java MIPS汇编器 assembler代写 CS2630: Computer Organization Project 1 MiniMa

CS2630: Computer Organization Project 1

MiniMa: (mini) MIPS assembler written in Java

Goals for this assignment

• Translate MAL instructions to TAL, and TAL to binary
• Resolve the addresses of branch and jump labels
• Build an assembler

  Before you start

  This project is fairly involved, so start early. To be prepared, you should:

• read through Stored programs readings
• complete the “Stored Programs” activity

  Read the document as soon as you can and ask questions in Debug Your Brain/discussion board/office hours.

  It is possible to get MiniMa working one phase at a time (there are 3 phases), so you can pace yourself.

  So that we know who is working together: you must declare your partner at https://uiowa.instructure.com/courses/87896/assignments/778615.

  Setup

  You can git clone (or download zip) the project from https://github.uiowa.edu/cs2630- assignments/minima.git

  If you are using NetBeans, setup instructions are here:

  https://piazza.com/class/jl2kzfti2br4n7?cid=27

  If you are using IntelliJ, setup instructions are here:

  https://piazza.com/class/jl2kzfti2br4n7?cid=28

  A note on collaboration: We encourage you and your partner to create a github.uiowa.edu repository to collaborate on your code more effectively. If you do so, you must mark your

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repository Private. Repositories marked Public will be considered an intent to cheat by sharing code with other students.

Introduction

In this project, you will be writing some components of a basic assembler for MIPS, called MiniMa (mini MIPS assembler). You will be writing MiniMa in Java.

The input to MiniMa is an array of Instruction objects. The Instruction class has several fields indicating different aspects of the instruction. MiniMa does not include a parser to turn a text file into Instruction objects, so you will write programs using an InstructionFactory that creates Instructions.

public class Instruction {
public final ID instruction_id;
public final int rd;
public final int rs;
public final int rt;
public final int immediate;
public final int jump_address; // jump address (not used, so it is always 0) public final int shift_amount; // shift amount (not used, so it is always 0) public final String label; // label for line
public final String branch_label; // label used by branch or jump instructions

}

MiniMa has three basic phases for translating a MIPS program into binary. The next three sections describe these phases. The section after that, “What you need to do”, will describe your job in Project 1.

1. Convert MAL to TAL

In this phase, MiniMa converts any pseudo instructions into TAL instructions. Specifically, MiniMa creates a new output array of Instruction objects and stores the TAL instructions into it in order. For any true instruction in the input, MiniMa just copies it from the input to the output. For any pseudo instruction, MiniMa writes 1-3 real instructions into the output.

Examples: Ex a)

label2: addu $t0,$zero,$zero

This instruction will be provided to you as the Instruction object:

Instruction_id rd rs rt imm jump_address shift_amount addu 8 0 0 0 0 0

label branch_label “label2” 0

// id indicating the instruction // register number destination
// register number source
// register number secondary source // immediate, may use up to 32 bits

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Because this instruction is already a TAL instruction, you will just copy it into the output array. Ex b)

blt $s0, $t0, label3

This pseudo instruction, will be provided to you as the instruction object:

Instruction_id rd rs rt imm jump_address shift_amount label branch_label blt 8000 0 0 “” “label3″

Note that label=”” because the line the instruction was on is unlabeled.

This instruction is a pseudo instruction, so we must translate it to TAL instructions. In this case:

slt $at,$s0,$t0
bne $at,$zero,label3

Which you will represent with the following two Instruction objects.
Instruction_id rd rs rt imm jump_address shift_amount label branch_label slt 116800 0 “”””

Instruction_id rd rs rt imm jump_address shift_amount label branch_label bne 0 1 0 0 0 0 “” “label3”

We used $at (the assembler register) to store the result of the comparison. Since MIPS programmers are not allowed to use $at themselves, we know we can safely use it for passing data between generated TAL instructions.

IMPORTANT: notice that branch instructions have Immediate=0 in phase 1. Instead, they specify the target using branch_label. In phase 2, the branch_label will get translated into the correct immediate.

You must also make sure that you detect I-type instructions that use an immediate using more than the bottom 16 bits of the immediate field and translate them to the appropriate sequence of instructions.

This is just the end of the Part 1 background information. There are no tasks to do yet, so keep reading!

2. Convert labels into addresses

This phase converts logical labels into actual addresses. This process requires two passes over the instruction array.

• –  Pass one: find the mapping of labels to the PC where that label occurs
• –  Pass two: for each instruction with a non-zero branch_label (jumps and branches)

  calculate the appropriate address using the mapping.

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Example

before phase2: branch target for branch instructions indicated using branch_label field

Address

0x00400000
0x00400004
0x00400008
0x0040000C
0x00400010

Label

label1:
label2:
label3:

Instruction

addu $t0,$t0,$t1
ori $t0,$t0,0xFF
beq $t0,$t2,label1
addiu $t1,$t1,-1
addiu $t2,$t2,-1

Important instruction field values

label=”label1″
label=”label2″, branch_label=”label1″ label=”label3″

after phase2: branch target for branch instructions indicated using immediate field

Address

0x00400000
0x00400004
0x00400008
0x0040000C
0x00400010

Label

label1:
label2:
label3:

Instruction

addu $t0,$t0,$t1
ori $t0,$t0,0xFF
beq $t0,$t2,-3
addiu $t1,$t1,-1
addiu $t2,$t2,-1

Important instruction field values

immediate = -3

This is just the end of the Part 2 background information. There are no tasks to do yet, so keep reading!

