Skip to content

Commit

Permalink
passed regression test, mode test case needed
Browse files Browse the repository at this point in the history
  • Loading branch information
@MayneMei
MayneMei committed Nov 18, 2024
1 parent 589165c commit 089b47f
Show file tree
Hide file tree
Showing 2 changed files with 57 additions and 64 deletions.
119 changes: 56 additions & 63 deletions core/LSU.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ namespace olympia
replay_buffer_size_(p->replay_buffer_size),
replay_issue_delay_(p->replay_issue_delay),
store_buffer_("store_buffer", p->ldst_inst_queue_size, getClock()), // Add this line
store_buffer_size_(p->ldst_inst_queue_size),
store_buffer_size_(p->ldst_inst_queue_size),
ready_queue_(),
load_store_info_allocator_(sparta::notNull(OlympiaAllocators::getOlympiaAllocators(node))
->load_store_info_allocator),
Expand Down Expand Up @@ -460,31 +460,6 @@ namespace olympia
const MemoryAccessInfoPtr & mem_access_info_ptr =
load_store_info_ptr->getMemoryAccessInfoPtr();
const bool phy_addr_is_ready = mem_access_info_ptr->getPhyAddrStatus();
const InstPtr & inst_ptr = mem_access_info_ptr->getInstPtr();

// first check physical address and bypass conditions
const bool is_already_hit =
(mem_access_info_ptr->getCacheState() == MemoryAccessInfo::CacheState::HIT);
const bool is_unretired_store =
inst_ptr->isStoreInst() && (inst_ptr->getStatus() != Inst::Status::RETIRED);
const bool cache_bypass = is_already_hit || !phy_addr_is_ready || is_unretired_store;

if (cache_bypass)
{
if (is_already_hit)
{
ILOG("Cache Lookup is skipped (Cache already hit)");
}
else if (is_unretired_store)
{
ILOG("Cache Lookup is skipped (store instruction not oldest)");
}
else
{
sparta_assert(false, "Cache access is bypassed without a valid reason!");
}
return;
}

// If we did not have an MMU hit from previous stage, invalidate and bail
if (false == phy_addr_is_ready)
Expand All @@ -494,7 +469,7 @@ namespace olympia
{
updateInstReplayReady_(load_store_info_ptr);
}
// There might not be a wake up because the cache cannot handle nay more instruction
// There might not be a wake up because the cache cannot handle any more instruction
// Change to nack wakeup when implemented
if (!load_store_info_ptr->isInReadyQueue())
{
Expand All @@ -509,42 +484,45 @@ namespace olympia
return;
}

const InstPtr & inst_ptr = mem_access_info_ptr->getInstPtr();
ILOG(load_store_info_ptr << " " << mem_access_info_ptr);

// If have passed translation and the instruction is a store,
// then it's good to be retired (i.e. mark it completed).
// Stores typically do not cause a flush after a successful
// translation. We now wait for the Retire block to "retire"
// translation. We now wait for the Retire block to "retire"
// it, meaning it's good to go to the cache
if (inst_ptr->isStoreInst())
if (inst_ptr->isStoreInst() && (inst_ptr->getStatus() == Inst::Status::SCHEDULED))
{
if (inst_ptr->getStatus() == Inst::Status::SCHEDULED)
ILOG("Store marked as completed " << inst_ptr);
inst_ptr->setStatus(Inst::Status::COMPLETED);
load_store_info_ptr->setState(LoadStoreInstInfo::IssueState::READY);
ldst_pipeline_.invalidateStage(cache_lookup_stage_);
if (allow_speculative_load_exec_)
{
ILOG("Store marked as completed " << inst_ptr);
inst_ptr->setStatus(Inst::Status::COMPLETED);
load_store_info_ptr->setState(LoadStoreInstInfo::IssueState::READY);
ldst_pipeline_.invalidateStage(cache_lookup_stage_);
if (allow_speculative_load_exec_)
{
updateInstReplayReady_(load_store_info_ptr);
}
return;
updateInstReplayReady_(load_store_info_ptr);
}
return;
}
else // Loads handling

