深入理解计算机系统第四章（4.55-4.58）
/*
***4.55
*/
思路：将valC的值通过E_valB传过流水线，valP的逻辑不变
#/* $begin pipe-all-hcl */
####################################################################
# HCL Description of Control for Pipelined Y86 Processor #
# Copyright (C) Randal E. Bryant, David R. O'Hallaron, 2010 #
####################################################################
## Your task is to modify the design so that conditional branches are
## predicted as being taken when backward and not-taken when forward
## The code here is nearly identical to that for the normal pipeline.
## Comments starting with keyword "BBTFNT" have been added at places
## relevant to the exercise.
####################################################################
# C Include's. Don't alter these #
####################################################################
quote '#include '
quote '#include "isa.h"'
quote '#include "pipeline.h"'
quote '#include "stages.h"'
quote '#include "sim.h"'
quote 'int sim_main(int argc, char *argv[]);'
quote 'int main(int argc, char *argv[]){return sim_main(argc,argv);}'
####################################################################
# Declarations. Do not change/remove/delete any of these #
####################################################################
##### Symbolic representation of Y86 Instruction Codes #############
intsig INOP 'I_NOP'
intsig IHALT 'I_HALT'
intsig IRRMOVL 'I_RRMOVL'
intsig IIRMOVL 'I_IRMOVL'
intsig IRMMOVL 'I_RMMOVL'
intsig IMRMOVL 'I_MRMOVL'
intsig IOPL 'I_ALU'
intsig IJXX 'I_JMP'
intsig ICALL 'I_CALL'
intsig IRET 'I_RET'
intsig IPUSHL 'I_PUSHL'
intsig IPOPL 'I_POPL'
##### Symbolic represenations of Y86 function codes #####
intsig FNONE 'F_NONE' # Default function code
##### Symbolic representation of Y86 Registers referenced #####
intsig RESP 'REG_ESP' # Stack Pointer
intsig RNONE 'REG_NONE' # Special value indicating "no register"
##### ALU Functions referenced explicitly ##########################
intsig ALUADD 'A_ADD' # ALU should add its arguments
## BBTFNT: For modified branch prediction, need to distinguish
## conditional vs. unconditional branches
##### Jump conditions referenced explicitly
intsig UNCOND 'C_YES' # Unconditional transfer
##### Possible instruction status values #####
intsig SBUB 'STAT_BUB' # Bubble in stage
intsig SAOK 'STAT_AOK' # Normal execution
intsig SADR 'STAT_ADR' # Invalid memory address
intsig SINS 'STAT_INS' # Invalid instruction
intsig SHLT 'STAT_HLT' # Halt instruction encountered
##### Signals that can be referenced by control logic ##############
##### Pipeline Register F ##########################################
intsig F_predPC 'pc_curr->pc' # Predicted value of PC
##### Intermediate Values in Fetch Stage ###########################
intsig imem_icode 'imem_icode' # icode field from instruction memory
intsig imem_ifun 'imem_ifun' # ifun field from instruction memory
intsig f_icode 'if_id_next->icode' # (Possibly modified) instruction code
intsig f_ifun 'if_id_next->ifun' # Fetched instruction function
intsig f_valC 'if_id_next->valc' # Constant data of fetched instruction
intsig f_valP 'if_id_next->valp' # Address of following instruction
boolsig imem_error 'imem_error' # Error signal from instruction memory
boolsig instr_valid 'instr_valid' # Is fetched instruction valid?
