From: Joseph Myers <joseph@codesourcery.com>
Date: Wed, 4 Jan 2017 17:15:39 +0000 (+0000)
Subject: Make MIPS soft-fp preserve NaN payloads for NAN2008.
X-Git-Tag: glibc-2.25~69
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5ee5362bf8c50e5a85bf758f3f5d91f262a446f;p=thirdparty%2Fglibc.git

Make MIPS soft-fp preserve NaN payloads for NAN2008.

This corresponds to a patch applied to libgcc.  In glibc it doesn't
actually affect much (only fma, I think).

The MIPS sfp-machine.h files have an _FP_CHOOSENAN implementation
which emulates hardware semantics of not preserving signaling NaN
payloads for an operation with two NaN arguments (although that
doesn't suffice to avoid sNaN payload preservation in any case with
just one NaN argument).

However, those are only hardware semantics in the legacy NaN case; in
the NAN2008 case, the architecture documentation says hardware
preserves payloads in such cases.  Furthermore, this implementation
assumes legacy NaN semantics, so in the NAN2008 case the
implementation actually has the effect of preserving sNaN payloads but
not preserving qNaN payloads, when both should be preserved.

This patch fixes the code just to copy from the first argument.

Tested for mips64 soft-float.

	* sysdeps/mips/mips32/sfp-machine.h (_FP_CHOOSENAN): Always
	preserve NaN payload if [__mips_nan2008].
	* sysdeps/mips/mips64/sfp-machine.h (_FP_CHOOSENAN): Likewise.
---

diff --git a/ChangeLog b/ChangeLog
index 32dee3fcb3d..0278dff4cc9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2017-01-04  Joseph Myers  <joseph@codesourcery.com>
 
+	* sysdeps/mips/mips32/sfp-machine.h (_FP_CHOOSENAN): Always
+	preserve NaN payload if [__mips_nan2008].
+	* sysdeps/mips/mips64/sfp-machine.h (_FP_CHOOSENAN): Likewise.
+
 	[BZ #21022]
 	* sysdeps/microblaze/backtrace.c (get_frame_size): Make static.
 
diff --git a/sysdeps/mips/mips32/sfp-machine.h b/sysdeps/mips/mips32/sfp-machine.h
index 4e23aa8b262..5215655029d 100644
--- a/sysdeps/mips/mips32/sfp-machine.h
+++ b/sysdeps/mips/mips32/sfp-machine.h
@@ -41,9 +41,20 @@
 # define _FP_QNANNEGATEDP 1
 #endif
 
+#ifdef __mips_nan2008
+/* NaN payloads should be preserved for NAN2008.  */
+# define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)	\
+  do						\
+    {						\
+      R##_s = X##_s;				\
+      _FP_FRAC_COPY_##wc (R, X);		\
+      R##_c = FP_CLS_NAN;			\
+    }						\
+  while (0)
+#else
 /* From my experiments it seems X is chosen unless one of the
    NaNs is sNaN,  in which case the result is NANSIGN/NANFRAC.  */
-#define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)			\
+# define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)			\
   do {								\
     if ((_FP_FRAC_HIGH_RAW_##fs(X) |				\
 	 _FP_FRAC_HIGH_RAW_##fs(Y)) & _FP_QNANBIT_##fs)		\
@@ -58,6 +69,7 @@
       }								\
     R##_c = FP_CLS_NAN;						\
   } while (0)
+#endif
 
 #define FP_EX_INVALID           (1 << 4)
 #define FP_EX_DIVZERO           (1 << 3)
diff --git a/sysdeps/mips/mips64/sfp-machine.h b/sysdeps/mips/mips64/sfp-machine.h
index 708afc783e9..35cc4ddeb1d 100644
--- a/sysdeps/mips/mips64/sfp-machine.h
+++ b/sysdeps/mips/mips64/sfp-machine.h
@@ -44,9 +44,20 @@
 # define _FP_QNANNEGATEDP 1
 #endif
 
+#ifdef __mips_nan2008
+/* NaN payloads should be preserved for NAN2008.  */
+# define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)	\
+  do						\
+    {						\
+      R##_s = X##_s;				\
+      _FP_FRAC_COPY_##wc (R, X);		\
+      R##_c = FP_CLS_NAN;			\
+    }						\
+  while (0)
+#else
 /* From my experiments it seems X is chosen unless one of the
    NaNs is sNaN,  in which case the result is NANSIGN/NANFRAC.  */
-#define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)			\
+# define _FP_CHOOSENAN(fs, wc, R, X, Y, OP)			\
   do {								\
     if ((_FP_FRAC_HIGH_RAW_##fs(X) |				\
 	 _FP_FRAC_HIGH_RAW_##fs(Y)) & _FP_QNANBIT_##fs)		\
@@ -61,6 +72,7 @@
       }								\
     R##_c = FP_CLS_NAN;						\
   } while (0)
+#endif
 
 #define _FP_DECL_EX		fpu_control_t _fcw