Merge pull request #2162 from svaarala/link-arm-mixed-endian

Add a link for legacy ARM mixed endian (FPA)

config/config-options/DUK_USE_BYTEORDER.yaml

@@ -9,7 +9,7 @@ description: >
 
   ARM mixed endian means integers are little endian but IEEE doubles have
   mixed endianness: big endian bytes 12345678 are ordered in memory as
-  43218765.
+  43218765.  See http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0056d/Bcfhgcgd.html.
 
   (This define should be produced by duk_config.h; currently Duktape internals
   use automatically derived defines DUK_USE_{INTEGER,DOUBLE}_{LE,BE_ME}

src-input/duk_dblunion.h

@@ -26,13 +26,14 @@
  *
  *    A B C D E F G H    Big endian (e.g. 68k)           DUK_USE_DOUBLE_BE
  *    H G F E D C B A    Little endian (e.g. x86)        DUK_USE_DOUBLE_LE
- *    D C B A H G F E    Mixed/cross endian (e.g. ARM)   DUK_USE_DOUBLE_ME
+ *    D C B A H G F E    Mixed endian (e.g. ARM FPA)     DUK_USE_DOUBLE_ME
  *
- *  ARM is a special case: ARM double values are in mixed/cross endian
- *  format while ARM duk_uint64_t values are in standard little endian
+ *  Legacy ARM (FPA) is a special case: ARM double values are in mixed
+ *  endian format while ARM duk_uint64_t values are in standard little endian
  *  format (H G F E D C B A).  When a double is read as a duk_uint64_t
  *  from memory, the register will contain the (logical) value
  *  E F G H A B C D.  This requires some special handling below.
+ *  See http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0056d/Bcfhgcgd.html.
  *
  *  Indexes of various types (8-bit, 16-bit, 32-bit) in memory relative to
  *  the logical (big endian) order:

website/guide/duktapebuiltins.html

@@ -150,6 +150,10 @@ ll u n p2 a4 x64 linux gcc     // l|b|m integer endianness, l|b|m IEEE double en
                                // gcc|clang|msvc|etc: compiler
 </pre>
 
+<p>For endianness, "l" stands for little endian, "b" for big endian, and "m"
+for mixed endian (legacy ARM devices, see e.g.
+<a href="http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0056d/Bcfhgcgd.html">The FPA architecture</a>).</p>
+
 <h3 id="builtin-duktape-fin">fin()</h3>
 
 <p>When called with a single argument, gets the current finalizer of an object:</p>