[llvm] [llvm-symbolizer] nfc, use map instead of vector (PR #69552)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 created https://github.com/llvm/llvm-project/pull/69552

Use map instead of vector for the symbols, so that:
- don't need to sort after collecting all symbols
- easily handle of symbols with same addresses.
- efficiently find the symbol which has same address when adding a new symbol. (A follow up patch needs this functionality.)

>From 1e39f569ec6412303f568512d2df84885763c03a Mon Sep 17 00:00:00 2001
From: Chen Zheng <czhengsz at cn.ibm.com>
Date: Wed, 18 Oct 2023 04:47:01 -0400
Subject: [PATCH] nfc, use map instead of vector

---
 .../Symbolize/SymbolizableObjectFile.h        |  8 +--
 .../Symbolize/SymbolizableObjectFile.cpp      | 49 +++++++++----------
 2 files changed, 24 insertions(+), 33 deletions(-)

diff --git a/llvm/include/llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h b/llvm/include/llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h
index 075dbe3e0e372ed..8a881acb010ac3c 100644
--- a/llvm/include/llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h
+++ b/llvm/include/llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h
@@ -17,6 +17,7 @@
 #include "llvm/DebugInfo/Symbolize/SymbolizableModule.h"
 #include "llvm/Support/Error.h"
 #include <cstdint>
+#include <map>
 #include <memory>
 #include <string>
 #include <utility>
@@ -73,7 +74,6 @@ class SymbolizableObjectFile : public SymbolizableModule {
   bool UntagAddresses;
 
   struct SymbolDesc {
-    uint64_t Addr;
     // If size is 0, assume that symbol occupies the whole memory range up to
     // the following symbol.
     uint64_t Size;
@@ -82,12 +82,8 @@ class SymbolizableObjectFile : public SymbolizableModule {
     // Non-zero if this is an ELF local symbol. See the comment in
     // getNameFromSymbolTable.
     uint32_t ELFLocalSymIdx;
-
-    bool operator<(const SymbolDesc &RHS) const {
-      return Addr != RHS.Addr ? Addr < RHS.Addr : Size < RHS.Size;
-    }
   };
-  std::vector<SymbolDesc> Symbols;
+  std::map<uint64_t, SymbolDesc> Symbols;
   // (index, filename) pairs of ELF STT_FILE symbols.
   std::vector<std::pair<uint32_t, StringRef>> FileSymbols;
 
diff --git a/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp b/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp
index 6b8068a531c05fa..3b5a0ce709f5c08 100644
--- a/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp
+++ b/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp
@@ -70,20 +70,6 @@ SymbolizableObjectFile::create(const object::ObjectFile *Obj,
         return std::move(E);
   }
 
-  std::vector<SymbolDesc> &SS = res->Symbols;
-  // Sort by (Addr,Size,Name). If several SymbolDescs share the same Addr,
-  // pick the one with the largest Size. This helps us avoid symbols with no
-  // size information (Size=0).
-  llvm::stable_sort(SS);
-  auto I = SS.begin(), E = SS.end(), J = SS.begin();
-  while (I != E) {
-    auto OI = I;
-    while (++I != E && OI->Addr == I->Addr) {
-    }
-    *J++ = I[-1];
-  }
-  SS.erase(J, SS.end());
-
   return std::move(res);
 }
 
@@ -134,7 +120,10 @@ Error SymbolizableObjectFile::addCoffExportSymbols(
     uint32_t NextOffset = I != E ? I->Offset : Export.Offset + 1;
     uint64_t SymbolStart = ImageBase + Export.Offset;
     uint64_t SymbolSize = NextOffset - Export.Offset;
-    Symbols.push_back({SymbolStart, SymbolSize, Export.Name, 0});
+    // If the SymbolStart exists, use the one with the large Size.
+    // This helps us avoid symbols with no size information (Size = 0).
+    if (!Symbols.count(SymbolStart) || SymbolSize >= Symbols[SymbolStart].Size)
+      Symbols[SymbolStart] = {SymbolSize, Export.Name, 0};
   }
   return Error::success();
 }
@@ -215,7 +204,14 @@ Error SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol,
 
   if (Obj.isELF() && ELFSymbolRef(Symbol).getBinding() != ELF::STB_LOCAL)
     ELFSymIdx = 0;
-  Symbols.push_back({SymbolAddress, SymbolSize, SymbolName, ELFSymIdx});
+
+  // If the SymbolAddress exists, use the one with the large Size.
+  // This helps us avoid symbols with no size information (Size = 0).
+  if (!Symbols.count(SymbolAddress) ||
+      SymbolSize >= Symbols[SymbolAddress].Size) {
+    Symbols[SymbolAddress] = {SymbolSize, SymbolName, ELFSymIdx};
+  }
+
   return Error::success();
 }
 
@@ -234,26 +230,25 @@ uint64_t SymbolizableObjectFile::getModulePreferredBase() const {
 bool SymbolizableObjectFile::getNameFromSymbolTable(
     uint64_t Address, std::string &Name, uint64_t &Addr, uint64_t &Size,
     std::string &FileName) const {
-  SymbolDesc SD{Address, UINT64_C(-1), StringRef(), 0};
-  auto SymbolIterator = llvm::upper_bound(Symbols, SD);
+  auto SymbolIterator = Symbols.upper_bound(Address);
   if (SymbolIterator == Symbols.begin())
     return false;
   --SymbolIterator;
-  if (SymbolIterator->Size != 0 &&
-      SymbolIterator->Addr + SymbolIterator->Size <= Address)
+
+  auto &SD = SymbolIterator->second;
+  if (SD.Size != 0 && SymbolIterator->first + SD.Size <= Address)
     return false;
-  Name = SymbolIterator->Name.str();
-  Addr = SymbolIterator->Addr;
-  Size = SymbolIterator->Size;
+  Name = SD.Name.str();
+  Addr = SymbolIterator->first;
+  Size = SD.Size;
 
-  if (SymbolIterator->ELFLocalSymIdx != 0) {
+  if (SD.ELFLocalSymIdx != 0) {
     // If this is an ELF local symbol, find the STT_FILE symbol preceding
     // SymbolIterator to get the filename. The ELF spec requires the STT_FILE
     // symbol (if present) precedes the other STB_LOCAL symbols for the file.
     assert(Module->isELF());
-    auto It = llvm::upper_bound(
-        FileSymbols,
-        std::make_pair(SymbolIterator->ELFLocalSymIdx, StringRef()));
+    auto It = llvm::upper_bound(FileSymbols,
+                                std::make_pair(SD.ELFLocalSymIdx, StringRef()));
     if (It != FileSymbols.begin())
       FileName = It[-1].second.str();
   }