In this commit, we add License for XiangShan project. 

* LoadQueue: send stFtqIdx via rollback request

* It will make it possible for setore set to update its SSIT

* StoreSet: setup store set update req

* StoreSet: add store set identifier table (SSIT)

* StoreSet: add last fetched store table (LFST)

* StoreSet: put SSIT into decode stage

* StoreSet: put LFST into dispatch1

* Future work: optimize timing

* RS: store rs now supports delayed issue

* StoreSet: add perf counter

* StoreSet: fix SSIT update logic

* StoreSet: delay LFST update input for 1 cycle

* StoreSet: fix LFST update logic

* StoreSet: fix LFST raddr width

* StoreSet: do not force store in ss issue in order

Classic store set requires store in the same store set issue in seq.
However, in current micro-architecture, such restrict will lead to
severe perf lost. We choose to disable it until we find another way
to fix it.

* StoreSet: support ooo store in the same store set

* StoreSet: fix store set merge logic

* StoreSet: check earlier store when read LFST

* If store-load pair is in the same dispatch bundle, loadWaitBit should
also be set for load

* StoreSet: increase default SSIT flush period

* StoreSet: fix LFST read logic

* Fix commit c0e541d1

* StoreSet: add StoreSetEnable parameter

* RSFeedback: add source type

* StoreQueue: split store addr and store data

* StoreQueue: update ls forward logic

* Now it supports splited addr and data

* Chore: force assign name for load/store unit

* RS: add rs'support for store a-d split

* StoreQueue: fix stlf logic

* StoreQueue: fix addr wb sq update logic

* AtomicsUnit: support splited a/d

* Parameters: disable store set by default

* WaitTable: wait table will not cause store delay

* WaitTable: recover default reset period to 2^17

* Fix dev-stad merge conflict

* StoreSet: enable storeset

* RS: disable store rs delay logic

CI perf shows that current delay logic will cause perf loss. Disable
unnecessary delay logic will help.

To be more specific, `io.readyVec` caused the problem. It will be
updated in future commits.

* RS: opt select logic with load delay (ldWait)

* StoreSet: disable 2-bit lwt
Co-authored-by: NZhangZifei <zhangzifei20z@ict.ac.cn>

This commit replaces src1, src2, src3 in Bundle ExuInput with Vec(3, UInt).
Should be easier for RS.

This commit fixes the bug when redirect.valid and the last valid instruction is in the last slot.
Previously the tailPtr becomes size.U when there're no instructions before headPtr. It works fine
when DispatchQueueSize is power2.

This commit uses Vec for lsrc, psrc, srcState and srcType in MicroOp bundle.
This makes uop easier to access.

In this commit, we add performance counters for dispatch and issue stages
to track the number of instructions dispatched and issued. Active regfile
read ports are counted as ready instruction source registers.

* difftest: use DPI-C to refactor difftest

In this commit, difftest is refactored with DPI-C calls.
There're a few reasons:
(1) From Verilator's manual, DPI-C calls should be more efficient than accessing from dut_ptr.
(2) DPI-C is cross-platform (Verilator, VCS, ...)
(3) difftest APIs are splited from emu.cpp to possibly support more backend platforms
(NEMU, Spike, ...)

The performance at this commit is quite slower than the original emu.
Performance issues will be fixed later.

* [WIP] SimTop: try to use 'XSTop' as soc

* CircularQueuePtr: ues F-bounded polymorphis instead implict helper

* Refactor parameters & Clean up code

* difftest: support basic difftest

* Support diffetst in new sim top

* Difftest; convert recode fmt to ieee754 when comparing fp regs

* Difftest: pass sign-ext pc to dpic functions && fix exception pc

* Debug: add int/exc inst wb to debug queue

* Difftest: pass sign-ext pc to dpic functions && fix exception pc

* Difftest: fix naive commit num limit
Co-authored-by: NYinan Xu <xuyinan1997@gmail.com>
Co-authored-by: NWilliam Wang <zeweiwang@outlook.com>

* csr: remove unused input perfcnt io

* perfcnt: add some in-core hardware performance counters

* perfcnt: optimize timing for hardware performance counters

XSPerfAccumulate: sum up performance values.
XSPerfHistogram: count the occurrence of performance values, split them
into bins, so that we can estimate their distribution.
XSPerfMax: get max of performance values.

* perf: set acc arg of XSPerf as false by default

* perf: add write-port competition counter for intBlock & floatBlock

* perf: remove prefix of perf signal

* perf: add perf-cnt for interface between frontend & backend

* perf: modify perf-cnt for prefetchers

* Ftq: bypass 'commit state' to fix dequeue bug

* perf: uptimize perf-cnt in ctrlblock & ftq

* perf: fix compilation problem in ftq

* perf: remove duplicate perf-cnt

* perf: calcu extra walk cycle exceeding frontend flush bubble

* Revert "perf: calcu extra walk cycle exceeding frontend flush bubble"

This reverts commit 2c30e9896b6af93a34e2d8d78055d810ebd0ac70.

* perf: add perf-cnt for ifu

* perf: add perf-cnt for rs

* RS: optimize numExist signal

* RS: fix some typo

* perf: add QueuePerf util to monitor usage info of queues

* perf: remove some duprecate perfcnt

In this commit, we add support for a simpler version of move elimination.

The original instruction sequences are:
move r1, r0
add r2, r1, r3

The optimized sequnces are:
move pr1, pr0
add pr2, pr0, pr3 # instead of add pr2, pr1, pr3

In this way, add can be issued once r0 is ready and move seems to be eliminated.

* perf: set acc arg of XSPerf as false by default

* perf: add write-port competition counter for intBlock & floatBlock

* perf: remove prefix of perf signal

* perf: add perf-cnt for interface between frontend & backend

* perf: modify perf-cnt for prefetchers

dispatch,MemBlock: optimize fuType usages

ReservationStation: change width of srcRegValue into (XLEN+1)