diff options
Diffstat (limited to 'bolt/unittests/Profile/PerfSpeEvents.cpp')
| -rw-r--r-- | bolt/unittests/Profile/PerfSpeEvents.cpp | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/bolt/unittests/Profile/PerfSpeEvents.cpp b/bolt/unittests/Profile/PerfSpeEvents.cpp index 8d023cd..4f060cd 100644 --- a/bolt/unittests/Profile/PerfSpeEvents.cpp +++ b/bolt/unittests/Profile/PerfSpeEvents.cpp @@ -161,4 +161,92 @@ TEST_F(PerfSpeEventsTestHelper, SpeBranchesWithBrstack) { parseAndCheckBrstackEvents(1234, ExpectedSamples); } +TEST_F(PerfSpeEventsTestHelper, SpeBranchesWithBrstackAndPbt) { + // Check perf input with SPE branch events as brstack format by + // combining with the previous branch target address (named as PBT). + // Example collection command: + // ``` + // perf record -e 'arm_spe_0/branch_filter=1/u' -- BINARY + // ``` + // How Bolt extracts the branch events: + // ``` + // perf script -F pid,brstack --itrace=bl + // ``` + + opts::ArmSPE = true; + opts::ReadPerfEvents = + // "<PID> <SRC>/<DEST>/PN/-/-/10/COND/- <NULL>/<PBT>/-/-/-/0//-\n" + " 4567 0xa002/0xa003/PN/-/-/10/COND/- 0x0/0xa001/-/-/-/0//-\n" + " 4567 0xb002/0xb003/P/-/-/4/RET/- 0x0/0xb001/-/-/-/0//-\n" + " 4567 0xc456/0xc789/P/-/-/13/-/- 0x0/0xc123/-/-/-/0//-\n" + " 4567 0xd456/0xd789/M/-/-/7/RET/- 0x0/0xd123/-/-/-/0//-\n" + " 4567 0xe005/0xe009/P/-/-/14/RET/- 0x0/0xe001/-/-/-/0//-\n" + " 4567 0xd456/0xd789/M/-/-/7/RET/- 0x0/0xd123/-/-/-/0//-\n" + " 4567 0xf002/0xf003/MN/-/-/8/COND/- 0x0/0xf001/-/-/-/0//-\n" + " 4567 0xc456/0xc789/P/-/-/13/-/- 0x0/0xc123/-/-/-/0//-\n"; + + // ExpectedSamples contains the aggregated information about + // a branch {{From, To, TraceTo}, {TakenCount, MispredCount}}. + // Where + // - From: is the source address of the sampled branch operation. + // - To: is the target address of the sampled branch operation. + // - TraceTo could be either + // - A 'Type = Trace::BR_ONLY', which means the trace only contains branch + // data. + // - Or an address, when the trace contains information about the previous + // branch. + // + // When FEAT_SPE_PBT is present, Arm SPE emits two records per sample: + // - the current branch (Spe.From/Spe.To), and + // - the previous taken branch target (PBT) (PBT.From, PBT.To). + // + // Together they behave like a depth-1 branch stack where: + // - the PBT entry is always taken + // - the current branch entry may represent a taken branch or a fall-through + // - the destination (Spe.To) is the architecturally executed target + // + // There can be fall-throughs to be inferred between the PBT entry and + // the current branch (Spe.From), but there cannot be between current + // branch's (Spe.From/Spe.To). + // + // PBT records only the target address (PBT.To), meaning we have no + // information as the branch source (PBT.From=0x0), branch type, and the + // prediction bit. + // + // Consider the trace pair: + // {{Spe.From, Spe.To, Type}, {TK, MP}}, + // {{PBT.From, PBT.To, TraceTo}, {TK, MP}} + // {{0xd456, 0xd789, Trace::BR_ONLY}, {2, 2}}, {{0x0, 0xd123, 0xd456}, {2, 0}} + // + // The first entry is the Spe record, which represents a trace from 0xd456 + // (Spe.From) to 0xd789 (Spe.To). Type = Trace::BR_ONLY, as Bolt processes the + // current branch event first. At this point we have no information about the + // previous trace (PBT). This entry has a TakenCount = 2, as we have two + // samples for (0xd456, 0xd789) in our input. It also has MispredsCount = 2, + // as 'M' misprediction flag appears in both cases. + // + // The second entry is the PBT record. TakenCount = 2 because the + // (PBT.From = 0x0, PBT.To = 0xd123) branch target appears twice in the input, + // and MispredsCount = 0 because prediction data is absent. There is no branch + // source information, so the PBT.From field is zero (0x0). TraceTo = 0xd456 + // connect the flow from the previous taken branch at 0xd123 (PBT.To) to the + // current source branch at 0xd456 (Spe.From), which then continues to 0xd789 + // (Spe.To). + std::vector<std::pair<Trace, TakenBranchInfo>> ExpectedSamples = { + {{0xa002, 0xa003, Trace::BR_ONLY}, {1, 0}}, + {{0x0, 0xa001, 0xa002}, {1, 0}}, + {{0xb002, 0xb003, Trace::BR_ONLY}, {1, 0}}, + {{0x0, 0xb001, 0xb002}, {1, 0}}, + {{0xc456, 0xc789, Trace::BR_ONLY}, {2, 0}}, + {{0x0, 0xc123, 0xc456}, {2, 0}}, + {{0xd456, 0xd789, Trace::BR_ONLY}, {2, 2}}, + {{0x0, 0xd123, 0xd456}, {2, 0}}, + {{0xe005, 0xe009, Trace::BR_ONLY}, {1, 0}}, + {{0x0, 0xe001, 0xe005}, {1, 0}}, + {{0xf002, 0xf003, Trace::BR_ONLY}, {1, 1}}, + {{0x0, 0xf001, 0xf002}, {1, 0}}}; + + parseAndCheckBrstackEvents(4567, ExpectedSamples); +} + #endif |