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Code Generation 2
COP-3402

Table of Contents

Overview

In this project you will compile function definitions and calls to x86 assembly. As with all programming projects, it will be submitted via git.

Setup the repo

  1. ssh into eustis, replacing NID with your UCF NID.

    ssh NID@eustis.eecs.ucf.edu
    
  2. Clone the compiler template to codegen2

    git clone https://www.cs.ucf.edu/~gazzillo/teaching/cop3402fall24/repos/compiler-template.git/ codegen2
    
  3. Enter the repo

    cd codegen2/
    

    If this doesn't, double-check step (2) and make sure you put codegen2 as the second argument to clone.

  4. Add the URL of your personal remote repository, replacing NID with your UCF NID.

    git remote add submission gitolite3@eustis3.eecs.ucf.edu:cop3402/NID/codegen2
    
  5. Synchronize your local repo with the remote eustis3 repo.

    git push --set-upstream submission master
    

    You only need to do this once. Use git commit and git push regularly to keep the remote repo up to date.

Setting up your development environment

  1. Be sure you are in the repo directory.

    cd ~/codegen2
    

    If you receive a warning about a managed python installation, then double-check that you are on eustis.

  2. Then create the development environment. This creates an "editable" installation of your project, so that you can modify its source and rerun without having to reinstall the project.

    pipenv install -e ./
    

    If you can't run pipenv but you've already installed it, trying logging out and back in again to eustis.

    If you haven't installed pipenv yet, please review the calc project.

  3. Enter your pipenv development environment. Do this everytime you log in to eustis to work on your project.

    pipenv shell
    

    Double-check that you are in the environment. Your prompt should look something like this:

    (compiler) NID@net1547:~/codegen2$
    

    You can later exit the dev environment with exit. You do not need to enter the dev environment again if you have already entered it.

  1. Get ANTLR and build the parser.

    make -C grammar/
    

Compiler project structure

File Description
Pipfile pipenv settings
compiler/CodeGen.py The code generator that you will write. Not provided by the template repo.
compiler/Interpreter.py A SimpleIR interpreter for comparing output
grammar/Makefile A build file for the grammar
grammar/SimpleIR.g4 The SimpleIR grammar
pyproject.toml python project settings

.gitignore files are for git and __init__.py are for python modules.

Implementation

Skeleton code

Here is the start to compiler/CodeGen.py

import os
import sys
import math
from textwrap import indent, dedent
from antlr4 import *
from grammar.SimpleIRLexer import SimpleIRLexer
from grammar.SimpleIRParser import SimpleIRParser
from grammar.SimpleIRListener import SimpleIRListener
import logging
logging.basicConfig(level=logging.DEBUG)

# This class defines a complete listener for a parse tree produced by SimpleIRParser.
class CodeGen(SimpleIRListener):
    def __init__(self, filename, outfile):
        self.filename = filename
        self.outfile = outfile
        self.symtab = {}
        self.bytewidth = 8

    def enterUnit(self, ctx:SimpleIRParser.UnitContext):
        """Creates the object file sections"""
        self.outfile.write(
f'''\t.file "{self.filename}"
\t.section .note.GNU-stack,"",@progbits
\t.text
''')

    def enterLocalvars(self, ctx:SimpleIRParser.LocalvarsContext):
        """Allocates space for local variables, including input parameters"""
        # get list of local variables
        locals = [ local.getText() for local in ctx.NAME() ]
        # create a list of offsets of the bytewidth
        offsets = map(lambda x: (x+1)*-self.bytewidth, range(len(locals)))
        # create a dictionary mapping locals to offsets
        self.symtab = dict(zip(locals, offsets))
        logging.debug(self.symtab)
        # compute the size of the stack space
        stackspace = len(self.symtab.keys()) * self.bytewidth
        logging.debug(stackspace)
        # ceiling to 8 bytes
        stackoffset = math.ceil(stackspace / 8) * 8
        # align to 16 bytes by adding 8 to account for rbx if already aligned to 16 bytes
        stackoffset += (stackoffset + 8) % 16
        logging.debug(stackoffset)
        # Emit an instruction to allocate stack space for locals
        self.outfile.write(indent(dedent(f'''\
            # allocate stack space for locals
            sub\t${stackoffset}, %rsp
        '''), '\t'))

