That effectively increased the miss latency by 5 cycles when there was
a store hit followed by a load miss. Since pending stores are drained
when releaseInFlight, the check I removed was redundant.
* dcache: put a flow Q to absorb back-pressure without restarting pipeline
When used with a RationalCrossing, pipelined MMIO does not come out cleanly.
The first beat works, but if the second beat gets stalled, the pipeline is
restarted. This is a quick hacky test to absorb the beats. Perhaps a better
fix can be made to achieve the same effect.
* dcache: provision as few stages as possible
This one's a little invasive. To flush a specific entry from the TLB, you
need to reuse its CAM port. Since the TLB lookup can be on the critical
path, we wish to avoid muxing in another address.
This is simple on the data side, where the datapath already carries rs1 to
the TLB (it's the same path as the AMO address calculation). It's trickier
for the I$, where the TLB lookup address comes from the fetch stage PC.
The trick is to temporarily redirect the PC to rs1, then redirect the PC
again to the instruction after SFENCE.VMA.
Fundamental new features:
* Added tile package: This package is intended to hold components re-usable across different types of tile. Will be the future location of TL2-RoCC accelerators and new diplomatic versions of intra-tile interfaces.
* Adopted [ModuleName]Params convention: Code base was very inconsistent about what to name case classes that provide parameters to modules. Settled on calling them [ModuleName]Params to distinguish them from config.Parameters and config.Config. So far applied mostly only to case classes defined within rocket and tile.
* Defined RocketTileParams: A nested case class containing case classes for all the components of a tile (L1 caches and core). Allows all such parameters to vary per-tile.
* Defined RocketCoreParams: All the parameters that can be varied per-core.
* Defined L1CacheParams: A trait defining the parameters common to L1 caches, made concrete in different derived case classes.
* Defined RocketTilesKey: A sequence of RocketTileParams, one for every tile to be created.
* Provided HeterogeneousDualCoreConfig: An example of making a heterogeneous chip with two cores, one big and one little.
* Changes to legacy code: ReplacementPolicy moved to package util. L1Metadata moved to package tile. Legacy L2 cache agent removed because it can no longer share the metadata array implementation with the L1. Legacy GroundTests on life support.
Additional changes that got rolled in along the way:
* rocket: Fix critical path through BTB for I$ index bits > pgIdxBits
* coreplex: tiles connected via :=*
* groundtest: updated to use TileParams
* tilelink: cache cork requirements are relaxed to allow more cacheless masters
* [rocket] Refactor Tile into cake pattern with traits
* [rocket] cacheDataBits &etc in HasCoreParameters
* [rocket] pass TLEdgeOut implicitly rather than relying on val edge in HasCoreParameters
* [rocket] frontend and icache now diplomatic
* [rocket] file name capitalization
* [rocket] re-add hook for inserting externally-defined Cores
* [rocket] add FPUCoreIO
* [groundtest] move TL1 Config instances to where they are used
* [unittest] remove legacy unit tests
* [groundtest] remove legacy device tests
* [rocket] file capitalization
* [rocket] cacheDataBits &etc in HasCoreParameters
* [rocket] pass TLEdgeOut implicitly rather than relying on val edge in HasCoreParameters
* [rocket] frontend and icache now diplomatic
