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PDP-10 Archives
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BB-JF16A-SB_1986
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flt.mic
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.TOC "FLOATING POINT -- FAD, FSB"
.DCODE
140: FL-R, FL-AC, J/FAD
142: FL-RW, FL-MEM, J/FAD
FL-RW, FL-BOTH, J/FAD
FL-R, FL-AC, ROUND, J/FAD
FL-I, FL-AC, ROUND, J/FAD
FL-RW, FL-MEM, ROUND, J/FAD
FL-RW, FL-BOTH, ROUND, J/FAD
150: FL-R, FL-AC, J/FSB
152: FL-RW, FL-MEM, J/FSB
FL-RW, FL-BOTH, J/FSB
FL-R, FL-AC, ROUND, J/FSB
FL-I, FL-AC, ROUND, J/FSB
FL-RW, FL-MEM, ROUND, J/FSB
FL-RW, FL-BOTH, ROUND, J/FSB
.UCODE
;BOTH FAD & FSB ARE ENTERED WITH THE MEMORY OPERAND IN AR
; SIGN SMEARED. THE EXPONENT IN BOTH SC AND FE.
1576:
FSB: [AR]_-[AR] ;MAKE MEMOP NEGATIVE
1577:
FAD: [BR]_AC, SC_SC-EXP-1, 3T, SCAD DISP
=0*
FAS1: READ [BR], SKIP DP0, J/FAS2 ;BR .LE. AR
[ARX]_[AR] ;SWAP AR AND BR
[AR]_[BR], SC_EXP
[BR]_[ARX], SC_SC-FE-1 ;NUMBER OF SHIFT STEPS
READ [AR], FE_EXP, 2T, SKIP DP0
=0 [AR]_+SIGN, J/FAS3
[AR]_-SIGN, J/FAS3
=0 ;SIGN SMEAR BR AND UNNORMALIZE
FAS2: [BR]_+SIGN, J/FAS3
[BR]_-SIGN, J/FAS3
FAS3: Q_0, STEP SC
=0
FAS4: [BR]_[BR]*.5 LONG, STEP SC, ASHC, J/FAS4
[AR]_[AR]+[BR], NORM DISP, J/SNORM
.TOC "FLAOTING POINT -- FMP"
.DCODE
160: FL-R, FL-AC, J/FMP
162: FL-RW, FL-MEM, J/FMP
FL-RW, FL-BOTH, J/FMP
FL-R, FL-AC, ROUND, J/FMP
FL-I, FL-AC, ROUND, J/FMP
FL-RW, FL-MEM, ROUND, J/FMP
FL-RW, FL-BOTH, ROUND, J/FMP
.UCODE
1570:
FMP: [BRX]_AC, ;GET AC
FE_SC+EXP, 3T, ;EXPONENT OF ANSWER
SKIP DP0 ;GET READY TO SMEAR SIGN
=0 [BRX]_+SIGN, J/FMP1 ;POSITIVE
[BRX]_-SIGN, J/FMP1 ;NEGATIVE
FMP1: Q_[AR], SC_27. ;GET MEMORY OPERAND
=01* [BRX]_[BRX]*.5 LONG, ;SHIFT RIGHT
CALL [MULSUB] ;MULTIPLY
Q_Q.AND.#, #/777000, ;WE ONLY COMPUTED
HOLD LEFT ; 27 BITS
[AR]_[ARX], FE_FE+2 ;SET SHIFT PATHS
[AR]_[AR]*.5 LONG, ;SHIFT OVER
FE_FE-200, ;ADJUST EXPONENT
NORM DISP, J/SNORM ;NORMALIZE & EXIT
.TOC "FLOATING POINT -- FDV"
.DCODE
170: FL-R, FL-AC, J/FDV
172: FL-RW, FL-MEM, J/FDV
FL-RW, FL-BOTH, J/FDV
FL-R, FL-AC, ROUND, J/FDV
FL-I, FL-AC, ROUND, J/FDV
FL-RW, FL-MEM, ROUND, J/FDV
FL-RW, FL-BOTH, ROUND, J/FDV
.UCODE
1574:
FDV: [BR]_[AR], SKIP AD.EQ.0, AC ;COPY DIVSOR SEE IF 0
=0
[AR]_AC, FE_SC-EXP, SKIP DP0, ;GET AC & COMPUTE NEW
J/FDV0 ; EXPONENT
FL NO DIVIDE ;DIVIDE BY ZERO
=0
FDV0: [AR]_+SIGN, J/FDV1
[AR]_-SIGN, J/FDV2
FDV1: [ARX]_[AR],FE_-FE+200,J/FDV3 ;COMPUTE 2*DVND
FDV2: [ARX]_-[AR],FE_-FE+200,J/FDV3 ;ABSOLUTE VALUE
FDV3: [BRX]_[BR]*2, SKIP DP0 ;ABSOLUTE VALUE
=0
FDV4: [ARX]-[BRX], SKIP CRY0, 3T, J/FDV5 ;FLOATING NO DIV?