    def enterAssign(self, ctx:SimpleIRParser.AssignContext):
        """Assign value to a variable"""
        if SimpleIRParser.NAME == ctx.operand.type:
            operand = f"{self.symtab[ctx.operand.text]}(%rbp)"
        elif SimpleIRParser.NUM == ctx.operand.type:
            operand = f"${ctx.operand.text}"
        self.outfile.write(indent(dedent(f'''\
            # assign {ctx.operand.text} to {ctx.NAME(0).getText()}
            mov\t{operand}, %rax
            mov\t%rax, {self.symtab[ctx.NAME(0).getText()]}(%rbp)
        '''), '\t'))

    def enterFunction(self, ctx:SimpleIRParser.FunctionContext):
        """Emits the label and prologue"""
        # TODO (same as codegen1)

    def exitFunction(self, ctx:SimpleIRParser.FunctionContext):
        """Emits the epilogue"""
        # TODO (same as codegen1)

    def enterParams(self, ctx:SimpleIRParser.ParamsContext):
        """Moves input parameters to their local variables"""
        # TODO

    def enterReturn(self, ctx:SimpleIRParser.ReturnContext):
        """Sets the return value"""
        # TODO

    def enterCall(self, ctx:SimpleIRParser.CallContext):
        """Function call"""
        # TODO


def main():
    import sys
    if len(sys.argv) > 1:
        filepath = sys.argv[1]
        input_stream = FileStream(filepath)
        filename = os.path.basename(filepath)
    else:
        input_stream = StdinStream()
        filename = "stdin"

    lexer = SimpleIRLexer(input_stream)
    stream = CommonTokenStream(lexer)
    parser = SimpleIRParser(stream)
    tree = parser.unit()
    if parser.getNumberOfSyntaxErrors() > 0:
        print("syntax errors")
        exit(1)
    # print(tree.toStringTree())
    walker = ParseTreeWalker()
    walker.walk(CodeGen(filename, sys.stdout), tree)

if __name__ == '__main__':
    main()

Emitting assembly code

The CodeGen class provides a self.outfile file to write to. In python, write a string using

self.outfile.write("The string to emit")

Alternatively, you can use a format string to make creating templates easier, where anything inside curly braces is evaluated, e.g., the following prints a string followed by the contents of a variable called name:

self.outfile.write(f"This is the what is in the name variable: {name}")

To retrive ANTLR parse tree contents, use the ctx context parameter provided to each listener using the name of the token, e.g., the following will get the NAME token from the syntax tree for a function production and store it in the name python variable.

name = ctx.NAME()

Laying out the assembly file

enterUnit

This function is given to you. It creates assembly code boilerplate for you.

Variables

Code to manage variables for this project is given to you.

enterLocalvars (given to you)

This function generates assembly instructions that allocate space on the stack for all local variables. In SimpleIR, all variables are 64-bit integers. enterLocalvars is given to you. It works by first collecting the set of variables to allocate space for from the syntax tree of the input program:

locals = [ local.getText() for local in ctx.NAME() ]

Then it creates space on the stack for each local variable. The memory location of each local variable can be determined by an offset from the base pointer %rbp per the System V AMD64 ABI. The compiler records each variables offset in a table that maps the name of the variable to its offset from %rbp, which the compiler will use to translate variable accesses and assignments whenever the variable is used in SimpleIR instructions. The given enterLocalvars function creates this dictionary with a little python cleverness, i.e.,

# create a list of offsets of the bytewidth
offsets = map(lambda x: (x+1)*-self.bytewidth, range(len(locals)))
# create a dictionary mapping locals to offsets
self.symtab = dict(zip(locals, offsets))

self.symtab now contains a mapping from each local variable to its own offset (which are multiples of the 8-byte width), e.g., -8, -16, -24, etc. (Do you remember why the offsets are negative in this ABI?)

