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Fix POWER7 logb results for negative subnormals (bug 19375)

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The optimized POWER7 logb implementation does not use the absolute
value of the word extracted from the input to apply the leading 0-bits
builtin (to ignore the float sign).  This patch fixes it by
clearing the signal bit in the resulting word.

It fixes the subnormal tests failures when running on POWER7 ou
newer chip.

Tested on powerpc64le (POWER8).

	[BZ# 19375]
	* sysdeps/powerpc/power7/fpu/s_logb.c (__logb): Fix return for
	negative subnormals.
This commit is contained in:
Adhemerval Zanella 2015-12-17 12:34:57 -02:00
parent d29d57eed9
commit 2094350c9c
2 changed files with 6 additions and 0 deletions
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ChangeLog
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@ -1,3 +1,8 @@
2015-12-17 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* sysdeps/powerpc/power7/fpu/s_logb.c (__logb): Fix return for
negative subnormals.
2015-12-16 H.J. Lu <hongjiu.lu@intel.com>
* sysdeps/unix/sysv/linux/x86_64/sysdep.h

1
sysdeps/powerpc/power7/fpu/s_logb.c
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@ -58,6 +58,7 @@ __logb (double x)
int ma;
EXTRACT_WORDS (ix, lx, x);
ix &= 0x7fffffff;
if (ix == 0)
ma = __builtin_clz (lx) + 32;
else