[BRX]_-[BR]*2, J/FDV4 ;FORCE ABSOLUTE VALUE
=0
FDV5: [BRX]_[BRX]*.5, J/FDV6 ;SHIFT BACK ARX
FL NO DIVIDE ;UNNORMALIZED INPUT
=0
FDV6: [AR]_[AR]*2, ;DO NOT DROP A BIT
CALL [SBRL] ;AT FDV7+1
[BRX]-[ARX], SKIP AD.LE.0 ;IS ANSWER .LE. 1?
=00100
FDV7: Q_0, SC_27., CALL [DIVSGN] ;DIVIDE
=00101 [AR]_[AR]*.5, FE_FE+1, J/FDV7 ;SCALE DV'END
=01100
FDV8: [AR]_Q*.5, J/FDV9 ;PUT ANSWER IN AR
=01101 READ [AR], SKIP AD.EQ.0, ;-VE ANSWER, LOOK AT RMDR
CALL [SETSN] ; SEE HOW TO NEGATE
=01110 READ [AR], SKIP AD.EQ.0, ;-VE ANSWER, LOOK AT RMDR
CALL [SETSN] ; SEE HOW TO NEGATE
=01111 [AR]_Q*.5, J/FDV9 ;PUT ANSWER IN AR
=11111 [AR]_-Q*.5, J/FDV9 ;ZERO RMDR
FDV9: Q_0, J/SNORM0 ;GO NORMALIZE
.TOC "FLOATING POINT -- FLTR, FSC"
.DCODE
127: R, FL-AC,ROUND, J/FLTR
132: I, FL-AC, J/FSC
.UCODE
1616:
FLTR: [AR].AND.#, #/777000, 3T, SKIP ADL.EQ.0 ;SMALL POS NUMBER?
=0 [BR]_-[AR], SKIP DP0, 3T, J/FLTR1 ;NO--SEE IF MINUS
Q_0, FE_S#, S#/233, J/SNORM0 ;FITS IN 27 BITS
=0
FLTR1: [BR].AND.#, #/777000, 3T,
SKIP ADL.EQ.0, J/FLTR1A ;SMALL NEGATIVE NUMBER
Q_0, FE_S#, S#/244, J/FLTR2 ;LARGE POS NUMBER
=0
FLTR1A: Q_0, FE_S#, S#/244, J/FLTR2 ;BIG NUMBER
Q_0, FE_S#, S#/233, J/SNORM0 ;FITS IN 27 BITS
;AT THIS POINT WE KNOW THE NUMBER TAKES MORE THAN 27 BITS. WE JUST
; SHIFT 8 PLACES RIGHT AND NORMALIZE. WE COULD BE MORE CLEVER BUT
; THIS IS THE RARE CASE ANYWAY.
