soft-fp: Support more precise "invalid" exceptions.

As previously discussed
<https://sourceware.org/ml/libc-alpha/2013-10/msg00345.html>, it would
be desirable to be able to use the same version of the soft-fp code in
the Linux kernel as well as in glibc and libgcc (instead of an old
version in the kernel that's missing ten years of bug fixes,
performance improvements and new features), and to that end it is
useful to add to glibc's copy features in the kernel's copy, even when
they are not directly useful in glibc.

To that end, this patch adds one of those features: support for more
precise "invalid" exceptions describing the particular kind of invalid
operation.  These are relevant for powerpc emulation, and are also as
described in IEEE 754-2008 as sub-exceptions.

The set of sub-exceptions here is the union of those supported on
powerpc and those from IEEE 754-2008 (the former adds a distinction
between 0/0 and Inf/Inf; the latter adds a distinction between Inf*0
from multiplication and the same from fma).  This includes
sub-exceptions for sqrt, conversions to integer and comparisons that
are not supported in the kernel; I see no obvious reason for these
being missing from the kernel support, given that they are supported
on powerpc so accurate powerpc emulation should generate them.

Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.

	* soft-fp/soft-fp.h (FP_EX_INVALID_SNAN): New macro.
	(FP_EX_INVALID_IMZ): Likewise.
	(FP_EX_INVALID_IMZ_FMA): Likewise.
	(FP_EX_INVALID_ISI): Likewise.
	(FP_EX_INVALID_ZDZ): Likewise.
	(FP_EX_INVALID_IDI): Likewise.
	(FP_EX_INVALID_SQRT): Likewise.
	(FP_EX_INVALID_CVI): Likewise.
	(FP_EX_INVALID_VC): Likewise.
	* soft-fp/op-common.h (_FP_UNPACK_CANONICAL): Specify more precise
	"invalid" exceptions.
	(_FP_CHECK_SIGNAN_SEMIRAW): Likewise.
	(_FP_ADD_INTERNAL): Likewise.
	(_FP_MUL): Likewise.
	(_FP_FMA): Likewise.
	(_FP_DIV): Likewise.
	(_FP_CMP_CHECK_NAN): Likewise.
	(_FP_SQRT): Likewise.
	(_FP_TO_INT): Likewise.
	(FP_EXTEND): Likewise.

2 files changed, 147 insertions, 81 deletions

diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index 3da234b..8344be5 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -93,7 +93,8 @@
 	      X##_c = FP_CLS_NAN;				\
 	      /* Check for signaling NaN.  */			\
 	      if (_FP_FRAC_SNANP (fs, X))			\
-		FP_SET_EXCEPTION (FP_EX_INVALID);		\
+		FP_SET_EXCEPTION (FP_EX_INVALID			\
+				  | FP_EX_INVALID_SNAN);	\
 	    }							\
 	  break;						\
 	}							\
@@ -144,14 +145,14 @@
 
 /* Check for a semi-raw value being a signaling NaN and raise the
    invalid exception if so.  */
-#define _FP_CHECK_SIGNAN_SEMIRAW(fs, wc, X)	\
-  do						\
-    {						\
-      if (X##_e == _FP_EXPMAX_##fs		\
-	  && !_FP_FRAC_ZEROP_##wc (X)		\
-	  && _FP_FRAC_SNANP_SEMIRAW (fs, X))	\
-	FP_SET_EXCEPTION (FP_EX_INVALID);	\
-    }						\
+#define _FP_CHECK_SIGNAN_SEMIRAW(fs, wc, X)			\
+  do								\
+    {								\
+      if (X##_e == _FP_EXPMAX_##fs				\
+	  && !_FP_FRAC_ZEROP_##wc (X)				\
+	  && _FP_FRAC_SNANP_SEMIRAW (fs, X))			\
+	FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_SNAN);	\
+    }								\
   while (0)
 
