[llvm] [BOLT] Add support for safe-icf (PR #116275)

[Davide Italiano via llvm-commits]

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@@ -340,6 +360,79 @@ typedef std::unordered_map<BinaryFunction *, std::vector<BinaryFunction *>,
 
 namespace llvm {
 namespace bolt {
+void IdenticalCodeFolding::initVTableReferences(const BinaryContext &BC) {
+  for (const auto &[Address, Data] : BC.getBinaryData()) {
+    // Filter out all symbols that are not vtables.
+    if (!Data->getName().starts_with("_ZTV"))
+      continue;
+    for (uint64_t I = Address, End = I + Data->getSize(); I < End; I += 8)
+      setAddressUsedInVTable(I);
+  }
+}
+
+void IdenticalCodeFolding::analyzeDataRelocations(BinaryContext &BC) {
+  initVTableReferences(BC);
+  // For static relocations there should be a symbol for function references.
+  for (const BinarySection &Sec : BC.sections()) {
+    if (!Sec.hasSectionRef() || !Sec.isData())
+      continue;
+    for (const auto &Rel : Sec.relocations()) {
+      const uint64_t RelAddr = Rel.Offset + Sec.getAddress();
+      if (isAddressInVTable(RelAddr))
+        continue;
+      if (BinaryFunction *BF = BC.getFunctionForSymbol(Rel.Symbol))
+        BF->setHasAddressTaken(true);
+    }
+    // For dynamic relocations there are two cases:
+    // 1: No symbol and only addend.
+    // 2: There is symbol, but it references undefined symbol, or things like
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dcci wrote:

"or things like" -> either enumerate all of them or remove this bit.

https://github.com/llvm/llvm-project/pull/116275