##### Pipeline Register D ##########################################
intsig D_icode 'if_id_curr->icode' # Instruction code
intsig D_rA 'if_id_curr->ra' # rA field from instruction
intsig D_rB 'if_id_curr->rb' # rB field from instruction
intsig D_valP 'if_id_curr->valp' # Incremented PC
intsig D_valC 'if_id_curr->valc'
##### Intermediate Values in Decode Stage #########################
intsig d_srcA 'id_ex_next->srca' # srcA from decoded instruction
intsig d_srcB 'id_ex_next->srcb' # srcB from decoded instruction
intsig d_rvalA 'd_regvala' # valA read from register file
intsig d_rvalB 'd_regvalb' # valB read from register file
##### Pipeline Register E ##########################################
intsig E_icode 'id_ex_curr->icode' # Instruction code
intsig E_ifun 'id_ex_curr->ifun' # Instruction function
intsig E_valC 'id_ex_curr->valc' # Constant data
intsig E_srcA 'id_ex_curr->srca' # Source A register ID
intsig E_valA 'id_ex_curr->vala' # Source A value
intsig E_srcB 'id_ex_curr->srcb' # Source B register ID
intsig E_valB 'id_ex_curr->valb' # Source B value
intsig E_dstE 'id_ex_curr->deste' # Destination E register ID
intsig E_dstM 'id_ex_curr->destm' # Destination M register ID
##### Intermediate Values in Execute Stage #########################
intsig e_valE 'ex_mem_next->vale' # valE generated by ALU
boolsig e_Cnd 'ex_mem_next->takebranch' # Does condition hold?
intsig e_dstE 'ex_mem_next->deste' # dstE (possibly modified to be RNONE)
##### Pipeline Register M #########################
intsig M_stat 'ex_mem_curr->status' # Instruction status
intsig M_icode 'ex_mem_curr->icode' # Instruction code
intsig M_ifun 'ex_mem_curr->ifun' # Instruction function
intsig M_valA 'ex_mem_curr->vala' # Source A value
intsig M_dstE 'ex_mem_curr->deste' # Destination E register ID
intsig M_valE 'ex_mem_curr->vale' # ALU E value
intsig M_dstM 'ex_mem_curr->destm' # Destination M register ID
boolsig M_Cnd 'ex_mem_curr->takebranch' # Condition flag
boolsig dmem_error 'dmem_error' # Error signal from instruction memory
##### Intermediate Values in Memory Stage ##########################
intsig m_valM 'mem_wb_next->valm' # valM generated by memory
intsig m_stat 'mem_wb_next->status' # stat (possibly modified to be SADR)
##### Pipeline Register W ##########################################
intsig W_stat 'mem_wb_curr->status' # Instruction status
intsig W_icode 'mem_wb_curr->icode' # Instruction code
intsig W_dstE 'mem_wb_curr->deste' # Destination E register ID
intsig W_valE 'mem_wb_curr->vale' # ALU E value
intsig W_dstM 'mem_wb_curr->destm' # Destination M register ID
intsig W_valM 'mem_wb_curr->valm' # Memory M value
####################################################################
# Control Signal Definitions. #
####################################################################
################ Fetch Stage ###################################
## What address should instruction be fetched at
int f_pc = [
# Mispredicted branch. Fetch at incremented PC
M_icode == IJXX && !M_Cnd && M_valE < M_valA : M_valA;
M_icode == IJXX && M_Cnd && M_valE >= M_valA: M_valE;
# Completion of RET instruction.
W_icode == IRET : W_valM;
# Default: Use predicted value of PC
1 : F_predPC;
];
## Determine icode of fetched instruction
int f_icode = [
imem_error : INOP;
1: imem_icode;
];
# Determine ifun
int f_ifun = [
imem_error : FNONE;
1: imem_ifun;
];
# Is instruction valid?
bool instr_valid = f_icode in
{ INOP, IHALT, IRRMOVL, IIRMOVL, IRMMOVL, IMRMOVL,
IOPL, IJXX, ICALL, IRET, IPUSHL, IPOPL };
# Determine status code for fetched instruction
int f_stat = [
imem_error: SADR;
!instr_valid : SINS;
f_icode == IHALT : SHLT;
1 : SAOK;
];
# Does fetched instruction require a regid byte?
bool need_regids =
f_icode in { IRRMOVL, IOPL, IPUSHL, IPOPL,
IIRMOVL, IRMMOVL, IMRMOVL };
# Does fetched instruction require a constant word?
bool need_valC =
f_icode in { IIRMOVL, IRMMOVL, IMRMOVL, IJXX, ICALL };
# Predict next value of PC
int f_predPC = [
# BBTFNT: This is where you'll change the branch prediction rule
f_icode in {ICALL} : f_valC;
f_icode in {IJXX} && f_ifun==0 :f_valC;
f_icode in {IJXX} && f_ifun!=0 && f_valC = E_valA)||
# BBTFNT: This condition will change
# Stalling at fetch while ret passes through pipeline
# but not condition for a load/use hazard
!(E_icode in { IMRMOVL, IPOPL } && E_dstM in { d_srcA, d_srcB }) &&
IRET in { D_icode, E_icode, M_icode };
