Ieee.mesa
Copyright © 1985 by Xerox Corporation. All rights reserved.
Stewart August 27, 1982 11:10 am
Rovner May 4, 1983 9:39 am
Levin, August 8, 1983 4:24 pm
Russ Atkinson (RRA) February 19, 1985 4:14:34 pm PST
Doug Wyatt (DKW), February 25, 1985 3:26:53 pm PST
Internal details of the IEEE floating-point implementation.
DIRECTORY
Basics USING [BITAND, LongNumber],
PrincOps USING [alpha, aFSTICKY, zMISC],
Real USING [ExceptionFlags, Extended, NumberType],
RealOps USING [Mode, RoundingMode];
Ieee: CEDAR DEFINITIONS
IMPORTS Basics
=
BEGIN
OPEN Real, RealOps;
LongNumber: TYPE = Basics.LongNumber;
SingleReal:
TYPE =
MACHINE
DEPENDENT
RECORD [
m2: CARDINAL, sign: BOOL, exp: [0..377B], m1: [0..177B]];
Details:
TYPE =
MACHINE
DEPENDENT
RECORD [
sign: BOOL, sticky: BOOL, blank: [0..7777B], type: Real.NumberType];
Ext: TYPE = RECORD [det: Details, exp: INTEGER, frac: LongNumber];
constants
HiBit: CARDINAL = 100000B;
NotHiBit: CARDINAL = 077777B;
ExponentBias: INTEGER = 127;
ExponentMask: INTEGER = 077600B;
ExponentShift: INTEGER = 7;
HiFractionMask: INTEGER = 177B;
LowSignificandMask: CARDINAL = 177400B;
FractionShift: INTEGER = 8;
LeastSignificandBit: INTEGER = 0400B;
HiddenBit: CARDINAL = 100000B;
StickyBits: CARDINAL = 77B;
NotStickyBits: CARDINAL = 177700B;
MagicLI: LONG INTEGER = LOOPHOLE[20000000000B];
HalfLC: LONG CARDINAL = LOOPHOLE[20000000000B];
MagicI: INTEGER = FIRST[INTEGER];
SignBit: CARDINAL = 100000B;
ExpSingleMax: INTEGER = 127;
ExpSingleMin: INTEGER = -126;
DenormalizedExponent: INTEGER = -127;
NaNExponent: INTEGER = 128;
LargestSignificand: LONG CARDINAL = 37777777400B;
BiasAdjust: INTEGER = 192;
global variables
fpmode: RealOps.Mode;
stickyFlags: ExceptionFlags;
thisTimeExceptions: ExceptionFlags;
other stuff
BitOn:
PROC [a, b:
WORD]
RETURNS [
BOOL] =
INLINE {
RETURN[Basics.BITAND[LOOPHOLE[a], LOOPHOLE[b]] # 0]; };
Normalized:
PROC [g:
INTEGER]
RETURNS [
BOOL] =
INLINE {
RETURN[Basics.BITAND[g, HiddenBit] # 0]; };
Add with Carry
ADC3:
PROC [a, b, c:
CARDINAL]
RETURNS [
CARDINAL,
CARDINAL] =
INLINE {
s: LongNumber;
s.lc ← LONG[a] + LONG[b] + LONG[c];
RETURN[s.highbits, s.lowbits];
};
Add two shorts to make a long
ADC2:
PROC [a, b:
CARDINAL]
RETURNS [
CARDINAL,
CARDINAL] =
INLINE {
s: LongNumber; s.lc ← LONG[a] + LONG[b]; RETURN[s.highbits, s.lowbits]; };
Separate the packed REAL into its component elements
Unpack: PROC [REAL] RETURNS [Ext];
Pack: PROC [POINTER TO Ext] RETURNS [REAL];
Round: PROC [POINTER TO Ext];
StepTwo: PROC [POINTER TO Ext];
GRS: PROC [g: INTEGER] RETURNS [INTEGER];
PostNormalize: PROC [POINTER TO Ext];
LongShift: PROC [z: LongNumber, count: INTEGER] RETURNS [LongNumber];
RShift: PROC [z: LongNumber] RETURNS [LongNumber];
LShift: PROC [z: LongNumber] RETURNS [LongNumber];
RShift1in1: PROC [z: LongNumber] RETURNS [LongNumber];
DeNormalize: PROC [z: POINTER TO Ext, count: INTEGER];
Mul32: PROC [x, y: LongNumber] RETURNS [LongNumber, LongNumber];
FixExtended:
PUBLIC
PROC [z: Ext, rmode: RoundingMode]
RETURNS [v: LONG INTEGER, invalid, overflow: BOOL];
SetInexactResult: PROC;
SetInvalidOperation: PROC;
SetDivisionByZero: PROC;
SetUnderflow: PROC [POINTER TO Ext];
SetOverflow: PROC [POINTER TO Ext];
SetFixOverflow: PROC;
CVExtended: PROC [Ext] RETURNS [Real.Extended];
CFExtended: PROC [zz: REF Extended, z: POINTER TO Ext];
NormalType: PROC [x, y: Details] RETURNS [INTEGER];
MicroStickySet: PROC;
IResultSticky: CARDINAL = 1;
IResultEnable: CARDINAL = 100000B;
MicroSticky:
PROC [
CARDINAL]
RETURNS [
CARDINAL] =
TRUSTED MACHINE CODE { PrincOps.zMISC, PrincOps.aFSTICKY; };
InitIeee: PROC;
Microcode: BOOL = TRUE; -- DKW: moved here from Real
funny: INTEGER = 02B;
TNnn: INTEGER = 00B;
TNnz: INTEGER = 01B;
TNzn: INTEGER = 02B;
TNzz: INTEGER = 03B;
END.
L. Stewart, July 6, 1980 12:28 PM, Added InitIeee
L. Stewart, July 6, 1980 4:15 PM, Added microcode sticky bit stuff
September 28, 1980 9:10 PM; Stewart, Added aSETS
June 3, 1982 11:09 am; Stewart, removed aSETS, what was it for?