Use named temporaries for directional labels.

Directional labels can show up in symbol tables (and we have a llvm-mc test for
that). Given that, we need to make sure they are named.

With that out of the way, use setUseNamesOnTempLabels in llvm-mc so that it
too benefits from the memory saving.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239914 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCContext.h

@@ -207,7 +207,7 @@ namespace llvm {
     bool AutoReset;
 
     MCSymbol *createSymbolImpl(const StringMapEntry<bool> *Name,
-                               bool IsTemporary);
+                               bool CanBeUnnamed);
     MCSymbol *createSymbol(StringRef Name, bool AlwaysAddSuffix,
                            bool IsTemporary);
 
@@ -249,9 +249,10 @@ namespace llvm {
 
     /// Create and return a new assembler temporary symbol with a unique but
     /// unspecified name.
-    MCSymbol *createTempSymbol();
+    MCSymbol *createTempSymbol(bool CanBeUnnamed = true);
 
-    MCSymbol *createTempSymbol(const Twine &Name, bool AlwaysAddSuffix);
+    MCSymbol *createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
+                               bool CanBeUnnamed = true);
 
     /// Create the definition of a directional local symbol for numbered label
     /// (used for "1:" definitions).

lib/MC/MCContext.cpp

@@ -176,14 +176,14 @@ MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
 }
 
 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
-                                  bool IsTemporary) {
-  if (IsTemporary && !UseNamesOnTempLabels)
+                                  bool CanBeUnnamed) {
+  if (CanBeUnnamed && !UseNamesOnTempLabels)
     return createSymbolImpl(nullptr, true);
 
   // Determine whether this is an user writter assembler temporary or normal
   // label, if used.
-  IsTemporary = false;
-  if (AllowTemporaryLabels)
+  bool IsTemporary = CanBeUnnamed;
+  if (AllowTemporaryLabels && !IsTemporary)
     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
 
   SmallString<128> NewName = Name;
@@ -206,10 +206,11 @@ MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
   llvm_unreachable("Infinite loop");
 }
 
-MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix) {
+MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
+                                      bool CanBeUnnamed) {
   SmallString<128> NameSV;
   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
-  return createSymbol(NameSV, AlwaysAddSuffix, true);
+  return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
 }
 
 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
@@ -218,8 +219,8 @@ MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
   return createSymbol(NameSV, true, false);
 }
 
-MCSymbol *MCContext::createTempSymbol() {
-  return createTempSymbol("tmp", true);
+MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
+  return createTempSymbol("tmp", true, CanBeUnnamed);
 }
 
 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
@@ -240,7 +241,7 @@ MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
                                                        unsigned Instance) {
   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
   if (!Sym)
-    Sym = createTempSymbol();
+    Sym = createTempSymbol(false);
   return Sym;
 }
 

tools/llvm-mc/llvm-mc.cpp

@@ -500,6 +500,9 @@ int main(int argc, char **argv) {
   } else {
     assert(FileType == OFT_ObjectFile && "Invalid file type!");
 
+    // Don't waste memory on names of temp labels.
+    Ctx.setUseNamesOnTempLabels(false);
+
     if (!Out->os().supportsSeeking()) {
       BOS = make_unique<buffer_ostream>(Out->os());
       OS = BOS.get();