Mini Language Compiler - Programming Language Concepts | CS 360, Assignments of Programming Languages

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Programming Languages

(CS 360)

Mini Language Compiler

Jeremy R. Johnson

Introduction

Objective: To illustrate how to map Mini Languageinstructions to RAL instructions. To do this in a systematicway that illustrates how to write a compiler to translate MiniLanguage programs to RAL programs. Show simpleoptimizations that can be used to reduce the number ofinstructions.

Algorithm

Construct code for expressions, assignments, if, and while.

Concatenate statements in stmt-list

Allocate temporaries as needed

Keep track of variables, constants, and temporaries in Symbol Table

Use symbolic instructions and fill in absolute addresses (linking)when complete code has been constructed

Instruction Set

LDA X; Load the AC with the contents of memory address X

LDI

X; Load the AC indirectly with the contents of address X

STA X; Store the contents of the AC at memory address X

STI

X; Store the contents of the AC indirectly at address X

ADD X; Add the contents of address X to the contents of the AC

SUB X; Subtract the contents of address X from the AC

MUL X; Multiply the contents of address X to the contents of the AC

JMP X; Jump to the instruction labeled X

JMZ X; Jump to the instruction labeled X if the AC contains 0

JMN X; Jump to the instruction labeled X if the contents of the AC isnegative

HLT

; Halt execution

Memory Organization

Constants

Prog. Variables

Temp. Variables

• Num_Consts • Num_Vars • get_temp() • Num_Temps

Symbol Table

Map from identifiers

Symbol table

entries

Symbol table entries contain: address [maybe unknown]

Indicate whether entry is an constant,variable, temporary or label

8

Expressions

expr

expr

1

op expr

2

Code

1

; result stored in t

1

Code

2

; result stored in t

2

LD t

1

; load result of exp

1

OP t

2

; apply op to result of exp

2

and result of exp

ST t

3

; store result of exp

1

op exp

2

Expressions

expr

IDENT

; check to see if IDENT in symbol table ; otherwise add to symbol table LD IDENT

; load constant from constant table

ST t

n

; next available temporary

Assignment

assign_stmt

IDENT = expr

; check to see if IDENT in symbol table ; otherwise add to symbol table Code LD t ST IDENT

While Statements

while_stmt

while expr do S od

while

expr > 0 then S od

L1: Code

e

; result stored in t

LD t

JMN L

; jump if t

JMZ L2 Code

S

JMP L

L2:

Statement List

stmt-list

stmt; stmt-list | stmt

code

code

… code

n

Example

LD ZERO ST T1 LD FIVE ST T2 LD T1 SUB T2 ST T3 LD T3 ST n

n := 0 - 5

Example

if n then i := n else i := 0 - n fi;

LD n ST T4 LD T4 JMN L1 JMZ L1 LD n ST T5 LD T5 ST i JMP L

L1: LD ZERO

ST T6LD nST T7LD T6SUB T7ST T8LD T8ST i

L2:

Example

while i do

fact := fact * i; i := i - 1

od L3: LD i

ST T10 LD T10 JMN L4 JMZ L4 LD fact ST T11 LD i ST T12 LD T11 MUL T12 ST T

LD T13ST factLD iST T14LD ONEST T15LD T14SUB T15ST T16LD T16ST iJMP L

L4:

Complete Example

LD ZERO ST T1 LD FIVE ST T2 LD T1 SUB T2 ST T3 LD T3 ST n LD n ST T4 LD T4 JMN L1 JMZ L1 LD n ST T5 LD T5 ST i JMP L

L3: LD i

ST T10JMN L4JMZ L4LD factST T11LD iST T12LD T11MUL T12ST T LD T13ST fact

LD iST T14LD ONEST T15LD T14SUB T15ST T16LD T16ST iJMP L

L4: HLT

L1: LD ZERO

ST T6LD nST T7LD T6SUB T7ST T8LD T8ST i

L2: LD ONE

ST T9 LD T

ST fact