2fb632dbda
branch prediction, and makes memory dependence work properly.
SConscript:
Added return address stack, tournament predictor.
cpu/base_cpu.cc:
Added debug break and print statements.
cpu/base_dyn_inst.cc:
cpu/base_dyn_inst.hh:
Comment out possibly unneeded variables.
cpu/beta_cpu/2bit_local_pred.cc:
2bit predictor no longer speculatively updates itself.
cpu/beta_cpu/alpha_dyn_inst.hh:
Comment formatting.
cpu/beta_cpu/alpha_full_cpu.hh:
Formatting
cpu/beta_cpu/alpha_full_cpu_builder.cc:
Added new parameters for branch predictors, and IQ parameters.
cpu/beta_cpu/alpha_full_cpu_impl.hh:
Register stats.
cpu/beta_cpu/alpha_params.hh:
Added parameters for IQ, branch predictors, and store sets.
cpu/beta_cpu/bpred_unit.cc:
Removed one class.
cpu/beta_cpu/bpred_unit.hh:
Add in RAS, stats. Changed branch predictor unit functionality
so that it holds a history of past branches so it can update, and also
hold a proper history of the RAS so it can be restored on branch
mispredicts.
cpu/beta_cpu/bpred_unit_impl.hh:
Added in stats, history of branches, RAS. Now bpred unit actually
modifies the instruction's predicted next PC.
cpu/beta_cpu/btb.cc:
Add in sanity checks.
cpu/beta_cpu/comm.hh:
Add in communication where needed, remove it where it's not.
cpu/beta_cpu/commit.hh:
cpu/beta_cpu/rename.hh:
cpu/beta_cpu/rename_impl.hh:
Add in stats.
cpu/beta_cpu/commit_impl.hh:
Stats, update what is sent back on branch mispredict.
cpu/beta_cpu/cpu_policy.hh:
Change the bpred unit being used.
cpu/beta_cpu/decode.hh:
cpu/beta_cpu/decode_impl.hh:
Stats.
cpu/beta_cpu/fetch.hh:
Stats, change squash so it can handle squashes from decode differently
than squashes from commit.
cpu/beta_cpu/fetch_impl.hh:
Add in stats. Change how a cache line is fetched. Update to work with
caches. Also have separate functions for different behavior if squash
is coming from decode vs commit.
cpu/beta_cpu/free_list.hh:
Remove some old comments.
cpu/beta_cpu/full_cpu.cc:
cpu/beta_cpu/full_cpu.hh:
Added function to remove instructions from back of instruction list
until a certain sequence number.
cpu/beta_cpu/iew.hh:
Stats, separate squashing behavior due to branches vs memory.
cpu/beta_cpu/iew_impl.hh:
Stats, separate squashing behavior for branches vs memory.
cpu/beta_cpu/inst_queue.cc:
Debug stuff
cpu/beta_cpu/inst_queue.hh:
Stats, change how mem dep unit works, debug stuff
cpu/beta_cpu/inst_queue_impl.hh:
Stats, change how mem dep unit works, debug stuff. Also add in
parameters that used to be hardcoded.
cpu/beta_cpu/mem_dep_unit.hh:
cpu/beta_cpu/mem_dep_unit_impl.hh:
Add in stats, change how memory dependence unit works. It now holds
the memory instructions that are waiting for their memory dependences
to resolve. It provides which instructions are ready directly to the
IQ.
cpu/beta_cpu/regfile.hh:
Fix up sanity checks.
cpu/beta_cpu/rename_map.cc:
Fix loop variable type.
cpu/beta_cpu/rob_impl.hh:
Remove intermediate DynInstPtr
cpu/beta_cpu/store_set.cc:
Add in debugging statements.
cpu/beta_cpu/store_set.hh:
Reorder function arguments to match the rest of the calls.
--HG--
extra : convert_revision : aabf9b1fecd1d743265dfc3b174d6159937c6f44
133 lines
3.4 KiB
C++
133 lines
3.4 KiB
C++
#include "base/trace.hh"
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#include "cpu/beta_cpu/2bit_local_pred.hh"
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DefaultBP::SatCounter::SatCounter(unsigned bits)
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: maxVal((1 << bits) - 1), counter(0)
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{
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}
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DefaultBP::SatCounter::SatCounter(unsigned bits, unsigned initial_val)
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: maxVal((1 << bits) - 1), counter(initial_val)
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{
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// Check to make sure initial value doesn't exceed the max counter value.
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if (initial_val > maxVal) {
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panic("BP: Initial counter value exceeds max size.");
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}
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}
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void
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DefaultBP::SatCounter::increment()
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{
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if(counter < maxVal) {
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++counter;
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}
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}
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void
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DefaultBP::SatCounter::decrement()
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{
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if(counter > 0) {
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--counter;
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}
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}
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DefaultBP::DefaultBP(unsigned _localPredictorSize,
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unsigned _localCtrBits,
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unsigned _instShiftAmt)
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: localPredictorSize(_localPredictorSize),
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localCtrBits(_localCtrBits),
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instShiftAmt(_instShiftAmt)
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{
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// Should do checks here to make sure sizes are correct (powers of 2).
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// Setup the index mask.
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indexMask = localPredictorSize - 1;
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DPRINTF(Fetch, "Branch predictor: index mask: %#x\n", indexMask);
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// Setup the array of counters for the local predictor.
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localCtrs = new SatCounter[localPredictorSize](localCtrBits);
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DPRINTF(Fetch, "Branch predictor: local predictor size: %i\n",
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localPredictorSize);
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DPRINTF(Fetch, "Branch predictor: local counter bits: %i\n", localCtrBits);
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DPRINTF(Fetch, "Branch predictor: instruction shift amount: %i\n",
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instShiftAmt);
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}
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inline
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bool
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DefaultBP::getPrediction(uint8_t &count)
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{
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// Get the MSB of the count
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return (count >> (localCtrBits - 1));
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}
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inline
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unsigned
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DefaultBP::getLocalIndex(Addr &branch_addr)
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{
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return (branch_addr >> instShiftAmt) & indexMask;
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}
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bool
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DefaultBP::lookup(Addr &branch_addr)
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{
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bool taken;
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uint8_t local_prediction;
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unsigned local_predictor_idx = getLocalIndex(branch_addr);
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DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n",
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local_predictor_idx);
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assert(local_predictor_idx < localPredictorSize);
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local_prediction = localCtrs[local_predictor_idx].read();
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DPRINTF(Fetch, "Branch predictor: prediction is %i.\n",
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(int)local_prediction);
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taken = getPrediction(local_prediction);
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#if 0
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// Speculative update.
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if (taken) {
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DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n");
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localCtrs[local_predictor_idx].increment();
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} else {
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DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n");
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localCtrs[local_predictor_idx].decrement();
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}
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#endif
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return taken;
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}
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void
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DefaultBP::update(Addr &branch_addr, bool taken)
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{
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unsigned local_predictor_idx;
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// Update the local predictor.
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local_predictor_idx = getLocalIndex(branch_addr);
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DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n",
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local_predictor_idx);
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assert(local_predictor_idx < localPredictorSize);
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// Increment or decrement twice to undo speculative update, then
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// properly update
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if (taken) {
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DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n");
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localCtrs[local_predictor_idx].increment();
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// localCtrs[local_predictor_idx].increment();
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} else {
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DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n");
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localCtrs[local_predictor_idx].decrement();
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// localCtrs[local_predictor_idx].decrement();
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}
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}
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