[BOLT][Linker][NFC] Remove lookupSymbol() in favor of lookupSymbolInfo() (#128070)

Sometimes we need to know the size of a symbol besides its address, so
maybe we can start using the existing `BOLTLinker::lookupSymbolInfo()`
(that returns symbol address and size) and remove
`BOLTLinker::lookupSymbol()` (that only returns symbol address). And for
both we need to check return value as it is wrapped in `std::optional<>`,
which makes the difference even smaller.

Author: yozhu

bolt/include/bolt/Core/Linker.h

@@ -46,13 +46,6 @@ class BOLTLinker {
   /// Return the address and size of a symbol or std::nullopt if it cannot be
   /// found.
   virtual std::optional<SymbolInfo> lookupSymbolInfo(StringRef Name) const = 0;
-
-  /// Return the address of a symbol or std::nullopt if it cannot be found.
-  std::optional<uint64_t> lookupSymbol(StringRef Name) const {
-    if (const auto Info = lookupSymbolInfo(Name))
-      return Info->Address;
-    return std::nullopt;
-  }
 };
 
 } // namespace bolt

bolt/lib/Core/BinaryFunction.cpp

@@ -4259,21 +4259,21 @@ void BinaryFunction::updateOutputValues(const BOLTLinker &Linker) {
 
   if (BC.HasRelocations || isInjected()) {
     if (hasConstantIsland()) {
-      const auto DataAddress =
-          Linker.lookupSymbol(getFunctionConstantIslandLabel()->getName());
-      assert(DataAddress && "Cannot find function CI symbol");
-      setOutputDataAddress(*DataAddress);
+      const auto IslandLabelSymInfo =
+          Linker.lookupSymbolInfo(getFunctionConstantIslandLabel()->getName());
+      assert(IslandLabelSymInfo && "Cannot find function CI symbol");
+      setOutputDataAddress(IslandLabelSymInfo->Address);
       for (auto It : Islands->Offsets) {
         const uint64_t OldOffset = It.first;
         BinaryData *BD = BC.getBinaryDataAtAddress(getAddress() + OldOffset);
         if (!BD)
           continue;
 
         MCSymbol *Symbol = It.second;
-        const auto NewAddress = Linker.lookupSymbol(Symbol->getName());
-        assert(NewAddress && "Cannot find CI symbol");
+        const auto SymInfo = Linker.lookupSymbolInfo(Symbol->getName());
+        assert(SymInfo && "Cannot find CI symbol");
         auto &Section = *getCodeSection();
-        const auto NewOffset = *NewAddress - Section.getOutputAddress();
+        const auto NewOffset = SymInfo->Address - Section.getOutputAddress();
         BD->setOutputLocation(Section, NewOffset);
       }
     }
@@ -4298,10 +4298,10 @@ void BinaryFunction::updateOutputValues(const BOLTLinker &Linker) {
         FF.setAddress(ColdStartSymbolInfo->Address);
         FF.setImageSize(ColdStartSymbolInfo->Size);
         if (hasConstantIsland()) {
-          const auto DataAddress = Linker.lookupSymbol(
+          const auto SymInfo = Linker.lookupSymbolInfo(
               getFunctionColdConstantIslandLabel()->getName());
-          assert(DataAddress && "Cannot find cold CI symbol");
-          setOutputColdDataAddress(*DataAddress);
+          assert(SymInfo && "Cannot find cold CI symbol");
+          setOutputColdDataAddress(SymInfo->Address);
         }
       }
     }

bolt/lib/Rewrite/JITLinkLinker.cpp

@@ -125,11 +125,11 @@ struct JITLinkLinker::Context : jitlink::JITLinkContext {
       std::string SymName = (*Symbol.first).str();
       LLVM_DEBUG(dbgs() << "BOLT: looking for " << SymName << "\n");
 