3. Translate instructions to binary

This phase converts each Instruction to a 32-bit integer using the MIPS instruction encoding, as specified by the MIPS reference card. We will be able to test the output of this final phase by using MARs to translate the same input instructions and compare them byte-for-byte.

To limit the work you have to do, MiniMa only needs to support the following instructions:

Instruction

addiu

addu
or
beq
bne
slt
lui
j
ori

blt bge

(whether it is MAL depends on imm)

 (whether it is MAL depends on imm)

  (always MAL)
(always MAL)

This is just the end of the Part 3 background information. Your tasks begin in the next section.

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What you need to do

1. You will complete the implementation of phase 1 by modifying the file Phase1.java.

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If a MAL Instruction is already in TAL format, then you should just copy that Instruction object into your output list. Important notes:

• If you need to copy an instruction verbatim, then use Instruction.copy.
• If you need to create a new instruction with different fields set, use the

  InstructionFactory’s methods not the Instruction constructor (see the tests in AssemblerTest for examples of using the InstructionFactory).

  If a MAL Instruction is a pseudo-instruction, such as blt, then you should create the TAL Instructions that it translates to in order in returned List.

  You must check I-type instructions for the case where the immediate does not fit into 16 bits and translate it to lui, ori, followed by the appropriate r-type instruction. Remember: the 16-bit immediate check does not need to be done on branch instructions because they do not have immediates in phase 1 (see phase 1 description above).

  Use the following translations for pseudo instructions. These translations are the same as MARS uses.

I. Instruction passed to mal_to_tal:
addiu r1,r2,Immediate # when immediate is too large! =>
Instructions returned from mal_to_tal:
lui $at,Upper 16-bit immediate
ori $at,$at,Lower 16-bit immediate
addu r1,r2,$at

The above formula shown for addiu also applies to ori.
Note that lui will never be given an immediate too large because it is not well-defined for more than 16 bits (MARS also disallows lui with >16-bit immediate, try it yourself).

II. Instruction passed to mal_to_tal: blt r1,r2,gohere
=>
Instructions returned from mal_to_tal: slt $at,r1,r2

bne $at,$zero,gohere

III. Instruction passed to mal_to_tal: bge rs,rt,hello
=>
Instructions returned from mal_to_tal: slt $at,r1,r2

beq $at,$zero,hello

2. You will complete the implementation of phase 2 by implementing the 2-pass address resolution in a function called resolve_addresses.

Using our example from the phase 2 description:

Address

0x00400000
0x00400004
0x00400008
0x0040000C
0x00400010

Label

label1:
label2:
label3:

Instruction Important instruction field values

addu $t0,$t0,$t1
ori $t0,$t0,0xFF
beq $t0,$t2,label1
addiu $t1,$t1,-1
addiu $t2,$t2,-1

label=”label1″
label=”label2″, branch_label=1 label=”label3″

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The first_pc argument is the address where the first instruction in unresolved would be written to memory after phase 3. Using the above example, resolve_addresses would be called with first_pc=0x00400000.

Refer to the earlier description of phase 2 for how to calculate the immediate field.
3. You will complete the implementation of phase 3 by implementing the function

     translation_instruction.

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This function produces an encoding of each R-type, I-type, or J-type instruction. Refer to the MIPS reference sheet for format of the 32-bit format.

Make sure to set unused fields to 0

This default value is not required by the MIPS language specification, but it is required by the MiniMa test code. You’ll also notice that MARS chooses to use 0 for unused fields.

Running and testing your code

The three phases are run on several test inputs by running the JUnit test file AssemblerTest.java. The provided test cases separately test the three Phases. Therefore, you’ll have good evidence for a correct Phase when all tests named by that Phase are passing.

You can add your own tests to AssemblerTest.java. Use an existing test as a template. If you don’t want to manual calculate what phase3_expected should be for your test, you can let MARS do it for you: assemble your input program in MARS and look at the Code column in the Text Segment.

You should add additional test cases to AssemblerTest.java. Find corner cases the tests do not cover:

• other input instructions
• I-type instructions that do or do not exceed 16 bits

• different label positions
• different combinations of instructions

  You are responsible for testing your assembler beyond the given tests. We will use additional tests during grading.

  What to submit

  For credit your MiniMa implementation must at least compile and be runnable. You should not depend on modifications to files other than those you are submitting:

  Required:

• Phase1.java (method implemented)
• Phase2.java (method implemented)
• Phase3.java (method implemented)

  You are responsible for double-checking that the files submitted to ICON are the version of the files that you intended.

  Good job!

  Once you have completed this project, if you added support for the rest of the MIPS instructions you could replace the assembler of MARS (i.e., the code behind this button ).

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