Introduction
Additional References
The text (or code) section is where the machine language is stored (ie 1s and 0s representing the code). Address data (hexadecimal representation) Data (ASCII representation) . string of numbers from sample code) or ASCII representation (ie declared strings).
MIPS Architecture Overview
Architecture Overview
When a program is executed, it must be copied from disk to RAM. This is similar to storing a short term paper on the disk drive, and when you write/edit the term paper, it is copied from the disk drive to memory.
Data Types/Sizes
Memory
Based on the little-endian architecture, the LSB is stored in the lowest memory address and the MSB is stored in the highest memory location.
Memory Layout
CPU Registers
Reserved Registers
Registers $k0 and $k1 are reserved for use by the operating system and may not be used in user programs. The $at register is used by the assembler and must not be used in user programs.
Miscellaneous Registers
The $gp register is used as a pointer to global data (as needed) and should not be used in user programs.
CPU / FPU Core Configuration
Additionally, there are some basic requirements for naming a "main" procedure (ie, the first procedure to execute). Calculate the sum of the floating point doubles in the registers FRsrc1 and FRsrc2 and put it in the register FRdest.
Data Representation
Integer Representation
Two's Complement
The same process is used to encode a decimal value into two's complement and from two's complement back to decimal.
Byte Example
Halfword Example
Unsigned and Signed Addition
Floating-point Representation
IEEE 32-bit Representation
- IEEE 32-bit Representation Examples
The numbers after the initial 1, not including the initial 1, are stored left aligned in the fractional part of the word. The result must be converted to a byte (8 bits) and stored in the biased exponent part of the word.
IEEE 64-bit Representation
Calculate the sum of the floating-point singles in registers FRsrc1 and FRsrc2 and place it in register FRdest. Calculate the quotient of the floating point double in registers FRsrc1 and FRsrc2 and place it in register FRdest.
QtSpim Program Formats
Assembly Process
Comments
Assembler Directives
Data Declarations
Integer Data Declarations
String Data Declarations
If you want to define a string with multiple lines, a NULL termination would only be required on the last or last line. When printing using the 'message' start address, anything up to (except . inclusive of) NULL will be displayed.
Floating-Point Data Declarations
As such, the declaration using multiple lines is irrelevant to the final displayed output.
Constants
Program Code
Labels
Program Template
Calculate the quotient of the floating-point singles in registers FRsrc1 and FRsrc2 and put it in register FRdest. Calculate the difference between floating point singles in registers FRsrc1 and FRsrc2 and put it in register FRdest.
Instruction Set Overview
Pseudo-Instructions vs Bare-Instructions
A pseudo-instruction is an instruction that the assembler or simulator will recognize but then convert to one or more bare instructions.
Notational Conventions
Hexadecimal or base-16 immediate values can be used, but must be prefixed with a 0x to indicate the value is hex.
Data Movement
Load and Store
For the halfword and byte instructions, only the lower 16 bits or the lower 8 bits are used.
Move
The floating point section will include examples for moving data between integer and floating point registers.
Integer Arithmetic Operations
Example Program, Integer Arithmetic
Refer to the system utilities section for information on displaying final results on the console.
Logical Operations
Shift Operations
- Logical Shift
- Arithmetic Shift
- Shift Operations, Examples
Each bit in the source operand is shifted the specified number of bit positions, and the newly freed bit positions are filled with zeros. Each bit in the source operand is shifted the specified number of bit positions, and the new free bit positions to the left are filled.
Control Instructions
Unconditional Control Instructions
Conditional Control Instructions
Conditional control instructions include the standard set; equal branch, unequal branch, less than branch, less than or equal branch, greater than branch, and greater than or equal branch. In addition, these conditional control instructions can be modified by adding or appending a 'z' at the end which means a comparison to zero (0) without typing the immediate 0 in the instruction.
Example Program, Sum of Squares
Floating-Point Instructions
Floating-Point Register Usage
Floating-Point Data Movement
The two double-precision operands (l.d and mov.d) reference registers $f6 and $f8, but use registers $f6/$f7 and $f8/$f9 to hold each of the two 64-bit values.
Integer / Floating-Point Register Data Movement
For example, assuming an integer value is in integer register $s0, to copy the value to floating point register $f12, the following instruction could be used. To copy the contents of $f12, into an integer register $t1, the following instruction could be used.
Integer / Floating-Point Conversion Instructions
In this example, the integer value in $s0 copied to $f12 still appears as a two's complement integer. This code snippet loads the integer value into variable iNum into $t0 and then copies the value into $f6.
Floating-Point Arithmetic Operations
Example Programs
- Example Program, Floating-Point Arithmetic
- Example Program, Integer / Floating-Point Conversion
A pop copies the top of the stack to the operand and then adds 4 bytes (in that order). Calculate the difference of the floating-point doubles in registers FRsrc1 and FRsrc2 and put it in register FRdest sub.s FRdest, FRsrc1,.
Addressing Modes
Direct Mode
Immediate Mode
Indirection
Bounds Checking
If the assembly language program attempts to access the 110th element of an array, the value in that memory location is returned without errors. In addition, no error is thrown when a program attempts to access a word (32-bit) in a half-word (16-bit) array.
Examples
Example Program, Sum and Average
If the memory access being attempted is outside the general scope of the program, an exception will be thrown. For example, attempting to access a memory location in a reserved section would not be allowed and would thus throw an exception.
Example Program, Median
Put the logical AND of the integers from register Rsrc1 and Src2 (or Imm) into register Rdest. FRsrc2 Floating-point Multiply, double - Calculate the product of the floating-point doubles in registers FRsrc1 and FRsrc2 and put it in register FRdest mul.s FRdest, FRsrc1,.
