
<<IFUPLAInstrDecode1.mesa>>
<<Copyright © 1984 by Xerox Corporation.  All rights reserved.>>
<<Last edited by TWilliams, August 27, 1984 4:58:00 pm PDT>>
<<Last edited by Curry, November 24, 1984 1:58:08 pm PST>>
<<>>
DIRECTORY
Basics,
Dragon,
DragOpsCross,
IFUPLA,
PLAOps;

IFUPLAInstrDecode1: CEDAR PROGRAM
IMPORTS IFUPLA, PLAOps EXPORTS IFUPLA =
BEGIN OPEN IFUPLA, PO: PLAOps;

GenInstrDecodePLA1:  PUBLIC PROC = {

<<Used in RR and RJB instructions>>
sdd:        PO.BoolExpr    _ BE[m:[beta: 200B],    d:[beta: 200B]];
opt:        PO.BoolExpr    _ BE[m:[beta: 040B],    d:[beta: 040B]];
sd:            PO.BoolExpr    _ BE[m:[beta: 100B],    d:[beta: 100B]];
aux:        PO.BoolExpr    _ BE[m:[beta: 020B],    d:[beta: 020B]];

instr, delay, trap, exception:        PO.BoolExpr;    -- Temporaries

m: InstrDecodeOut;

exception _ BE[m:[stateException: TRUE],    d:[stateException: TRUE]];
current _ PO.And[exception, BE[m:[state: prioritySig], d:[state: highPriority]]];
<<Do High Priority Exceptions>>
Set[s:current, m:[state: exceptionSig], d:[state: reseting],    out: [
doMacroJump: FALSE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen,
lSource: [ zero, one ],
sSource: [ zero, zero ] ]];
Set[s:current, m:[state: exceptionSig], d:[state: reset],        out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen,
lSource: [ zero, one ],
sSource: [ zero, zero ] ]];
m _ [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen,
lSource: [ l3, zero ],
sSource: [ s3, zero ],
restoreTrap3: TRUE];
Set[s:current, m:[state: exceptionSig], d:[state: euCC],    out: m];
Set[s:current, m:[state: exceptionSig], d:[state: epFault],    out: m];
Set[s:current, m:[state: exceptionSig], d:[state: cJump],    out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: pipe3,
lSource: [ l3, zero ],
sSource: [ s3, zero ],
restoreTrap3: TRUE ]];

<<Delayed Low Priority Exceptions>>
current _ PO.And[exception, PO.Not[BE[m:[state: prioritySig], d:[state: highPriority]]]];
Set[s:current, m:[stateDelay: TRUE],        d:[stateDelay: TRUE], out: Delayed];

<<Do Low Priority Exceptions>>
Set[s:current, m:[stateDelay: TRUE],    d:[stateDelay: FALSE], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen,
iStackPostEffect: push,
trappingControl: disable ] ];


<<Not An Exception>>

current _ BE[m:[stateException: TRUE],    d:[stateException: FALSE]];
Set[s:current, m:[stateDelay: TRUE],        d:[stateDelay: TRUE], out: Delayed];

current _ PO.And[current, BE[m:[stateDelay: TRUE],    d:[stateDelay: FALSE]]];
<<>>
<<Instruction not ready>>
Set[s:current, m:[instReady: TRUE], d:[instReady: FALSE], out: Delayed];
current _ PO.And[current, BE[m:[instReady: TRUE],        d:[instReady: TRUE]]];

<<Check for Delays and IStack Underflow traps in dRET, dRETT, dRETN, dLIFUR>>
<<Temporary BE's used by dRET, dRETT, dRETN, dLIFUR>>
delay _ PO.Or[
BE[m:[pushPending: TRUE],    d:[pushPending: TRUE]],
BE[m:[popPending: TRUE],        d:[popPending: TRUE]]];
trap _ PO.And[
PO.Not[delay],
BE[m:[iStkEmpty: TRUE],        d:[iStkEmpty: TRUE]]];
Set[s: PO.And[current, delay],                m:[op: instrIsSig], d:[op: dRET],    out: Delayed];
Set[s: PO.And[current, delay],                m:[op: instrIsSig], d:[op: dRETT],    out: Delayed];
Set[s: PO.And[current, delay],                m:[op: instrIsSig], d:[op: dRETN],    out: Delayed];
m _ [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen, -- Underflow is the default
sSource: [ l, alpha ],
trappingControl:    disable ];
Set[s: PO.And[current, trap],                        m:[op: instrIsSig], d:[op: dRET],    out: m];
m.sSource _ [ s, zero ];
Set[s: PO.And[current, trap],                        m:[op: instrIsSig], d:[op: dRETT],    out: m];
Set[s: PO.And[current, trap],                        m:[op: instrIsSig], d:[op: dRETN],    out: m];
Set[s: PO.And[current, PO.Not[PO.Or[delay, trap]]],    m:[op: instrIsSig], d:[op: dRET],    out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: stack,
lSource: [ l3, zero ],
sSource: [ l, alpha ],
iStackPostEffect: pop ]];
Set[s: PO.And[current, PO.Not[PO.Or[delay, trap]]],    m:[op: instrIsSig], d:[op: dRETT],    out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: stack,
lSource: [ l3, zero ],
iStackPostEffect: pop,
trappingControl: enable ]];
Set[s: PO.And[current, PO.Not[PO.Or[delay, trap]]],    m:[op: instrIsSig], d:[op: dRETN],    out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: stack,
lSource: [ l3, zero ],
iStackPostEffect: pop ]];
Set[s: PO.And[current, delay],                        m:[op: instrIsSig], d:[op: dLIFUR], out: Delayed];
Set[s: PO.And[current, PO.Not[delay]],                m:[op: instrIsSig], d:[op: dLIFUR], out:[
bReg: [zero, alpha],
xASource: bReg,
cReg: [ s, one ],
deltaSc: push ]];