 /* Choose a NaN result from an operation on two semi-raw NaN
@@ -764,7 +765,8 @@
 			      R##_s = _FP_NANSIGN_##fs;			\
 			      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);	\
 			      _FP_FRAC_SLL_##wc (R, _FP_WORKBITS);	\
-			      FP_SET_EXCEPTION (FP_EX_INVALID);		\
+			      FP_SET_EXCEPTION (FP_EX_INVALID		\
+						| FP_EX_INVALID_ISI);	\
 			    }						\
 			  else						\
 			    {						\
@@ -916,7 +918,7 @@
 	  R##_s = _FP_NANSIGN_##fs;				\
 	  R##_c = FP_CLS_NAN;					\
 	  _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);		\
-	  FP_SET_EXCEPTION (FP_EX_INVALID);			\
+	  FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_IMZ);	\
 	  break;						\
 								\
 	default:						\
@@ -1080,7 +1082,7 @@
 	  _FP_FMA_T##_s = _FP_NANSIGN_##fs;				\
 	  _FP_FMA_T##_c = FP_CLS_NAN;					\
 	  _FP_FRAC_SET_##wc (_FP_FMA_T, _FP_NANFRAC_##fs);		\
-	  FP_SET_EXCEPTION (FP_EX_INVALID);				\
+	  FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_IMZ_FMA);	\
 	  break;							\
 									\
 	default:							\
@@ -1125,7 +1127,7 @@
 	      R##_s = _FP_NANSIGN_##fs;					\
 	      R##_c = FP_CLS_NAN;					\
 	      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);			\
-	      FP_SET_EXCEPTION (FP_EX_INVALID);				\
+	      FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_ISI);	\
 	    }								\
 	  break;							\
 									\
@@ -1199,7 +1201,10 @@
 	  R##_s = _FP_NANSIGN_##fs;				\
 	  R##_c = FP_CLS_NAN;					\
 	  _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);		\
-	  FP_SET_EXCEPTION (FP_EX_INVALID);			\
+	  FP_SET_EXCEPTION (FP_EX_INVALID			\
+			    | (X##_c == FP_CLS_INF		\
+			       ? FP_EX_INVALID_IDI		\
+			       : FP_EX_INVALID_ZDZ));		\
 	  break;						\
 								\
 	default:						\
@@ -1211,19 +1216,36 @@
 
 /* Helper for comparisons.  EX is 0 not to raise exceptions, 1 to
    raise exceptions for signaling NaN operands, 2 to raise exceptions
-   for all NaN operands.  */
+   for all NaN operands.  Conditionals are organized to allow the
+   compiler to optimize away code based on the value of EX.  */
 
-#define _FP_CMP_CHECK_NAN(fs, wc, X, Y, ex)		\
-  do							\
-    {							\
-      if (ex)						\
-	{						\
-	  if ((ex) == 2					\
-	      || _FP_ISSIGNAN (fs, wc, X)		\
-	      || _FP_ISSIGNAN (fs, wc, Y))		\
-	    FP_SET_EXCEPTION (FP_EX_INVALID);		\
-	}						\
-    }							\
+#define _FP_CMP_CHECK_NAN(fs, wc, X, Y, ex)				\
+  do									\
+    {									\
+      /* The arguments are unordered, which may or may not result in	\
+	 an exception.  */						\
+      if (ex)								\
+	{								\
+	  /* At least some cases of unordered arguments result in	\
+	     exceptions; check whether this is one.  */			\
+	  if (FP_EX_INVALID_SNAN || FP_EX_INVALID_VC)			\
+	    {								\
+	      /* Check separately for each case of "invalid"		\
+		 exceptions.  */					\
+	      if ((ex) == 2)						\
+		FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_VC);	\
+	      if (_FP_ISSIGNAN (fs, wc, X)				\
+		  || _FP_ISSIGNAN (fs, wc, Y))				\
+		FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_SNAN);	\
+	    }								\
+	  /* Otherwise, we only need to check whether to raise an	\
+	     exception, not which case or cases it is.  */		\
+	  else if ((ex) == 2						\
+		   || _FP_ISSIGNAN (fs, wc, X)				\
+		   || _FP_ISSIGNAN (fs, wc, Y))				\
+	    FP_SET_EXCEPTION (FP_EX_INVALID);				\
+	}								\
+    }									\
   while (0)
 
 /* Main differential comparison routine.  The inputs should be raw not
@@ -1314,58 +1336,58 @@
 