# Should I stall or inject a bubble into Pipeline Register E?
# At most one of these can be true.
bool E_stall = 0;
bool E_bubble =
# Mispredicted branch
(E_icode == IJXX && !e_Cnd && E_valB < E_valA)||(E_icode == IJXX && e_Cnd && E_valB >= E_valA) ||
# BBTFNT: This condition will change
# Conditions for a load/use hazard
E_icode in { IMRMOVL, IPOPL } &&
E_dstM in { d_srcA, d_srcB};
# Should I stall or inject a bubble into Pipeline Register M?
# At most one of these can be true.
bool M_stall = 0;
# Start injecting bubbles as soon as exception passes through memory stage
bool M_bubble = m_stat in { SADR, SINS, SHLT } || W_stat in { SADR, SINS, SHLT };
# Should I stall or inject a bubble into Pipeline Register W?
bool W_stall = W_stat in { SADR, SINS, SHLT };
bool W_bubble = 0;
#/* $end pipe-all-hcl */
/*
***4.56
*/
#/* $begin pipe-all-hcl */
####################################################################
# HCL Description of Control for Pipelined Y86 Processor #
# Copyright (C) Randal E. Bryant, David R. O'Hallaron, 2010 #
####################################################################
## Your task is to modify the design so that on any cycle, only
## one of the two possible (valE and valM) register writes will occur.
## This requires special handling of the popl instruction.
## Overall strategy: IPOPL passes through pipe,
## treated as stack pointer increment, but not incrementing the PC
## On refetch, modify fetched icode to indicate an instruction "IPOP2",
## which reads from memory.
## This requires modifying the definition of f_icode
## and lots of other changes. Relevant positions to change
## are indicated by comments starting with keyword "1W".
####################################################################
# C Include's. Don't alter these #
####################################################################
quote '#include '
quote '#include "isa.h"'
quote '#include "pipeline.h"'
quote '#include "stages.h"'
quote '#include "sim.h"'
quote 'int sim_main(int argc, char *argv[]);'
quote 'int main(int argc, char *argv[]){return sim_main(argc,argv);}'
####################################################################
# Declarations. Do not change/remove/delete any of these #
####################################################################
##### Symbolic representation of Y86 Instruction Codes #############
intsig INOP 'I_NOP'
intsig IHALT 'I_HALT'
intsig IRRMOVL 'I_RRMOVL'
intsig IIRMOVL 'I_IRMOVL'
intsig IRMMOVL 'I_RMMOVL'
intsig IMRMOVL 'I_MRMOVL'
intsig IOPL 'I_ALU'
intsig IJXX 'I_JMP'
intsig ICALL 'I_CALL'
intsig IRET 'I_RET'
intsig IPUSHL 'I_PUSHL'
intsig IPOPL 'I_POPL'
# 1W: Special instruction code for second try of popl
intsig IPOP2 'I_POP2'
##### Symbolic represenations of Y86 function codes #####
intsig FNONE 'F_NONE' # Default function code
##### Symbolic representation of Y86 Registers referenced #####
intsig RESP 'REG_ESP' # Stack Pointer
intsig RNONE 'REG_NONE' # Special value indicating "no register"
##### ALU Functions referenced explicitly ##########################
intsig ALUADD 'A_ADD' # ALU should add its arguments
##### Possible instruction status values #####
intsig SBUB 'STAT_BUB' # Bubble in stage
intsig SAOK 'STAT_AOK' # Normal execution
intsig SADR 'STAT_ADR' # Invalid memory address
intsig SINS 'STAT_INS' # Invalid instruction
intsig SHLT 'STAT_HLT' # Halt instruction encountered
##### Signals that can be referenced by control logic ##############
##### Pipeline Register F ##########################################
intsig F_predPC 'pc_curr->pc' # Predicted value of PC
##### Intermediate Values in Fetch Stage ###########################
intsig imem_icode 'imem_icode' # icode field from instruction memory
intsig imem_ifun 'imem_ifun' # ifun field from instruction memory
intsig f_icode 'if_id_next->icode' # (Possibly modified) instruction code
intsig f_ifun 'if_id_next->ifun' # Fetched instruction function
intsig f_valC 'if_id_next->valc' # Constant data of fetched instruction
intsig f_valP 'if_id_next->valp' # Address of following instruction
## 1W: Provide access to the PC value for the current instruction
intsig f_pc 'f_pc' # Address of fetched instruction
boolsig imem_error 'imem_error' # Error signal from instruction memory
boolsig instr_valid 'instr_valid' # Is fetched instruction valid?