<<Check for Delay and IStack Underflow trap in EP>>
<<Look for the case of a Call - EP sequence broken by a Reschedule which returns with an empty IStack.  EP (L_S+alpha) => that the 
stack is expected to contain some local values which (if IStack is empty) have been swapped out.>>
<<Temporary BE's used by EP:>>
delay _ PO.And[
BE[m:[popPending: TRUE],            d:[popPending: TRUE]],
BE[m:[iStkEmpty: TRUE],            d:[iStkEmpty: FALSE]]];
trap _ PO.And[
PO.Not[delay], 
BE[m:[iStkEmpty: TRUE],            d:[iStkEmpty: TRUE]],
BE[m:[pushPending: TRUE],        d:[pushPending: FALSE]] ];
Set[s: PO.And[current, delay],        m:[op: instrIsSig], d:[op: dEP],    out: Delayed];
Set[s: PO.And[current, trap],        m:[op: instrIsSig], d:[op: dEP],    out: [
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: trapGen,
lSource: [ s, alpha ],
pclsPipe: seqPCnewLS,
iStackPostEffect: push,  -- this push differentiates this trap from the following
trappingControl: disable ]];
Set[s: PO.And[current, PO.Not[PO.Or[delay, trap]]],    m:[op: instrIsSig], d:[op: dEP],    out:
[lSource: [ s, alpha]]];

<<Do the rest of the S and L modifiers here>>
Set[s:current, m:[op: instrIsSig], d:[op: dDIS],    out:[deltaSa: pop]];
Set[s:current, m:[op: instrIsSig], d:[op: dAS],        out:[sSource: [s, alpha]]];
Set[s:current, m:[op: instrIsSig], d:[op: dAL],        out:[lSource: [l, alpha]]];
Set[s:current, m:[op: instrIsSig], d:[op: dASL],    out:[sSource: [l, alpha]]];

m _ [
aReg: abStackTop,
xASource: beta,
deltaSa: pop,
aluOp: VSub,
condEffect: macroJump,
condSel: EZ,
doMacroJump: FALSE,
dontGetNextMacro: FALSE,
pclsPipe: offSetPCnewLS, pcOffSetSrc: alphaS];
Set[s:current, m:[op: instrIsSig],    d:[op: dJEBB],    out:m];
m.condSel _ NE;
Set[s:current, m:[op: instrIsSig],    d:[op: dJNEBB],    out:m];

m _ [
aReg: abStackTop,
xASource: beta,
deltaSa: pop,
aluOp: VSub,
condEffect: macroJump,
condSel: EZ,
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: alphaS,
pclsPipe: seqPCnewLS];
Set[s:current, m:[op: instrIsSig],    d:[op: dJNEBBJ],    out:m];
m.condSel _ NE;
Set[s:current, m:[op: instrIsSig],    d:[op: dJEBBJ],    out:m];

