Load-Store Queue LSQ

Sub-module List

Sub-module	Description
VirtualLoadQueue	TODO
LoadQueueRAR	TODO
LoadQueueRAW	TODO
LoadQueueReplay	DONE
LoadQueueUncache	TODO
LoadExceptionBuffer	TODO
StoreQueue	DONE

Function Description

LSQ includes two parts, LoadQueue and StoreQueue, and has a wrapper layer to facilitate port connections. The primary function of the Lsqwrapper is just wiring.

LoadQueue
- LoadQueueRAR: RAR violation check queue
- LoadQueueRAW: RAW violation check queue
- LoadQueueUncache: MMIO/Noncacheable load instruction processing queue
- LoadQueueReplay: Load instruction scheduling and re-dispatch queue
- LoadExceptionBuffer: Load instruction exception handling queue
- VirtualLoadQueue: Load instruction order maintenance queue
StoreQueue

Feature 1: Update LqPtr for Load Instructions and SqPtr for Store Instructions

Due to timing effects, the allocation of LqPtr and SqPtr is split into two parts, as shown in the figure

LSQ Allocation
- Dispatch stage
  - Count the number of LoadFlow or StoreFlow for each instruction, and calculate LqPtr or SqPtr in a cumulative manner
- LSQ enqueue stage
  - Calculate the accurate LqPtr or SqPtr in a cumulative manner based on the enqPtr maintained by LoadQueue or StoreQueue
- LsqEnqCtrl update logic
  - If a pipeline flush occurs, update based on the number of flushed Load or Store instructions and the number of committed instructions
  - If no pipeline flush occurs, but there is an allocation request, update based on the number of enqueued and committed instructions
  - Otherwise, update based on the number of committed instructions

Overall Block Diagram

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Interface Timing

Interface Timing Example for Load and Store Instruction Enqueue