[clang] [llvm] [PseudoProbe] Mix and reorder block and call probe ID in lexical order (PR #75092)
Lei Wang via cfe-commits
cfe-commits at lists.llvm.org
Wed Jan 24 19:00:32 PST 2024
================
@@ -471,6 +471,66 @@ ProfileGenerator::getTopLevelFunctionProfile(FunctionId FuncName) {
return ProfileMap.Create(Context);
}
+// Use a heuristic to determine probe order by checking callsite insertion
+// position relative to the BB probes. Sort all the BB probes is in a list, for
+// each calliste, compute "ratio = insert position / length of the list". For
+// the old order, the probe ids for BB should be all before(smaller than) the
+// probe ids for callsite, this ratio should be equal to or close to 1.
+bool checkProbeIDIsInMixedOrder(const SampleProfileMap &Profiles) {
+ // Use flattned profile to maximize the callsites in the profile.
+ SampleProfileMap flattenProfile;
+ ProfileConverter::flattenProfile(Profiles, flattenProfile);
+
+ uint32_t PossibleOldOrderNum = 0;
+ uint32_t PossibleNewOrderNum = 0;
+
+ for (const auto &I : flattenProfile) {
+ const FunctionSamples &FS = I.second;
+ // Skip small functions whose profile order are likely random.
+ if (FS.getBodySamples().size() < 10)
+ continue;
+
+ std::set<uint32_t> PossibleBBProbeIDs;
+ std::set<uint32_t> CallsiteIDs;
+ for (const auto &I : FS.getBodySamples()) {
+ if (I.second.getCallTargets().empty())
+ PossibleBBProbeIDs.insert(I.first.LineOffset);
+ else
+ CallsiteIDs.insert(I.first.LineOffset);
+ }
+
+ if (PossibleBBProbeIDs.empty() || CallsiteIDs.empty())
+ continue;
+
+ uint32_t DistanceToBeginSum = 0;
+ for (const auto &ID : CallsiteIDs)
+ DistanceToBeginSum += std::distance(PossibleBBProbeIDs.begin(),
+ PossibleBBProbeIDs.upper_bound(ID));
+ uint32_t LengthSum = PossibleBBProbeIDs.size() * CallsiteIDs.size();
+
+ // Note that PossibleBBProbeIDs could contains some callsite probe id, the
----------------
wlei-llvm wrote:
> I'm curious what lead to empty call targets for a call location covered by LBR..
yeah, I need to investigate where the empty call targets comes from.(I'm sure I saw a lot of empty callsite names, the count are all zero)
https://github.com/llvm/llvm-project/pull/75092
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