##### Pipeline Register D ##########################################
intsig D_icode 'if_id_curr->icode' # Instruction code
intsig D_rA 'if_id_curr->ra' # rA field from instruction
intsig D_rB 'if_id_curr->rb' # rB field from instruction
intsig D_valP 'if_id_curr->valp' # Incremented PC
##### Intermediate Values in Decode Stage #########################
intsig d_srcA 'id_ex_next->srca' # srcA from decoded instruction
intsig d_srcB 'id_ex_next->srcb' # srcB from decoded instruction
intsig d_rvalA 'd_regvala' # valA read from register file
intsig d_rvalB 'd_regvalb' # valB read from register file
##### Pipeline Register E ##########################################
intsig E_icode 'id_ex_curr->icode' # Instruction code
intsig E_ifun 'id_ex_curr->ifun' # Instruction function
intsig E_valC 'id_ex_curr->valc' # Constant data
intsig E_srcA 'id_ex_curr->srca' # Source A register ID
intsig E_valA 'id_ex_curr->vala' # Source A value
intsig E_srcB 'id_ex_curr->srcb' # Source B register ID
intsig E_valB 'id_ex_curr->valb' # Source B value
intsig E_dstE 'id_ex_curr->deste' # Destination E register ID
intsig E_dstM 'id_ex_curr->destm' # Destination M register ID
##### Intermediate Values in Execute Stage #########################
intsig e_valE 'ex_mem_next->vale' # valE generated by ALU
boolsig e_Cnd 'ex_mem_next->takebranch' # Does condition hold?
intsig e_dstE 'ex_mem_next->deste' # dstE (possibly modified to be RNONE)
##### Pipeline Register M #########################
intsig M_stat 'ex_mem_curr->status' # Instruction status
intsig M_icode 'ex_mem_curr->icode' # Instruction code
intsig M_ifun 'ex_mem_curr->ifun' # Instruction function
intsig M_valA 'ex_mem_curr->vala' # Source A value
intsig M_dstE 'ex_mem_curr->deste' # Destination E register ID
intsig M_valE 'ex_mem_curr->vale' # ALU E value
intsig M_dstM 'ex_mem_curr->destm' # Destination M register ID
boolsig M_Cnd 'ex_mem_curr->takebranch' # Condition flag
boolsig dmem_error 'dmem_error' # Error signal from instruction memory
##### Intermediate Values in Memory Stage ##########################
intsig m_valM 'mem_wb_next->valm' # valM generated by memory
intsig m_stat 'mem_wb_next->status' # stat (possibly modified to be SADR)
##### Pipeline Register W ##########################################
intsig W_stat 'mem_wb_curr->status' # Instruction status
intsig W_icode 'mem_wb_curr->icode' # Instruction code
intsig W_dstE 'mem_wb_curr->deste' # Destination E register ID
intsig W_valE 'mem_wb_curr->vale' # ALU E value
intsig W_dstM 'mem_wb_curr->destm' # Destination M register ID
intsig W_valM 'mem_wb_curr->valm' # Memory M value
####################################################################
# Control Signal Definitions. #
####################################################################
################ Fetch Stage ###################################
## What address should instruction be fetched at
int f_pc = [
# Mispredicted branch. Fetch at incremented PC
M_icode == IJXX && !M_Cnd : M_valA;
