201506 CSE340 Lecture 22

CSE340 - Principles of
Programming Languages
Lecture 22:
Intermediate Code III
Javier Gonzalez-Sanchez
BYENG M1-38
Office Hours: By appointment

Javier Gonzalez-Sanchez | CSE340 | Summer 2015 | 3
Review
Programming Assignment 4
Level 1
LIT, LOD, STO, OPR

Code
PROGRAM
OPR 0, 0

Code
BODY

Code
PRINT
OPR 21, 0

Code
ASSIGNMENT
STO identifier, 0

Code
VARIABLE
identifier, <type>

Code
RETURN
OPR 1, 0

Parser
EXPRESSION
if (twice) {
OPR 8, 0
}

Parser
X
if (twice) {
OPR 9, 0
}

Parser
Y
if (operatorUsed) {
OPR 10, 0
}

Parser
R
if (twice) {
OPR <operatorNumber>, 0
}

Parser
E
if (twice) {
}

Parser
A
if (twice) {
}

Parser
B
if (operatorUsed) {
OPR 3, 0
}
LIT 0, 0

Assignment 2 | Code
C
LIT <value>, 0
LOD identifier, 0

Review
Programming Assignment 4
Level 2
JMP, JMC

Instructions
•  JMP <line>, 0
Put the value <line> in the program counter;
thus, the next line to be executed will be <line>
Examples:
JMP 1, 0
JMP 14, 0
JMP 75, 0

Instructions
•  JMC <line>, <condition>
Read one value from the CPU register
If the value is equal to <condition>, put the value
<line> in the program counter; thus, the next line to
be executed will be <line>
Examples:
JMC 1, true
JMC 14, false
JMC 75, true

Example
{
int a; int b;
a = 10;
while (a>1){
print (a);
}
return;
}
int a global 0
int b global 0
@
LIT 10, 0
STO a, 0
LOD a, 0
LIT 1, 0
OPR 11, 0 ; >
JMC #e1, false
LOD a, 0
OPR 20, 0 ; print
JMP #e2, 0
OPR 1, 0
OPR 0, 0

Labels
•  Compiler creates variables and adds them to the
symbol table to remember positions in the code.
•  This is useful for loops and conditions.

Labels | how while works
while (a < b) {
//code
}
label#1
if (a < b) {
//code
} else
goto label#2
}
goto label#1
label #2

Labels | how if works
if (a < b) {
//code1
} else {
// code2
}
if (a < b) {
if (a>b) goto label #1
//code1
} else
goto label#2
label #1
// code2
}
label #2

Example | while
{
int a; int b;
a = 10;
while (a>1){
print (a);
}
return;
}
int a global 0
int b global 0
int #e1 global 10
int #e2 global 3
LIT 10, 0
STO a, 0
LOD a, 0
LIT 1, 0
OPR 11, 0 ; >
JMC #e1, false
LOD a, 0
OPR 20, 0 ;print
JMP #e2, 0
OPR 1, 0
OPR 0, 0

Example | if
{
int a; int b;
a = 10;
if (a>1) {
print (a);
} else {
print (b);
}
return;
}
int a global 0
int b global 0
int #e1 global 10
int #e2 global 12
LIT 10, 0
STO a, 0
LOD a, 0
LIT 1, 0
OPR 11, 0 ; >
JMC #e1, false
LOD a, 0
OPR 20, 0 ;print
JMP #e2, 0
LOD b, 0
OPR 20, 0 ;print
OPR 1, 0
OPR 0, 0

Exercise
{
int a; int b;
a = 10;
while (a>1) {
if (a != 0) {
print (a);
} else {
print (b);
}
a = a -1;
}
}

Handwritten notes

Code
WHILE

Code
IF

What about a switch-case

Handwritten notes
Add the symbol table here…

Homework
Translate this source code to intermediate code:
int a, b;
switch (a) {
case 1: { b = 11; break;}
default:{ b = 99; break;}
}

Homework
Assignment #4

CSE340 - Principles of Programming Languages
Javier Gonzalez-Sanchez
javiergs@asu.edu
Summer 2015
Disclaimer. These slides can only be used as study material for the class CSE340 at ASU. They cannot be distributed or used for another purpose.

201506 CSE340 Lecture 22

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201506 CSE340 Lecture 22