Do not define various fenv.h macros for MIPS soft-float (bug 23479).

MIPS soft-float glibc does not support floating-point exceptions and
rounding modes, and uses a different ABI from hard-float so a
soft-float compilation cannot use a glibc that does support
floating-point exceptions and rounding modes.  Thus, bits/fenv.h
should not, when compiling for soft-float, define macros for the
unsupported features.

This patch changes it accordingly to define those macros only for
hard-float.  None of the exception macros are defined for soft-float,
with FE_ALL_EXCEPT defined to 0 in that case, and only FE_TONEAREST is
defined of the rounding-mode macros, and FE_NOMASK_ENV is not defined;
this is consistent with how architectures lacking exception and
rounding mode support generally define things in this header.  As well
as making the header more correct for this case, this also means the
generic math_private.h optimizations for this case automatically apply
(inlining libm-internal fenv.h function calls that are trivial when
exceptions and rounding modes are not supported).

The mips64 sfp-machine.h then needs similar changes to disable more of
the exception and rounding mode handling for soft-float.  (The mips32
sfp-machine.h is already used only for soft-float, has no integration
with hardware exceptions or rounding modes and so needs no changes.)

Existing binaries might use the old FE_NOMASK_ENV value as an argument
to fesetenv / feupdateenv and expect an error for it (given that it
was defined in a header that also defined FE_ALL_EXCEPT to a nonzero
value).  To preserve that error, wrappers for the fallback fesetenv
and feupdateenv are created in sysdeps/mips/nofpu/.

Tested for mips64 (hard-float and soft-float, all three ABIs).

	[BZ #23479]
	* sysdeps/mips/bits/fenv.h (FE_INEXACT): Define only if
	[__mips_hard_float].
	(FE_UNDERFLOW): Likewise.
	(FE_OVERFLOW): Likewise.
	(FE_DIVBYZERO): Likewise.
	(FE_INVALID): Likewise.
	(FE_ALL_EXCEPT): Define to 0 if [!__mips_hard_float].
	(FE_TOWARDZERO): Define only if [__mips_hard_float].
	(FE_UPWARD): Likewise.
	(FE_DOWNWARD): Likewise.
	(__FE_UNDEFINED): Define if [!__mips_hard_float]
	(FE_NOMASK_ENV): Define only if [__mips_hard_float].
	* sysdeps/mips/mips64/sfp-machine.h (_FP_DECL_EX): Define only if
	[__mips_hard_float].
	(FP_ROUNDMODE): Likewise.
	(FP_RND_NEAREST): Likewise.
	(FP_RND_ZERO): Likewise.
	(FP_RND_PINF): Likewise.
	(FP_RND_MINF): Likewise.
	(FP_EX_INVALID): Likewise.
	(FP_EX_OVERFLOW): Likewise.
	(FP_EX_UNDERFLOW): Likewise.
	(FP_EX_DIVZERO): Likewise.
	(FP_EX_INEXACT): Likewise.
	(FP_INIT_ROUNDMODE): Likewise.
	* sysdeps/mips/nofpu/fesetenv.c: New file.
	* sysdeps/mips/nofpu/feupdateenv.c: Likewise.

1 files changed, 4 insertions, 5 deletions

diff --git a/sysdeps/mips/mips64/sfp-machine.h b/sysdeps/mips/mips64/sfp-machine.h
index 35cc4dd..c769ee8 100644
--- a/sysdeps/mips/mips64/sfp-machine.h
+++ b/sysdeps/mips/mips64/sfp-machine.h
@@ -74,6 +74,10 @@
   } while (0)
 #endif
 
+#define _FP_TININESS_AFTER_ROUNDING 1
+
+#ifdef __mips_hard_float
+
 #define _FP_DECL_EX		fpu_control_t _fcw
 
 #define FP_ROUNDMODE		(_fcw & 0x3)
@@ -89,9 +93,6 @@
 #define FP_EX_DIVZERO		FE_DIVBYZERO
 #define FP_EX_INEXACT		FE_INEXACT
 
-#define _FP_TININESS_AFTER_ROUNDING 1
-
-#ifdef __mips_hard_float
 #define FP_INIT_ROUNDMODE			\
 do {						\
   _FPU_GETCW (_fcw);				\
@@ -103,6 +104,4 @@ do {						\
     _FPU_SETCW (_fcw | _fex | (_fex << 10));	\
 } while (0)
 #define FP_TRAPPING_EXCEPTIONS ((_fcw >> 5) & 0x7c)
-#else
-#define FP_INIT_ROUNDMODE	_fcw = FP_RND_NEAREST
 #endif