FLTR2: [AR]_[AR]*.5 LONG, ASHC, SC_6 ;SHOVE OVER TO THE RIGHT
=0
FLTR3: [AR]_[AR]*.5 LONG, ASHC, ;SHIFT RIGHT 9 PLACES
STEP SC, J/FLTR3 ; SO IT WILL FIT
SNORM0: READ [AR], NORM DISP, J/SNORM ;NORMALIZE ANSWER
1621:
FSC: READ [AR], SC_SHIFT
Q_0, AC ;DON'T SHIFT IN JUNK
[AR]_AC, FE_SC+EXP, SKIP DP0 ;SIGN SMEAR
=0 [AR]_+SIGN, J/SNORM0
[AR]_-SIGN, J/SNORM0
.TOC "FLOATING POINT -- FIX AND FIXR"
.DCODE
122: FL-R, FL-AC, J/FIX
126: FL-R, FL-AC,ROUND, J/FIX
.UCODE
1626:
FIX: Q_0, SCAD/A+B, SCADA/S#, ;CLEAR Q, SEE IF
S#/1534, SCADB/FE, 3T, ; ANSWER FITS IN
SCAD DISP ; 35 BITS.
=0* SET AROV, J/NIDISP ;TOO BIG
SC_FE+S#, S#/1544, 3T, SCAD DISP ;NEED TO MOVE LEFT?
=0* STEP SC, J/FIXL
SC_S#-FE, S#/232 ;NUMBER OF PLACES TO SHIFT
; RIGHT
STEP SC ;ALREADY THERE
=0
FIXR: [AR]_[AR]*.5 LONG, ASHC, ;SHIFT BINARY POINT
STEP SC, J/FIXR ; TO BIT 35.5
[BR]_[ONE]*.5, B DISP, J/FIXX ;WHICH KIND OF FIX?
=0
FIXL: [AR]_[AR]*2, STEP SC, J/FIXL ;SHIFT LEFT
AC_[AR], NEXT INST ;WE ARE NOW DONE
=0*11
FIXX: READ [AR], SKIP DP0, J/FIXT ;FIX--SEE IF MINUS
FIXX1: [AR]_[AR]+[BR], FL-EXIT ;FIXR--ROUND UP
=0
FIXT: AC_[AR], NEXT INST ;FIX & +, TRUNCATE
READ Q, SKIP AD.EQ.0 ;NEGATIVE--ANY FRACTION?
=0 [AR]_[AR]+1, FL-EXIT ;YES--ROUND UP
[BR]_.NOT.[MASK], ;MAYBE--GENERATE .75
J/FIXX1 ;ROUND UP IF BIT 36 OR
; 37 SET
.TOC "FLOATING POINT -- SINGLE PRECISION NORMALIZE"
;NORMALIZE DISPATCH IS A 9-WAY DISPATCH. THE HARDWARE LOOKS AT
; 4 SIGNALS: DP=0, DP BIT 8, DP BIT 9, DP BIT -2. THE 9 CASES
; ARE:
; DP=0 DP08 DP09 DP00 ACTION TO TAKE
; 0 0 0 0 SHIFT LEFT
;
; 0 0 0 1 NEGATE AND RETRY
;
; 0 0 1 0 ALL DONE
;
; 0 0 1 1 NEGATE AND RETRY
;
; 0 1 0 0 SHIFT RIGHT
;
; 0 1 0 1 NEGATE AND RETRY
;
; 0 1 1 0 SHIFT RIGHT
;
; 0 1 1 1 NEGATE AND RETRY
;
; 1 - - - LOOK AT Q BITS
;ENTER HERE WITH UNNORMALIZED NUMBER IN AR!Q. FE HOLDS THE NEW
; EXPONENT. CALL WITH NORM DISP
=0000 ;9-WAY DISPATCH
SNORM: [AR]_[AR]*2 LONG, DIV, FE_FE-1, NORM DISP, J/SNORM