Stack
Stack Example
Since the stack is last-in, first-out, the first item to pop off the stack is the last item to be pushed, or 37 in this example.
Stack Implementation
Push
Pop
Multiple push's/pop's
Example Program, Stack Usage
Place the logical NOR of the integers from register Rsrc1 and Src2 into register Rdest. FRsrc2 Floating-point Multiply, Single - Compute the product of the floating-point units in the FRsrc1 and FRsrc2 registers and place it in the FRdest neg.d FRdest register, FRsrc Negate, Double.
Procedures/Functions
MIPS Calling Conventions
The standard calling convention specifies actions for the caller (routine calling) and the callee (routine being called).
Procedure/Function Format
Caller Conventions
On completion of the procedure, the caller procedure should restore all stored unsaved registers and adjust the stack point ($sp) if necessary if arguments have been passed on the stack.
Linkage
Argument Transmission
Call-by-Value
Call-by-Reference
Argument Transmission Conventions
Function Results
Registers Preservation Conventions
Miscellaneous Register Usage
Summary, Callee Conventions
Call Frame
Stack Dynamic Local Variables
Procedure Examples
Example Program, Power Function
Example program, Summation Function
Example Program, Pythagorean Theorem Procedure
Place logical OR of integers from register Rsrc1 and Imm to register Rdest role Rdest, Rsrc1, Src2 Rotate left. Place the logical XOR of the integers from the Rsrc1 register and Imm into the Rdest register.
QtSpim System Service Calls
Supported QtSpim System Services
QtSpim System Services Examples
Example Program, Display String and Integer
The console window can be shown or hidden in the Windows menu (on the top bar).
Example Program, Display Array
Example Program, Read Integer
Note, the default console window will typically be larger than the one shown above.
Example Program, Read String
Logical OR of integers from register Rsrc1 and Src2 to register Rdest or Rdest, Rsrc1, Imm OR Immediate. Put logical XOR of integers from register Rsrc1 and Src2 into register Rdest output Rdest, Rsrc1, Imm XOR Immediate.
Multi-dimension Array Implementation
High-Level Language View
It is expected that the reader is generally familiar with the use of the high-level language of two-dimensional arrays.
Row-Major
Column-Major
Example Program, Matrix Diagonal Summation
Branch conditionally to the instruction at the label if the content of Rsrc is greater than 0. Branch conditionally to the instruction at the label if the content of Rsrc is less than 0.
Recursion
Recursion Example, Factorial
Example Program, Recursive Factorial Function
Recursive Factorial Function Call Tree
Arguments and temporary values for each instance are different since they are held on the stack as required by the standard calling convention. It should also be noted that the height of the recursion tree is directly related to the amount of stack memory used by the function.
Recursion Example, Fibonacci
Example Program, Recursive Fibonacci Function
Recursive Fibonacci Function Call Tree
Convert the single-precision floating-point number in the FRsrc register to a double-precision number and place it in the FRdest register. Convert the double-precision floating-point number in the FRsrc register to a single-precision number and place it in the FRdest register.
Appendix A – Example Program
Appendix B – QtSpim Tutorial
Downloading and Installing QtSpim
QtSpim Download URLs
Installing QtSpim
Working Directory
Sample Program
QtSpim – Loading and Executing Programs
- Starting QtSpim
- Main Screen
- Load Program
- Data Window
- Program Execution
- Log File
- Making Updates
However, it is usually easier to select the Reinitialize and load icon from the main screen (second file icon in the top left). However, it is usually easier to select the Save Log File icon from the main screen.
Debugging
Convert the single precision floating point number in the FRsrc register to an integer and put it in the FRdest register div.d FRdest, FRsrc1,. Move double floating point from register FRsrc to register FRdest mov.s FRdest, FRsrc Move floating point, single.
Appendix C – MIPS Instruction Set
Arithmetic Instructions
Set $lo = Rsrc / Src (or imm) Remainder is set to $hi divu Rsrc1, Rsrc2 Divide (no overflow). Set $lo = Rsrc / Src (or imm) Remainder is set to $hi div Rdest, Rsrc, Src Divide (with overflow).
Comparison Instructions
Set register Rdest to 1 if register Rsrc1 is less than Src2 (or Imm) and to 0 otherwise. Set register Rdest to 1 if register Rsrc1 is not equal to Src2 and to 0 otherwise.
Branch and Jump Instructions
Conditionally branch to the statement on the label if the content of Rsrc equals 0 bge Rsrc1, Src2, label Branch on Greater Than or Equal. Conditionally branch to the statement on the label if the contents of Rsrc are greater than or equal to 0.
Load Instructions
Load the left bytes from the word at the possibly outstanding address into the Rdest register. Load the right bytes from the word at the address, which may be outstanding, into the Rdest register.
Logical Instructions
Rotate the contents of the Rsrc1 register to the left by the distance indicated by Src2 and put the result in the Rdest register. Shift the contents of the Rsrc1 register to the left by the distance indicated by Src2 and put the result in the Rdest register.
Store Instructions
Store the low halfword from the Rsrc register at the possible address of the unaligned usw Rsrc, Unaligned Store Word address.
Data Movement Instructions
Shift the contents of CPU integer registers Rsrc and Rsrc+1 into coprocessor 1 float registers Frdest and FRdest+1.
Floating-Point Instructions
Compare the floating-point double in the FRsrc1 register with the one in FRsrc2 and set the condition flag true if the first is less than the second. Convert the double precision floating point number in the FRsrc register to an integer and put it in the FRdest register cvt.w.s FRdest, FRsrc Convert single to integer.
Exception and Trap Handling Instructions
For additional information and a more complete list of ASCII codes (including extended ASCII characters), refer to http://www.asciitable.com/.
Appendix D – ASCII Table
Alphabetical Index
Representation
Representation
