diff --git a/llvm/docs/CommandGuide/llvm-size.rst b/llvm/docs/CommandGuide/llvm-size.rst
--- a/llvm/docs/CommandGuide/llvm-size.rst
+++ b/llvm/docs/CommandGuide/llvm-size.rst
@@ -6,10 +6,193 @@
 SYNOPSIS
 --------
 
-:program:`llvm-size` [*options*]
+:program:`llvm-size` [*options*] [*input...*]
 
 DESCRIPTION
 -----------
 
-:program:`llvm-size` is a tool that prints size information for object files.
-The goal is to make it a drop-in replacement for GNU's :program:`size`.
+:program:`llvm-size` is a tool that prints size information for binary files.
+It is intended to be a drop-in replacement for GNU's :program:`size`.
+
+The tool prints size information for each ``input`` specified. If no input is
+specified, the program prints size information for ``a.out``. If "``-``" is
+specified as an input file, :program:`llvm-size` reads a file from the standard
+input stream. If an input is an archive, size information will be displayed for
+all its members.
+
+OPTIONS
+-------
+
+.. option:: -A
+
+ Equivalent to :option:`--format` with a value of ``sysv``.
+
+.. option:: --arch=<arch>
+
+ Architecture(s) from Mach-O universal binaries to display information for.
+
+.. option:: -B
+
+ Equivalent to :option:`--format` with a value of ``berkeley``.
+
+.. option:: --common
+
+ Include ELF common symbol sizes in bss size for ``berkeley`` output format, or
+ as a separate section entry for ``sysv`` output. If not specified, these
+ symbols are not ignored.
+
+.. option:: -d
+
+ Equivalent to :option:`--radix` with a value of ``10``.
+
+.. option:: -l
+
+ Display verbose address and offset information for segments and sections in
+ Mach-O files in ``darwin`` format.
+
+.. option:: --format=<format>
+
+ Set the output format to the ``<format>`` specified. Available ``<format>``
+ options are ``berkeley`` (the default), ``sysv`` and ``darwin``.
+
+ Berkeley output summarises text, data and bss sizes in each file, as shown
+ below for a typical pair of ELF files:
+
+.. code-block:: console
+
+ $ llvm-size --format=berkeley test.o test2.o
+    text    data     bss     dec     hex filename
+     182      16       5     203      cb test.elf
+      82       8       1      91      5b test2.o
+
+ For Mach-O files, the output format is slightly different:
+
+.. code-block:: console
+
+ $ llvm-size --format=berkeley macho.obj macho2.obj
+ __TEXT  __DATA  __OBJC  others  dec     hex
+ 4       8       0       0       12      c       macho.obj
+ 16      32      0       0       48      30      macho2.obj
+
+ Sysv output displays size and address information for most sections, with each
+ file being listed separately:
+
+.. code-block:: console
+
+ $ llvm-size --format=sysv test.elf test2.o
+    test.elf  :
+    section       size      addr
+    .eh_frame       92   2097496
+    .text           90   2101248
+    .data           16   2105344
+    .bss             5   2105360
+    .comment       209         0
+    Total          412
+
+    test2.o  :
+    section             size   addr
+    .text                 26      0
+    .data                  8      0
+    .bss                   1      0
+    .comment             106      0
+    .note.GNU-stack        0      0
+    .eh_frame             56      0
+    .llvm_addrsig          2      0
+    Total                199
+
+ ``darwin`` format only affects Mach-O input files. If an input of a different
+ file format is specified, :program:`llvm-size` falls back to ``berkeley``
+ format. When producing ``darwin`` format, the tool displays information about
+ segments and sections:
+
+.. code-block:: console
+
+ $ llvm-size --format=darwin macho.obj macho2.obj
+    macho.obj:
+    Segment : 12
+            Section (__TEXT, __text): 4
+            Section (__DATA, __data): 8
+            total 12
+    total 12
+    macho2.obj:
+    Segment : 48
+            Section (__TEXT, __text): 16
+            Section (__DATA, __data): 32
+            total 48
+    total 48
+
+.. option:: --help, -h
+
+ Display a summary of command line options.
+
+.. option:: --help-list
+
+ Display an uncategorized summary of command line options.
+
+.. option:: -m
+
+ Equivalent to :option:`--format` with a value of ``darwin``.
+
+.. option:: -o
+
+ Equivalent to :option:`--radix` with a value of ``8``.
+
+.. option:: --radix=<value>
+
+ Display size information in the specified radix. Permitted values are ``8``,
+ ``10`` (the default) and ``16`` for octal, decimal and hexadecimal output
+ respectively.
+
+ Example:
+
+.. code-block:: console
+
+ $ llvm-size --radix=8 test.o
+    text    data     bss     oct     hex filename
+    0152      04      04     162      72 test.o
+
+ $ llvm-size --radix=10 test.o
+    text    data     bss     dec     hex filename
+     106       4       4     114      72 test.o
+
+ $ llvm-size --radix=16 test.o
+    text    data     bss     dec     hex filename
+    0x6a     0x4     0x4     114      72 test.o
+
+.. option:: --totals, -t
+
+ Applies only to ``berkeley`` output format. Display the totals for all listed
+ fields, in addition to the individual file listings.
+
+ Example:
+
+.. code-block:: console
+
+ $ llvm-size --totals test.elf test2.o
+    text    data     bss     dec     hex filename
+     182      16       5     203      cb test.elf
+      82       8       1      91      5b test2.o
+     264      24       6     294     126 (TOTALS)
+
+.. option:: --version
+
+ Display the version of the :program:`llvm-size` executable.
+
+.. option:: -x
+
+ Equivalent to :option:`--radix` with a value of ``16``.
+
+.. option:: @<FILE>
+
+ Read command-line options from response file ``<FILE>``.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-size` exits with a non-zero exit code if there is an error.
+Otherwise, it exits with code 0.
+
+BUGS
+----
+
+To report bugs, please visit <http://llvm.org/bugs/>.