Added a commitlog post-processor for Rocket
- Useful for taking Rocket's out-of-order writebacks and generating an
in-order commit log.
- Resulting commit log can be diffed against Spike's commit log.
This commit is contained in:
Christopher Celio
256
csrc/comlog.cc
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256
csrc/comlog.cc
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//*****************************************************
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// Christopher Celio
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// 2015 Feb 2
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//
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// Utility for taking a raw commit log from a processor and post-processing it
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// into a diff-able format against the spike ISA simulator's commit log.
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//
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// INPUT : a raw commit log via std::cin
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// OUTPUT: a cleaned up commit log via std::cout
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//
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// PROBLEM: some writebacks can occur after the commit point in a processor.
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// These partial entries will be marked as appropriate, and the writebacks will
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// be written to the log as soon as they occur (possibly out-of-order). This
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// program will put the writebacks in their proper place.
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//
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// FUNFACT: with processors that use renaming to break WAW hazards, it is
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// possible for writes to the same ISA register to also occur OoO. Thus, the
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// raw commit log must tell give us the physical destination (pdst)
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// indentifiers for matching write-backs to the appropriate partial commit
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// entry.
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/*
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// Typical (raw) commit log...
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-----------------------------------------------------------
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0 0x0000000000002ccc (0x00973423)
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0 0x0000000000002cd0 (0x00a73023)
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0 0x0000000000002cd4 (0x05070113) x2 0x0000000000025180
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0 0x0000000000002cd8 (0xd8070713) x14 0x0000000000024eb0
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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0 0x000000000000208c (0x00b6b72f) x14 p 1 0xXXXXXXXXXXXXXXXX
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0 0x0000000000002090 (0x80000eb7) x29 0xffffffff80000000
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x14 p 1 0xffffffff80000000
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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// Note: the first number is the current privileged mode of the committed
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// instruction.
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//
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-----------------------------------------------------------
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The "x14 p 1 0xXXXXXXXXXXXXXXXX" segment needs to be replaced with the later
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"x14 0xffffffff80000000" segment.
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The physical tags must be used for matching writebacks to partial commits,
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as it is possible with renaming to break the write-after-write hazard and
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have out-of-order writebacks to the same ISA/logical register! However, the
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physical tag needs to be deleted in the final output, as the ISA simulator
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does not know or care about renamed registers.
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// Final (cleaned up) commit log
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-----------------------------------------------------------
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0 0x0000000000002ccc (0x00973423)
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0 0x0000000000002cd0 (0x00a73023)
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0 0x0000000000002cd4 (0x05070113) x2 0x0000000000025180
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0 0x0000000000002cd8 (0xd8070713) x14 0x0000000000024eb0
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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0 0x000000000000208c (0x00b6b72f) x14 0xffffffff80000000
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0 0x0000000000002090 (0x80000eb7) x29 0xffffffff80000000
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0 0x0000000000002cdc (0xea5ff0ef) x1 0x0000000000002ce0
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-----------------------------------------------------------
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*/
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#include <stdio.h>
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#include <iostream>
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#include <array>
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#include <queue>
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#include <assert.h>
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// data-structures
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typedef struct RobEntry
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{
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bool ready; // is entry ready to be committed?
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int pdst; // the wb physical dest. register
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std::string str; // the commit string to print out
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} RobEntry;
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std::deque <RobEntry> rob;
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// partial entries are also stored in a side buffer, for faster CAM searching.
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// When a write-back occurs, it needs to search the ROB for the matching pdst
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// tag. But since that CAM search is generally painful in software (and the ROB
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// will be mostly full of ready-to-commit entries) let's only do the CAM search
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// on a smaller queue of still-busy entries. We will delete partial entries
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// once the write-back has returned. TODO... since there will only be one "pdst"
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// outstanding at a time, we could use a map for fast lookup instead of a
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// linear search.
