PATCH: Add -mlong-double-128 and make it default for 64-bit Bionic

[H.J. Lu]

On Fri, Jan 31, 2014 at 10:19:12AM -0800, H.J. Lu wrote:
> On Fri, Jan 31, 2014 at 10:12 AM, Joseph S. Myers
> <joseph@codesourcery.com> wrote:
> > On Fri, 31 Jan 2014, Andrew Pinski wrote:
> >
> >> On Fri, Jan 31, 2014 at 5:59 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> >> > Hi,
> >> >
> >> > For 64-bit Android, long double is 128-bit IEEE-754 floating point type.
> >> > This patch adds -mlong-double-128 to i386 and makes it default for 64-bit
> >> > Bionic.  I only added MASK_LONG_DOUBLE_128.  I made -mlong-double-128,
> >> > -mlong-double-64 and -mlong-double-80 negate each other so that the
> >> > last one on command line wins.  It os OK since we don't support
> >> > -mlong-double-xxx in target attribute. I added some testcases to verify
> >> > it works correctly.  OK for trunk?
> >>
> >> I don't see any where in the documentation that explains the
> >> difference between -mlong-double-128 and -m128bit-long-double.  Can
> >> you please add that  -mlong-double-128 causes soft-floating point.
> 
> I will update it together with -m128bit-long-double clarification.
> 
> >> Also what about the interactions between these two options.
> 
> They have nothing to do with each other.   -m128bit-long-double
> controls the storage size of __float80 amd -mlong-double-XXX
> controls the size of long double, 64, 80 and 128 bits.

I checked in my patch.  Here is a patch to update invoke.texi.  OK
for trunk?

Thanks.

H.J.
---
2014-02-03  H.J. Lu  <hongjiu.lu@intel.com>

	* doc/invoke.texi: Document -m96bit-long-double/-m128bit-long-double
	for the storage size of 80-bit long double.  Mention software
	floating-point for __float128.

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 89e80ac..e2193a9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -15027,28 +15027,28 @@ without that switch.
 @itemx -m128bit-long-double
 @opindex m96bit-long-double
 @opindex m128bit-long-double
-These switches control the size of @code{long double} type.  The i386
-application binary interface specifies the size to be 96 bits,
+These switches control the storage size of 80-bit @code{long double} type.
+The i386 application binary interface specifies the size to be 96 bits,
 so @option{-m96bit-long-double} is the default in 32-bit mode.
 
-Modern architectures (Pentium and newer) prefer @code{long double}
+Modern architectures (Pentium and newer) prefer 80-bit @code{long double}
 to be aligned to an 8- or 16-byte boundary.  In arrays or structures
 conforming to the ABI, this is not possible.  So specifying
-@option{-m128bit-long-double} aligns @code{long double}
-to a 16-byte boundary by padding the @code{long double} with an additional
-32-bit zero.
+@option{-m128bit-long-double} aligns 80-bit @code{long double}
+to a 16-byte boundary by padding the 80-bit @code{long double} with an
+additional 32-bit zero.
 
 In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as
-its ABI specifies that @code{long double} is aligned on 16-byte boundary.
+its ABI specifies that 80-bit @code{long double} is aligned on 16-byte boundary.
 
 Notice that neither of these options enable any extra precision over the x87
-standard of 80 bits for a @code{long double}.
+standard of 80 bits for an 80-bit @code{long double}.
 
 @strong{Warning:} if you override the default value for your target ABI, this
 changes the size of 
-structures and arrays containing @code{long double} variables,
+structures and arrays containing 80-bit @code{long double} variables,
 as well as modifying the function calling convention for functions taking
-@code{long double}.  Hence they are not binary-compatible
+80-bit @code{long double}.  Hence they are not binary-compatible
 with code compiled without that switch.
 
 @item -mlong-double-64
@@ -15061,7 +15061,8 @@ These switches control the size of @code{long double} type. A size
 of 64 bits makes the @code{long double} type equivalent to the @code{double}
 type. This is the default for 32-bit Bionic C library.  A size
 of 128 bits makes the @code{long double} type equivalent to the
-@code{__float128} type. This is the default for 64-bit Bionic C library.
+@code{__float128} type, which is implemented with software floating-point
+support.  This is the default for 64-bit Bionic C library.
 
 @strong{Warning:} if you override the default value for your target ABI, this
 changes the size of