// Loads dont perform a cache lookup if there are older stores haven't issued in the load store queue
if (!inst_ptr->isStoreInst() && !allOlderStoresIssued_(inst_ptr)
&& allow_speculative_load_exec_)
{
// Check for speculative execution constraints
// since we use data forwarding, we only need to check whether all older store was issued
if (allow_speculative_load_exec_ && !allOlderStoresIssued_(inst_ptr))
ILOG("Dropping speculative load " << inst_ptr);
load_store_info_ptr->setState(LoadStoreInstInfo::IssueState::READY);
ldst_pipeline_.invalidateStage(cache_lookup_stage_);
if (allow_speculative_load_exec_)
{
ILOG("Dropping speculative load " << inst_ptr << " due to unissued older stores");
load_store_info_ptr->setState(LoadStoreInstInfo::IssueState::READY);
ldst_pipeline_.invalidateStage(cache_lookup_stage_);
updateInstReplayReady_(load_store_info_ptr);
return;
}
return;
}

//check if we can forward from store buffer first
uint64_t load_addr = inst_ptr->getTargetVAddr();
// Add store forwarding check here for loads
if (!inst_ptr->isStoreInst())
{
const uint64_t load_addr = inst_ptr->getTargetVAddr();
auto forwarding_store = findYoungestMatchingStore_(load_addr);

if (forwarding_store)
Expand All @@ -554,14 +532,32 @@ namespace olympia
mem_access_info_ptr->setCacheState(MemoryAccessInfo::CacheState::HIT);
return;
}
}

// No forwarding possible - need cache access
if (!mem_access_info_ptr->isCacheHit()) {
out_cache_lookup_req_.send(mem_access_info_ptr);
const bool is_already_hit =
(mem_access_info_ptr->getCacheState() == MemoryAccessInfo::CacheState::HIT);
const bool is_unretired_store =
inst_ptr->isStoreInst() && (inst_ptr->getStatus() != Inst::Status::RETIRED);
const bool cache_bypass = is_already_hit || !phy_addr_is_ready || is_unretired_store;

if (cache_bypass)
{
if (is_already_hit)
{
ILOG("Cache Lookup is skipped (Cache already hit)");
}
else if (is_unretired_store)
{
ILOG("Cache Lookup is skipped (store instruction not oldest)");
}
else
{
sparta_assert(false, "Cache access is bypassed without a valid reason!");
}
return;
}


out_cache_lookup_req_.send(mem_access_info_ptr);
}

void LSU::getAckFromCache_(const MemoryAccessInfoPtr & mem_access_info_ptr)
Expand Down Expand Up @@ -946,19 +942,15 @@ namespace olympia
ILOG("Store added to store buffer: " << inst_ptr);
}

LoadStoreInstInfoPtr LSU::findYoungestMatchingStore_(uint64_t addr)
LoadStoreInstInfoPtr LSU::findYoungestMatchingStore_(const uint64_t addr) const
{
LoadStoreInstInfoPtr matching_store = nullptr;

for (auto it = store_buffer_.begin(); it != store_buffer_.end(); ++it)
{
auto & store = *it;
if (store->getInstPtr()->getTargetVAddr() == addr)
{
matching_store = store;
}
}
return matching_store;
auto it = std::find_if(store_buffer_.rbegin(), store_buffer_.rend(),
[addr](const auto& store) {
return store->getInstPtr()->getTargetVAddr() == addr;
});
return (it != store_buffer_.rend()) ? *it : nullptr;
}

LoadStoreInstInfoPtr LSU::getOldestStore_() const
Expand Down Expand Up @@ -1450,6 +1442,7 @@ namespace olympia
auto inst_ptr = (*sb_iter)->getInstPtr();
if(criteria.includedInFlush(inst_ptr)) {
auto delete_iter = sb_iter++;
// store buffer didn't return an iterator
store_buffer_.erase(delete_iter);
ILOG("Flushed store from store buffer: " << inst_ptr);
} else {
Expand Down
2 changes: 1 addition & 1 deletion core/LSU.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -267,7 +267,7 @@ namespace olympia
void allocateInstToStoreBuffer_(const InstPtr & inst_ptr);

// Search store buffer in FIFO order for youngest matching store
LoadStoreInstInfoPtr findYoungestMatchingStore_(uint64_t addr);
LoadStoreInstInfoPtr findYoungestMatchingStore_(const uint64_t addr) const ;

// get oldest store
LoadStoreInstInfoPtr getOldestStore_() const;
Expand Down

0 comments on commit 089b47f

Please sign in to comment.