1814a85a05
Previously, the O3 CPU could stop in the middle of a microcode sequence. This patch makes sure that the pipeline stops when it has committed a normal instruction or exited from a microcode sequence. Additionally, it makes sure that the pipeline has no instructions in flight when it is drained, which should make draining more robust. Draining is controlled in the commit stage, which checks if the next PC after a committed instruction is in microcode. If this isn't the case, it requests a squash of all instructions after that the instruction that just committed and immediately signals a drain stall to the fetch stage. The CPU then continues to execute until the pipeline and all associated buffers are empty.
299 lines
8.8 KiB
C++
299 lines
8.8 KiB
C++
/*
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* Copyright (c) 2012 ARM Limited
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* All rights reserved
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Copyright (c) 2006 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Kevin Lim
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*/
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#ifndef __CPU_O3_DEP_GRAPH_HH__
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#define __CPU_O3_DEP_GRAPH_HH__
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#include "cpu/o3/comm.hh"
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/** Node in a linked list. */
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template <class DynInstPtr>
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class DependencyEntry
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{
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public:
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DependencyEntry()
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: inst(NULL), next(NULL)
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{ }
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DynInstPtr inst;
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//Might want to include data about what arch. register the
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//dependence is waiting on.
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DependencyEntry<DynInstPtr> *next;
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};
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/** Array of linked list that maintains the dependencies between
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* producing instructions and consuming instructions. Each linked
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* list represents a single physical register, having the future
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* producer of the register's value, and all consumers waiting on that
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* value on the list. The head node of each linked list represents
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* the producing instruction of that register. Instructions are put
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* on the list upon reaching the IQ, and are removed from the list
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* either when the producer completes, or the instruction is squashed.
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*/
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template <class DynInstPtr>
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class DependencyGraph
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{
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public:
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typedef DependencyEntry<DynInstPtr> DepEntry;
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/** Default construction. Must call resize() prior to use. */
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DependencyGraph()
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: numEntries(0), memAllocCounter(0), nodesTraversed(0), nodesRemoved(0)
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{ }
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~DependencyGraph();
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/** Resize the dependency graph to have num_entries registers. */
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void resize(int num_entries);
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/** Clears all of the linked lists. */
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void reset();
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/** Inserts an instruction to be dependent on the given index. */
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void insert(PhysRegIndex idx, DynInstPtr &new_inst);
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/** Sets the producing instruction of a given register. */
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void setInst(PhysRegIndex idx, DynInstPtr &new_inst)
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{ dependGraph[idx].inst = new_inst; }
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/** Clears the producing instruction. */
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void clearInst(PhysRegIndex idx)
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{ dependGraph[idx].inst = NULL; }
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/** Removes an instruction from a single linked list. */
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void remove(PhysRegIndex idx, DynInstPtr &inst_to_remove);
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/** Removes and returns the newest dependent of a specific register. */
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DynInstPtr pop(PhysRegIndex idx);
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/** Checks if the entire dependency graph is empty. */
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bool empty() const;
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/** Checks if there are any dependents on a specific register. */
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bool empty(PhysRegIndex idx) const { return !dependGraph[idx].next; }
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/** Debugging function to dump out the dependency graph.
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*/
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void dump();
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private:
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/** Array of linked lists. Each linked list is a list of all the
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* instructions that depend upon a given register. The actual
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* register's index is used to index into the graph; ie all
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* instructions in flight that are dependent upon r34 will be
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* in the linked list of dependGraph[34].
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*/
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DepEntry *dependGraph;
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/** Number of linked lists; identical to the number of registers. */
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int numEntries;
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// Debug variable, remove when done testing.
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unsigned memAllocCounter;
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public:
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// Debug variable, remove when done testing.
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uint64_t nodesTraversed;
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// Debug variable, remove when done testing.
