arch/m68k/fpsp040/sacos.S

Source file repositories/reference/linux-study-clean/arch/m68k/fpsp040/sacos.S

File Facts

System
Linux kernel
Corpus path
arch/m68k/fpsp040/sacos.S
Extension
.S
Size
2827 bytes
Lines
115
Domain
Architecture Layer
Bucket
arch/m68k
Inferred role
Architecture Layer: arch/m68k
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

|
|	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
|
|       For details on the license for this file, please see the
|       file, README, in this same directory.

|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

Annotation

Implementation Notes