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Diffstat (limited to 'arch/m68k/fpsp040/slog2.S')
| -rw-r--r-- | arch/m68k/fpsp040/slog2.S | 187 |
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diff --git a/arch/m68k/fpsp040/slog2.S b/arch/m68k/fpsp040/slog2.S new file mode 100644 index 000000000..fac2c7383 --- /dev/null +++ b/arch/m68k/fpsp040/slog2.S @@ -0,0 +1,187 @@ +| +| slog2.sa 3.1 12/10/90 +| +| The entry point slog10 computes the base-10 +| logarithm of an input argument X. +| slog10d does the same except the input value is a +| denormalized number. +| sLog2 and sLog2d are the base-2 analogues. +| +| INPUT: Double-extended value in memory location pointed to +| by address register a0. +| +| OUTPUT: log_10(X) or log_2(X) returned in floating-point +| register fp0. +| +| ACCURACY and MONOTONICITY: The returned result is within 1.7 +| ulps in 64 significant bit, i.e. within 0.5003 ulp +| to 53 bits if the result is subsequently rounded +| to double precision. The result is provably monotonic +| in double precision. +| +| SPEED: Two timings are measured, both in the copy-back mode. +| The first one is measured when the function is invoked +| the first time (so the instructions and data are not +| in cache), and the second one is measured when the +| function is reinvoked at the same input argument. +| +| ALGORITHM and IMPLEMENTATION NOTES: +| +| slog10d: +| +| Step 0. If X < 0, create a NaN and raise the invalid operation +| flag. Otherwise, save FPCR in D1; set FpCR to default. +| Notes: Default means round-to-nearest mode, no floating-point +| traps, and precision control = double extended. +| +| Step 1. Call slognd to obtain Y = log(X), the natural log of X. +| Notes: Even if X is denormalized, log(X) is always normalized. +| +| Step 2. Compute log_10(X) = log(X) * (1/log(10)). +| 2.1 Restore the user FPCR +| 2.2 Return ans := Y * INV_L10. +| +| +| slog10: +| +| Step 0. If X < 0, create a NaN and raise the invalid operation +| flag. Otherwise, save FPCR in D1; set FpCR to default. +| Notes: Default means round-to-nearest mode, no floating-point +| traps, and precision control = double extended. +| +| Step 1. Call sLogN to obtain Y = log(X), the natural log of X. +| +| Step 2. Compute log_10(X) = log(X) * (1/log(10)). +| 2.1 Restore the user FPCR +| 2.2 Return ans := Y * INV_L10. +| +| +| sLog2d: +| +| Step 0. If X < 0, create a NaN and raise the invalid operation +| flag. Otherwise, save FPCR in D1; set FpCR to default. +| Notes: Default means round-to-nearest mode, no floating-point +| traps, and precision control = double extended. +| +| Step 1. Call slognd to obtain Y = log(X), the natural log of X. +| Notes: Even if X is denormalized, log(X) is always normalized. +| +| Step 2. Compute log_10(X) = log(X) * (1/log(2)). +| 2.1 Restore the user FPCR +| 2.2 Return ans := Y * INV_L2. +| +| +| sLog2: +| +| Step 0. If X < 0, create a NaN and raise the invalid operation +| flag. Otherwise, save FPCR in D1; set FpCR to default. +| Notes: Default means round-to-nearest mode, no floating-point +| traps, and precision control = double extended. +| +| Step 1. If X is not an integer power of two, i.e., X != 2^k, +| go to Step 3. +| +| Step 2. Return k. +| 2.1 Get integer k, X = 2^k. +| 2.2 Restore the user FPCR. +| 2.3 Return ans := convert-to-double-extended(k). +| +| Step 3. Call sLogN to obtain Y = log(X), the natural log of X. +| +| Step 4. Compute log_2(X) = log(X) * (1/log(2)). +| 4.1 Restore the user FPCR +| 4.2 Return ans := Y * INV_L2. +| + +| Copyright (C) Motorola, Inc. 1990 +| All Rights Reserved +| +| For details on the license for this file, please see the +| file, README, in this same directory. + +|SLOG2 idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + + |xref t_frcinx + |xref t_operr + |xref slogn + |xref slognd + +INV_L10: .long 0x3FFD0000,0xDE5BD8A9,0x37287195,0x00000000 + +INV_L2: .long 0x3FFF0000,0xB8AA3B29,0x5C17F0BC,0x00000000 + + .global slog10d +slog10d: +|--entry point for Log10(X), X is denormalized + movel (%a0),%d0 + blt invalid + movel %d1,-(%sp) + clrl %d1 + bsr slognd | ...log(X), X denorm. + fmovel (%sp)+,%fpcr + fmulx INV_L10,%fp0 + bra t_frcinx + + .global slog10 +slog10: +|--entry point for Log10(X), X is normalized + + movel (%a0),%d0 + blt invalid + movel %d1,-(%sp) + clrl %d1 + bsr slogn | ...log(X), X normal. + fmovel (%sp)+,%fpcr + fmulx INV_L10,%fp0 + bra t_frcinx + + + .global slog2d +slog2d: +|--entry point for Log2(X), X is denormalized + + movel (%a0),%d0 + blt invalid + movel %d1,-(%sp) + clrl %d1 + bsr slognd | ...log(X), X denorm. + fmovel (%sp)+,%fpcr + fmulx INV_L2,%fp0 + bra t_frcinx + + .global slog2 +slog2: +|--entry point for Log2(X), X is normalized + movel (%a0),%d0 + blt invalid + + movel 8(%a0),%d0 + bnes continue | ...X is not 2^k + + movel 4(%a0),%d0 + andl #0x7FFFFFFF,%d0 + tstl %d0 + bnes continue + +|--X = 2^k. + movew (%a0),%d0 + andl #0x00007FFF,%d0 + subl #0x3FFF,%d0 + fmovel %d1,%fpcr + fmovel %d0,%fp0 + bra t_frcinx + +continue: + movel %d1,-(%sp) + clrl %d1 + bsr slogn | ...log(X), X normal. + fmovel (%sp)+,%fpcr + fmulx INV_L2,%fp0 + bra t_frcinx + +invalid: + bra t_operr + + |end |