every
+            strict constructor field that fullfills the size restriction. (see
+            <xref linkend="unpack-pragma"/>).
+            </para>
+
+            <para>This option is less of a sledgehammer than
+            <option>-funbox-strict-fields</option>: it should rarely make things
+            worse. If you use <option>-funbox-strict-primitive-fields</option>
+            to turn on unboxing by default you can disable it for certain
+            constructor fields using the <literal>NOUNPACK</literal> pragma (see
+            <xref linkend="nounpack-pragma"/>).</para>
+          </listitem>
+        </varlistentry>
+
         <varlistentry>
           <term>
             <option>-fspec-constr</option>