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uint64_t nodesRemoved;
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};
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template <class DynInstPtr>
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DependencyGraph<DynInstPtr>::~DependencyGraph()
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{
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delete [] dependGraph;
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}
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template <class DynInstPtr>
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void
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DependencyGraph<DynInstPtr>::resize(int num_entries)
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{
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numEntries = num_entries;
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dependGraph = new DepEntry[numEntries];
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}
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template <class DynInstPtr>
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void
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DependencyGraph<DynInstPtr>::reset()
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{
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// Clear the dependency graph
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DepEntry *curr;
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DepEntry *prev;
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for (int i = 0; i < numEntries; ++i) {
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curr = dependGraph[i].next;
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while (curr) {
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memAllocCounter--;
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prev = curr;
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curr = prev->next;
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prev->inst = NULL;
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delete prev;
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}
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if (dependGraph[i].inst) {
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dependGraph[i].inst = NULL;
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}
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dependGraph[i].next = NULL;
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}
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}
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template <class DynInstPtr>
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void
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DependencyGraph<DynInstPtr>::insert(PhysRegIndex idx, DynInstPtr &new_inst)
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{
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//Add this new, dependent instruction at the head of the dependency
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//chain.
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// First create the entry that will be added to the head of the
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// dependency chain.
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DepEntry *new_entry = new DepEntry;
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new_entry->next = dependGraph[idx].next;
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new_entry->inst = new_inst;
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// Then actually add it to the chain.
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dependGraph[idx].next = new_entry;
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++memAllocCounter;
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}
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template <class DynInstPtr>
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void
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DependencyGraph<DynInstPtr>::remove(PhysRegIndex idx,
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DynInstPtr &inst_to_remove)
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{
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DepEntry *prev = &dependGraph[idx];
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DepEntry *curr = dependGraph[idx].next;
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// Make sure curr isn't NULL. Because this instruction is being
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// removed from a dependency list, it must have been placed there at
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// an earlier time. The dependency chain should not be empty,
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// unless the instruction dependent upon it is already ready.
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if (curr == NULL) {
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return;
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}
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nodesRemoved++;
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// Find the instruction to remove within the dependency linked list.
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while (curr->inst != inst_to_remove) {
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prev = curr;
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curr = curr->next;
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nodesTraversed++;
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assert(curr != NULL);
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}
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// Now remove this instruction from the list.
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prev->next = curr->next;
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--memAllocCounter;
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// Could push this off to the destructor of DependencyEntry
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curr->inst = NULL;
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delete curr;
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}
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template <class DynInstPtr>
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DynInstPtr
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DependencyGraph<DynInstPtr>::pop(PhysRegIndex idx)
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{
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DepEntry *node;
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node = dependGraph[idx].next;
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DynInstPtr inst = NULL;
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if (node) {
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inst = node->inst;
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dependGraph[idx].next = node->next;
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node->inst = NULL;
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memAllocCounter--;
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delete node;
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}
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return inst;
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}
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template <class DynInstPtr>
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bool
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DependencyGraph<DynInstPtr>::empty() const
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{
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for (int i = 0; i < numEntries; ++i) {
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if (!empty(i))
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return false;
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}
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return true;
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}
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template <class DynInstPtr>
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void
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DependencyGraph<DynInstPtr>::dump()
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{
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DepEntry *curr;
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for (int i = 0; i < numEntries; ++i)
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{
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curr = &dependGraph[i];
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if (curr->inst) {
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cprintf("dependGraph[%i]: producer: %s [sn:%lli] consumer: ",
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i, curr->inst->pcState(), curr->inst->seqNum);
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} else {
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cprintf("dependGraph[%i]: No producer. consumer: ", i);
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}
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while (curr->next != NULL) {
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curr = curr->next;
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cprintf("%s [sn:%lli] ",
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curr->inst->pcState(), curr->inst->seqNum);
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}
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cprintf("\n");
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}
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cprintf("memAllocCounter: %i\n", memAllocCounter);
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}
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#endif // __CPU_O3_DEP_GRAPH_HH__
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