AsmPrinter: Make DIEString small

Expose the `DwarfStringPool` entry in a header, and store a pointer to
it directly in `DIEString`.  Instead of choosing at creation time how to
emit it, use the `dwarf::Form` to determine that at emission time.
Besides avoiding the other `DIEValue`, this shaves two pointers off of
`DIEString`; the data is now a single pointer.  This is a nice cleanup
on its own -- and drops memory usage from 861 MB down to 853 MB, around
0.9% -- but it's also preparation for passing `DIEValue`s by value.

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

llvm-svn: 238117

2 files changed, 38 insertions, 29 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
index c927bad4855..47f2dec018b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -420,19 +420,49 @@ void DIEDelta::printImpl(raw_ostream &O) const {
 /// EmitValue - Emit string value.
 ///
 void DIEString::EmitValueImpl(const AsmPrinter *AP, dwarf::Form Form) const {
-  Access->EmitValue(AP, Form);
+  assert(
+      (Form == dwarf::DW_FORM_strp || Form == dwarf::DW_FORM_GNU_str_index) &&
+      "Expected valid string form");
+
+  // Index of string in symbol table.
+  if (Form == dwarf::DW_FORM_GNU_str_index) {
+    DIEInteger(S.getIndex()).EmitValue(AP, Form);
+    return;
+  }
+
+  // Relocatable symbol.
+  assert(Form == dwarf::DW_FORM_strp);
+  if (AP->MAI->doesDwarfUseRelocationsAcrossSections()) {
+    DIELabel(S.getSymbol()).EmitValue(AP, Form);
+    return;
+  }
+
+  // Offset into symbol table.
+  DIEInteger(S.getOffset()).EmitValue(AP, Form);
 }
 
 /// SizeOf - Determine size of delta value in bytes.
 ///
 unsigned DIEString::SizeOfImpl(const AsmPrinter *AP, dwarf::Form Form) const {
-  return Access->SizeOf(AP, Form);
+  assert(
+      (Form == dwarf::DW_FORM_strp || Form == dwarf::DW_FORM_GNU_str_index) &&
+      "Expected valid string form");
+
+  // Index of string in symbol table.
+  if (Form == dwarf::DW_FORM_GNU_str_index)
+    return DIEInteger(S.getIndex()).SizeOf(AP, Form);
+
+  // Relocatable symbol.
+  if (AP->MAI->doesDwarfUseRelocationsAcrossSections())
+    return DIELabel(S.getSymbol()).SizeOf(AP, Form);
+
+  // Offset into symbol table.
+  return DIEInteger(S.getOffset()).SizeOf(AP, Form);
 }
 
 #ifndef NDEBUG
 void DIEString::printImpl(raw_ostream &O) const {
-  O << "String: " << Str << "\tSymbol: ";
-  Access->print(O);
+  O << "String: " << S.getString();
 }
 #endif
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 018d2b9918d..04836c61404 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -223,31 +223,10 @@ void DwarfUnit::addSInt(DIELoc &Die, Optional<dwarf::Form> Form,
 
 void DwarfUnit::addString(DIE &Die, dwarf::Attribute Attribute,
                           StringRef String) {
-  if (!isDwoUnit())
-    return addLocalString(Die, Attribute, String);
-
-  addIndexedString(Die, Attribute, String);
-}
-
-void DwarfUnit::addIndexedString(DIE &Die, dwarf::Attribute Attribute,
-                                 StringRef String) {
-  unsigned idx = DU->getStringPool().getIndex(*Asm, String);
-  DIEValue *Value = new (DIEValueAllocator) DIEInteger(idx);
-  DIEValue *Str = new (DIEValueAllocator) DIEString(Value, String);
-  Die.addValue(Attribute, dwarf::DW_FORM_GNU_str_index, Str);
-}
-
-void DwarfUnit::addLocalString(DIE &Die, dwarf::Attribute Attribute,
-                               StringRef String) {
-  DIEValue *Value;
-  if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-    Value = new (DIEValueAllocator)
-        DIELabel(DU->getStringPool().getSymbol(*Asm, String));
-  else
-    Value = new (DIEValueAllocator)
-        DIEInteger(DU->getStringPool().getOffset(*Asm, String));
-  DIEValue *Str = new (DIEValueAllocator) DIEString(Value, String);
-  Die.addValue(Attribute, dwarf::DW_FORM_strp, Str);
+  Die.addValue(Attribute,
+               isDwoUnit() ? dwarf::DW_FORM_GNU_str_index : dwarf::DW_FORM_strp,
+               new (DIEValueAllocator)
+               DIEString(DU->getStringPool().getEntry(*Asm, String)));
 }
 
 void DwarfUnit::addLabel(DIE &Die, dwarf::Attribute Attribute, dwarf::Form Form,