 /* Main square root routine.  The input value should be cooked.  */
 
-#define _FP_SQRT(fs, wc, R, X)					\
-  do								\
-    {								\
-      _FP_FRAC_DECL_##wc (_FP_SQRT_T);				\
-      _FP_FRAC_DECL_##wc (_FP_SQRT_S);				\
-      _FP_W_TYPE _FP_SQRT_q;					\
-      switch (X##_c)						\
-	{							\
-	case FP_CLS_NAN:					\
-	  _FP_FRAC_COPY_##wc (R, X);				\
-	  R##_s = X##_s;					\
-	  R##_c = FP_CLS_NAN;					\
-	  break;						\
-	case FP_CLS_INF:					\
-	  if (X##_s)						\
-	    {							\
-	      R##_s = _FP_NANSIGN_##fs;				\
-	      R##_c = FP_CLS_NAN; /* NAN */			\
-	      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);		\
-	      FP_SET_EXCEPTION (FP_EX_INVALID);			\
-	    }							\
-	  else							\
-	    {							\
-	      R##_s = 0;					\
-	      R##_c = FP_CLS_INF; /* sqrt(+inf) = +inf */	\
-	    }							\
-	  break;						\
-	case FP_CLS_ZERO:					\
-	  R##_s = X##_s;					\
-	  R##_c = FP_CLS_ZERO; /* sqrt(+-0) = +-0 */		\
-	  break;						\
-	case FP_CLS_NORMAL:					\
-	  R##_s = 0;						\
-	  if (X##_s)						\
-	    {							\
-	      R##_c = FP_CLS_NAN; /* NAN */			\
-	      R##_s = _FP_NANSIGN_##fs;				\
-	      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);		\
-	      FP_SET_EXCEPTION (FP_EX_INVALID);			\
-	      break;						\
-	    }							\
-	  R##_c = FP_CLS_NORMAL;				\
-	  if (X##_e & 1)					\
-	    _FP_FRAC_SLL_##wc (X, 1);				\
-	  R##_e = X##_e >> 1;					\
-	  _FP_FRAC_SET_##wc (_FP_SQRT_S, _FP_ZEROFRAC_##wc);	\
-	  _FP_FRAC_SET_##wc (R, _FP_ZEROFRAC_##wc);		\
-	  _FP_SQRT_q = _FP_OVERFLOW_##fs >> 1;			\
-	  _FP_SQRT_MEAT_##wc (R, _FP_SQRT_S, _FP_SQRT_T, X,	\
-			      _FP_SQRT_q);			\
-	}							\
-    }								\
+#define _FP_SQRT(fs, wc, R, X)						\
+  do									\
+    {									\
+      _FP_FRAC_DECL_##wc (_FP_SQRT_T);					\
+      _FP_FRAC_DECL_##wc (_FP_SQRT_S);					\
+      _FP_W_TYPE _FP_SQRT_q;						\
+      switch (X##_c)							\
+	{								\
+	case FP_CLS_NAN:						\
+	  _FP_FRAC_COPY_##wc (R, X);					\
+	  R##_s = X##_s;						\
+	  R##_c = FP_CLS_NAN;						\
+	  break;							\
+	case FP_CLS_INF:						\
+	  if (X##_s)							\
+	    {								\
+	      R##_s = _FP_NANSIGN_##fs;					\
+	      R##_c = FP_CLS_NAN; /* NAN */				\
+	      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);			\
+	      FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_SQRT);	\
+	    }								\
+	  else								\
+	    {								\
+	      R##_s = 0;						\
+	      R##_c = FP_CLS_INF; /* sqrt(+inf) = +inf */		\
+	    }								\
+	  break;							\
+	case FP_CLS_ZERO:						\
+	  R##_s = X##_s;						\
+	  R##_c = FP_CLS_ZERO; /* sqrt(+-0) = +-0 */			\
+	  break;							\
+	case FP_CLS_NORMAL:						\
+	  R##_s = 0;							\
+	  if (X##_s)							\
+	    {								\
+	      R##_c = FP_CLS_NAN; /* NAN */				\
+	      R##_s = _FP_NANSIGN_##fs;					\
+	      _FP_FRAC_SET_##wc (R, _FP_NANFRAC_##fs);			\
+	      FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_SQRT);	\
+	      break;							\
+	    }								\
+	  R##_c = FP_CLS_NORMAL;					\
+	  if (X##_e & 1)						\
+	    _FP_FRAC_SLL_##wc (X, 1);					\
+	  R##_e = X##_e >> 1;						\
+	  _FP_FRAC_SET_##wc (_FP_SQRT_S, _FP_ZEROFRAC_##wc);		\
+	  _FP_FRAC_SET_##wc (R, _FP_ZEROFRAC_##wc);			\
+	  _FP_SQRT_q = _FP_OVERFLOW_##fs >> 1;				\
+	  _FP_SQRT_MEAT_##wc (R, _FP_SQRT_S, _FP_SQRT_T, X,		\
+			      _FP_SQRT_q);				\
+	}								\
+    }									\
   while (0)
 
