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).

llvm-svn: 301498

6 files changed, 45 insertions, 28 deletions

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index ae11181f791..ce0d7e3116c 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -1614,11 +1614,7 @@ public:
   DIScopeRef getScope() const { return DIScopeRef(getRawScope()); }
 
   StringRef getName() const { return getStringOperand(2); }
-  StringRef getDisplayName() const { return getStringOperand(3); }
-  StringRef getLinkageName() const { return getStringOperand(4); }
-
-  MDString *getRawName() const { return getOperandAs<MDString>(2); }
-  MDString *getRawLinkageName() const { return getOperandAs<MDString>(4); }
+  StringRef getLinkageName() const { return getStringOperand(3); }
 
   DISubroutineType *getType() const {
     return cast_or_null<DISubroutineType>(getRawType());
@@ -1630,7 +1626,7 @@ public:
   DICompileUnit *getUnit() const {
     return cast_or_null<DICompileUnit>(getRawUnit());
   }
-  void replaceUnit(DICompileUnit *CU) { replaceOperandWith(7, CU); }
+  void replaceUnit(DICompileUnit *CU) { replaceOperandWith(5, CU); }
   DITemplateParameterArray getTemplateParams() const {
     return cast_or_null<MDTuple>(getRawTemplateParams());
   }
@@ -1645,13 +1641,21 @@ public:
   }
 
   Metadata *getRawScope() const { return getOperand(1); }
-  Metadata *getRawType() const { return getOperand(5); }
-  Metadata *getRawContainingType() const { return getOperand(6); }
-  Metadata *getRawUnit() const { return getOperand(7); }
-  Metadata *getRawTemplateParams() const { return getOperand(8); }
-  Metadata *getRawDeclaration() const { return getOperand(9); }
-  Metadata *getRawVariables() const { return getOperand(10); }
-  Metadata *getRawThrownTypes() const { return getOperand(11); }
+  MDString *getRawName() const { return getOperandAs<MDString>(2); }
+  MDString *getRawLinkageName() const { return getOperandAs<MDString>(3); }
+  Metadata *getRawType() const { return getOperand(4); }
+  Metadata *getRawUnit() const { return getOperand(5); }
+  Metadata *getRawDeclaration() const { return getOperand(6); }
+  Metadata *getRawVariables() const { return getOperand(7); }
+  Metadata *getRawContainingType() const {
+    return getNumOperands() > 8 ? getOperand(8) : nullptr;
+  }
+  Metadata *getRawTemplateParams() const {
+    return getNumOperands() > 9 ? getOperand(9) : nullptr;
+  }
+  Metadata *getRawThrownTypes() const {
+    return getNumOperands() > 10 ? getOperand(10) : nullptr;
+  }
 
   /// Check if this subprogram describes the given function.
   ///
diff --git a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
index 7ca2e167da0..24fdca33c23 100644
--- a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
+++ b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
@@ -474,8 +474,8 @@ class MetadataLoader::MetadataLoaderImpl {
     for (auto CU_SP : CUSubprograms)
       if (auto *SPs = dyn_cast_or_null<MDTuple>(CU_SP.second))
         for (auto &Op : SPs->operands())
-          if (auto *SP = dyn_cast_or_null<MDNode>(Op))
-            SP->replaceOperandWith(7, CU_SP.first);
+          if (auto *SP = dyn_cast_or_null<DISubprogram>(Op))
+            SP->replaceUnit(CU_SP.first);
     CUSubprograms.clear();
   }
 
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())
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 498617c4460..3db9a3de92e 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -214,6 +214,10 @@ void GenericDINode::recalculateHash() {
 #define DEFINE_GETIMPL_STORE_NO_CONSTRUCTOR_ARGS(CLASS, OPS)                   \
   return storeImpl(new (array_lengthof(OPS)) CLASS(Context, Storage, OPS),     \
                    Storage, Context.pImpl->CLASS##s)
+#define DEFINE_GETIMPL_STORE_N(CLASS, ARGS, OPS, NUM_OPS)                      \
+  return storeImpl(new (NUM_OPS)                                               \
+                       CLASS(Context, Storage, UNWRAP_ARGS(ARGS), OPS),        \
+                   Storage, Context.pImpl->CLASS##s)
 
 DISubrange *DISubrange::getImpl(LLVMContext &Context, int64_t Count, int64_t Lo,
                                 StorageType Storage, bool ShouldCreate) {
@@ -449,13 +453,22 @@ DISubprogram *DISubprogram::getImpl(
                      IsDefinition, ScopeLine, ContainingType, Virtuality,
                      VirtualIndex, ThisAdjustment, Flags, IsOptimized, Unit,
                      TemplateParams, Declaration, Variables, ThrownTypes));
-  Metadata *Ops[] = {File,           Scope,       Name,           Name,
-                     LinkageName,    Type,        ContainingType, Unit,
-                     TemplateParams, Declaration, Variables,      ThrownTypes};
-  DEFINE_GETIMPL_STORE(DISubprogram, (Line, ScopeLine, Virtuality, VirtualIndex,
-                                      ThisAdjustment, Flags, IsLocalToUnit,
-                                      IsDefinition, IsOptimized),
-                       Ops);
+  SmallVector<Metadata *, 11> Ops = {
+      File,        Scope,     Name,           LinkageName,    Type,       Unit,
+      Declaration, Variables, ContainingType, TemplateParams, ThrownTypes};
+  if (!ThrownTypes) {
+    Ops.pop_back();
+    if (!TemplateParams) {
+      Ops.pop_back();
+      if (!ContainingType)
+        Ops.pop_back();
+    }
+  }
+  DEFINE_GETIMPL_STORE_N(DISubprogram,
+                         (Line, ScopeLine, Virtuality, VirtualIndex,
+                          ThisAdjustment, Flags, IsLocalToUnit, IsDefinition,
+                          IsOptimized),
+                         Ops, Ops.size());
 }
 
 bool DISubprogram::describes(const Function *F) const {
diff --git a/llvm/tools/opt/BreakpointPrinter.cpp b/llvm/tools/opt/BreakpointPrinter.cpp
index 33b3edcd123..e5614ed061e 100644
--- a/llvm/tools/opt/BreakpointPrinter.cpp
+++ b/llvm/tools/opt/BreakpointPrinter.cpp
@@ -51,7 +51,7 @@ struct BreakpointPrinter : public ModulePass {
         if (!SP)
           continue;
         getContextName(SP->getScope().resolve(), Name);
-        Name = Name + SP->getDisplayName().str();
+        Name = Name + SP->getName().str();
         if (!Name.empty() && Processed.insert(Name).second) {
           Out << Name << "\n";
         }