SAYAC Compiler

Authors: Rayhaneh Einolahi, Bahareh Einolahi, Mahdis Mirzaei, Hasti Abolhasani
Supervisor: Professor Navabi

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Overview

The SAYAC compiler translates Mini-C ASTs into SAYAC assembly. Its backend consists of:

• Memory Manager: Handles globals, locals, temps, stack frames, and alignment.
• Register Manager: Allocates CPU registers, handles spills/reloads.
• Instruction Emitter: Generates SAYAC syntax for ALU, memory, and control operations.
• Code Generator: Handles main conversion of AST nodes to assembly.

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Memory Manager

• Globals: Absolute addresses [0x7000–0xDFFF].
• Locals/Temps: FP-relative stack slots.
• Alignment: 2-byte enforced.

Example Prologue/Epilogue:

PUSH FP
MOV  FP, SP
SUB  SP, SP, #frame_size
; ... body ...
ADD  SP, SP, #frame_size
POP  FP
RET

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Register Manager

• Maps variable names ↔ registers.
• Uses register actions to separate allocation from emission.
• Linear-scan allocation: reuse free registers; spill if needed.

Key Methods:

• allocateForRead(varName, actions)
• allocateForWrite(varName, actions)
• allocateTwoForRead(varNames, actions)
• allocateTwoForWrite(varNames, actions)

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Instruction Emitter

Provides high-level methods to generate SAYAC assembly:

• ALU: ADD, SUB, MUL, ADDI, AND, OR, XOR, NOT, SHL, SHR
• Memory: LI, LW, SW
• Control: CMP, Bxx, JMP, CALL, RET
• Labels: emitLabel(name)

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Code Generation

• Variables: Globals get absolute addresses; locals get FP-relative offsets.

• Expressions:

  • Unary & binary: direct instruction or temporary reuse.
  • Boolean: use true/false labels.
  • Bitwise OR/XOR: emulated using AND/NOT.
  • Compound assignments: use helper variables.

• Function Calls: Push arguments on stack; use RA for return.

• Control Flow:

  • While/For: Labels for condition, body, step, end; handle break/continue with stacks.
  • If/Else: Conditional branch, jump to end label.

• Functions: Prologue/epilogue, save FP & RA, allocate locals.

Example Mini-C → SAYAC:

int main() {
    int i;
    for (i = 0; i < 5; i++) {
        if (i == 3) break;
    }
    return 0;
}

func_main:
    STR FP SP
    ADR ZR SP FP
    ADI -2 SP
    MSI 0 R1
    ADI -2 R2
    LDR FP R2
    ADI 2 R2
for_condition_0:
    CMI 5 R1
    BRR > for_body_1
    JMP for_end_2
for_body_1:
    CMI 3 R1
    BRR == If_4
    JMP After_If_6
If_4:
    JMP for_end_2
    JMP After_If_6
After_If_6:
    JMP for_step_3
for_step_3:
    ADR ZR R1 R2
    ADI 1 R1
    JMP for_condition_0
for_end_2:
    MSI 0 R3
    ADR ZR R3 RT
    JMP func_ret_main
func_ret_main:
    ADR ZR FP SP
    LDR FP FP
    JMR 0 RA R0

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Assembler

• Converts SAYAC assembly → machine code.
• Supports all SAYAC instructions + JMP and BRR and STI and LDI.
• Resolves labels for control flow.

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Build & Run from Terminal

Step 1 – Generate Parser/Lexer with ANTLR

Linux/macOS:

java -jar lib/antlr-4.13.1-complete.jar \
  -Dlanguage=Java \
  -visitor \
  -package main.grammar \
  -o out/gen/main/grammar \
  src/main/grammar/SimpleLang.g4

Windows (CMD/PowerShell):

java -jar lib\antlr-4.13.1-complete.jar ^
  -Dlanguage=Java ^
  -visitor ^
  -package main.grammar ^
  -o out\gen\main\grammar ^
  src\main\grammar\SimpleLang.g4

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Step 2 – Compile Sources

Linux/macOS:

mkdir -p out
javac -cp lib/antlr-4.13.1-complete.jar \
     -d out \
     $(find out/gen -type f -name "*.java") \
     $(find src -type f -name "*.java")

Windows (CMD):

mkdir out
dir /s /b out\gen\*.java > classes.txt
dir /s /b src\*.java >> classes.txt

javac -cp lib\antlr-4.13.1-complete.jar;out ^
     -d out ^
     @classes.txt

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Step 3 – Run Compiler

Linux/macOS:

java -cp "out:lib/antlr-4.13.1-complete.jar" SimpleLang tests/CodeGeneration/Array/array_1.c -o out/output.s

Windows (CMD):

java -cp "out;lib\antlr-4.13.1-complete.jar" SimpleLang tests\CodeGeneration\Array\array_1.c -o out\output.s