[PATCH] libstdc++: Add C++ runtime support for new 128-bit long double format

[Jonathan Wakely]

On 04/12/20 00:35 +0000, Jonathan Wakely wrote:
>On 03/12/20 20:07 -0300, Tulio Magno Quites Machado Filho via Libstdc++ wrote:
>>Jonathan Wakely via Libstdc++ <libstdc++@gcc.gnu.org> writes:
>>
>>>diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
>>>index cbfdf4c6bad..d25842fef35 100644
>>>--- a/libstdc++-v3/configure.ac
>>>+++ b/libstdc++-v3/configure.ac
>>>@@ -421,12 +425,43 @@ case "$target" in
>>>     port_specific_symbol_files="\$(top_srcdir)/config/os/gnu-linux/ldbl-extra.ver"
>>>     case "$target" in
>>>       powerpc*-*-linux*)
>>>-	LONG_DOUBLE_COMPAT_FLAGS="$LONG_DOUBLE_COMPAT_FLAGS -mno-gnu-attribute" ;;
>>>+	LONG_DOUBLE_COMPAT_FLAGS="$LONG_DOUBLE_COMPAT_FLAGS -mno-gnu-attribute"
>>>+        # Check for IEEE128 support in libm:
>>>+        AC_CHECK_LIB(m, frexpf128,
>>
>>I suggest to replace frexpf128 with __frexpieee128.
>>
>>The former is available on a glibc that support _Float128 (since glibc 2.26).
>>The later is available on a glibc that supports binary128 long double (since
>>glibc 2.32)
>
>Hmm, yes, you pointed me to __frexpieee128 a few months ago, but for
>some reason I either didn't switch to using it, or lost a patch when
>squashing and rebasing branches. Hopefully I just forgot to change it,
>but I'll double check to make sure I haven't left any work on an old
>branch. Thanks for suggesting it (again!)

As expected, it still works with a check for __frexpieee128 instead.

So are you happy for me to push this to master with that change?

(It won't be until Tuesday now, as I have some time off).