Do not raise "inexact" from generic ceil (bug 15479).

C99 and C11 allow but do not require ceil, floor, round and trunc to
raise the "inexact" exception for noninteger arguments.  TS 18661-1
requires that this exception not be raised by these functions.  This
aligns them with general IEEE semantics, where "inexact" is only
raised if the final step of rounding the infinite-precision result to
the result type is inexact; for these functions, the
infinite-precision integer result is always representable in the
result type, so "inexact" should never be raised.

The generic implementations of ceil, floor and round functions contain
code to force "inexact" to be raised.  This patch removes it for ceil
functions to align them with TS 18661-1 in this regard.  Note that
some architecture-specific versions may still raise "inexact", so the
tests are not updated and the bug is not yet fixed.

Tested for x86_64, x86 and mips64.

	[BZ #15479]
	* sysdeps/ieee754/dbl-64/s_ceil.c: Do not mention "inexact"
	exception in comment.
	(huge): Remove variable.
	(__ceil): Do not force "inexact" exception.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c: Do not mention
	"inexact" exception in comment.
	(huge): Remove variable.
	(__ceil): Do not force "inexact" exception.
	* sysdeps/ieee754/flt-32/s_ceilf.c (huge): Remove variable.
	(__ceilf): Do not force "inexact" exception.
	* sysdeps/ieee754/ldbl-128/s_ceill.c: Do not mention "inexact"
	exception in comment.
	(huge): Remove variable.
	(__ceill): Do not force "inexact" exception.

5 files changed, 36 insertions, 42 deletions

diff --git a/ChangeLog b/ChangeLog
index 055316f86e..b074f4d980 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2016-05-24  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #15479]
+	* sysdeps/ieee754/dbl-64/s_ceil.c: Do not mention "inexact"
+	exception in comment.
+	(huge): Remove variable.
+	(__ceil): Do not force "inexact" exception.
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c: Do not mention
+	"inexact" exception in comment.
+	(huge): Remove variable.
+	(__ceil): Do not force "inexact" exception.
+	* sysdeps/ieee754/flt-32/s_ceilf.c (huge): Remove variable.
+	(__ceilf): Do not force "inexact" exception.
+	* sysdeps/ieee754/ldbl-128/s_ceill.c: Do not mention "inexact"
+	exception in comment.
+	(huge): Remove variable.
+	(__ceill): Do not force "inexact" exception.
+
 2016-05-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* config.h.in (BIND_NOW): New.
diff --git a/sysdeps/ieee754/dbl-64/s_ceil.c b/sysdeps/ieee754/dbl-64/s_ceil.c
index b2154b407d..c291c26f57 100644
--- a/sysdeps/ieee754/dbl-64/s_ceil.c
+++ b/sysdeps/ieee754/dbl-64/s_ceil.c
@@ -15,15 +15,11 @@
  * Return x rounded toward -inf to integral value
  * Method:
  *	Bit twiddling.
- * Exception:
- *	Inexact flag raised if x not equal to ceil(x).
  */
 
 #include <math.h>
 #include <math_private.h>
 
-static const double huge = 1.0e300;
-
 double
 __ceil (double x)
 {
@@ -33,9 +29,8 @@ __ceil (double x)
   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
   if (j0 < 20)
     {
-      if (j0 < 0)       /* raise inexact if x != 0 */
+      if (j0 < 0)
 	{
-	  math_force_eval (huge + x);
 	  /* return 0*sign(x) if |x|<1 */
 	  if (i0 < 0)
 	    {
@@ -51,7 +46,6 @@ __ceil (double x)
 	  i = (0x000fffff) >> j0;
 	  if (((i0 & i) | i1) == 0)
 	    return x;                        /* x is integral */
-	  math_force_eval (huge + x);           /* raise inexact flag */
 	  if (i0 > 0)
 	    i0 += (0x00100000) >> j0;
 	  i0 &= (~i); i1 = 0;
@@ -69,7 +63,6 @@ __ceil (double x)
       i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
       if ((i1 & i) == 0)
 	return x;                       /* x is integral */
-      math_force_eval (huge + x);               /* raise inexact flag */
       if (i0 > 0)
 	{
 	  if (j0 == 20)
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c
index c687525d4b..faaaf90208 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c
@@ -15,15 +15,11 @@
  * Return x rounded toward -inf to integral value
  * Method:
  *	Bit twiddling.
- * Exception:
- *	Inexact flag raised if x not equal to ceil(x).
  */
 
