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//
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//      $Id: satanh.S,v 1.2 2001-09-27 12:01:22 chris Exp $
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//
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//      satanh.sa 3.3 12/19/90
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//
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//      The entry point satanh computes the inverse
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//      hyperbolic tangent of
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//      an input argument; satanhd does the same except for denormalized
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//      input.
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//
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//      Input: Double-extended number X in location pointed to
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//              by address register a0.
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//
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//      Output: The value arctanh(X) returned in floating-point register Fp0.
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//
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//      Accuracy and Monotonicity: The returned result is within 3 ulps in
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//              64 significant bit, i.e. within 0.5001 ulp to 53 bits if the
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//              result is subsequently rounded to double precision. The
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//              result is provably monotonic in double precision.
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//
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//      Speed: The program satanh takes approximately 270 cycles.
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//
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//      Algorithm:
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//
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//      ATANH
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//      1. If |X| >= 1, go to 3.
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//
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//      2. (|X| < 1) Calculate atanh(X) by
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//              sgn := sign(X)
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//              y := |X|
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//              z := 2y/(1-y)
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//              atanh(X) := sgn * (1/2) * logp1(z)
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//              Exit.
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//
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//      3. If |X| > 1, go to 5.
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//
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//      4. (|X| = 1) Generate infinity with an appropriate sign and
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//              divide-by-zero by
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//              sgn := sign(X)
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//              atan(X) := sgn / (+0).
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//              Exit.
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//
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//      5. (|X| > 1) Generate an invalid operation by 0 * infinity.
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//              Exit.
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//
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//              Copyright (C) Motorola, Inc. 1990
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//                      All Rights Reserved
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//
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//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
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//      The copyright notice above does not evidence any
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//      actual or intended publication of such source code.
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//satanh        idnt    2,1 | Motorola 040 Floating Point Software Package
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        |section        8
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        |xref   t_dz
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        |xref   t_operr
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        |xref   t_frcinx
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        |xref   t_extdnrm
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        |xref   slognp1
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        .global satanhd
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satanhd:
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//--ATANH(X) = X FOR DENORMALIZED X
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        bra             t_extdnrm
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        .global satanh
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satanh:
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        movel           (%a0),%d0
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        movew           4(%a0),%d0
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        andil           #0x7FFFFFFF,%d0
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        cmpil           #0x3FFF8000,%d0
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        bges            ATANHBIG
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//--THIS IS THE USUAL CASE, |X| < 1
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//--Y = |X|, Z = 2Y/(1-Y), ATANH(X) = SIGN(X) * (1/2) * LOG1P(Z).
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        fabsx           (%a0),%fp0      // ...Y = |X|
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        fmovex          %fp0,%fp1
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        fnegx           %fp1            // ...-Y
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        faddx           %fp0,%fp0               // ...2Y
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        fadds           #0x3F800000,%fp1        // ...1-Y
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        fdivx           %fp1,%fp0               // ...2Y/(1-Y)
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        movel           (%a0),%d0
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        andil           #0x80000000,%d0
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        oril            #0x3F000000,%d0 // ...SIGN(X)*HALF
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        movel           %d0,-(%sp)
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        fmovemx %fp0-%fp0,(%a0) // ...overwrite input
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        movel           %d1,-(%sp)
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        clrl            %d1
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        bsr             slognp1         // ...LOG1P(Z)
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        fmovel          (%sp)+,%fpcr
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        fmuls           (%sp)+,%fp0
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        bra             t_frcinx
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ATANHBIG:
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        fabsx           (%a0),%fp0      // ...|X|
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        fcmps           #0x3F800000,%fp0
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        fbgt            t_operr
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        bra             t_dz
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        |end

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