Finally, the functions computes the total amount of space required for the local variables (number of variables times 8 bytes each), aligns the stack to 16 bytes (required by the ABI), and emits a assembly instruction that updates the stack pointer to allocate the space, i.e.,

# compute the size of the stack space
stackspace = len(self.symtab.keys()) * self.bytewidth
logging.debug(stackspace)
# ceiling to 8 bytes
stackoffset = math.ceil(stackspace / 8) * 8
# align to 16 bytes by adding 8 to account for rbx if already aligned to 16 bytes
stackoffset += (stackoffset + 8) % 16
logging.debug(stackoffset)
# Emit an instruction to allocate stack space for locals
self.outfile.write(indent(dedent(f'''\
    # allocate stack space for locals
    sub\t${stackoffset}, %rsp
'''), '\t'))

Because of this function, self.symtab will tell you how to translate variable uses into offsets from the base pointer %rbp for generating equivalent assembly instructions.

enterAssign (given to you)

The syntax of the assignment statement is

assign: NAME ':=' operand=(NAME | NUM);

Notice that operand may either be a NAME (which is the syntax of an identifier) or a NUM (which is the syntax for an integer literal). An assignment takes either a constant integer literal or a variable identifier and copies that data to the left-hand side variable. This translates to either a mov immediate to a register (integer literal) or a load from memory to a register (variable name on right-hand side), followed by a store of that value to the memory location associated with the variable name.

If the right-hand side is a variable name, the compiler will generate a load from the memory location of the variable to a temporary register (we'll use %rax for the temporary register). To determine the memory location, recall that our compiler assigns each local variable an offset from %rbp that we stored in a offset table created by enterLocalvars. For example, if variable b has offset -24 from %rbp, to load that memory location's value into %rax, we use the following instruction:

mov -24(%rbp), %rax

-24(%rbp) means, take the value of %rbp (which is a pointer to the current stack) frame, add -24 to it, then dereference the address and load that value into %rax.

To implement this in our compiler, enterAssign first determies whether the operand is a NAME or a NUM, i.e.,

if SimpleIRParser.NAME == ctx.operand.type:

When the operand is a NAME, the compiler creates the %rbp-indirect offset argument, e.g., -24(%rbp), i.e.,

operand = f"{self.symtab[ctx.operand.text]}(%rbp)"

When the operand is a NUM, we only need to use an immediate value argument, i.e.,

elif SimpleIRParser.NUM == ctx.operand.type:
    operand = f"${ctx.operand.text}"

Either way, the operand python variable now contains the corresponding assembly instruction argument for the right-hand side of the SimpleIR statement.

Finally, enterAssign generates the copy of the right-hand side to the temporary register %rax, then stores the value into the memory location of the left-hand side variable:

self.outfile.write(indent(dedent(f'''\
    # assign {ctx.operand.text} to {ctx.NAME(0).getText()}
    mov\t{operand}, %rax
    mov\t%rax, {self.symtab[ctx.NAME(0).getText()]}(%rbp)
'''), '\t'))

The left-hand size variable's memory location can also be found using the offset table (self.symtab). The name of the variable is retrieved from syntax tree with ctx.NAME(0).getText(), since the left-hand side variable is the first NAME in the grammar for the assignment.

Defining functions

enterFunction (same as codegen1)

To create the function, emit the assembly pseudo-ops .globl and .type with the name of the function (ctx.NAME()), as well as a label for the function. Then emit the prologue. Use whatever the name of the function is for all three, e.g., for the function factorial the function creation and prologue would look like this:

        .globl factorial
        .type factorial, @function
factorial:
  # prologue
        pushq	%rbp # save old base ponter
        movq	%rsp, %rbp # set new base pointer
        push	%rbx # %rbx is callee-saved

exitFunction (same as codegen1)

Emit the assembly function epilogue and return instruction, i.e.,

# epilogue
mov	%rbp, %rsp # restore old stack pointer
pop	%rbp # restore old base pointer
ret

This is the same for all functions.

enterParams (new for codegen2)

In SimpleIR, the input program first declares all local variables, e.g.,

localvars x a b c d e f g h

then it declares which of those local variables is a parameter, e.g.,

params a b c d e f g h

In the above example, all local variables, except for x are also parameters. The set of parameters is a subset of the local variables (or the same set).

