GNU C Library master sources branch master updated. glibc-2.25-255-gc064f6a

[tuliom at sourceware dot org]

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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c064f6a613844181f411aabb2662384a6aefb69e

commit c064f6a613844181f411aabb2662384a6aefb69e
Author: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
Date:   Fri Apr 28 19:45:52 2017 -0300

    powerpc: Fix logbl on power7 [BZ# 21280]
    
     1. Fix the results for negative subnormals by ignoring the signal when
        normalizing the value.
     2. Fix the output when the high part is a power of 2 and the low part
        is a nonzero number with opposite sign.  This fix is based on commit
        380bd0fd2418f8988217de950f8b8ff18af0cb2b.
    
    After applying this patch, logbl() tests pass cleanly on POWER >= 7.
    
    Tested on powerpc, powerpc64 and powerpc64le
    
    	[BZ #21280]
    	* sysdeps/powerpc/power7/fpu/s_logbl.c (__logbl): Ignore the
    	signal of subnormals and adjust the exponent of power of 2 down
    	when low part has opposite sign.

diff --git a/ChangeLog b/ChangeLog
index 29c05dd..a5c806a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-04-28  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
+
+	[BZ #21280]
+	* sysdeps/powerpc/power7/fpu/s_logbl.c (__logbl): Ignore the
+	signal of subnormals and adjust the exponent of power of 2 down
+	when low part has opposite sign.
+
 2017-04-28  Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/powerpc64le/Implies: New file.
diff --git a/sysdeps/powerpc/power7/fpu/s_logbl.c b/sysdeps/powerpc/power7/fpu/s_logbl.c
index f7ecbd1..3ae383a 100644
--- a/sysdeps/powerpc/power7/fpu/s_logbl.c
+++ b/sysdeps/powerpc/power7/fpu/s_logbl.c
@@ -35,14 +35,16 @@ static const union {
 long double
 __logbl (long double x)
 {
-  double xh;
+  double xh, xl;
   double ret;
+  int64_t hx;
 
   if (__builtin_expect (x == 0.0L, 0))
     /* Raise FE_DIVBYZERO and return -HUGE_VAL[LF].  */
     return -1.0L / __builtin_fabsl (x);
 
-  xh = ldbl_high (x);
+  ldbl_unpack (x, &xh, &xl);
+  EXTRACT_WORDS64 (hx, xh);
   /* ret = x & 0x7ff0000000000000;  */
   asm (
     "xxland %x0,%x1,%x2\n"
@@ -58,10 +60,20 @@ __logbl (long double x)
     {
       /* POSIX specifies that denormal number is treated as
          though it were normalized.  */
-      int64_t hx;
-
-      EXTRACT_WORDS64 (hx, xh);
-      return (long double) (-1023 - (__builtin_clzll (hx) - 12));
+      return (long double) (- (__builtin_clzll (hx & 0x7fffffffffffffffLL) \
+			       - 12) - 1023);
+    }
+  else if ((hx & 0x000fffffffffffffLL) == 0)
+    {
+      /* If the high part is a power of 2, and the low part is nonzero
+	 with the opposite sign, the low part affects the
+	 exponent.  */
+      int64_t lx, rhx;
+      EXTRACT_WORDS64 (lx, xl);
+      rhx = (hx & 0x7ff0000000000000LL) >> 52;
+      if ((hx ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0)
+	rhx--;
+      return (long double) (rhx - 1023);
     }
   /* Test to avoid logb_downward (0.0) == -0.0.  */
   return ret == -0.0 ? 0.0 : ret;

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                            |    7 +++++++
 sysdeps/powerpc/power7/fpu/s_logbl.c |   24 ++++++++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)


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