PowerPC floating point little-endian [10 of 15]

http://sourceware.org/ml/libc-alpha/2013-07/msg00201.html

These two functions oddly test x+1>0 when a double x is >= 0.0, and
similarly when x is negative.  I don't see the point of that since the
test should always be true.  I also don't see any need to convert x+1
to integer rather than simply using xr+1.  Note that the standard
allows these functions to return any value when the input is outside
the range of long long, but it's not too hard to prevent xr+1
overflowing so that's what I've done.

(With rounding mode FE_UPWARD, x+1 can be a lot more than what you
might naively expect, but perhaps that situation was covered by the
x - xrf < 1.0 test.)

	* sysdeps/powerpc/fpu/s_llround.c (__llround): Rewrite.
	* sysdeps/powerpc/fpu/s_llroundf.c (__llroundf): Rewrite.

3 files changed, 37 insertions, 34 deletions

diff --git a/ChangeLog b/ChangeLog
index 9d2d856729..6bfeb63aaa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2013-10-04  Alan Modra  <amodra@gmail.com>
 
+	* sysdeps/powerpc/fpu/s_llround.c (__llround): Rewrite.
+	* sysdeps/powerpc/fpu/s_llroundf.c (__llroundf): Rewrite.
+
+2013-10-04  Alan Modra  <amodra@gmail.com>
+
 	* sysdeps/powerpc/fpu/s_float_bitwise.h (__float_and_test28): Don't
 	use vector int constants.
 	(__float_and_test24, __float_and8, __float_get_exp): Likewise.
diff --git a/sysdeps/powerpc/fpu/s_llround.c b/sysdeps/powerpc/fpu/s_llround.c
index 9a01826539..995d0a724a 100644
--- a/sysdeps/powerpc/fpu/s_llround.c
+++ b/sysdeps/powerpc/fpu/s_llround.c
@@ -19,29 +19,28 @@
 #include <math.h>
 #include <math_ldbl_opt.h>
 
-/* I think that what this routine is supposed to do is round a value
-   to the nearest integer, with values exactly on the boundary rounded
-   away from zero.  */
-/* This routine relies on (long long)x, when x is out of range of a long long,
-   clipping to MAX_LLONG or MIN_LLONG.  */
+/* Round to the nearest integer, with values exactly on a 0.5 boundary
+   rounded away from zero, regardless of the current rounding mode.
+   If (long long)x, when x is out of range of a long long, clips at
+   LLONG_MAX or LLONG_MIN, then this implementation also clips.  */
 
 long long int
 __llround (double x)
 {
-  double xrf;
-  long long int xr;
-  xr = (long long int) x;
-  xrf = (double) xr;
+  long long xr = (long long) x;
+  double xrf = (double) xr;
+
   if (x >= 0.0)
-    if (x - xrf >= 0.5 && x - xrf < 1.0 && x+1 > 0)
-      return x+1;
-    else
-      return x;
+    {
+      if (x - xrf >= 0.5)
+	xr += (long long) ((unsigned long long) xr + 1) > 0;
+    }
   else
-    if (xrf - x >= 0.5 && xrf - x < 1.0 && x-1 < 0)
-      return x-1;
-    else
-      return x;
+    {
+      if (xrf - x >= 0.5)
+	xr -= (long long) ((unsigned long long) xr - 1) < 0;
+    }
+  return xr;
 }
 weak_alias (__llround, llround)
 #ifdef NO_LONG_DOUBLE
diff --git a/sysdeps/powerpc/fpu/s_llroundf.c b/sysdeps/powerpc/fpu/s_llroundf.c
index 07d12adbfb..0935de6624 100644
--- a/sysdeps/powerpc/fpu/s_llroundf.c
+++ b/sysdeps/powerpc/fpu/s_llroundf.c
@@ -18,28 +18,27 @@
 
 #include <math.h>
 
-/* I think that what this routine is supposed to do is round a value
-   to the nearest integer, with values exactly on the boundary rounded
-   away from zero.  */
-/* This routine relies on (long long)x, when x is out of range of a long long,
-   clipping to MAX_LLONG or MIN_LLONG.  */
+/* Round to the nearest integer, with values exactly on a 0.5 boundary
+   rounded away from zero, regardless of the current rounding mode.
+   If (long long)x, when x is out of range of a long long, clips at
+   LLONG_MAX or LLONG_MIN, then this implementation also clips.  */
 
 long long int
 __llroundf (float x)
 {
-  float xrf;
-  long long int xr;
-  xr = (long long int) x;
-  xrf = (float) xr;
+  long long xr = (long long) x;
+  float xrf = (float) xr;
+
   if (x >= 0.0)
-    if (x - xrf >= 0.5 && x - xrf < 1.0 && x+1 > 0)
-      return x+1;
-    else
-      return x;
+    {
+      if (x - xrf >= 0.5)
+	xr += (long long) ((unsigned long long) xr + 1) > 0;
+    }
   else
-    if (xrf - x >= 0.5 && xrf - x < 1.0 && x-1 < 0)
-      return x-1;
-    else
-      return x;
+    {
+      if (xrf - x >= 0.5)
+	xr -= (long long) ((unsigned long long) xr - 1) < 0;
+    }
+  return xr;
 }
 weak_alias (__llroundf, llroundf)