The enterLocalvars function emits code that creates space for all local variables, including parameters. enterParams then copies the parameter values set by the caller to the corresponding parameter local variables. For instance, for the above set of params, the following assembly code copies the caller's values to the callee's local variables:

# move register parameter a to local variable
mov	%rdi, -16(%rbp)
# move register parameter b to local variable
mov	%rsi, -24(%rbp)
# move register parameter c to local variable
mov	%rdx, -32(%rbp)
# move register parameter d to local variable
mov	%rcx, -40(%rbp)
# move register parameter e to local variable
mov	%r8, -48(%rbp)
# move register parameter f to local variable
mov	%r9, -56(%rbp)
# move stack parameter h to local variable
mov	16(%rbp), %rax
mov	%rax, -72(%rbp)
# move stack parameter g to local variable
mov	24(%rbp), %rax
mov	%rax, -64(%rbp)

The caller passes parameters both via registers and the stack, the first six via registers and the rest via the stack. To copy these parameters to the memory locations for the callee's local variable, enterParams generates mov instructions for the first size parameters from the ABI-defined set of parameter registers, i.e.,

registers = [ "%rdi", "%rsi", "%rdx", "%rcx", "%r8", "%r9" ]

enterParams can retrieve the list of parameters names for the input program from the ANTLR syntax tree, i.e.,

params = [ param.getText() for param in ctx.NAME() ]

The list of register and stack parameters can be spliced with

register_params = params[0:6]
stack_params = params[6:]

For each of the register parameters, generate a mov from the corresponding register to the local variable's memory location. The local variables' memory locations are offsets from the base pointer, as described in enterLocalvars, i.e., by passing the name of the variable to self.symtab to get the offset. Then generate the mov instruction from the register, e.g., from the example above

# move register parameter c to local variable
mov	%rdx, -32(%rbp)

This instruction stores the value in %rdx, i.e., the third parameter, into -32(%rbp), which is the memory location of the local variable c for the above program. See enterAssign for more details on getting the memory location of local variables.

For the stack allocated parameters, mov them from the stack to the local variable. Since this is move between two memory location, the instruction set requires first copying to a temporary register (we'll use %rax), resulting in two move instructions. The first instruction copies from the parameter's memory location on the stack to %rax, e.g.,

mov	16(%rbp), %rax

Then the next instruction copies from %rax to the location variable's memory location, given by self.symtab, e.g.,

mov	%rax, -72(%rbp)

The offsets are positive from the %rbp (why is this the case?) and they start from 16. This is because %rbp plus 0 is the old base pointer, %rbp plus 8 is the return address, then %rbp plus 16 is the 7th parameter (the first after the register parameters), %rbp plus 24 is the 8th, etc.

Calling functions

For this project, you will need to support an arbitrary number of parameters to function calls and support storing return values. There are several steps to calling a function in assembly:

  • Passing parameters
  • Making the call
  • Restoring the stack pointer
  • Saving the return value

The following is an example of a SimpleIR function call. Note that this assumes that the variable names have already been declared (enterLocalvars) and defined (enterAssign), both of which are already given to you.

x := call paramtest a b c d e f g h

The first step, parameter passing, using both registers and the stack to pass the parameters (per the System V AMD64 ABI).

# pass the first size parameters via the pre-defined set of registers
      mov	-32(%rbp), %rdi
      mov	-40(%rbp), %rsi
      mov	-48(%rbp), %rdx
      mov	-56(%rbp), %rcx
      mov	-64(%rbp), %r8
      mov	-72(%rbp), %r9
# pass the remaining arguments via the stack
      push	-80(%rbp)
      push	-88(%rbp)
# make the call
      call	paramtest
# restore the stack pointer
      add	$16, %rsp
# save the return value
      mov	%rax, -24(%rbp)

There is one mov instruction for each of the first six parameters (recall that the System V AMD64 ABI passes the first six via registers instead of the stack). These instruction copy the local variable's value to one of the predefined registers. The local variables' memory locations are offsets from the base pointer, as described in enterLocalvars. The predefined set of registers for the first size parameters, in python, is

registers = [ "%rdi", "%rsi", "%rdx", "%rcx", "%r8", "%r9" ]

You can retrieve the left-hand side variable (to assign the return value to), the function name to call, and the parameters with the following python code:

call = [ name.getText() for name in ctx.NAME() ]
varname = call[0]
funname = call[1]
params = call[2:]

param is a list containing all the parameters in order. Take the first six with

register_params = params[0:6]

and the remaining stack parameters with

stack_params = params[6:]

For the register parameters, generate a mov instruction that copies the local variable's value (from the stack frame, e.g., -32(%rbp)) to the corresponding parameter register (listed in registers above). Then for each stack parameters (if there are any), generate a push instruction that pushes the local variables value.

