[BPF] Use heterogeneous lookup with std::map (NFC) (#143395)

Author: kazutakahirata

llvm/lib/Target/BPF/BTFDebug.cpp

@@ -1438,7 +1438,7 @@ void BTFDebug::processGlobals(bool ProcessingMapDef) {
     // constant with private linkage and if it won't be in .rodata.str<#>
     // and .rodata.cst<#> sections.
     if (SecName == ".rodata" && Global.hasPrivateLinkage() &&
-        DataSecEntries.find(std::string(SecName)) == DataSecEntries.end()) {
+        DataSecEntries.find(SecName) == DataSecEntries.end()) {
       // skip .rodata.str<#> and .rodata.cst<#> sections
       if (!GVKind->isMergeableCString() && !GVKind->isMergeableConst()) {
         DataSecEntries[std::string(SecName)] =

llvm/lib/Target/BPF/BTFDebug.h

@@ -300,7 +300,8 @@ class BTFDebug : public DebugHandlerBase {
   std::map<uint32_t, std::vector<BTFLineInfo>> LineInfoTable;
   std::map<uint32_t, std::vector<BTFFieldReloc>> FieldRelocTable;
   StringMap<std::vector<std::string>> FileContent;
-  std::map<std::string, std::unique_ptr<BTFKindDataSec>> DataSecEntries;
+  std::map<std::string, std::unique_ptr<BTFKindDataSec>, std::less<>>
+      DataSecEntries;
   std::vector<BTFTypeStruct *> StructTypes;
   std::map<const GlobalVariable *, std::pair<int64_t, uint32_t>> PatchImms;
   std::map<const DICompositeType *,