<<dRJ*B and dRJ*BJ  - Bit 4 distinguishes between them>>
instr _ PO.And[current, BE[m:[op: instrBot4NotSig], d:[op: dRJEB]]];    -- RJ*B and RJ*BJ
<<Main Body>>
Set[s:current, m:[op: instrBot3NotSig],    d:[op: dRJEB],    out:[    -- RJ*B
aluOp: VSub,
condSel: op57,    --  Low 3 bits distinguish between 2 * 8 Jumps
condEffect: macroJump,
doMacroJump: FALSE,
dontGetNextMacro: FALSE,
pclsPipe: offSetPCnewLS, pcOffSetSrc: alphaS] ];
Set[s:current, m:[op: instrBot3NotSig],    d:[op: dRJEBJ],    out:[    -- RJ*BJ
aluOp: VSub,
condSel: op57,
condEffect: macroJump,
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: alphaS,
pclsPipe: seqPCnewLS] ];
<<AReg depends only on sd>>
Set[s: PO.And[        sd,    instr],    out:[aReg:[ s, minus1 ]]];
Set[s: PO.And[PO.Not[sd],    instr],    out:[aReg:[ s, zero ]]];
<<BReg>>
Set[s: PO.And[ PO.Not[opt],            aux,    instr],                out:[bReg:[ aBase,    beta47 ]]];
Set[s: PO.And[ PO.Not[opt],    PO.Not[aux],    instr],                out:[bReg:[ l,            beta47 ]]];
Set[s: PO.And[opt,    instr],    m:[beta: 010B], d:[beta: 000B],    out:[bReg:[ cBase,    beta47 ]]];
Set[s: PO.And[opt,    instr],    m:[beta: 004B], d:[beta: 000B],    out:[bReg:[ cBase,    beta47 ]]];
Set[s: PO.And[opt,    instr],    m:[beta: 015B], d:[beta: 014B],    out:[bReg:[ s,        zero ]]];
Set[s: PO.And[opt,    instr],    m:[beta: 015B], d:[beta: 015B],    out:[bReg:[ s,        minus1 ]]];
<<Stack>>
Set[s: PO.And[sdd,    instr],                                         out:[deltaSa: pop]];
Set[s: PO.And[opt,    instr], m:[beta:    016B],    d:[beta:    016B],    out:[deltaSb: pop]];

Set[s:current, m:[op: instrIsSig],    d:[op: dJ1],    out:DefaultMicro]; -- Just too mark as ~Xops
Set[s:current, m:[op: instrIsSig],    d:[op: dJ2],    out:DefaultMicro]; -- Just too mark as ~Xops
Set[s:current, m:[op: instrIsSig],    d:[op: dJ3],    out:DefaultMicro]; -- Just too mark as ~Xops
Set[s:current, m:[op: instrIsSig],    d:[op: dJ5],    out:DefaultMicro]; -- Just too mark as ~Xops

Set[s:current, m:[op: instrIsSig],    d:[op: dJB], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: alphaS ]];

Set[s:current, m:[op: instrIsSig],    d:[op: dJDB], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: betaAlphaS ]];

Set[s:current, m:[op: instrIsSig],    d:[op: dDJ], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: delGamBetAlp ]];

instr _ PO.And[current, BE[m:[op: instrIsSig], d:[op: dSJ]]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 0], out:[ -- ifuXBus _ [S]
dontGetNextMacro: TRUE,
pcNext: pcBus,
bReg: abStackTop,
cReg: ifuXBus ]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 1], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 2], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 3], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 4], out:[ -- S _ S-1
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: xA,
deltaSa: pop ]];

Set[s:current, m:[op: instrIsSig], d:[op: dLFC], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: offSetPC, pcOffSetSrc: betaAlphaS,
pclsPipe: seqPCnewLS,
iStackPostEffect: push ]];

Set[s:current, m:[op: instrIsSig], d:[op: dDFC], out:[
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: delGamBetAlp,
pclsPipe: seqPCnewLS,
iStackPostEffect: push ]];

instr _ PO.And[current, BE[m:[op: instrIsSig], d:[op: dSFC]]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 0], out:[ -- ifuXBus _ [S]
dontGetNextMacro: TRUE,
pcNext: pcBus,
bReg: abStackTop,
cReg: ifuXBus ]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 1], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 2], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 3], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 4], out:[ -- S _ S-1
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: xA,
deltaSa: pop,
pclsPipe: seqPCnewLS,
iStackPostEffect: push ]];

instr _ PO.And[current, BE[m:[op: instrIsSig], d:[op: dSFCI]]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 0], out:[ -- ifuXBus _ [S]^
dontGetNextMacro: TRUE,
pcNext: pcBus,
bReg: abStackTop,
cReg: ifuXBus,
euPBusCmd: Fetch ]];
Set[s:instr, m:[state: byteIsSig],    d:[state: 1], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 2], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 3], out:NoOpMicro];    -- to allow Xa to latch Result3
Set[s:instr, m:[state: byteIsSig],    d:[state: 4], out:[ -- S _ S-1
doMacroJump: TRUE,
dontGetNextMacro: TRUE,
pcNext: pcBus, pcBusSrc: xA,
<<deltaS: 0, -- shouldn't SFCI pop S?>>
pclsPipe: seqPCnewLS,
iStackPostEffect: push ]];

GenInstrDecodePLA2[]; -- Arbitrary break
}; -- of GenInstrDecodePLA1

END.