After processing the parameters, generate the call to the function (given in funname), e.g., call paramtest above. After the call, generate an instruction to remove any parameters from the stack (what instruction(s) could be used to do this? How do we know how much space was used on the stack?) This is done in the example above with

add $16, %rsp

Finally, the return value is stored in %rax according to the System V AMD64 ABI convention (which your functions will also follow). The left-hand side variable name is given in varname. Recall how to access the memory location of a variable, i.e., using the offset table (self.symtab). Use a mov to store the return value (%rax) into the memory location of the left-hand side variable, e.g.,

mov	%rax, -24(%rbp)

Returning

SimpleIR allows for either a return of an integer constant or a variable. Similarly to enterAssign you can check for this by checking ctx.operand.type and use the same if-then-else statement to generate the assembly instruction argument (either a load from an offset from %rbp or an immediate constant). Then store this value into %rax, per the ABI, e.g., mov -8(%rbp), %rax.

Testing your compiler

This example compiles two functions, main and paramtest. If successful, you will have two assembly files, main.s and paramtest.s. main calls paramtest and returns the constant 3. While paramtest returns 3, this value is never used by main.

codegen << EOT | tee main.s
function main
localvars argc argv x a b c d e f g h
params argc argv
a := 1
b := 2
c := 3
d := 4
e := 5
f := 6
g := 7
h := 8
x := call paramtest a b c d e f g h
return x
EOT
codegen << EOT | tee paramtest.s
function paramtest
localvars x a b c d e f g h
params a b c d e f g h
x := c
return x
EOT
gcc -o main main.s paramtest.s
./main
echo $? # you should see 3 as the exit code

Debugging with GDB

One way to help trace the function call is to use gdb. The following will rebuild the main program with debugging symbols on, run gdb, then step through each assembly instructions.

gcc -g -o main main.s func.s  # compile with debugging symbols (-g)
gdb main 
b main # setup breakpoint at main
r # start running, breaks at main
si # step instruction to see next instruction
# hitting enter will repeat last command, e.g., si
c # one done use c to continue running without stopping

Debugging tutorials

See these resources for more information on gdb.

Full example

main.ir

function main
localvars argc argv x a b c d e f g h
params argc argv
a := 1
b := 2
c := 3
d := 4
e := 5
f := 6
g := 7
h := 8
x := call paramtest a b c d e f g h
return x
  • main.s

    Running codegen main.ir > main.s should produce similar assembly output. Note that # denotes a comment.

            .file "main.ir"
            .section .note.GNU-stack,"",@progbits
            .text
            .globl main
            .type main, @function
    main:
            # prologue, update stack pointer
            pushq	%rbp # save old base ponter
            movq	%rsp, %rbp # set new base pointer
            push	%rbx # %rbx is callee-saved
            # allocate stack space for locals
            sub	$88, %rsp
            # move register parameter argc to local variable
            mov	%rdi, -8(%rbp)
            # move register parameter argv to local variable
            mov	%rsi, -16(%rbp)
            # assign 1 to a
            mov	$1, %rax
            mov	%rax, -32(%rbp)
            # assign 2 to b
            mov	$2, %rax
            mov	%rax, -40(%rbp)
            # assign 3 to c
            mov	$3, %rax
            mov	%rax, -48(%rbp)
            # assign 4 to d
            mov	$4, %rax
            mov	%rax, -56(%rbp)
            # assign 5 to e
            mov	$5, %rax
            mov	%rax, -64(%rbp)
            # assign 6 to f
            mov	$6, %rax
            mov	%rax, -72(%rbp)
            # assign 7 to g
            mov	$7, %rax
            mov	%rax, -80(%rbp)
            # assign 8 to h
            mov	$8, %rax
            mov	%rax, -88(%rbp)
            # call paramtest
            mov	-32(%rbp), %rdi
            mov	-40(%rbp), %rsi
            mov	-48(%rbp), %rdx
            mov	-56(%rbp), %rcx
            mov	-64(%rbp), %r8
            mov	-72(%rbp), %r9
            push	-88(%rbp)
            push	-80(%rbp)
            call	paramtest
            add	$16, %rsp
            mov	%rax, -24(%rbp)
            # set return value
            mov	-24(%rbp), %rax
            # epilogue
            mov	%rbp, %rsp # restore old stack pointer
            pop	%rbp # restore old base pointer
            ret
    

paramtest.ir

Try assigning x to different input parameters to test that parameters are being passed correctly both through registers and through the stack.

function paramtest
localvars x a b c d e f g h
params a b c d e f g h
x := c
return x
  • paramtest.s

    Running codegen paramtest.ir > paramtest.s should produce similar assembly output. Note that # denotes a comment.