Q_-Q, SKIP CRY0, 3T, J/SNNEG
READ [AR], NORM DISP, CALL [SROUND]
Q_-Q, SKIP CRY0, 3T, J/SNNEG
[AR]_[AR]*.5, FE_FE+1, CALL [SROUND]
Q_-Q, SKIP CRY0, 3T, J/SNNEG
[AR]_[AR]*.5, FE_FE+1, CALL [SROUND]
Q_-Q, SKIP CRY0, 3T, J/SNNEG
READ Q, SKIP AD.EQ.0, J/SNORM1
=1110 [AR]_EXP, J/FLEX
=
=0
SNORM1: [AR]_[AR]*2 LONG, DIV, FE_FE-1, NORM DISP, J/SNORM
FLEX: FL-EXIT
=0
SNNEG: [AR]_.NOT.[AR], NORM DISP, J/SNNORM ;NEGATE HIGH WORD
; (NO CARRY)
[AR]_-[AR], NORM DISP, J/SNNORM ;NEGATE HIGH WORD (W/CARRY)
=0000
SNNORM: [AR]_[AR]*2 LONG, DIV, FE_FE-1, NORM DISP, J/SNNORM
=0010 READ [AR], NORM DISP, CALL [SROUND]
=0100 [AR]_[AR]*.5, FE_FE+1, CALL [SROUND]
=0110 [AR]_[AR]*.5, FE_FE+1, CALL [SROUND]
=1000 [AR]_[AR]*2 LONG, DIV, FE_FE-1, NORM DISP, J/SNNORM
=1110 [AR]_EXP, B DISP
=
=0111 TL [FLG], FLG.SN/1, J/SNNOT
[AR]_[AR].AND.[MASK], ;CLEAR ANY LEFT OVER BITS
J/SNNOT1
=0
SNNOT: [AR]_.NOT.[AR], J/SNNOT2
READ Q, SKIP AD.EQ.0
=0 [AR]_.NOT.[AR], J/SNNOT2
SNNOT1: [AR]_-[AR], J/SNNOT2 ;NORMAL NEGATE AND EXIT
SNNOT2: [FLG]_0, FL-EXIT
.TOC "FLOATING POINT -- ROUND ANSWER"
=*01*
SROUND: [BR]_[ONE]*.5, B DISP, J/SRND1
[AR]_[AR]*.5, FE_FE+1, J/SROUND ;WE WENT TOO FAR
=0111
SRND1: RETURN [16] ;NOT ROUNDING INSTRUCTION
[AR]_[AR]+[BR], NORM DISP
=*01* RETURN [16]
[AR]_[AR]*.5, FE_FE+1, RETURN [16]
.TOC "FLOATING POINT -- DFAD, DFSB"
.DCODE
110: DBL FL-R, J/DFAD
111: DBL FL-R, J/DFSB
.UCODE
;ENTER FROM A-READ CODE WITH:
;FE/ EXP
;SC/ EXP
;AR/ C(E) SHIFT RIGHT 2 PLACES
;ARX/ C(E+1) SHIFTED RIGHT 1 PLACE
1635:
DFSB: [ARX]_-[ARX] ;NEGATE LOW WORD
[AR]_-[AR]-.25, MULTI PREC/1
1637:
DFAD: [BRX]_(AC[1].AND.[MAG])*.5, 3T ;GET LOW WORD
[BR]_AC*.5, 3T, ;GET AC AND START TO SHIFT
SC_SC-EXP-1, ;NUMBER OF PLACES TO SHIFT
SKIP DP0 ;SEE WHAT SIGN
=0 [BR]_+SIGN*.5, 3T, ;SIGN SMEAR
AC, SKIP/SC, J/DFAS1 ;SEE WHICH IS BIGGER
[BR]_-SIGN*.5, 3T, ;SIGN SMEAR
AC, SKIP/SC, J/DFAS1 ;SEE WHICH IS BIGGER
=0
DFAS1: Q_[BRX], ;AR IS BIGGER
J/DFAS2 ;ADJUST BR!Q