 /* Convert from FP to integer.  Input is raw.  */
@@ -1434,12 +1456,17 @@
 			})						\
 		      : 0);						\
 	      if (!_FP_FRAC_ZEROP_##wc (X))				\
-		FP_SET_EXCEPTION (FP_EX_INVALID);			\
+		FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_CVI);	\
 	      else if (_FP_TO_INT_inexact)				\
 		FP_SET_EXCEPTION (FP_EX_INEXACT);			\
 	    }								\
 	  else								\
-	    FP_SET_EXCEPTION (FP_EX_INVALID);				\
+	    FP_SET_EXCEPTION (FP_EX_INVALID				\
+			      | FP_EX_INVALID_CVI			\
+			      | ((FP_EX_INVALID_SNAN			\
+				  && _FP_ISSIGNAN (fs, wc, X))		\
+				 ? FP_EX_INVALID_SNAN			\
+				 : 0));					\
 	}								\
       else								\
 	{								\
@@ -1601,7 +1628,8 @@
 	      if (!_FP_FRAC_ZEROP_##swc (S))				\
 		{							\
 		  if (_FP_FRAC_SNANP (sfs, S))				\
-		    FP_SET_EXCEPTION (FP_EX_INVALID);			\
+		    FP_SET_EXCEPTION (FP_EX_INVALID			\
+				      | FP_EX_INVALID_SNAN);		\
 		  _FP_FRAC_SLL_##dwc (D, (_FP_FRACBITS_##dfs		\
 					  - _FP_FRACBITS_##sfs));	\
 		  _FP_SETQNAN (dfs, dwc, D);				\
diff --git a/soft-fp/soft-fp.h b/soft-fp/soft-fp.h
index 3ac269e..05fcca0 100644
--- a/soft-fp/soft-fp.h
+++ b/soft-fp/soft-fp.h
@@ -83,6 +83,44 @@
 # define FP_EX_DENORM		0
 #endif
 
+/* Sub-exceptions of "invalid".  */
+/* Signaling NaN operand.  */
+#ifndef FP_EX_INVALID_SNAN
+# define FP_EX_INVALID_SNAN	0
+#endif
+/* Inf * 0.  */
+#ifndef FP_EX_INVALID_IMZ
+# define FP_EX_INVALID_IMZ	0
+#endif
+/* fma (Inf, 0, c).  */
+#ifndef FP_EX_INVALID_IMZ_FMA
+# define FP_EX_INVALID_IMZ_FMA	0
+#endif
+/* Inf - Inf.  */
+#ifndef FP_EX_INVALID_ISI
+# define FP_EX_INVALID_ISI	0
+#endif
+/* 0 / 0.  */
+#ifndef FP_EX_INVALID_ZDZ
+# define FP_EX_INVALID_ZDZ	0
+#endif
+/* Inf / Inf.  */
+#ifndef FP_EX_INVALID_IDI
+# define FP_EX_INVALID_IDI	0
+#endif
+/* sqrt (negative).  */
+#ifndef FP_EX_INVALID_SQRT
+# define FP_EX_INVALID_SQRT	0
+#endif
+/* Invalid conversion to integer.  */
+#ifndef FP_EX_INVALID_CVI
+# define FP_EX_INVALID_CVI	0
+#endif
+/* Invalid comparison.  */
+#ifndef FP_EX_INVALID_VC
+# define FP_EX_INVALID_VC	0
+#endif
+
 /* _FP_STRUCT_LAYOUT may be defined as an attribute to determine the
    struct layout variant used for structures where bit-fields are used
    to access specific parts of binary floating-point numbers.  This is