math: xfail some pown and compoundn tests for ibm128-libgcc

math: xfail some pown and compoundn tests for ibm128-libgcc

On powerpc math/test-ibm128-pown shows below failures:

testing long double (without inline functions)
infinity has wrong sign.
Failure: Test: pown_downward (-inf, 0x7fffffffffffffffLL)
Result:
 is:          inf   inf
 should be:  -inf  -inf
Failure: Test: pown_downward (-0, 9223372036854775807LL)
Result:
 is:          0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 should be:  -0.00000000000000000000000000000000e+00  -0x0.000000000000000000000000000p+0
 difference:  0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 ulp       :  0.0000
 max.ulp   :  16.0000
Failure: pown_downward (-0x1p+0, 9223372036854775807LL): Exception "Invalid operation" set
Failure: pown_downward (-0x1p+0, 9223372036854775807LL): errno set to 34, expected 0 (unchanged)
Failure: Test: pown_downward (-0x1p+0, 9223372036854775807LL)
Result:
 is:         qNaN
 should be:  -1.00000000000000000000000000000000e+00  -0x1.000000000000000000000000000p+0
infinity has wrong sign.
Failure: Test: pown_towardzero (-0, -0x7fffffffffffffffLL)
Result:
 is:          inf   inf
 should be:  -inf  -inf
infinity has wrong sign.
Failure: Test: pown_towardzero (-inf, 0x7fffffffffffffffLL)
Result:
 is:          inf   inf
 should be:  -inf  -inf
Failure: Test: pown_towardzero (-inf, -0x7fffffffffffffffLL)
Result:
 is:          0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 should be:  -0.00000000000000000000000000000000e+00  -0x0.000000000000000000000000000p+0
 difference:  0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 ulp       :  0.0000
 max.ulp   :  16.0000
Failure: Test: pown_towardzero (-0, 9223372036854775807LL)
Result:
 is:          0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 should be:  -0.00000000000000000000000000000000e+00  -0x0.000000000000000000000000000p+0
 difference:  0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 ulp       :  0.0000
 max.ulp   :  16.0000
Failure: pown_towardzero (-0x1p+0, -9223372036854775807LL): Exception "Invalid operation" set
Failure: pown_towardzero (-0x1p+0, -9223372036854775807LL): errno set to 34, expected 0 (unchanged)
Failure: Test: pown_towardzero (-0x1p+0, -9223372036854775807LL)
Result:
 is:         qNaN
 should be:  -1.00000000000000000000000000000000e+00  -0x1.000000000000000000000000000p+0
Failure: pown_towardzero (-0x1p+0, 9223372036854775807LL): Exception "Invalid operation" set
Failure: pown_towardzero (-0x1p+0, 9223372036854775807LL): errno set to 34, expected 0 (unchanged)
Failure: Test: pown_towardzero (-0x1p+0, 9223372036854775807LL)
Result:
 is:         qNaN
 should be:  -1.00000000000000000000000000000000e+00  -0x1.000000000000000000000000000p+0
infinity has wrong sign.
Failure: Test: pown_upward (-0, -0x7fffffffffffffffLL)
Result:
 is:          inf   inf
 should be:  -inf  -inf
Failure: Test: pown_upward (-inf, -0x7fffffffffffffffLL)
Result:
 is:          0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 should be:  -0.00000000000000000000000000000000e+00  -0x0.000000000000000000000000000p+0
 difference:  0.00000000000000000000000000000000e+00   0x0.000000000000000000000000000p+0
 ulp       :  0.0000
 max.ulp   :  16.0000
Failure: pown_upward (-0x1p+0, -9223372036854775807LL): Exception "Invalid operation" set
Failure: pown_upward (-0x1p+0, -9223372036854775807LL): errno set to 34, expected 0 (unchanged)
Failure: Test: pown_upward (-0x1p+0, -9223372036854775807LL)
Result:
 is:         qNaN
 should be:  -1.00000000000000000000000000000000e+00  -0x1.000000000000000000000000000p+0

Likewise, math/test-ibm128-compoundn shows below failure:

testing long double (without inline functions)
Failure: compoundn_upward (0xf.ffffffffffff8p+1020, 1LL): Exception "Overflow" set
Failure: compoundn_upward (0xf.ffffffffffff8p+1020, 1LL): errno set to 34, expected 0 (unchanged)
Failure: Test: compoundn_upward (0xf.ffffffffffff8p+1020, 1LL)
Result:
 is:          inf   inf
 should be:   1.79769313486231570814527423731707e+308   0x1.fffffffffffff00000000000008p+1023

Signed-off-by: Sachin Monga <smonga@linux.ibm.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>