arch/m68k/fpsp040/scale.S

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

File Facts

System
Linux kernel
Corpus path
arch/m68k/fpsp040/scale.S
Extension
.S
Size
8926 bytes
Lines
371
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

|
|	scale.sa 3.3 7/30/91
|
|	The entry point sSCALE computes the destination operand
|	scaled by the source operand.  If the absolute value of
|	the source operand is (>= 2^14) an overflow or underflow
|	is returned.
|
|	The entry point sscale is called from do_func to emulate
|	the fscale unimplemented instruction.
|
|	Input: Double-extended destination operand in FPTEMP,
|		double-extended source operand in ETEMP.
|
|	Output: The function returns scale(X,Y) to fp0.
|
|	Modifies: fp0.
|
|	Algorithm:
|
|		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.

|SCALE    idnt    2,1 | Motorola 040 Floating Point Software Package

	|section	8

#include "fpsp.h"

	|xref	t_ovfl2
	|xref	t_unfl
	|xref	round
	|xref	t_resdnrm

SRC_BNDS: .short	0x3fff,0x400c

|
| This entry point is used by the unimplemented instruction exception
| handler.
|
|
|
|	FSCALE
|
	.global	sscale
sscale:
	fmovel		#0,%fpcr		|clr user enabled exc
	clrl		%d1
	movew		FPTEMP(%a6),%d1	|get dest exponent
	smi		L_SCR1(%a6)	|use L_SCR1 to hold sign
	andil		#0x7fff,%d1	|strip sign
	movew		ETEMP(%a6),%d0	|check src bounds
	andiw		#0x7fff,%d0	|clr sign bit
	cmp2w		SRC_BNDS,%d0
	bccs		src_in
	cmpiw		#0x400c,%d0	|test for too large
	bge		src_out
|
| The source input is below 1, so we check for denormalized numbers
| and set unfl.
|
src_small:
	moveb		DTAG(%a6),%d0
	andib		#0xe0,%d0
	tstb		%d0
	beqs		no_denorm
	st		STORE_FLG(%a6)	|dest already contains result

Annotation

Implementation Notes