mars.mips.instructions
Class ExtendedInstruction

java.lang.Object
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  +--mars.mips.instructions.Instruction
        |
        +--mars.mips.instructions.ExtendedInstruction

public class ExtendedInstruction

extends Instruction

ExtendedInstruction represents a MIPS extended (a.k.a pseudo) instruction. This assembly language instruction does not have a corresponding machine instruction. Instead it is translated by the extended assembler into one or more basic instructions (operations that have a corresponding machine instruction). The TranslationCode object is responsible for performing the translation.

Field Summary

Fields inherited from class mars.mips.instructions.Instruction

description, exampleFormat, INSTRUCTION_LENGTH, INSTRUCTION_LENGTH_BITS, mnemonic, operandMask, tokenList

Constructor Summary

ExtendedInstruction(java.lang.String example, java.lang.String translation)
Constructor for ExtendedInstruction, where no instruction description is provided.

ExtendedInstruction(java.lang.String example, java.lang.String translation, java.lang.String description)
Constructor for ExtendedInstruction.

Method Summary

java.util.ArrayList	getBasicIntructionTemplateList() Get ArrayList of Strings that represent list of templates for basic instructions generated by this extended instruction.
int	getInstructionLength() Get length in bytes that this extended instruction requires in its binary form.
static java.lang.String	makeTemplateSubstitutions(MIPSprogram program, java.lang.String template, TokenList theTokenList) Given a basic instruction template and the list of tokens from an extended instruction statement, substitute operands from the token list appropriately into the template to generate the basic statement.

Methods inherited from class mars.mips.instructions.Instruction

createExampleTokenList, extractOperator, getDescription, getExampleFormat, getName, getTokenList

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExtendedInstruction

public ExtendedInstruction(java.lang.String example,
                           java.lang.String translation,
                           java.lang.String description)

Constructor for ExtendedInstruction.

Parameters:

example - A String containing example use of the MIPS extended instruction.

translation - Specifications for translating this instruction into a sequence of one or more MIPS basic instructions.

description - a helpful description to be included on help requests

ExtendedInstruction

public ExtendedInstruction(java.lang.String example,
                           java.lang.String translation)

Constructor for ExtendedInstruction, where no instruction description is provided.

Parameters:

example - A String containing example use of the MIPS extended instruction.

translation - Specifications for translating this instruction into a sequence of one or more MIPS basic instructions.

Method Detail

getInstructionLength

public int getInstructionLength()

Get length in bytes that this extended instruction requires in its binary form. The answer depends on how many basic instructions it expands to. Each requires 4 bytes.

Overrides:

getInstructionLength in class Instruction

Returns:

int length in bytes of corresponding binary instruction(s).

getBasicIntructionTemplateList

public java.util.ArrayList getBasicIntructionTemplateList()

Get ArrayList of Strings that represent list of templates for basic instructions generated by this extended instruction.

Returns:

ArrayList of Strings.

makeTemplateSubstitutions

public static java.lang.String makeTemplateSubstitutions(MIPSprogram program,
                                                         java.lang.String template,
                                                         TokenList theTokenList)

Given a basic instruction template and the list of tokens from an extended instruction statement, substitute operands from the token list appropriately into the template to generate the basic statement. Assumes the extended instruction statement has been translated from source form to basic assembly form (e.g. register mnemonics translated to corresponding register numbers). Operand format of source statement is already verified correct. Assume the template has correct number and positions of operands. Template is String with special markers. In the list below, n represents token position (1,2,3,etc) in source statement (operator is token 0, parentheses count but commas don't):

• RGn means substitute register found in n'th token of source statement
• NRn means substitute next higher register than the one in n'th token of source code
• OPn means substitute n'th token of source code as is
• LLn means substitute low order 16 bits from label address in source token n.
• LLnPm (m=1,2,3,4) means substitute low order 16 bits from label address in source token n, after adding m.
• LHn means substitute high order 16 bits from label address in source token n. Must add 1 if address bit 15 is 1.
• LHnPm (m=1,2,3,4) means substitute high order 16 bits from label address in source token n, after adding m. Must then add 1 if bit 15 is 1.
• VLn means substitute low order 16 bits from 32 bit value in source token n.
• VLnPm (m=1,2,3,4) means substitute low order 16 bits from 32 bit value in source token n, after adding m to value.
• VHn means substitute high order 16 bits from 32 bit value in source token n. Must add 1 if value's bit 15 is 1.
• VHnPm (m=1,2,3,4) means substitute high order 16 bits from 32 bit value in source token n, after adding m. Must then add 1 if bit 15 is 1.
• LLP is similar to LLn, but is needed for "label+100000" address offset. Immediate is added before taking low order 16.
• LLPPm (m=1,2,3,4) is similar to LLP except m is added along with mmediate before taking low order 16. LHPA is similar to LHn, but is needed for "label+100000" address offset. Immediate is added before taking high order 16.
• LHPN is similar to LHPA, used only by "la" instruction. Address resolved by "ori" so do not add 1 if bit 15 is 1.
• LHPAPm (m=1,2,3,4) is similar to LHPA except value m is added along with immediate before taking high order 16.
• LHL means substitute high order 16 bits from label address in token 2 of "la" (load address) source statement.
• VHLn means substitute high order 16 bits from 32 bit value in token n.
• LAB means substitute textual label from last token of source statement. Used for various branches.
• S32 means substitute the result of subtracting the constant value in last token from 32. Used by "ror", "rol".

Parameters:

template - a String containing template for basic statement.

Returns:

String representing basic assembler statement.