2025-02-Compiler/notes/7.md

Code Generation 2

Stack Machine

Consider two instructions

• push i
• add i

It is not efficient because all stack is considered as memory (which is slower than register).

Utilizing Register Files

Keep the top of the stack in a register, so add requires only a single memory access.

• acc <- i
• push acc
• pop
• add

Code Generation From Stack Machine

Assume that stack grows towards lower addresses.

MIPS

32 regs

$sp, $a0, $t1

• lw
• add
• sw
• addi
• li
• mv

Converting Stack to MIPS ISA

• acc <- i
  • li $a0 i

Optimizing

Branch

beq $1 $2 lbl b lbl

Function