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typedef struct PartialEntry
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{
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RobEntry* rob_entry; // point to the ROB entry we correspond to
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int pdst;
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} PartialEntry;
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std::deque <PartialEntry> pdst_cam;
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// functions
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void push (std::string& line);
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void commit ();
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void writeback (std::string& line);
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bool is_instruction (std::string& line);
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bool is_partial_commit (std::string& line);
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int get_ldst (std::string& line);
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int get_pdst (std::string& line);
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// add instruction to the ROB
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// mark as "not ready" if writeback data not ready
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void push (std::string& line)
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{
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bool is_partial = is_partial_commit(line);
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RobEntry rob_entry;
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rob_entry.str = line;
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rob_entry.ready = !(is_partial);
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rob_entry.pdst = is_partial ? get_pdst(line) : 0;
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rob.push_back(rob_entry);
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if (is_partial)
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{
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PartialEntry new_entry = (PartialEntry)
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{ .rob_entry = &(rob.back()),
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.pdst = rob_entry.pdst
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};
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pdst_cam.push_back(new_entry);
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}
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}
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void commit ()
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{
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while (!rob.empty() && rob.front().ready)
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{
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std::cout << rob.front().str << std::endl;
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rob.pop_front();
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}
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}
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int get_ldst (std::string& line)
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{
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assert (line.length() > 46);
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int idx = line.find_first_of('x');
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int dst = atoi(line.substr(idx+1,2).c_str());
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return dst;
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}
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int get_pdst (std::string& line)
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{
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assert (line.length() > 46);
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int idx = line.find_first_of('p');
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int dst = atoi(line.substr(idx+1,2).c_str());
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return dst;
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}
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bool is_partial_commit (std::string& line)
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{
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if (line.length() > 46 && (line.at(34) == 'x' || line.at(34) == 'f') && line.at(46) == 'X')
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return true;
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else
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return false;
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}
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bool is_instruction (std::string& line)
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{
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return !(line.at(0) == 'x' || line.at(0) == 'f');
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}
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// find instruction in ROB and substitute in the writeback data
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// and mark it as ready for commit
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void writeback (std::string& line)
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{
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assert (line.at(0) == 'x' || line.at(0) == 'f');
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int ldst = atoi(line.substr(1,2).c_str());
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int idx = line.find_first_of('p');
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assert (idx != std::string::npos);
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int pdst = atoi(line.substr(idx+1,2).c_str());
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// search the partial queue for writeback, then modify the ROB entry, mark as ready
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RobEntry* rob_entry;
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bool found_entry = false;
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// order of search doesn't matter; there should be a unique
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// pdst identifier (to deal with WAW hazards).
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// we then delete the entry once we've matched against it so
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// future matches will be fast.
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for (auto it = pdst_cam.begin(); it != pdst_cam.end();/*NOTE: no incrementation here*/ )
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{
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if (pdst == it->pdst)
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{
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// verify there is only ever one match!
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assert (!found_entry);
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rob_entry = it->rob_entry;
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it = pdst_cam.erase(it);
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found_entry = true;
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}
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else
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{
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++it;
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}
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}
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// update ROB
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assert (found_entry);
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assert (rob_entry->str.length() > 32);
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std::string* rob_str = &(rob_entry->str);
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rob_entry->ready = true;
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idx = line.find("0x");
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std::string wbdata = line.substr(idx+2,16);
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idx = rob_str->find("0x",32); // actually want to find the 3rd occurrence
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int p_idx = rob_str->find_first_of('p');
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rob_str->replace(idx+2,16,wbdata);
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rob_str->erase(p_idx, (idx-p_idx));
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}
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int main (int argc, char** argv)
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{
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std::string line;
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// check for errno
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while (getline(std::cin, line))
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{
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if (is_instruction(line))
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{
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push(line);
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}
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else
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{
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writeback(line);
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}
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// check if head of the rob is ready, commit
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// instructions until either empty or not ready
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commit();
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}
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if (std::cin.bad())
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{
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// IO error
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std::cout << "\nIO ERROR: cin.bad()\n\n";
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return 1;
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}
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return 0;
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}
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