Final Project:

A Study of CISC on RISC

Phil Katz, Connie Li, Katie Stockhammer

May 6, 2005

Abstract:

For our final project, we decided we to implement a CISC on RISC computer system in C. This is a virtual machine, because it is written entirely in C. We wanted to restrict the number of RISC instructions, while still allowing a large number of CISC instructions to be implemented. We give our program a file containing a list of CISC instructions for an algorithm. Our C program (interpreter) then decodes these CISC instructions into RISC instructions which actually carry out the program.

The CISC vs RISC debate:

CISC (Complex Instruction Set Computer):

Lots of instructions, varying length
Lots of addressing modes
Lots of flexibility
Fewer registers, since operands can be in memory
+ More instructions -> shorter programs
+ More instructions -> more flexibility for compiler

RISC (Reduced Instruction Set Computer):

Small number of instructions
Small number of addressing modes
Only load and store instructions access memory
All arithmetic and logic instructions must use registers
Usually uses lots of registers
+ Faster decoding
+ Easier execution
+ Easier to incorporate into a pipelined superscalar format
+ Fewer instructions -> CU and CPU faster and simpler

Conclusion:

Even though CISC gives you more options and more flexibility, RISC makes the CPU faster, and that is all that matters. The Pentium IV is CISC on RISC, the PowerPC is RISC. Nearly all modern systems function as a RISC computer at the hardware level, because it is so much faster.

Why CISC on RISC?:

Using CISC on RISC combines the versatility of CISC with the speed of RISC. In a CISC on RISC computer, programs are interpreted as lists of CISC instructions. These CISC instructions are then translated into RISC instructions which are computed in hardware. A CPU can interpret CISC instructions that come much farther in the program than the one currently being executed and thus create a large RISC instruction buffer to be used for pipelining and superscalar processing. Our particular project is a virtual machine, since we are only using an upper level programming language, instead of hardware and machine code.

Our Computer's CISC instruction set:

CISC Load Instructions
CISC Instruction	Argument 1	Argument 2	Description
LOADM	memory location	immediate value	Load the arg2 immediate value into the arg1 memory location
LOADR	register location	immediate value	Load the arg2 immediate value into the arg1 register

CISC Addition Instructions
CISC Instruction	Argument 1	Argument 2	Description
ADDRM	register location	memory location	Add value in arg1 register to the value in arg2 memory location, store in arg1 register
ADDRR	register location	register location	Add the value in the arg1 register to the value in the arg2 register, store in arg1 register
ADDRI	register location	immediate value	Add value in the arg1 register to the immediate value of arg2, store in arg1 register
ADDRN	register location	indirect register	Add value in the arg1 register to the value stored in the value of arg2's register, store in arg1 register
ADDMM	memory location	memory location	Add the value in arg1 memory location to the value in arg2 memory location, store in arg1 memory location
ADDMR	memory location	register location	Add the value in arg1 memory location to the value in arg2 register, store in arg1 memory location
ADDMI	memory location	immediate value	Add the value in arg1 memory location to the immediate value of arg2, store in arg1 memory location
ADDMN	memory location	indirect register	Add the value in arg1 memory location to the value stored in the value of arg2's register, store in the arg1 memory location
ADDNM	indirect register	memory location	Add the value in the value of arg1's register to the memory location, store in the arg1 indirect register
ADDNI	indirect register	immediate value	Add the value in the value of arg1's register to the immediate value of arg2, store in the arg1 indirect register
ADDNN	indirect register	indirect register	Add the value in the value of arg1's register to the value in the value of arg2's register, store in the arg1 indirect register

CISC Subtraction Instructions
CISC Instruction	Argument 1	Argument 2	Description
SUBRM	register location	memory location	Subtract the value in arg2 memory location from the value in arg1 register, store in arg1 register
SUBRR	register location	register location	Subtract the value in the arg2 register from the value in the arg1 register, store in arg1 register
SUBRI	register location	immediate value	Subtract the value in the immediate value of arg2 from the arg1 register, store in arg1 register
SUBRN	register location	indirect register	Subtract the value stored in the value of arg2's register from the value in the arg1 register, store in arg1 register
SUBMM	memory location	memory location	Subtract the value in arg2 memory location to the value in arg1 memory location, store in arg1 memory location
SUBMR	memory location	register location	Subtract the value in arg2 register from the value in the arg1 memory location, store in arg1 memory location
SUBMI	memory location	immediate value	Subtract the immediate value of arg2 from the value of arg1 memory location, store in arg1 memory location
SUBMN	memory location	indirect register	Subtract the value in the value stored in the value of arg2's register from the value of the arg1 memory location, store in the arg1 memory location
SUBNM	indirect register	memory location	Subtract the value in the arg2 memory location from the value of the value of arg2's register, store in the arg1 indirect register
SUBNI	indirect register	immediate value	Subtract the the immediate value of arg2 from the value in the value of arg1's register, store in the arg1 indirect register
SUBNN	indirect register	indirect register	Subtract the value in the value of arg2's register from the value in the value of arg1's register, store in the arg1 indirect register

