Separate fpresetsticky() from the other fpset functions so that the

others can be replaced cleanly by the amd64 versions.   There is no
current amd64 version to merge, but there is an old one which is
similar.

Fix the following bugs in fpresetsticky():
- garbage args clobbered non-sticky bits in the status register
- the return value was usually garbage since it was masked with the
  arg instead of with the field selector.

Optimize fpresetsticky() to avoid using the environment as in
feclearexcept() (use only fnclex() if possible) and also to avoid
using fnclex() for null changes.  The second of these optimizations
might not be so good since its branch might cost more than it saves.

1 files changed, 27 insertions, 4 deletions

diff --git a/sys/i386/include/ieeefp.h b/sys/i386/include/ieeefp.h
index 37068e7..22b4f5d 100644
--- a/sys/i386/include/ieeefp.h
+++ b/sys/i386/include/ieeefp.h
@@ -115,6 +115,7 @@ typedef enum {
 #ifdef __GNUCLIKE_ASM
 
 #define	__fldenv(addr)	__asm __volatile("fldenv %0" : : "m" (*(addr)))
+#define	__fnclex()	__asm __volatile("fnclex")
 #define	__fnstcw(addr)	__asm __volatile("fnstcw %0" : "=m" (*(addr)))
 #define	__fnstenv(addr)	__asm __volatile("fnstenv %0" : "=m" (*(addr)))
 #define	__fnstsw(addr)	__asm __volatile("fnstsw %0" : "=m" (*(addr)))
@@ -165,8 +166,6 @@ __fpsetreg(int _m, int _reg, int _fld, int _off)
 	return _p;
 }
 
-#endif /* __GNUCLIKE_ASM */
-
 /*
  * SysV/386 FP control interface
  */
@@ -185,8 +184,32 @@ __fpsetreg(int _m, int _reg, int _fld, int _off)
 	    (FP_MSKS_FLD >> FP_MSKS_OFF))
 #define	fpgetsticky()	((fp_except_t)					\
 	((__fpgetreg(FP_STKY_REG) & FP_STKY_FLD) >> FP_STKY_OFF))
-#define	fpresetsticky(m) ((fp_except_t)					\
-	__fpsetreg(0, FP_STKY_REG, (m), FP_STKY_OFF))
+
+static __inline fp_except_t
+fpresetsticky(fp_except_t _m)
+{
+	struct {
+		unsigned _cw;
+		unsigned _sw;
+		unsigned _other[5];
+	} _env;
+	fp_except_t _p;
+
+	_m &= FP_STKY_FLD >> FP_STKY_OFF;
+	_p = fpgetsticky();
+	if ((_p & ~_m) == _p)
+		return (_p);
+	if ((_p & ~_m) == 0) {
+		__fnclex();
+		return (_p);
+	}
+	__fnstenv(&_env);
+	_env._sw &= ~_m;
+	__fldenv(&_env);
+	return (_p);
+}
+
+#endif /* __GNUCLIKE_ASM */
 
 /* Suppress prototypes in the MI header. */
 #define	_IEEEFP_INLINED_	1