powerpc: hypot refactor and optimization

powerpc: hypot refactor and optimization

The powerpc hypot is slight optimized by:

  - Commit 8df4e219e43, both isnan and isinf are always inlined and thus
    the check TEST_INF_NAN does not make sense anymore.  The generic
    check for POWER7 should be faster on all powerpc configuration.

  - The redundant check 'y > two60factor && (x / y) > two60' is removed.

Both changes leads to unrequired ifunc especialization for power7 and
thus they are removed.  Finally The code is also cleanup a bit by inlining
the constants floating points.

The performance changes using the hypot benchtests are:

  - POWER9 without patch:
    "hypot": {
     "overflow": {
      "duration": 4.98585e+09,
      "iterations": 4.84932e+08,
      "max": 46.551,
      "min": 10.229,
      "mean": 10.2815
     },
     "higher_two500": {
      "duration": 5.00192e+09,
      "iterations": 4.24843e+08,
      "max": 33.319,
      "min": 11.606,
      "mean": 11.7736
     },
     "subnormal": {
      "duration": 5.0075e+09,
      "iterations": 4.06792e+08,
      "max": 22.178,
      "min": 12.15,
      "mean": 12.3097
     },
     "less_two500": {
      "duration": 5.00685e+09,
      "iterations": 4.08772e+08,
      "max": 22.784,
      "min": 12.052,
      "mean": 12.2485
     },
     "default": {
      "duration": 5.06002e+09,
      "iterations": 4.09894e+08,
      "max": 20.648,
      "min": 11.874,
      "mean": 12.3447
     }
    }

  - POWER9 with patch:
    "hypot": {
     "overflow": {
      "duration": 4.91848e+09,
      "iterations": 7.28039e+08,
      "max": 47.958,
      "min": 6.436,
      "mean": 6.75579
     },
     "higher_two500": {
      "duration": 4.9359e+09,
      "iterations": 6.63376e+08,
      "max": 20.783,
      "min": 7.321,
      "mean": 7.44057
     },
     "subnormal": {
      "duration": 4.9479e+09,
      "iterations": 6.19772e+08,
      "max": 18.856,
      "min": 7.817,
      "mean": 7.98341
     },
     "less_two500": {
      "duration": 4.94275e+09,
      "iterations": 6.3889e+08,
      "max": 17.452,
      "min": 7.597,
      "mean": 7.73647
     },
     "default": {
      "duration": 5.03645e+09,
      "iterations": 5.70718e+08,
      "max": 18.904,
      "min": 8.55,
      "mean": 8.82476
     }
    }

  - POWER7 without patch
    "hypot": {
     "overflow": {
      "duration": 4.86637e+09,
      "iterations": 6.43196e+08,
      "max": 53.958,
      "min": 7.328,
      "mean": 7.56592
     },
     "higher_two500": {
      "duration": 4.99842e+09,
      "iterations": 3.11012e+08,
      "max": 78.227,
      "min": 15.696,
      "mean": 16.0715
     },
     "subnormal": {
      "duration": 4.99841e+09,
      "iterations": 3.08935e+08,
      "max": 51.392,
      "min": 15.983,
      "mean": 16.1795
     },
     "less_two500": {
      "duration": 5.00108e+09,
      "iterations": 2.99464e+08,
      "max": 73.247,
      "min": 16.416,
      "mean": 16.7001
     },
     "default": {
      "duration": 5.04645e+09,
      "iterations": 3.52608e+08,
      "max": 70.073,
      "min": 13.38,
      "mean": 14.3118
     }
    }

  - POWER7 with patch
    "hypot": {
     "overflow": {
      "duration": 4.80785e+09,
      "iterations": 8.00001e+08,
      "max": 66.262,
      "min": 5.888,
      "mean": 6.00981
     },
     "higher_two500": {
      "duration": 4.9859e+09,
      "iterations": 3.39449e+08,
      "max": 5148.44,
      "min": 14.539,
      "mean": 14.6882
     },
     "subnormal": {
      "duration": 4.9905e+09,
      "iterations": 3.28874e+08,
      "max": 64.905,
      "min": 14.971,
      "mean": 15.1745
     },
     "less_two500": {
      "duration": 4.99494e+09,
      "iterations": 3.19755e+08,
      "max": 103.696,
      "min": 14.972,
      "mean": 15.6211
     },
     "default": {
      "duration": 5.03951e+09,
      "iterations": 4.02502e+08,
      "max": 61.008,
      "min": 12.368,
      "mean": 12.5205
     }
    }

Checked on powerpc-linux-gnu (built without --with-cpu, with
--with-cpu=power4 and with --with-cpu=power5+ and --disable-multi-arch),
powerpc64-linux-gnu (built without --with-cp and with --with-cpu=power5+
and --disable-multi-arch).

	* sysdeps/powerpc/fpu/e_hypot.c (two60, two500, two600, two1022,
	twoM500, twoM600, two60factor, pdnum): Remove.
	(TEST_INFO_NAN, GET_TW0_HIGH_WORD): Remove macro.
	(__ieee754_hypot): Replace static variables with inline definition,
	remove ununsed branches.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
	(libm-sysdep_routines): Remove e_hypot-* objects.
	(CFLAGS-e_hypot-power7.c, CFLAGS-e_hypotf-power7.c): Remove rule.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypot-power7.c: Remove
	file.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypot-ppc64.c: Likewise.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypot.c: Likewise.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypotf-power7.c: Likewise.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypotf-ppc64.c: Likewise.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/e_hypotf.c: Likewise.

Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>