CISC Multiplication Instructions
CISC Instruction	Argument 1	Argument 2	Description
MULTRM	register location	memory location	Multiply the value in arg1 register with the value in arg2 memory location, store in arg1 register
MULTRR	register location	register location	Multiply the value in the arg1 register with the value in the arg2 register, store in arg1 register
MULTRI	register location	immediate value	Multiply value in the arg1 register with the immediate value of arg2, store in arg1 register
MULTRN	register location	indirect register	Multiply value in the arg1 register with the value stored in the value of arg2's register, store in arg1 register
MULTMM	memory location	memory location	Multiply the value in arg1 memory location with the value in arg2 memory location, store in arg1 memory location
MULTMR	memory location	register location	Multiply the value in arg1 memory location with the value in arg2 register, store in arg1 memory location
MULTMI	memory location	immediate value	Multiply the value in arg1 memory location with the immediate value of arg2, store in arg1 memory location
MULTMN	memory location	indirect register	Multiply the value in arg1 memory location with the value stored in the value of arg2's register, store in the arg1 memory location
MULTNM	indirect register	memory location	Multiply the value in the value of arg1's register with the memory location, store in the arg1 indirect register
MULTNI	indirect register	immediate value	Multiply the value in the value of arg1's register with the immediate value of arg2, store in the arg1 indirect register
MULTNN	indirect register	indirect register	Multiply the value in the value of arg1's register with the value in the value of arg2's register, store in the arg1 indirect register

CISC Increment/Decrement Instructions
CISC Instruction	Argument 1	Argument 2	Description
INCR	register location	dummy argument	Increment the value in the arg1 register by 1, store in arg1 register
INCM	memory location	dummy argument	Increment the value in the arg1 memory location by 1, store in arg1 register
DECR	register location	dummy argument	Decrement the value in the arg1 register by 1, store in arg1 register
DECM	memory location	dummy argument	Decrement the value in the arg1 memory location by 1, store in arg1 register

CISC Swap Instructions
CISC Instruction	Argument 1	Argument 2	Description
SWAPRR	register location	register location	Swap the value in arg1 register with value in arg2 register
SWAPMM	memory location	memory location	Swap the value in arg1 memory location with the value in the arg2 memory location
SWAPRM	register location	memory location	Swap the the value in arg1 register location with the value in the arg2 memory location

CISC Logic Instructions
CISC Instruction	Argument 1	Argument 2	Description
ANDRM	register location	memory location	And the value in the arg1 register location with the value in the arg2 memory location, store in arg1 register
ANDRR	register location	register location	And the value in the arg1 register with the value in the arg2 register, store in the arg1 register
ANDRI	register location	immediate value	And the value in the arg1 register with the immediate value of arg2, store in the arg1 register
ANDMM	memory location	memory location	And the value in the arg1 memory location with the value in the arg2 memory location, store in the arg1 register
ANDMR	memory location	register location	And the value in the arg1 memory location with the value in the arg2 register, store in the arg1 register
ANDMI	memory location	immediate value	And the value in the arg1 memory location with the immediate value of arg2, store in the arg1 register
ORRM	register location	memory location	Or the value in the arg1 register location with the value in the arg2 memory location, store in arg1 register
ORRR	register location	register location	Or the value in the arg1 register with the value in the arg2 register, store in the arg1 register
ORRI	register location	immediate value	Or the value in the arg1 register with the immediate value of arg2, store in the arg1 register
ORMM	memory location	memory location	Or the value in the arg1 memory location with the value in the arg2 memory location, store in the arg1 register
ORMR	memory location	register location	Or the value in the arg1 memory location with the value in the arg2 register, store in the arg1 register
ORMI	memory location	immediate value	Or the value in the arg1 memory location with the immediate value of arg2, store in the arg1 register
NOTR	register location	dummy argument	NOT the value of the arg1 register, store in the arg1 register
NOTM	memory location	dummy argument	NOT the value of the arg1 memory location, store in the arg1 register
XORRM	register location	memory location	XOR the value in the arg1 register location with the value in the arg2 memory location, store in arg1 register
XORRR	register location	register location	XOR the value in the arg1 register with the value in the arg2 register, store in the arg1 register
XORRI	register location	immediate value	XOR the value in the arg1 register with the immediate value of arg2, store in the arg1 register
XORMM	memory location	memory location	XOR the value in the arg1 memory location with the value in the arg2 memory location, store in the arg1 register
XORMR	memory location	register location	XOR the value in the arg1 memory location with the value in the arg2 register, store in the arg1 register
XORMI	memory location	immediate value	XOR the value in the arg1 memory location with the immediate value of arg2, store in the arg1 register

