AsmPrinter: Convert DIE::Values to a linked list

Change `DIE::Values` to a singly linked list, where each node is
allocated on a `BumpPtrAllocator`.  In order to support `push_back()`,
the list is circular, and points at the tail element instead of the
head.  I abstracted the core list logic out to `IntrusiveBackList` so
that it can be reused for `DIE::Children`, which also cares about
`push_back()`.

This drops llc memory usage from 799 MB down to 735 MB, about 8%.

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)

llvm-svn: 240733

1 files changed, 6 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 50e4a54eb3e..03721a21ee1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -31,7 +31,7 @@ class LexicalScope;
 class DwarfCompileUnit : public DwarfUnit {
   /// The attribute index of DW_AT_stmt_list in the compile unit DIE, avoiding
   /// the need to search for it in applyStmtList.
-  unsigned stmtListIndex;
+  DIE::value_iterator StmtListValue;
 
   /// Skeleton unit associated with this unit.
   DwarfCompileUnit *Skeleton;
@@ -92,8 +92,8 @@ public:
                             const MCSymbol *Label);
 
   /// addSectionDelta - Add a label delta attribute data and value.
-  void addSectionDelta(DIE &Die, dwarf::Attribute Attribute, const MCSymbol *Hi,
-                       const MCSymbol *Lo);
+  DIE::value_iterator addSectionDelta(DIE &Die, dwarf::Attribute Attribute,
+                                      const MCSymbol *Hi, const MCSymbol *Lo);
 
   DwarfCompileUnit &getCU() override { return *this; }
 
@@ -106,8 +106,9 @@ public:
 
   /// addSectionLabel - Add a Dwarf section label attribute data and value.
   ///
-  void addSectionLabel(DIE &Die, dwarf::Attribute Attribute,
-                       const MCSymbol *Label, const MCSymbol *Sec);
+  DIE::value_iterator addSectionLabel(DIE &Die, dwarf::Attribute Attribute,
+                                      const MCSymbol *Label,
+                                      const MCSymbol *Sec);
 
   /// \brief Find DIE for the given subprogram and attach appropriate
   /// DW_AT_low_pc and DW_AT_high_pc attributes. If there are global