include/elf/

	* mips.h (EF_MIPS_NAN2008): New macro.

	bfd/
	* elfxx-mips.c (_bfd_mips_elf_merge_private_bfd_data): Handle
	EF_MIPS_NAN2008.
	(_bfd_mips_elf_print_private_bfd_data): Likewise.

	binutils/
	* readelf.c (get_machine_flags): Handle EF_MIPS_NAN2008.

	gas/
	* config/tc-mips.c (mips_flag_nan2008): New variable.
	(options): Add OPTION_NAN enum value.
	(md_longopts): Handle it.
	(md_parse_option): Likewise.
	(s_nan): New function.
	(mips_elf_final_processing): Handle EF_MIPS_NAN2008.
	(md_show_usage): Add -mnan.

	* doc/as.texinfo (Overview): Add -mnan.
	* doc/c-mips.texi (MIPS Opts): Document -mnan.
	(MIPS NaN Encodings): New node.  Document .nan directive.
	(MIPS-Dependent): List the new node.

	gas/testsuite/
	* gas/mips/nan-2008-1.d: New test.
	* gas/mips/nan-2008-2.d: New test.
	* gas/mips/nan-2008-3.d: New test.
	* gas/mips/nan-2008-4.d: New test.
	* gas/mips/nan-legacy-1.d: New test.
	* gas/mips/nan-legacy-2.d: New test.
	* gas/mips/nan-legacy-3.d: New test.
	* gas/mips/nan-legacy-4.d: New test.
	* gas/mips/nan-legacy-5.d: New test.
	* gas/mips/nan-error-1.l: New list test.
	* gas/mips/nan-error-2.l: New list test.
	* gas/mips/nan-2008-override.s: New test source.
	* gas/mips/nan-2008.s: New test source.
	* gas/mips/nan-legacy-override.s: New test source.
	* gas/mips/nan-legacy.s: New test source.
	* gas/mips/nan-error-1.s: New test source.
	* gas/mips/nan-error-2.s: New test source.
	* gas/mips/mips.exp: Run the new tests.

	ld/testsuite/
	* ld-mips-elf/nan-2008.d: New test.
	* ld-mips-elf/nan-legacy.d: New test.
	* ld-mips-elf/nan-mixed-1.d: New test.
	* ld-mips-elf/nan-mixed-2.d: New test.
	* ld-mips-elf/nan-2008.s: New test source.
	* ld-mips-elf/nan-legacy.s: New test source.

2 files changed, 57 insertions, 0 deletions

diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo
index d1e397f8d3..a2771d7b27 100644
--- a/gas/doc/as.texinfo
+++ b/gas/doc/as.texinfo
@@ -402,6 +402,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
    [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
    [@b{-mips64}] [@b{-mips64r2}]
    [@b{-construct-floats}] [@b{-no-construct-floats}]
+   [@b{-mnan=@var{encoding}}]
    [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
    [@b{-mips16}] [@b{-no-mips16}]
    [@b{-mmicromips}] [@b{-mno-micromips}]
@@ -1363,6 +1364,10 @@ The @samp{--relax-branch} option enables the relaxation of out-of-range
 branches.  By default @samp{--no-relax-branch} is selected, causing any
 out-of-range branches to produce an error.
 
+@item -mnan=@var{encoding}
+Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
+(@option{-mnan=legacy}) NaN encoding format.  The latter is the default.
+
 @cindex emulation
 @item --emulation=@var{name}
 This option was formerly used to switch between ELF and ECOFF output
diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 741237acef..8a25a7626a 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -30,6 +30,7 @@ Assembly Language Programming'' in the same work.
 * MIPS assembly options:: Directives to control code generation
 * MIPS autoextend::	Directives for extending MIPS 16 bit instructions
 * MIPS insn::		Directive to mark data as an instruction
+* MIPS NaN Encodings::	Directives to record which NaN encoding is being used
 * MIPS Option Stack::	Directives to save and restore options
 * MIPS ASE Instruction Generation Overrides:: Directives to control
   			generation of MIPS ASE instructions
@@ -416,6 +417,16 @@ Also no MIPS16 branches are ever relaxed.
 By default @samp{--no-relax-branch} is selected, causing any out-of-range
 branches to produce an error.
 
+@cindex @option{-mnan=} command line option, MIPS
+@item -mnan=@var{encoding}
+This option indicates whether the source code uses the IEEE 2008
+NaN encoding (@option{-mnan=2008}) or the original MIPS encoding
+(@option{-mnan=legacy}).  It is equivalent to adding a @code{.nan}
+directive to the beginning of the source file.  @xref{MIPS NaN Encodings}.
+
+@option{-mnan=legacy} is the default if no @option{-mnan} option or
+@code{.nan} directive is used.
+
 @item --trap
 @itemx --no-break
 @c FIXME!  (1) reflect these options (next item too) in option summaries;
@@ -722,6 +733,47 @@ baz:
 
 @end example
 
+@node MIPS NaN Encodings
+@section Directives to record which NaN encoding is being used
+
+@cindex MIPS IEEE 754 NaN data encoding selection
+@cindex @code{.nan} directive, MIPS
+The IEEE 754 floating-point standard defines two types of not-a-number
+(NaN) data: ``signalling'' NaNs and ``quiet'' NaNs.  The original version
+of the standard did not specify how these two types should be
+distinguished.  Most implementations followed the i387 model, in which
+the first bit of the significand is set for quiet NaNs and clear for
+signalling NaNs.  However, the original MIPS implementation assigned the
+opposite meaning to the bit, so that it was set for signalling NaNs and
+clear for quiet NaNs.
+
+The 2008 revision of the standard formally suggested the i387 choice
+and as from Sep 2012 the current release of the MIPS architecture
+therefore optionally supports that form.  Code that uses one NaN encoding
+would usually be incompatible with code that uses the other NaN encoding,
+so MIPS ELF objects have a flag (@code{EF_MIPS_NAN2008}) to record which
+encoding is being used.
+
+Assembly files can use the @code{.nan} directive to select between the
+two encodings.  @samp{.nan 2008} says that the assembly file uses the
+IEEE 754-2008 encoding while @samp{.nan legacy} says that the file uses
+the original MIPS encoding.  If several @code{.nan} directives are given,
+the final setting is the one that is used.
+
+The command-line options @option{-mnan=legacy} and @option{-mnan=2008}
+can be used instead of @samp{.nan legacy} and @samp{.nan 2008}
+respectively.  However, any @code{.nan} directive overrides the
+command-line setting.
+
+@samp{.nan legacy} is the default if no @code{.nan} directive or
+@option{-mnan} option is given.
+
+Note that @sc{gnu} @code{@value{AS}} does not produce NaNs itself and
+therefore these directives do not affect code generation.  They simply
+control the setting of the @code{EF_MIPS_NAN2008} flag.
+
+Traditional MIPS assemblers do not support these directives.
+
 @node MIPS Option Stack
 @section Directives to save and restore options