# Completion of RET instruction.
W_icode == IRET : W_valM;
# Default: Use predicted value of PC
1 : F_predPC;
];
## Determine icode of fetched instruction
## 1W: To split ipopl into two cycles, need to be able to
## modify value of icode,
## so that it will be IPOP2 when fetched for second time.
int f_icode = [
imem_error : INOP;
imem_icode == IPOPL && D_icode == IPOPL :IPOP2;
1: imem_icode;
];
# Determine ifun
int f_ifun = [
imem_error : FNONE;
1: imem_ifun;
];
# Is instruction valid?
bool instr_valid = f_icode in
{ INOP, IHALT, IRRMOVL, IIRMOVL, IRMMOVL, IMRMOVL,
IOPL, IJXX, ICALL, IRET, IPUSHL, IPOPL,IPOP2 };
# Determine status code for fetched instruction
int f_stat = [
imem_error: SADR;
!instr_valid : SINS;
f_icode == IHALT : SHLT;
1 : SAOK;
];
# Does fetched instruction require a regid byte?
bool need_regids =
f_icode in { IRRMOVL, IOPL, IPUSHL, IPOPL,
IIRMOVL, IRMMOVL, IMRMOVL,IPOP2 };
# Does fetched instruction require a constant word?
bool need_valC =
f_icode in { IIRMOVL, IRMMOVL, IMRMOVL, IJXX, ICALL };
# Predict next value of PC
int f_predPC = [
f_icode in { IJXX, ICALL } : f_valC;
## 1W: Want to refetch popl one time
f_icode == IPOPL && D_icode != IPOPL:f_pc;
1 : f_valP;
];
################ Decode Stage ######################################
## W1: Strategy. Decoding of popl rA should be treated the same
## as would iaddl $4, %esp
## Decoding of pop2 rA treated same as mrmovl -4(%esp), rA
## What register should be used as the A source?
int d_srcA = [
D_icode in { IRRMOVL, IRMMOVL,IOPL, IPUSHL } : D_rA;
D_icode in { IRET } : RESP;
1 : RNONE; # Don't need register
];
## What register should be used as the B source?
int d_srcB = [
D_icode in { IOPL, IRMMOVL, IMRMOVL } : D_rB;
D_icode in { IPUSHL, IPOPL, ICALL, IRET,IPOP2} : RESP;
1 : RNONE; # Don't need register
];
## What register should be used as the E destination?
int d_dstE = [
D_icode in { IRRMOVL, IIRMOVL, IOPL} : D_rB;
D_icode in { IPUSHL, IPOPL, ICALL, IRET } : RESP;
1 : RNONE; # Don't write any register
];
## What register should be used as the M destination?
int d_dstM = [
D_icode in { IMRMOVL, IPOP2 } : D_rA;
1 : RNONE; # Don't write any register
];
## What should be the A value?
## Forward into decode stage for valA
int d_valA = [
D_icode in { ICALL, IJXX } : D_valP; # Use incremented PC
d_srcA == e_dstE : e_valE; # Forward valE from execute
d_srcA == M_dstM : m_valM; # Forward valM from memory
d_srcA == M_dstE : M_valE; # Forward valE from memory
d_srcA == W_dstM : W_valM; # Forward valM from write back
d_srcA == W_dstE : W_valE; # Forward valE from write back
1 : d_rvalA; # Use value read from register file
];
int d_valB = [
d_srcB == e_dstE : e_valE; # Forward valE from execute
d_srcB == M_dstM : m_valM; # Forward valM from memory
d_srcB == M_dstE : M_valE; # Forward valE from memory
d_srcB == W_dstM : W_valM; # Forward valM from write back
d_srcB == W_dstE : W_valE; # Forward valE from write back
1 : d_rvalB; # Use value read from register file
];
################ Execute Stage #####################################
## Select input A to ALU
int aluA = [
E_icode in { IRRMOVL, IOPL } : E_valA;
E_icode in { IIRMOVL, IRMMOVL, IMRMOVL } : E_valC;
E_icode in { ICALL, IPUSHL ,IPOP2} : -4;
E_icode in { IRET, IPOPL } : 4;
# Other instructions don't need ALU
];
## Select input B to ALU
int aluB = [
E_icode in { IRMMOVL, IMRMOVL, IOPL, ICALL,
IPUSHL, IRET, IPOPL ,IPOP2} : E_valB;
E_icode in { IRRMOVL, IIRMOVL } : 0;
# Other instructions don't need ALU
];
## Set the ALU function
int alufun = [
E_icode == IOPL : E_ifun;
1 : ALUADD;
];