-      if (auto Address = Linker.lookupSymbol(SymName)) {
+      if (auto SymInfo = Linker.lookupSymbolInfo(SymName)) {
         LLVM_DEBUG(dbgs() << "Resolved to address 0x"
-                          << Twine::utohexstr(*Address) << "\n");
+                          << Twine::utohexstr(SymInfo->Address) << "\n");
         AllResults[Symbol.first] = orc::ExecutorSymbolDef(
-            orc::ExecutorAddr(*Address), JITSymbolFlags());
+            orc::ExecutorAddr(SymInfo->Address), JITSymbolFlags());
         continue;
       }
 

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -5907,9 +5907,9 @@ void RewriteInstance::writeEHFrameHeader() {
 }
 
 uint64_t RewriteInstance::getNewValueForSymbol(const StringRef Name) {
-  auto Value = Linker->lookupSymbol(Name);
+  auto Value = Linker->lookupSymbolInfo(Name);
   if (Value)
-    return *Value;
+    return Value->Address;
 
   // Return the original value if we haven't emitted the symbol.
   BinaryData *BD = BC->getBinaryDataByName(Name);

bolt/lib/RuntimeLibs/HugifyRuntimeLibrary.cpp

@@ -68,10 +68,11 @@ void HugifyRuntimeLibrary::link(BinaryContext &BC, StringRef ToolPath,
 
   assert(!RuntimeStartAddress &&
          "We don't currently support linking multiple runtime libraries");
-  RuntimeStartAddress = Linker.lookupSymbol("__bolt_hugify_self").value_or(0);
-  if (!RuntimeStartAddress) {
+  auto StartSymInfo = Linker.lookupSymbolInfo("__bolt_hugify_self");
+  if (!StartSymInfo) {
     errs() << "BOLT-ERROR: hugify library does not define __bolt_hugify_self: "
            << LibPath << "\n";
     exit(1);
   }
+  RuntimeStartAddress = StartSymInfo->Address;
 }

bolt/lib/RuntimeLibs/InstrumentationRuntimeLibrary.cpp

@@ -203,27 +203,35 @@ void InstrumentationRuntimeLibrary::link(
   if (BC.isMachO())
     return;
 
-  RuntimeFiniAddress = Linker.lookupSymbol("__bolt_instr_fini").value_or(0);
-  if (!RuntimeFiniAddress) {
+  std::optional<BOLTLinker::SymbolInfo> FiniSymInfo =
+      Linker.lookupSymbolInfo("__bolt_instr_fini");
+  if (!FiniSymInfo) {
     errs() << "BOLT-ERROR: instrumentation library does not define "
               "__bolt_instr_fini: "
            << LibPath << "\n";
     exit(1);
   }
-  RuntimeStartAddress = Linker.lookupSymbol("__bolt_instr_start").value_or(0);
-  if (!RuntimeStartAddress) {
+  RuntimeFiniAddress = FiniSymInfo->Address;
+
+  std::optional<BOLTLinker::SymbolInfo> StartSymInfo =
+      Linker.lookupSymbolInfo("__bolt_instr_start");
+  if (!StartSymInfo) {
     errs() << "BOLT-ERROR: instrumentation library does not define "
               "__bolt_instr_start: "
            << LibPath << "\n";
     exit(1);
   }
+  RuntimeStartAddress = StartSymInfo->Address;
+
   outs() << "BOLT-INFO: output linked against instrumentation runtime "
             "library, lib entry point is 0x"
          << Twine::utohexstr(RuntimeStartAddress) << "\n";
+
+  std::optional<BOLTLinker::SymbolInfo> ClearSymInfo =
+      Linker.lookupSymbolInfo("__bolt_instr_clear_counters");
+  const uint64_t ClearSymAddress = ClearSymInfo ? ClearSymInfo->Address : 0;
   outs() << "BOLT-INFO: clear procedure is 0x"
-         << Twine::utohexstr(
-                Linker.lookupSymbol("__bolt_instr_clear_counters").value_or(0))
-         << "\n";
+         << Twine::utohexstr(ClearSymAddress) << "\n";
 
   emitTablesAsELFNote(BC);
 }