patch-1.3.94 linux/arch/m68k/fpsp040/slog2.S

• Lines: 189
• Date: Sat Feb 24 22:58:44 1996
• Orig file: v1.3.93/linux/arch/m68k/fpsp040/slog2.S
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.93/linux/arch/m68k/fpsp040/slog2.S linux/arch/m68k/fpsp040/slog2.S
@@ -0,0 +1,188 @@
+|
+|	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
+|
+|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 
+|	The copyright notice above does not evidence any  
+|	actual or intended publication of such source code.
+
+|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