[gcc(refs/users/meissner/heads/work100)] Update ChangeLog.meissner.

[Michael Meissner <meissner@gcc.gnu.org>]

https://gcc.gnu.org/g:1958caeba256da4615eeffc83f71380a1f4772ba

commit 1958caeba256da4615eeffc83f71380a1f4772ba
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Fri Sep 9 17:04:49 2022 -0400

    Update ChangeLog.meissner.
    
    2022-09-09   Michael Meissner  <meissner@linux.ibm.com>
    
    gcc/
    
            * ChangeLog.meissner: Update.

Diff:
---
 gcc/ChangeLog.meissner | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/gcc/ChangeLog.meissner b/gcc/ChangeLog.meissner
index 726276a9168..fa224a0d206 100644
--- a/gcc/ChangeLog.meissner
+++ b/gcc/ChangeLog.meissner
@@ -1,3 +1,79 @@
+==================== work100, patch #6
+
+Make __float128 use the _Float128 type.
+
+Currently GCC uses the long double type node for __float128 if long double is
+IEEE 128-bit.  It did not use the node for _Float128.
+
+Problems showed up if you call the nansq function to make a signaling NaN (nansq
+is mapped to nansf128).  Because the type node for _Float128 is different from
+__float128, the machine independent code converts signaling NaNs to quiet NaNs
+if the types are  not compatible.  The following tests used to fail when run on
+a system where long double is IEEE 128-bit:
+
+	gcc.dg/torture/float128-nan.c
+	gcc.target/powerpc/nan128-1.c
+
+This patch makes both __float128 and _Float128 use the same type node.
+
+One side effect of not using the long double type node for __float128 is that we
+must only use KFmode for _Float128/__float128.  The libstdc++ library won't
+build if we use TFmode for _Float128 and __float128 when long double is IEEE
+128-bit.
+
+Another minor side effect is that the f128 round to odd fused multiply-add
+function will not merge negatition with the FMA operation when the type is long
+double.  If the type is __float128 or _Float128, then it will continue to do the
+optimization.  The round to odd functions are defined in terms of __float128
+arguments.  For example:
+
+	long double
+	do_fms (long double a, long double b, long double c)
+	{
+	    return __builtin_fmaf128_round_to_odd (a, b, -c);
+	}
+
+will generate (assuming -mabi=ieeelongdouble):
+
+	xsnegqp 4,4
+	xsmaddqpo 4,2,3
+	xxlor 34,36,36
+
+while:
+
+	__float128
+	do_fms (__float128 a, __float128 b, __float128 c)
+	{
+	    return __builtin_fmaf128_round_to_odd (a, b, -c);
+	}
+
+will generate:
+
+	xsmsubqpo 4,2,3
+	xxlor 34,36,36
+
+2022-09-09   Michael Meissner  <meissner@linux.ibm.com>
+
+gcc/
+
+	* config/rs6000/rs6000-builtin.cc (rs6000_init_builtins): Always use the
+	_Float128 type for __float128.
+	(rs6000_expand_builtin): Only change a KFmode built-in to TFmode, if the
+	built-in passes or returns TFmode.  If the predicate failed because the
+	modes were different, use convert_move to load up the value instead of
+	copy_to_mode_reg.
+	* config/rs6000/rs6000.cc (rs6000_translate_mode_attribute): Don't
+	translate __float128 modes to long double modes (TFmode or TCmode).
+	(rs6000_libgcc_floating_mode_supported_p): Support KFmode all of the
+	time if we support IEEE 128-bit floating point.
+	(rs6000_floatn_mode): _Float128 and _Float128x always uses KFmode.
+
+gcc/testsuite/
+
+	* gcc.target/powerpc/float128-hw12.c: New test.
+	* gcc.target/powerpc/float128-hw13.c: Likewise.
+	* gcc.target/powerpc/float128-hw4.c: Update insns.
+
 ==================== work100, patch #5
 
 Rework 128-bit complex multiply and divide.