[T0]_AC, ;BR IS BIGGER OR EQUAL
SC_EXP, 2T, J/DFAS3 ;SET SC TO THAT EXPONENT
;HERE IF AR!ARX IS GREATER THAN BR!BRX
=0
DFAS2: [T0]_[BR], CALL [DFADJ] ;ADJUST BR!Q
[BR]_[T0] ;PUT ANSWER BACK
Q_Q+[ARX], J/DFAS5 ;ADD LOW WORDS
;HERE IS BR!BRX IF GREATER THAN OR EQUAL TO AR!ARX
DFAS3: Q_[ARX], ;SETUP TO SHIFT AR!ARX
SC_SC-FE-1 ;COMPUTE # OF PLACES
READ [T0], FE_EXP ;EXPONENT OF ANSWER
=0 [T0]_[AR], CALL [DFADJ] ;ADJUST AR!Q
[AR]_[T0] ;PUT ANSWER BACK
Q_Q+[BRX], J/DFAS5 ;ADD LOW WORDS
;BIT DIDDLE TO GET THE ANSWER (INCLUDING 2 GUARD BITS) INTO
; AR!Q
DFAS5: [AR]_([AR]+[BR])*.5 LONG, ;ADD HIGH WORDS
MULTI PREC/1, ASHC ;INJECT SAVED CRY2
[AR]_[AR]*2 LONG, ;SHIFT BACK LEFT
ASHC, MUL DISP ;SEE IF WE LOST A 1
=1011
DFAS6: [T1]_[T1].AND.NOT.[MASK], J/DFAS7
Q_Q+.25, J/DFAS6
DFAS7: [AR]_[AR]*2 LONG, ASHC, ;PUT IN GUARD BITS
FE_FE-1
[AR]_[AR]*2 LONG, ASHC,
FE_FE-1
Q_[T1].OR.Q, HOLD LEFT, J/DNORM0
;SUBROUTINE TO ADJUST NUMBER IN T0!Q
;RETURNS 1 WITH
; T0!Q ADJUSTED
; FLG.SN=1 IF WE SHIFTED OUT ANY 1 BITS (STICKY BIT)
; T1 HAS Q TWO STEPS PRIOR TO BEING DONE
DFADJ "STEP SC, ASHC, MUL DISP"
=0**11
DFADJ: [T0]_[T0]*2 LONG, DIV, ;MOVE EVERYTHING 2 PLACES
CALL [CLRSN]
[T0]_[T0]*2 LONG, DIV
[T0]_[T0]*2 LONG, DIV
[T0]_[T0]*.5 LONG, ASHC, ;SHIFT AT LEAST 1 PLACE
STEP SC
=1010
DFADJ1: [T0]_[T0]*.5 LONG, ;UNNORMALIZE T0!Q
DFADJ, J/DFADJ1 ;LOOP TILL DONE
DFADJ2: [T1]_Q, ;SAVE GUARD BITS
MUL DISP, J/DFADJ5 ;LOOK AT LAST BIT
[FLG]_[FLG].OR.#, FLG.SN/1, HOLD RIGHT, J/DFADJ3
[FLG]_[FLG].OR.#, FLG.SN/1, HOLD RIGHT, J/DFADJ4
=0
DFADJ3: [T0]_[T0]*.5 LONG, ASHC, STEP SC, J/DFADJ3
DFADJ4: [T1]_Q ;SAVE 2 GUARD BITS
=1011
DFADJ5: [T0]_[T0]*.5 LONG, ASHC, J/DFADJ6
[FLG]_[FLG].OR.#, FLG.SN/1, HOLD RIGHT, J/DFADJ5
DFADJ6: [T0]_[T0]*.5 LONG, ASHC, RETURN [1]
.TOC "FLOATING POINT -- DFMP"
.DCODE
112: DBL FL-R, DAC, J/DFMP
.UCODE
;SAME ENTRY CONDITIONS AS DFAD/DFSB
1631:
DFMP: Q_[ARX], SC_6 ;SHIFT MEM OP 8 PLACES
=0
DFMP1: [AR]_[AR]*2 LONG, ASHC, ;SHIFT
