[llvm] [MemProf] Suppress duplicate clones in the LTO backend (PR #161551)

[Teresa Johnson via llvm-commits]

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@@ -5186,19 +5191,129 @@ bool CallsiteContextGraph<DerivedCCG, FuncTy, CallTy>::assignFunctions() {
   return Changed;
 }
 
+// Compute a SHA1 hash of the callsite and alloc version information of clone I
+// in the summary, to use in detection of duplicate clones.
+std::string ComputeHash(StringMap<Function *> &HashToFunc, FunctionSummary *FS,
+                        unsigned I) {
+  SHA1 Hasher;
+  // Update hash with any callsites that call non-default (non-zero) callee
+  // versions.
+  for (auto &SN : FS->callsites()) {
+    // In theory all callsites and allocs in this function should have the same
+    // number of clone entries, but handle any discrepancies gracefully below
+    // for NDEBUG builds.
+    assert(
+        SN.Clones.size() > I &&
+        "Callsite summary has fewer entries than other summaries in function");
+    if (SN.Clones.size() <= I || !SN.Clones[I])
+      continue;
+    uint8_t Data[4];
+    support::endian::write32le(Data, SN.Clones[I]);
+    Hasher.update(Data);
+  }
+  // Update hash with any allocs that have non-default (non-None) hints.
+  for (auto &AN : FS->allocs()) {
+    // In theory all callsites and allocs in this function should have the same
+    // number of clone entries, but handle any discrepancies gracefully below
+    // for NDEBUG builds.
+    assert(AN.Versions.size() > I &&
+           "Alloc summary has fewer entries than other summaries in function");
+    if (AN.Versions.size() <= I ||
+        (AllocationType)AN.Versions[I] == AllocationType::None)
+      continue;
+    Hasher.update(ArrayRef<uint8_t>(&AN.Versions[I], 1));
+  }
+  return toHex(Hasher.result());
+}
+
 static SmallVector<std::unique_ptr<ValueToValueMapTy>, 4> createFunctionClones(
     Function &F, unsigned NumClones, Module &M, OptimizationRemarkEmitter &ORE,
     std::map<const Function *, SmallPtrSet<const GlobalAlias *, 1>>
-        &FuncToAliasMap) {
+        &FuncToAliasMap,
+    FunctionSummary *FS) {
+  auto TakeDeclNameAndReplace = [](GlobalValue *DeclGV, GlobalValue *NewGV) {
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teresajohnson wrote:

This lambda and the one below were refactored out of existing code to enable reuse

https://github.com/llvm/llvm-project/pull/161551