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Cacheway Exclude FlushStage=1 when SetValidWay=1

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We determined that this case is not hit even for i$, so this
case is also excluded separately for i$. It could be a better
idea to remove the ~FlushStage check completely (if we're sure).

My reasoning for this one is written as a comment in the exclusion
script: since a pipeline stall is asserted by the cache in the fetch
stage (which happens before going into the WRITE_LINE state and
asserting SetValidWay), there seems to be no way to trigger
a FlushStage (FlushW for D$) while the stallM is active.
This commit is contained in:
Alec Vercruysse 2023-04-25 20:30:46 -07:00
parent 857956ac1e
commit 5612f30029
2 changed files with 6 additions and 2 deletions
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6
sim/coverage-exclusions-rv64gc.do
View File

@ -77,7 +77,7 @@ for {set i 0} {$i < $numcacheways} {incr i} {
coverage exclude -scope /dut/core/ifu/bus/icache/icache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: icache SetDirtyWay"] -item e 1
coverage exclude -scope /dut/core/ifu/bus/icache/icache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: icache SelectedWiteWordEn"] -item e 1 -fecexprrow 4 6
# below: flushD can't go high during an icache write b/c of pipeline stall
coverage exclude -scope /dut/core/ifu/bus/icache/icache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: icache SetValidEN"] -item e 1 -fecexprrow 4
coverage exclude -scope /dut/core/ifu/bus/icache/icache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: cache SetValidEN"] -item e 1 -fecexprrow 4
}
## D$ Exclusions.
@ -89,6 +89,10 @@ coverage exclude -scope /dut/core/lsu/bus/dcache/dcache/cachefsm -linerange [Get
set numcacheways 4
for {set i 0} {$i < $numcacheways} {incr i} {
coverage exclude -scope /dut/core/lsu/bus/dcache/dcache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: dcache invalidateway"] -item bes 1 -fecexprrow 4
# FlushStage=1 will never happen when SetValidWay=1 since a pipeline stall is asserted by the cache in the fetch stage, which happens before
# going into the WRITE_LINE state (and asserting SetValidWay). No TrapM can fire and since StallW is high, a stallM caused by WFIStallM would not cause a flushW.
coverage exclude -scope /dut/core/lsu/bus/dcache/dcache/CacheWays[$i] -linerange [GetLineNum ../src/cache/cacheway.sv "exclusion-tag: cache SetValidEN"] -item e 1 -fecexprrow 4
}
# D$ writeback, flush, write_line, or flush_writeback states can't be cancelled by a flush
coverage exclude -scope /dut/core/lsu/bus/dcache/dcache/cachefsm -ftrans CurrState STATE_WRITEBACK->STATE_READY STATE_FLUSH->STATE_READY STATE_WRITE_LINE->STATE_READY STATE_FLUSH_WRITEBACK->STATE_READY

2
src/cache/cacheway.sv vendored
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@ -102,7 +102,7 @@ module cacheway #(parameter NUMLINES=512, LINELEN = 256, TAGLEN = 26,
assign SetDirtyWay = SetDirty & SelData; // exclusion-tag: icache SetDirtyWay
assign ClearDirtyWay = ClearDirty & SelData;
assign SelectedWriteWordEn = (SetValidWay | SetDirtyWay) & ~FlushStage; // exclusion-tag: icache SelectedWiteWordEn
assign SetValidEN = SetValidWay & ~FlushStage; // exclusion-tag: icache SetValidEN
assign SetValidEN = SetValidWay & ~FlushStage; // exclusion-tag: cache SetValidEN
// If writing the whole line set all write enables to 1, else only set the correct word.
assign FinalByteMask = SetValidWay ? '1 : LineByteMask; // OR