Add a RAW mode to StringTableBuilder.

In this mode it just tries to tail merge the strings without imposing any other
format constrains. It will not, for example, add a null byte between them.

Also add support for keeping a tentative size and offset if we decide to
not optimize after all.

This will be used shortly in lld for merging SHF_STRINGS sections.

llvm-svn: 251153

4 files changed, 21 insertions, 10 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 5fdfcf9ef2d..230d3d775b1 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -109,7 +109,7 @@ class ELFObjectWriter : public MCObjectWriter {
 
     BumpPtrAllocator Alloc;
     StringSaver VersionSymSaver{Alloc};
-    StringTableBuilder StrTabBuilder;
+    StringTableBuilder StrTabBuilder{StringTableBuilder::ELF};
 
     /// @}
 
@@ -880,7 +880,7 @@ void ELFObjectWriter::computeSymbolTable(
   for (const std::string &Name : FileNames)
     StrTabBuilder.add(Name);
 
-  StrTabBuilder.finalize(StringTableBuilder::ELF);
+  StrTabBuilder.finalize();
 
   for (const std::string &Name : FileNames)
     Writer.writeSymbol(StrTabBuilder.getOffset(Name),
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index d5184f1d9a4..17023d82d62 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -520,7 +520,7 @@ void MachObjectWriter::computeSymbolTable(
 
     StringTable.add(Symbol.getName());
   }
-  StringTable.finalize(StringTableBuilder::MachO);
+  StringTable.finalize();
 
   // Build the symbol arrays but only for non-local symbols.
   //
diff --git a/llvm/lib/MC/StringTableBuilder.cpp b/llvm/lib/MC/StringTableBuilder.cpp
index fc6c3bc0902..6210238e72a 100644
--- a/llvm/lib/MC/StringTableBuilder.cpp
+++ b/llvm/lib/MC/StringTableBuilder.cpp
@@ -16,6 +16,8 @@
 
 using namespace llvm;
 
+StringTableBuilder::StringTableBuilder(Kind K) : K(K) {}
+
 static int compareBySuffix(std::pair<StringRef, size_t> *const *AP,
                            std::pair<StringRef, size_t> *const *BP) {
   StringRef A = (*AP)->first;
@@ -32,7 +34,7 @@ static int compareBySuffix(std::pair<StringRef, size_t> *const *AP,
   return SizeB - SizeA;
 }
 
-void StringTableBuilder::finalize(Kind K) {
+void StringTableBuilder::finalize() {
   std::vector<std::pair<StringRef, size_t> *> Strings;
   Strings.reserve(StringIndexMap.size());
   for (std::pair<StringRef, size_t> &P : StringIndexMap)
@@ -41,6 +43,8 @@ void StringTableBuilder::finalize(Kind K) {
   array_pod_sort(Strings.begin(), Strings.end(), compareBySuffix);
 
   switch (K) {
+  case RAW:
+    break;
   case ELF:
   case MachO:
     // Start the table with a NUL byte.
@@ -59,17 +63,19 @@ void StringTableBuilder::finalize(Kind K) {
       assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
 
     if (Previous.endswith(S)) {
-      P->second = StringTable.size() - 1 - S.size();
+      P->second = StringTable.size() - S.size() - (K != RAW);
       continue;
     }
 
     P->second = StringTable.size();
     StringTable += S;
-    StringTable += '\x00';
+    if (K != RAW)
+      StringTable += '\x00';
     Previous = S;
   }
 
   switch (K) {
+  case RAW:
   case ELF:
     break;
   case MachO:
@@ -85,6 +91,8 @@ void StringTableBuilder::finalize(Kind K) {
         StringTable.data(), Size);
     break;
   }
+
+  Size = StringTable.size();
 }
 
 void StringTableBuilder::clear() {
@@ -99,7 +107,10 @@ size_t StringTableBuilder::getOffset(StringRef S) const {
   return I->second;
 }
 
-void StringTableBuilder::add(StringRef S) {
+size_t StringTableBuilder::add(StringRef S) {
   assert(!isFinalized());
-  StringIndexMap.insert(std::make_pair(S, 0));
+  auto P = StringIndexMap.insert(std::make_pair(S, Size));
+  if (P.second)
+    Size += S.size() + (K != RAW);
+  return P.first->second;
 }
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index f251942161d..8d4d3df21ab 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -127,7 +127,7 @@ public:
   COFF::header Header;
   sections Sections;
   symbols Symbols;
-  StringTableBuilder Strings;
+  StringTableBuilder Strings{StringTableBuilder::WinCOFF};
 
   // Maps used during object file creation.
   section_map SectionMap;
@@ -908,7 +908,7 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
   for (const auto &S : Symbols)
     if (S->should_keep() && S->Name.size() > COFF::NameSize)
       Strings.add(S->Name);
-  Strings.finalize(StringTableBuilder::WinCOFF);
+  Strings.finalize();
 
   // Set names.
   for (const auto &S : Sections)