[Demangle] make llvm::demangle take std::string_view rather than const std::string&

As suggested by @erichkeane in
https://reviews.llvm.org/D141451#inline-1429549

There's potential for a lot more cleanups around these APIs. This is
just a start.

Callers need to be more careful about sub-expressions producing strings
that don't outlast the expression using ``llvm::demangle``. Add a
release note.

Reviewed By: MaskRay, #lld-macho

Differential Revision: https://reviews.llvm.org/D149104

5 files changed, 14 insertions, 13 deletions

diff --git a/lld/COFF/Symbols.cpp b/lld/COFF/Symbols.cpp
index c042386e0106..f4efcf2266cd 100644
--- a/lld/COFF/Symbols.cpp
+++ b/lld/COFF/Symbols.cpp
@@ -38,9 +38,9 @@ static std::string maybeDemangleSymbol(const COFFLinkerContext &ctx,
     StringRef demangleInput = prefixless;
     if (ctx.config.machine == I386)
       demangleInput.consume_front("_");
-    std::string demangled = demangle(demangleInput.str());
+    std::string demangled = demangle(demangleInput);
     if (demangled != demangleInput)
-      return prefix + demangle(demangleInput.str());
+      return prefix + demangled;
     return (prefix + prefixless).str();
   }
   return std::string(symName);
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index f09d0d7f9095..c5ef6d3f0cbf 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -145,13 +145,16 @@ StringMap<SmallVector<Symbol *, 0>> &SymbolTable::getDemangledSyms() {
       if (canBeVersioned(*sym)) {
         StringRef name = sym->getName();
         size_t pos = name.find('@');
+        std::string substr;
         if (pos == std::string::npos)
-          demangled = demangle(name.str());
-        else if (pos + 1 == name.size() || name[pos + 1] == '@')
-          demangled = demangle(name.substr(0, pos).str());
-        else
-          demangled =
-              (demangle(name.substr(0, pos).str()) + name.substr(pos)).str();
+          demangled = demangle(name);
+        else if (pos + 1 == name.size() || name[pos + 1] == '@') {
+          substr = name.substr(0, pos);
+          demangled = demangle(substr);
+        } else {
+          substr = name.substr(0, pos);
+          demangled = (demangle(substr) + name.substr(pos)).str();
+        }
         (*demangledSyms)[demangled].push_back(sym);
       }
   }
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index 62a8a3c30664..840385aabea3 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -45,9 +45,7 @@ LLVM_ATTRIBUTE_UNUSED static inline void assertSymbols() {
 
 // Returns a symbol for an error message.
 static std::string maybeDemangleSymbol(StringRef symName) {
-  if (elf::config->demangle)
-    return demangle(symName.str());
-  return symName.str();
+  return elf::config->demangle ? demangle(symName.str()) : symName.str();
 }
 
 std::string lld::toString(const elf::Symbol &sym) {
diff --git a/lld/MachO/Symbols.cpp b/lld/MachO/Symbols.cpp
index cb3b271a1912..660826edc4f8 100644
--- a/lld/MachO/Symbols.cpp
+++ b/lld/MachO/Symbols.cpp
@@ -32,7 +32,7 @@ static_assert(sizeof(SymbolUnion) == sizeof(Defined),
 static std::string maybeDemangleSymbol(StringRef symName) {
   if (config->demangle) {
     symName.consume_front("_");
-    return demangle(symName.str());
+    return demangle(symName);
   }
   return symName.str();
 }
diff --git a/lld/wasm/Symbols.cpp b/lld/wasm/Symbols.cpp
index 567ff49dfa44..2adf72b6965c 100644
--- a/lld/wasm/Symbols.cpp
+++ b/lld/wasm/Symbols.cpp
@@ -35,7 +35,7 @@ std::string maybeDemangleSymbol(StringRef name) {
   if (name == "__main_argc_argv")
     return "main";
   if (wasm::config->demangle)
-    return demangle(name.str());
+    return demangle(name);
   return name.str();
 }