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[BOLT] Adding a unittest that covers Arm SPE PBT aggregation #160095

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[BOLT] Adding a unittest that covers Arm SPE PBT aggregation #160095

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72 changes: 72 additions & 0 deletions bolt/unittests/Profile/PerfSpeEvents.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -161,4 +161,76 @@ 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}}.
// When the SPE previous branch target address (named as PBT)
// feature is available, an SPE sample by combining this PBT feature,
// has two entries.
// Arm SPE records SRC/DEST addresses of the latest sampled branch operation,
// and it stores into the first entry. PBT records the target address of
// most recently taken branch in program order before the sampled operation,
// it places into the second entry.
// They are formed a chain of two consecutive branches.
// Where:
// - The previous branch operation (PBT) is always taken.
// - In SPE entry, the current source branch (SRC) may be either
// fall-through or taken.
// - The target address (DEST) of the recorded
// branch operation is always what was architecturally executed.
// However PBT lacks associated information such as branch
// source address, branch type, and prediction bit.
// Considering this Trace pair:
// {{0xd456, 0xd789, Trace::BR_ONLY}, {2, 2}},
// {{0x0, 0xd123, 0xd456}, {2, 0}}
// For SPE trace please see the description above.
// The second entry is the PBT trace:
// {{0x0, 0xd123, 0xd456}, {2, 0}}.
// The PBT entry has a TakenCount = 2, as we have two samples for
// (0x0, 0xd123) entry in our input. The 'MispredsCount = 0' is
// always zero, because it lacks prediction information.
// It also has no information about source branch address therefore
// Bolt doesn't evaluate the 'From' field, and leaves it as zero (0x0).
// TraceTo = 0xc456, means the execution jumped from
// 0xc123 (PBT) to 0xc456 (SRC), and jumped further to 0xd789 (DEST).
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
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