CISC Boolean Instructions
CISC Instruction	Argument 1	Argument 2	Description
EQRM	register location	memory location	Test to see if the value in the arg1 register and the value in the arg2 memory location are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
EQRR	register location	register location	Test to see if the value in the arg1 register and the value in the arg2 register location are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
EQRI	register location	immediate value	Test to see if the value in the arg1 register and the value in the immediate value in arg2 are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
EQMM	memory location	memory location	Test to see if the value in the arg1 memory location and the value in the arg2 memory location are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
EQMR	memory location	register location	Test to see if the value in the arg1 memory location and the value in the arg2 register location are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
EQMI	memory location	immediate value	Test to see if the value in the arg1 memory location and the immediate value of arg2 are equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTRM	register location	memory location	Test to see if the value in the arg1 register is greater than the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTRR	register location	register location	Test to see if the value in the arg1 register is greater than the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTRI	register location	immediate value	Test to see if the value in the arg1 register is greater than the value in the immediate value in arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTMM	memory location	memory location	Test to see if the value in the arg1 memory location is greater than the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTMR	memory location	register location	Test to see if the value in the arg1 memory location is greater than the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRTMI	memory location	immediate value	Test to see if the value in the arg1 memory location is greater than the immediate value of arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRERM	register location	memory location	Test to see if the value in the arg1 register is greater than or equal to the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRERR	register location	register location	Test to see if the value in the arg1 register is greater than or equal tothe value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GRERI	register location	immediate value	Test to see if the value in the arg1 register is greater than or equal to the value in the immediate value in arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GREMM	memory location	memory location	Test to see if the value in the arg1 memory location is greater than or equal to the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GREMR	memory location	register location	Test to see if the value in the arg1 memory location is greater than or equal to the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
GREMI	memory location	immediate value	Test to see if the value in the arg1 memory location is greater than or equal to the immediate value of arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTRM	register location	memory location	Test to see if the value in the arg1 register is less than the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTRR	register location	register location	Test to see if the value in the arg1 register is less than the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTRI	register location	immediate value	Test to see if the value in the arg1 register is less than the value in the immediate value in arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTMM	memory location	memory location	Test to see if the value in the arg1 memory location is less than the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTMR	memory location	register location	Test to see if the value in the arg1 memory location is less than the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSTMI	memory location	immediate value	Test to see if the value in the arg1 memory location is less than the immediate value of arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSERM	register location	memory location	Test to see if the value in the arg1 register is less than or equal to the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSERR	register location	register location	Test to see if the value in the arg1 register is less than or equal to the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSERI	register location	immediate value	Test to see if the value in the arg1 register is less than or equal to the value in the immediate value in arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSEMM	memory location	memory location	Test to see if the value in the arg1 memory location is less than or equal to the value in the arg2 memory location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSEMR	memory location	register location	Test to see if the value in the arg1 memory location is less than or equal to the value in the arg2 register location. If so, store MAXINTVALUE in arg1, else store 0 in arg1
LSEMI	memory location	immediate value	Test to see if the value in the arg1 memory location is less than or equal to the immediate value of arg2. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQRM	register location	memory location	Test to see if the value in the arg1 register and the value in the arg2 memory location are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQRR	register location	register location	Test to see if the value in the arg1 register and the value in the arg2 register location are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQRI	register location	immediate value	Test to see if the value in the arg1 register and the value in the immediate value in arg2 are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQMM	memory location	memory location	Test to see if the value in the arg1 memory location and the value in the arg2 memory location are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQMR	memory location	register location	Test to see if the value in the arg1 memory location and the value in the arg2 register location are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1
NEQMI	memory location	immediate value	Test to see if the value in the arg1 memory location and the immediate value of arg2 are not equal. If so, store MAXINTVALUE in arg1, else store 0 in arg1