            .file "paramtest.ir"
            .section .note.GNU-stack,"",@progbits
            .text
            .globl paramtest
            .type paramtest, @function
    paramtest:
            # prologue, update stack pointer
            pushq	%rbp # save old base ponter
            movq	%rsp, %rbp # set new base pointer
            push	%rbx # %rbx is callee-saved
            # allocate stack space for locals
            sub	$72, %rsp
            # move register parameter a to local variable
            mov	%rdi, -16(%rbp)
            # move register parameter b to local variable
            mov	%rsi, -24(%rbp)
            # move register parameter c to local variable
            mov	%rdx, -32(%rbp)
            # move register parameter d to local variable
            mov	%rcx, -40(%rbp)
            # move register parameter e to local variable
            mov	%r8, -48(%rbp)
            # move register parameter f to local variable
            mov	%r9, -56(%rbp)
            # move stack parameter g to local variable
            mov	16(%rbp), %rax
            mov	%rax, -64(%rbp)
            # move stack parameter h to local variable
            mov	24(%rbp), %rax
            mov	%rax, -72(%rbp)
            # assign c to x
            mov	-32(%rbp), %rax
            mov	%rax, -8(%rbp)
            # set return value
            mov	-8(%rbp), %rax
            # epilogue
            mov	%rbp, %rsp # restore old stack pointer
            pop	%rbp # restore old base pointer
            ret
    

More full examples

cd ~/codegen2
wget https://www.cs.ucf.edu/~gazzillo/teaching/cop3402fall24/files/compiler-examples.tar
tar -xvf compiler-examples.tar

Submitting your project

Stage, commit, and push to the grading server

The only file you need to submit is compiler/CodeGen.py.

Once you have set up the repo, all you need to do is use git add, git commit, and git push to stage, commit, and sync your repo to the grading git server.

Self-check

You can check that you've submitted correctly by cloning, building, and testing your repo.

cd ~
git clone gitolite3@eustis3.eecs.ucf.edu:cop3402/NID/codegen2 codegen2_new
cd codegen2_new
pipenv install -e ./
pipenv shell
make -C grammar/
codegen << EOT > main.s
function main
return 10
EOT
gcc -o main main.s
./main
echo $? # you should see 10 as the exit code

What should be the correct output, i.e., assignments of the variables, for these arithmetic operations?

(Only if instructed) Updating from the start repo

If the original repo gets updated after you have already started implementing your project, you can get those updates by pulling. Otherwise, you will never need to do this step. Be sure to commit any changes you have made before proceeding.

git pull origin master --rebase
git push -f

If you encounter a conflict, it may be that you modified some files from the original repo that didn't need to be modified. Come to office hours if you need help resolving the conflict.

Troubleshooting

  • If you make a mistake in typing the URL, you can remove the submission remote and try the add step again:

    git remote rm submission
    git remote add submission gitolite3@eustis3.eecs.ucf.edu:cop3402/NID/codegen2  # replace NID with yours
    
  • Do not try creating a new repo if you make a mistake. You will not be able to push the new repo to gitolite3, since there already is one there. You can always make new changes and commit them to fix mistakes.
  • If in self-check codegen2_new already exists, just use a fresh directory name.
  • The program must be run inside of the pipenv environment. You can see that you have successfully entered the environment because your prompt is prefixed with (compiler), e.g.,

    (compiler) NID@net1547:~/codegen2$
    

    You can exit the environment with exit.

Self-grading

cd ~/
git clone https://www.cs.ucf.edu/~gazzillo/teaching/cop3402fall24/repos/codegen2-grading.git
cd codegen2-grading
make

Look at README.md for usage instructions.

Grading schema

Criterion Points
The git repo exists 1
compiler/CodeGen.py exists 1
codegen runs the given example correctly 2
codegen runs new example inputs correctly 2
TOTAL 6

Author: Paul Gazzillo

Created: 2024-11-25 Mon 09:11

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