STEP SC, J/DFMP1
Q_Q*.5
Q_Q.AND.#, #/077777, HOLD RIGHT
[BR]_Q ;COPY LOW WORD
;
; BRX * BR ==> C(E+1) * C(AC+1)
;
[BRX]_(AC[1].AND.[MAG])*.5 ;GET LOW AC
=0** [BRX]_[BRX]*.5, SC_35., CALL [MULSB1]
;
; BRX * Q ==> C(E) * C(AC+1)
;
Q_[AR], SC_35. ;GO MULT NEXT HUNK
=0** CALL [MULTIPLY]
[T0]_[ARX] ;SAVE PRODUCT
[ARX]_Q*.5, SC_FE ;PUT IN NEXT STEP
;
; BRX * BR ==> C(AC) * C(E+1)
;
[BRX]_AC*.5, ;PREPARE TO DO HIGH HALF
FE_SC+EXP, ;EXPONENT ON ANSWER
SKIP DP0, 3T
=0 [BRX]_+SIGN*.5, 3T, J/DFMP2
[BRX]_-SIGN*.5, 3T
=0**
DFMP2: Q_[BR], SC_35., CALL [MULTIPLY] ;GO MULTIPLY
[T1]_Q ;SAVE FOR ROUNDING
[ARX]_[ARX]+[T0] ;PREPARE FOR LAST MUL
;
; BRX * Q ==> C(AC) * C(E)
;
=0** Q_[AR], SC_35., ;DO THE LAST MULTIPLY
CALL [MULTIPLY] ; ..
;OK, WE NOW HAVE THE PRODUCT IN ARX!Q!T1. ALL WE NEED TO DO
; IS SOME BIT DIDDLES TO GET EVERYTHING IN THE RIGHT PLACE
[AR]_[ARX]*.5 LONG, ;SHIFT THE ANSWER
FE_FE+S#, S#/1576 ;CORRECT EXPONENT
=0**11 READ [T1], SKIP AD.EQ.0, ;SEE IF LOW ORDER 1
CALL [SETSN] ; BITS AROUND SOMEPLACE
[AR]_[AR]*2 LONG, ASHC ;SHIFT LEFT
[BR]_[ONE]*.5 ;PLACE TO INSTERT BITS
TL [T1], #/200000 ;ANYTHING TO INJECT?
=0 Q_Q+[BR] ;YES--PUT IT IN
[AR]_[AR]*2 LONG, ASHC ;MAKE ROOM FOR MORE
TL [T1], #/100000 ;ANOTHER BIT NEEDED
=0 Q_Q+[BR] ;YES--PUT IN LAST BIT
DNORM0: READ [AR], NORM DISP, ;SEE WHAT WE NEED TO DO
FE_FE+S#, S#/2, J/DNORM ;ADJUST FOR INITIAL SHIFTS
.TOC "FLOATING POINT -- DFDV"
.DCODE
113: DBL FL-R, DAC, J/DFDV
.UCODE
1636:
DFDV: [BRX]_[ARX] ;COPY OPERAND (COULD SAVE TIME
; WITH SEPERATE A-READ FOR DFDV)
=1**10 [T1]_0, CALL [CLRSN] ;CLEAR FLAG
[BR]_[AR], SKIP AD.LE.0, ;SEE IF POSITIVE
AC[1] ;WARM UP RAM
=0
DFDV1: [ARX]_(AC[1].AND.[MAG])*.5, ;POSITIVE--GET AC
J/DFDV2 ; AND CONTINUE BELOW
[T1]_.NOT.[T1] ;DV'SOR NEGATIVE (OR ZERO)
[BRX]_-[BRX] ;NEGATE LOW WORD
AD/-B-.25, B/BR, DEST/AD, ;NEGATE HIGH WORD
MULTI PREC/1, 3T, ;ADDING IN CRY02
SKIP DP0, AC[1], ;SEE IF STILL NEGATIVE
J/DFDV1 ; ..
