Questions

Design a lexical analyzer using transition diagram that recognizes:

• Identifiers (letter followed by letters/digits)
• Integer constants
• Operators: +, -, *, /, <, <=, >, >=, ==, =
• Keywords: if, then, else, while

1. read x
2. i = 1
3. sum = 0
4. prod = 1
5. if i > x goto 13
6. square = i * i
7. sum = sum + square  
8. prod = prod * i
9. i = i + 1
10. if i <= x goto 6
11. write sum
12. write prod
13. halt

• Redundant load/store elimination
• Constant folding
• Strength reduction
• Use of machine idioms

Apply these optimizations to the following assembly code:

MOV R0, a

MOV b, R0

MOV R0, b

ADD R0, R0, #0

MUL R0, R0, #2

MOV R1, #10

ADD R1, R1, #5

MOV R2, #0