Mips/Assembly - Revision history

Mzxrules: /* Variable Directives */

2018-04-02T16:00:03Z

‎Variable Directives

Mzxrules: /* Multiplication and Division */

2018-03-28T21:31:51Z

‎Multiplication and Division

Mzxrules: /* Directives */

2018-03-09T05:59:58Z

‎Directives

Mzxrules: /* Pseudo Instructions */

2018-03-09T05:59:01Z

‎Pseudo Instructions

Mzxrules: /* Syntax */

2018-03-09T05:37:25Z

‎Syntax

Mzxrules: /* Directives */

2018-03-09T05:12:36Z

‎Directives

Mzxrules at 04:56, 9 March 2018

2018-03-09T04:56:19Z

Mzxrules: Still working

2018-03-08T23:38:43Z

Still working

New page

The following is a guide on how to write MIPS assembly using the GCC compiler.

== Pseudo Instructions ==

Pseudo instructions (or pseudo ops) are operations that expand into one or two valid MIPS instructions, which simplifies certain common operations. Some pseudo instructions that expand into two instructions use the $at register to store an intermediate state, so extra care must be made when writing code that relies on $at as a temporary register. This is compounded by the fact that several pseudo instructions share the same mnemonic as proper MIPS instructions.

=== Data ===

{|class="wikitable"
! Name || Syntax || Expansion || Result || Notes
|-
| move || move $target, $source || addiu $target, $source || $target = $source ||
|-
| clear || clear $target || addu $target, $zero, $zero || $target = 0 ||
|-
| load 16-bit immediate
| rowspan = 2 | li $target, constant
| addiu $target, $zero, %lo(constant)
| rowspan = 2| target = constant
|
|-
| load 32-bit immediate
| lui $target, %hi(constant) ori $target, $target, %lo(constant)
|
|-
| load label address
| la $target, address
| lui $target, %hi(address) ori $target, $target, %lo(address)
| $target = address
| address can either be a label or a constant
|}

=== Branches ===

{|class="wikitable"
! Name || Syntax || Expansion || Result
|-
| branch unconditionally || b label || beq $zero, $zero, label || goto label
|-
| branch unconditionally and link || bal label || bgezal $zero, label || $ra = PC + 4; goto label
|-
| branch if greater than || bgt $left, $right, label
| slt $at, $right, $left bne $at, $zero, label
| if $left > $right goto label
|-
| branch if less than || blt $left, $right, label
| slt $at, $left, $right bne $at, $zero, label
| if $left < $right goto label
|-
| branch if greater than or equal || bge $left, $right
| slt $at, $left, $right beq $at, $zero, label
| if $left >= $right goto label
|-
| branch if less than than or equal || ble $left, $right
| slt $at, $right, $left beq $at, $zero, label
| if $left <= $right goto label
|}

== Directives ==

[[Category: Mips]]

@@ Line 172: / Line 172: @@
 | .ascii str || Store a non-null terminated string str in memory
 |-
-| .asciiz str || Store a non-null terminated string str in memory
+| .asciiz str || Store a null terminated string str in memory
 |-
 | .byte b1, ..., bn || Stores 8-bit values in successive memory locations

@@ Line 120: / Line 120: @@
 | mult $left, $right<br>mflo $result
 | $result = ($left * $right) & 0xFFFFFFFF
 |}
 == Other ==
 {|class="wikitable

@@ Line 186: / Line 186: @@
 If you need to initialize multiple instances of a common numerical type, you can postfix the value with :n, where n is the number of times that value should occur. For example:
-  # Create an array of 10 two-byte timers, initialized to 10 frames
+  # Create an array of 7 two-byte timers, initialized to 10 frames
-  Timers: .half 0x000A:10
+  Timers: .half 0x000A:7
 == Preprocessor Directives ==

@@ Line 87: / Line 87: @@
 | if $left < $right<br>goto label
 |-
-| branch if greater than or equal || bge $left, $right
+| branch if greater than or equal || bge $left, $right, label
 | slt $at, $left, $right<br>beq $at, $zero, label
 | if $left >= $right<br>goto label
 |-
-| branch if less than than or equal || ble $left, $right
+| branch if less than than or equal || ble $left, $right, label
 | slt $at, $right, $left<br>beq $at, $zero, label
 | if $left <= $right<br>goto label
 |}

@@ Line 23: / Line 23: @@
   ## In-line label declaration
   LoopFor: .word 8
 === Special Characters ===

@@ Line 85: / Line 85: @@
 == Directives ==
 === Segment Directives ===
@@ Line 121: / Line 135: @@
 | .align n || aligns the next variable on an address that is a multiple of 2^n
 |}
 == Preprocessor Directives ==

@@ Line 1: / Line 1: @@
 The following is a guide on how to write MIPS assembly using the GCC compiler.
 == Pseudo Instructions ==
@@ Line 59: / Line 86: @@
 == Directives ==
 [[Category: Mips]]