CISC Jump Instructions
CISC Instruction	Argument 1	Argument 2	Description
JUMPUM	dummy argument	memory location	Unconditionally jumps to the instuction that is the value in the arg2 memory location
JUMPUR	dummy argument	register location	Unconditionally jumps to the instruction that is the value in the arg2 reigster location
JUMPUI	dummy argument	immediate value	Unconditionally jumps to the arg2 instruction
JUMPUN	dummy argument	indirect register	Unconditionally jumps to the instruction that is the value of the value in the arg2 register
JUMPTRM	register location	memory location	If the value in arg1 register is true, jump to the instuction that is the value in the arg2 memory location
JUMPTRR	register location	register location	If the value in arg1 register is true, jump to the instruction that is the value in arg2 register
JUMPTRI	register location	immediate value	If the value in arg1 register is true, jump to the arg2 instruction
JUMPTRN	register location	indirect register	If the value in arg1 register is true, jump to the instruction that is the value of the value in arg2 register
JUMPTMM	memory location	memory location	If the value in arg1 memory location is true, jump to the instruction that is the value of arg2 memory location
JUMPTMR	memory location	register location	If the value in arg1 memory location is true, jump to the instruction that is the value of arg2 register
JUMPTMI	memory location	immediate value	If the value in arg1 memory location is true, jump to the arg2 instruction
JUMPTMN	memory location	indirect register	If the value in arg1 memory location is true, jump to the instruction that is the value of the value in arg2 register.
JUMPFRM	register location	memory location	If the value in arg1 register is false, jump to the instruction that is the value of arg2 memory location
JUMPFRR	register location	register location	If the value in arg1 register is false, jump to the instruction that is the value of arg2 register
JUMPFRI	register location	immediate value	If the value in arg1 register is false, jump to the arg2 instruction
JUMPFRN	register location	indirect register	If the value in arg1 register is false, jump to the instruction that is the value of the value in arg2 register
JUMPFMM	memory location	memory location	If the value in arg1 memory location is false, jump to the instruction that is the value of the arg2 memory location
JUMPFMR	memory location	register location	If the value in arg1 memory location is false, jump to the instruction that is the value in arg2 register
JUMPFMI	memory location	immediate value	If the value in arg1 memory location is false, jump to the arg2 instruction
JUMPFMN	memory location	indirect register	If the value in arg1 memory location is false, jump to the instruction that is the value of the value in arg2 register
JUMPNRM	register location	memory location	If the value in arg1 register is negative, jump to the instruction that is the value in arg2 memory location
JUMPNRR	register location	register location	If the value in arg1 register is negative, jump to the instruction that is the value in arg2 register location
JUMPNRI	register location	immediate value	If the value in arg1 register is negative, jump to the arg2 instruction
JUMPNRN	register location	indirect register	If the value in arg1 register is negative, jump to the instruction that is the value of the value in arg2 register
JUMPNMM	memory location	memory location	If the value in arg1 memory location is negative, jump to the instruction that is the value in arg2 memory location
JUMPNMR	memory location	register location	If the value in arg1 memory location is negative, jump to the instruction that is the value in arg2 register
JUMPNMI	memory location	immediate value	If the value in arg1 memory location is negative, jump to the arg2 instruction
JUMPNMN	memory location	indirect register	If the value in arg1 memory location is negative, jump to the instruction that is the value of the value in arg2 register

Our Computer's RISC instruction set:

All of the risc instructions are passed 2 arguments

RISC Instructions

RISC Instruction Description

LOAD Loads value in arg2 into register[arg1]

LOADI Loads immediate value of arg2 into register[arg1]

STORE Stores value in arg1 to memory location arg2

ADD Adds value in arg1 and value in arg2, stores result in register[arg1]

MULT Multipies value in arg1 and value in arg2, stores result in register[arg1]

NEG Negates value in arg1

JUMPNZ Jump if not zero

AND ANDs value in arg1 and value in arg2, stores result in register[arg1]

OR ORs value in arg1 and value arg2, stores result in register[arg1]

NOT NOTs value in arg1, stores result in register[arg1]

EQUAL If value of arg1 is equal to value of arg2, register[arg1]is 1, otherwise 0

LST If value of arg1 is less than value of arg2, register[arg1] is 1, otherwise 0

WRITELN Outputs a newline

WRITE Outputs value of arg1

RISC Instructions
RISC Instruction	Description
LOAD	Loads value in arg2 into register[arg1]
LOADI	Loads immediate value of arg2 into register[arg1]
STORE	Stores value in arg1 to memory location arg2
ADD	Adds value in arg1 and value in arg2, stores result in register[arg1]
MULT	Multipies value in arg1 and value in arg2, stores result in register[arg1]
NEG	Negates value in arg1
JUMPNZ	Jump if not zero
AND	ANDs value in arg1 and value in arg2, stores result in register[arg1]
OR	ORs value in arg1 and value arg2, stores result in register[arg1]
NOT	NOTs value in arg1, stores result in register[arg1]
EQUAL	If value of arg1 is equal to value of arg2, register[arg1]is 1, otherwise 0
LST	If value of arg1 is less than value of arg2, register[arg1] is 1, otherwise 0
WRITELN	Outputs a newline
WRITE	Outputs value of arg1

Our Code:

Our CPU code is here.

Algorithms & Programs:

Our Example CISC algorithms and RISC programs are here.

Extensions

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