DFDV2: [AR]_AC*.5, ;GET AC AND SHIFT
FE_SC-EXP, 3T, ;COMPUTE NEW EXPONENT
SKIP DP0 ;SEE IF NEGATIVE
=0 [AR]_+SIGN*.5, 3T, J/DFDV3 ;POSITIVE
[T1]_.NOT.[T1] ;NEGATIVE OR ZERO
[AR]_-SIGN*.5, 3T ;SIGN SMEAR
Q_-[ARX] ;NEGATE OPERAND
[AR]_(-[AR]-.25)*.5 LONG, ;NEGATE HIGH WORD
MULTI PREC/1, ;USE SAVED CARRY
ASHC, J/DFDV4 ;CONTINUE BELOW
=0
DFDV3: Q_[ARX], ;COPY OPERAND
CALL [DDIVS] ;SHIFT OVER
DFDV4: [AR]-[BR], 3T, SKIP DP0 ;SEE IF OVERFLOW
=0 FL NO DIVIDE
[ARX]_Q ;START DIVISION
=0* Q_0, SC_26., CALL [DBLDIV]
[T0]_Q, SC_35.
=0* Q_Q.AND.NOT.[MAG], ;SEE IF ODD
SKIP AD.EQ.0, ;SKIP IF EVEN
CALL [DBLDIV] ;GO DIVIDE
Q_Q*.5 ;MOVE ANSWER OVER
=
[T0]_[T0]*2 LONG, ASHC, ;DO FIRST NORM STEP
MUL DISP ; SEE IF A 1 FELL OUT
=1011
DFDV4A: READ [T1], SKIP DP0, ;SHOULD RESULT BE NEGATIVE
FE_S#-FE, S#/202, ;CORRECT EXPONENT
J/DFDV4B ;LOOK BELOW
Q_Q+.25, J/DFDV4A ;PUT BACK THE BIT
=0
DFDV4B: [AR]_[T0], NORM DISP, J/DNORM ;PLUS
[AR]_[T0], NORM DISP, J/DNNORM ;MINUS
.TOC "FLOATING POINT -- DOUBLE PRECISION NORMALIZE"
;NORMALIZE AR!Q
;DNORM0: READ [AR], NORM DISP, ;SEE WHAT WE NEED TO DO
; FE_FE+S#, S#/2, J/DNORM ;ADJUST FOR INITIAL SHIFTS
=0000
DNORM: [AR]_[AR]*2 LONG, ;SHIFT LEFT
FE_FE-1, ASHC, ;ADJUST EXPONENT
NORM DISP, J/DNORM ;TRY AGAIN
TL [FLG], FLG.SN/1, J/DNEG ;RESULT IS NEGATIVE
READ [AR], NORM DISP, ;SEE IF WE WENT TOO FAR
CALL [DROUND] ; AND ROUND ANSWER
TL [FLG], FLG.SN/1, J/DNEG ;RESULT IS NEGATIVE
[AR]_[AR]*.5 LONG, ASHC,
FE_FE+1, CALL [DROUND]
TL [FLG], FLG.SN/1, J/DNEG ;RESULT IS NEGATIVE
[AR]_[AR]*.5 LONG, ASHC,
FE_FE+1, CALL [DROUND]
TL [FLG], FLG.SN/1, J/DNEG ;RESULT IS NEGATIVE
Q_[MAG].AND.Q, ;HIGH WORD IS ZERO
HOLD RIGHT, J/DNORM1 ;GO TEST LOW WORD
=1110 [FLG]_0 ;[122] CLEAR FLAG WORD
=
AC[1]_[ARX].AND.[MAG], ;STORE LOW WORD
J/STAC ;GO DO HIGH WORD
DNORM1: READ Q, SKIP AD.EQ.0 ;TEST LOW WORD
=0 [AR]_[AR]*2 LONG, ;LOW WORD IS NON-ZERO
FE_FE-1, ASHC, ;ADJUST EXPONENT
NORM DISP, J/DNORM ;KEEP LOOKING
AC[1]_[AR], J/STAC ;WHOLE ANSWER IS ZERO
;HERE TO NORMALIZE NEGATIVE D.P. RESULTS
