ReorderBuffer Class Reference

Simulated instruction re-order buffer. More...

#include <ReorderBuffer.h>

Public Member Functions
	ReorderBuffer (unsigned int numSlots, unsigned int numRetireablePerCycle, bool fake=false)
	Constructor: create and clear data.
	~ReorderBuffer ()
	Destructor: report stats.
bool	dispatch (Token *token, CycleCount atCycle)
	Dispatch an instruction to the reorder buffer.
bool	isFull ()
	True if buffer is currently full.
void	incFullStall ()
int	updateStatus (CycleCount currentCycle)
	Update: retire instructions in order, or cancel instructions.
InstructionCount	retiredCount ()

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Detailed Description

Simulated instruction re-order buffer.

This class is responsible for retiring instructions in order and for canceling all outstanding instructions in case of a branch mispredict. It was expected to be a singleton class, but we are currently instantiating a second object which acts as a "fake" retirement buffer for fake LEA instructions that are created for FP instructions that have a memop on them. This way the fake LEAs are not counted, but are retired and cleaned up properly (ooh, except for mispredicted branches! -- does it matter?)

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Constructor & Destructor Documentation

ReorderBuffer::ReorderBuffer	(	unsigned int	numSlots,
		unsigned int	numRetireablePerCycle,
		bool	fake = false
	)

Constructor: create and clear data.

Parameters:

	numSlots	is the total number of instruction slots in the buffer
	numRetireablePerCycle	is the maximum # of instructions retireable per cycle

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Member Function Documentation

bool ReorderBuffer::dispatch	(	Token *	token,
		CycleCount	atCycle
	)

Dispatch an instruction to the reorder buffer.

This assumes that isFull() was already checked; it will silently fail to add the instruction if the buffer is full.

Parameters:

	token	is the instruction to add to the buffer
	atCycle	is the cycle count at which it is being added

int ReorderBuffer::updateStatus

(

CycleCount

currentCycle

)

Update: retire instructions in order, or cancel instructions.

This retires instructions in order, only up to numPerCycle per cycle, and if it hits a mispredicted branch instruction, it cancels all instructions behind it. The counter 'retireSlot' is an index that is always pointing to the next instruction in-order that should retire.

Parameters:

currentCycle

is the current cycle count

References Token::cancelInstruction(), and Token::retireInstruction().

Referenced by McOpteron::simCycle().

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The documentation for this class was generated from the following files:

• sst/elements/mcopteron/ReorderBuffer.h
• sst/elements/mcopteron/ReorderBuffer.cc