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Diffstat (limited to 'c/src/lib/libcpu/m68k/m68040/fpsp/sacos.s')
| -rw-r--r-- | c/src/lib/libcpu/m68k/m68040/fpsp/sacos.s | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/c/src/lib/libcpu/m68k/m68040/fpsp/sacos.s b/c/src/lib/libcpu/m68k/m68040/fpsp/sacos.s new file mode 100644 index 0000000000..83390a8ebb --- /dev/null +++ b/c/src/lib/libcpu/m68k/m68040/fpsp/sacos.s @@ -0,0 +1,115 @@ +// +// sacos.sa 3.3 12/19/90 +// +// Description: The entry point sAcos computes the inverse cosine of +// an input argument; sAcosd does the same except for denormalized +// input. +// +// Input: Double-extended number X in location pointed to +// by address register a0. +// +// Output: The value arccos(X) returned in floating-point register Fp0. +// +// Accuracy and Monotonicity: The returned result is within 3 ulps in +// 64 significant bit, i.e. within 0.5001 ulp to 53 bits if the +// result is subsequently rounded to double precision. The +// result is provably monotonic in double precision. +// +// Speed: The program sCOS takes approximately 310 cycles. +// +// Algorithm: +// +// ACOS +// 1. If |X| >= 1, go to 3. +// +// 2. (|X| < 1) Calculate acos(X) by +// z := (1-X) / (1+X) +// acos(X) = 2 * atan( sqrt(z) ). +// Exit. +// +// 3. If |X| > 1, go to 5. +// +// 4. (|X| = 1) If X > 0, return 0. Otherwise, return Pi. Exit. +// +// 5. (|X| > 1) Generate an invalid operation by 0 * infinity. +// Exit. +// + +// Copyright (C) Motorola, Inc. 1990 +// All Rights Reserved +// +// THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA +// The copyright notice above does not evidence any +// actual or intended publication of such source code. + +//SACOS idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + +PI: .long 0x40000000,0xC90FDAA2,0x2168C235,0x00000000 +PIBY2: .long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000 + + |xref t_operr + |xref t_frcinx + |xref satan + + .global sacosd +sacosd: +//--ACOS(X) = PI/2 FOR DENORMALIZED X + fmovel %d1,%fpcr // ...load user's rounding mode/precision + fmovex PIBY2,%fp0 + bra t_frcinx + + .global sacos +sacos: + fmovex (%a0),%fp0 // ...LOAD INPUT + + movel (%a0),%d0 // ...pack exponent with upper 16 fraction + movew 4(%a0),%d0 + andil #0x7FFFFFFF,%d0 + cmpil #0x3FFF8000,%d0 + bges ACOSBIG + +//--THIS IS THE USUAL CASE, |X| < 1 +//--ACOS(X) = 2 * ATAN( SQRT( (1-X)/(1+X) ) ) + + fmoves #0x3F800000,%fp1 + faddx %fp0,%fp1 // ...1+X + fnegx %fp0 // ... -X + fadds #0x3F800000,%fp0 // ...1-X + fdivx %fp1,%fp0 // ...(1-X)/(1+X) + fsqrtx %fp0 // ...SQRT((1-X)/(1+X)) + fmovemx %fp0-%fp0,(%a0) // ...overwrite input + movel %d1,-(%sp) //save original users fpcr + clrl %d1 + bsr satan // ...ATAN(SQRT([1-X]/[1+X])) + fmovel (%sp)+,%fpcr //restore users exceptions + faddx %fp0,%fp0 // ...2 * ATAN( STUFF ) + bra t_frcinx + +ACOSBIG: + fabsx %fp0 + fcmps #0x3F800000,%fp0 + fbgt t_operr //cause an operr exception + +//--|X| = 1, ACOS(X) = 0 OR PI + movel (%a0),%d0 // ...pack exponent with upper 16 fraction + movew 4(%a0),%d0 + cmpl #0,%d0 //D0 has original exponent+fraction + bgts ACOSP1 + +//--X = -1 +//Returns PI and inexact exception + fmovex PI,%fp0 + fmovel %d1,%FPCR + fadds #0x00800000,%fp0 //cause an inexact exception to be put +// ;into the 040 - will not trap until next +// ;fp inst. + bra t_frcinx + +ACOSP1: + fmovel %d1,%FPCR + fmoves #0x00000000,%fp0 + rts //Facos ; of +1 is exact + + |end |