 #include <math.h>
 #include <math_private.h>
 
-static const double huge = 1.0e300;
-
 double
 __ceil(double x)
 {
@@ -32,14 +28,13 @@ __ceil(double x)
 	EXTRACT_WORDS64(i0,x);
 	j0 = ((i0>>52)&0x7ff)-0x3ff;
 	if(j0<=51) {
-	    if(j0<0) {	/* raise inexact if x != 0 */
-	      math_force_eval(huge+x);/* return 0*sign(x) if |x|<1 */
+	    if(j0<0) {
+	      /* return 0*sign(x) if |x|<1 */
 	      if(i0<0) {i0=INT64_C(0x8000000000000000);}
 	      else if(i0!=0) { i0=INT64_C(0x3ff0000000000000);}
 	    } else {
 		i = INT64_C(0x000fffffffffffff)>>j0;
 		if((i0&i)==0) return x; /* x is integral */
-		math_force_eval(huge+x);	/* raise inexact flag */
 		if(i0>0) i0 += UINT64_C(0x0010000000000000)>>j0;
 		i0 &= (~i);
 	    }
diff --git a/sysdeps/ieee754/flt-32/s_ceilf.c b/sysdeps/ieee754/flt-32/s_ceilf.c
index 37659ea2ae..bff26c33cb 100644
--- a/sysdeps/ieee754/flt-32/s_ceilf.c
+++ b/sysdeps/ieee754/flt-32/s_ceilf.c
@@ -17,8 +17,6 @@
 #include <math_private.h>
 
 
-static const float huge = 1.0e30;
-
 float
 __ceilf(float x)
 {
@@ -28,14 +26,13 @@ __ceilf(float x)
 	GET_FLOAT_WORD(i0,x);
 	j0 = ((i0>>23)&0xff)-0x7f;
 	if(j0<23) {
-	    if(j0<0) {	/* raise inexact if x != 0 */
-		math_force_eval(huge+x);/* return 0*sign(x) if |x|<1 */
+	    if(j0<0) {
+		/* return 0*sign(x) if |x|<1 */
 		if(i0<0) {i0=0x80000000;}
 		else if(i0!=0) { i0=0x3f800000;}
 	    } else {
 		i = (0x007fffff)>>j0;
 		if((i0&i)==0) return x; /* x is integral */
-		math_force_eval(huge+x);	/* raise inexact flag */
 		if(i0>0) i0 += (0x00800000)>>j0;
 		i0 &= (~i);
 	    }
diff --git a/sysdeps/ieee754/ldbl-128/s_ceill.c b/sysdeps/ieee754/ldbl-128/s_ceill.c
index 9f6bc4ce15..6b736733c1 100644
--- a/sysdeps/ieee754/ldbl-128/s_ceill.c
+++ b/sysdeps/ieee754/ldbl-128/s_ceill.c
@@ -22,15 +22,11 @@ static char rcsid[] = "$NetBSD: $";
  * Return x rounded toward -inf to integral value
  * Method:
  *	Bit twiddling.
- * Exception:
- *	Inexact flag raised if x not equal to ceil(x).
  */
 
 #include <math.h>
 #include <math_private.h>
 
-static const long double huge = 1.0e4930L;
-
 long double __ceill(long double x)
 {
 	int64_t i0,i1,j0;
@@ -38,18 +34,15 @@ long double __ceill(long double x)
 	GET_LDOUBLE_WORDS64(i0,i1,x);
 	j0 = ((i0>>48)&0x7fff)-0x3fff;
 	if(j0<48) {
-	    if(j0<0) { 	/* raise inexact if x != 0 */
-		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
-		    if(i0<0) {i0=0x8000000000000000ULL;i1=0;}
-		    else if((i0|i1)!=0) { i0=0x3fff000000000000ULL;i1=0;}
-		}
+	    if(j0<0) {
+		/* return 0*sign(x) if |x|<1 */
+		if(i0<0) {i0=0x8000000000000000ULL;i1=0;}
+		else if((i0|i1)!=0) { i0=0x3fff000000000000ULL;i1=0;}
 	    } else {
 		i = (0x0000ffffffffffffULL)>>j0;
 		if(((i0&i)|i1)==0) return x; /* x is integral */
-		if(huge+x>0.0) {	/* raise inexact flag */
-		    if(i0>0) i0 += (0x0001000000000000LL)>>j0;
-		    i0 &= (~i); i1=0;
-		}
+		if(i0>0) i0 += (0x0001000000000000LL)>>j0;
+		i0 &= (~i); i1=0;
 	    }
 	} else if (j0>111) {
 	    if(j0==0x4000) return x+x;	/* inf or NaN */
@@ -57,17 +50,15 @@ long double __ceill(long double x)
 	} else {
 	    i = -1ULL>>(j0-48);
 	    if((i1&i)==0) return x;	/* x is integral */
-	    if(huge+x>0.0) { 		/* raise inexact flag */
-		if(i0>0) {
-		    if(j0==48) i0+=1;
-		    else {
-			j = i1+(1LL<<(112-j0));
-			if(j<i1) i0 +=1 ; 	/* got a carry */
-			i1=j;
-		    }
+	    if(i0>0) {
+		if(j0==48) i0+=1;
+		else {
+		    j = i1+(1LL<<(112-j0));
+		    if(j<i1) i0 +=1 ; 	/* got a carry */
+		    i1=j;
 		}
-		i1 &= (~i);
 	    }
+	    i1 &= (~i);
 	}
 	SET_LDOUBLE_WORDS64(x,i0,i1);
 	return x;