Turn DISubprogram into a variable-length node.

DISubprogram currently has 10 pointer operands, several of which are
often nullptr. This patch reduces the amount of memory allocated by
DISubprogram by rearranging the operands such that containing type,
template params, and thrown types come last, and are only allocated
when they are non-null (or followed by non-null operands).

This patch also eliminates the entirely unused DisplayName operand.

This saves up to 4 pointer operands per DISubprogram. (I tried
measuring the effect on peak memory usage on an LTO link of an X86
llc, but the results were very noisy).

This reapplies r301498 with an attempted workaround for g++.

Differential Revision: https://reviews.llvm.org/D32560

llvm-svn: 301501

2 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index d99065b1b67..b11e30c359b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -820,7 +820,7 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
 
   const DILocalVariable *V = MI->getDebugVariable();
   if (auto *SP = dyn_cast<DISubprogram>(V->getScope())) {
-    StringRef Name = SP->getDisplayName();
+    StringRef Name = SP->getName();
     if (!Name.empty())
       OS << Name << ":";
   }
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 2571f686965..665dbc0b614 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -237,7 +237,7 @@ TypeIndex CodeViewDebug::getFuncIdForSubprogram(const DISubprogram *SP) {
 
   // The display name includes function template arguments. Drop them to match
   // MSVC.
-  StringRef DisplayName = SP->getDisplayName().split('<').first;
+  StringRef DisplayName = SP->getName().split('<').first;
 
   const DIScope *Scope = SP->getScope().resolve();
   TypeIndex TI;
@@ -657,7 +657,7 @@ void CodeViewDebug::emitInlineeLinesSubsection() {
 
     OS.AddBlankLine();
     unsigned FileId = maybeRecordFile(SP->getFile());
-    OS.AddComment("Inlined function " + SP->getDisplayName() + " starts at " +
+    OS.AddComment("Inlined function " + SP->getName() + " starts at " +
                   SP->getFilename() + Twine(':') + Twine(SP->getLine()));
     OS.AddBlankLine();
     // The filechecksum table uses 8 byte entries for now, and file ids start at
@@ -759,9 +759,9 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
 
   // If we have a display name, build the fully qualified name by walking the
   // chain of scopes.
-  if (!SP->getDisplayName().empty())
+  if (!SP->getName().empty())
     FuncName =
-        getFullyQualifiedName(SP->getScope().resolve(), SP->getDisplayName());
+        getFullyQualifiedName(SP->getScope().resolve(), SP->getName());
 
   // If our DISubprogram name is empty, use the mangled name.
   if (FuncName.empty())