Various pow function implementations mishandle sNaN arguments in
various ways. This includes returning sNaN instead of qNaN for sNaN
arguments. For arguments (1, sNaN) and (sNaN, 0), TS 18661-1
semantics are also that the result should be qNaN, whereas with a qNaN
argument there the result should be 1, but for the dbl-64
implementation of pow there are issues with sNaN arguments beyond not
implementing the TS 18661-1 semantics in those special cases.
This patch makes the implementations in sysdeps/ieee754 follow the TS
18661-1 semantics consistently. Because x86 / x86_64 implementations
still need fixing, testcases are not included with this patch; they
will be included with the fix for the x86 / x86_64 versions.
Tested for x86_64, x86, mips64 and powerpc (with such testcases, which
pass in the mips64 and powerpc cases).
[BZ #20916]
* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return 1
for arguments (sNaN, 0) or (1, sNaN). Do arithmetic on NaN
arguments to compute result.
* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Do not return
1 for arguments (sNaN, 0) or (1, sNaN).
* sysdeps/ieee754/ldbl-128/e_powl.c (__ieee754_powl): Likewise.
* sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Likewise.
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