## Should the condition codes be updated?
bool set_cc = E_icode == IOPL &&
# State changes only during normal operation
!m_stat in { SADR, SINS, SHLT } && !W_stat in { SADR, SINS, SHLT };
## Generate valA in execute stage
int e_valA = E_valA; # Pass valA through stage
## Set dstE to RNONE in event of not-taken conditional move
int e_dstE = [
E_icode == IRRMOVL && !e_Cnd : RNONE;
1 : E_dstE;
];
################ Memory Stage ######################################
## Select memory address
int mem_addr = [
M_icode in { IRMMOVL, IPUSHL, ICALL, IMRMOVL,IPOP2 } : M_valE;
M_icode in { IRET } : M_valA;
# Other instructions don't need address
];
## Set read control signal
bool mem_read = M_icode in { IMRMOVL, IPOP2, IRET };
## Set write control signal
bool mem_write = M_icode in { IRMMOVL, IPUSHL, ICALL };
#/* $begin pipe-m_stat-hcl */
## Update the status
int m_stat = [
dmem_error : SADR;
1 : M_stat;
];
#/* $end pipe-m_stat-hcl */
################ Write back stage ##################################
## 1W: For this problem, we introduce a multiplexor that merges
## valE and valM into a single value for writing to register port E.
## DO NOT CHANGE THIS LOGIC
## Merge both write back sources onto register port E
## Set E port register ID
int w_dstE = [
## writing from valM
W_dstM != RNONE : W_dstM;
1: W_dstE;
];
## Set E port value
int w_valE = [
W_dstM != RNONE : W_valM;
1: W_valE;
];
## Disable register port M
## Set M port register ID
int w_dstM = RNONE;
## Set M port value
int w_valM = 0;
## Update processor status
int Stat = [
W_stat == SBUB : SAOK;
1 : W_stat;
];
################ Pipeline Register Control #########################
# Should I stall or inject a bubble into Pipeline Register F?
# At most one of these can be true.
bool F_bubble = 0;
bool F_stall =
# Conditions for a load/use hazard
E_icode in { IMRMOVL, IPOP2 } &&
E_dstM in { d_srcA, d_srcB } ||
# Stalling at fetch while ret passes through pipeline
IRET in { D_icode, E_icode, M_icode };
# Should I stall or inject a bubble into Pipeline Register D?
# At most one of these can be true.
bool D_stall =
# Conditions for a load/use hazard
E_icode in { IMRMOVL, IPOP2 } &&
E_dstM in { d_srcA, d_srcB };
bool D_bubble =
# Mispredicted branch
(E_icode == IJXX && !e_Cnd) ||
# Stalling at fetch while ret passes through pipeline
# but not condition for a load/use hazard
!(E_icode in { IMRMOVL, IPOP2 } && E_dstM in { d_srcA, d_srcB }) &&
# 1W: This condition will change
IRET in { D_icode, E_icode, M_icode };
# Should I stall or inject a bubble into Pipeline Register E?
# At most one of these can be true.
bool E_stall = 0;
bool E_bubble =
# Mispredicted branch
(E_icode == IJXX && !e_Cnd) ||
# Conditions for a load/use hazard
E_icode in { IMRMOVL, IPOP2 } &&
E_dstM in { d_srcA, d_srcB};
# Should I stall or inject a bubble into Pipeline Register M?
# At most one of these can be true.
bool M_stall = 0;
# Start injecting bubbles as soon as exception passes through memory stage
bool M_bubble = m_stat in { SADR, SINS, SHLT } || W_stat in { SADR, SINS, SHLT };
# Should I stall or inject a bubble into Pipeline Register W?
bool W_stall = W_stat in { SADR, SINS, SHLT };
bool W_bubble = 0;
#/* $end pipe-all-hcl */ /*
***4.57
*/
A. E_icode in {IMRMOVL,IPOPL} && E_dstM in {d_srcA,d_srcB} && !(D_icode in {IPUSHL}
B. 只要把e_valA 和 加载/使用冒险用上面表达式替换即可
/*
***4.58
*/
使用条件传送的版本不存在分支预测使得流水线能够更好的执行，所以比第一个版本更快。