=0
DNEG: Q_.NOT.Q, J/DNEG1 ;ONES COMP
Q_-Q, SKIP CRY2, J/DNEG2
DNEG1: [FLG]_0
=0
DNEG2: [AR]_.NOT.[AR], ;NO CARRY
NORM DISP, J/DNNORM ;GO NORMALIZE
[AR]_-[AR], ;CARRY
NORM DISP, J/DNNORM ;NORMALIZE
=000*
DNNORM: [AR]_[AR]*2 LONG, ;SHIFT 1 PLACE
FE_FE-1, ASHC, ;ADJUST EXPONENT
NORM DISP, J/DNNORM ;LOOP TILL DONE
=001* READ [AR], NORM DISP, ;SEE IF WE WENT TOO FAR
CALL [DROUND] ; AND ROUND ANSWER
=010* [AR]_[AR]*.5 LONG, ASHC,
FE_FE+1, CALL [DROUND]
=011* [AR]_[AR]*.5 LONG, ASHC,
FE_FE+1, CALL [DROUND]
=100* Q_[MAG].AND.Q, ;HIGH WORD IS ZERO
HOLD RIGHT, J/DNNRM1 ;GO TEST LOW WORD
=111* [ARX]_[ARX].AND.[MASK] ;REMOVE ROUNDING BIT
=
=00 [ARX]_[ARX].AND.[MAG], ;ALSO CLEAR SIGN
CALL [CHKSN] ;ONES COMP?
=10 [ARX]_[ARX].XOR.[MAG], ;YES--ONES COMP
J/DNN1 ;CONTINUE BELOW
=11 [ARX]_-[ARX], 3T, ;NEGATE RESULT
SKIP CRY1, J/DNN2
=
DNN1: [FLG]_0 ;CLEAR FLAG
=0
DNN2: AC_.NOT.[AR], J/DNORM2
AC_-[AR], 3T
DNORM2: AC[1]_[ARX].AND.[MAG], ;STORE LOW WORD
NEXT INST ;ALL DONE
DNNRM1: READ Q, SKIP AD.EQ.0 ;TEST LOW WORD
=0 [AR]_[AR]*2 LONG, ;LOW WORD IS NON-ZERO
FE_FE-1, ASHC, ;ADJUST EXPONENT
NORM DISP, J/DNNORM ;KEEP LOOKING
AC[1]_[AR], J/STAC ;WHOLE ANSWER IS ZERO
CHKSN: TL [FLG], FLG.SN/1, RETURN [2]
;SUBROUTINE TO SET/CLEAR FLG.SN
;CALL WITH:
; CALL [SETSN], SKIP IF WE SHOULD CLEAR
;RETURNS 23
=0
SETSN: [FLG]_[FLG].OR.#, FLG.SN/1, HOLD RIGHT, RETURN [23]
CLRSN: [FLG]_[FLG].AND.NOT.#, FLG.SN/1, HOLD RIGHT, RETURN [23]
;SUBROUTINE TO ROUND A FLOATING POINT NUMBER
;CALL WITH:
; NUMBER IN AR!Q AND NORM DISP
;RETURNS 16 WITH ROUNDED NUMBER IN AR!ARX
;
=*01*
DROUND: [ARX]_(Q+1)*.5, ;ROUND AND SHIFT
SKIP CRY2, ;SEE IF OVERFLOW
J/DRND1 ;COMPLETE ROUNDING
[AR]_[AR]*.5 LONG, ;WE WENT TOO FAR
FE_FE+1, ASHC, J/DROUND ;SHIFT BACK AND ROUND
=*010
DRND1: [AR]_EXP, RETURN [16] ;NO OVERFLOW
=011 [AR]_[AR]+.25, ;ADD CARRY (BITS 36 AND 37
; ARE COPIES OF Q BITS)
NORM DISP, ;SEE IF OVERFLOW
J/DRND1 ; ..
=110 [AR]_[AR]*.5, ;SHIFT RIGHT
FE_FE+1, ;KEEP EXP RIGHT
J/DRND1 ;ALL SET NOW
=