DebugInfo: Introduce DebugLocList to encapsulate a list of DebugLocEntries and an MC Label to refer to them

This removes the magic-number-esque code creating/retrieving the same
label for a debug_loc entry from two places and removes the last small
piece of reusable logic from emitDebugLoc so that there will be less
duplication when refactoring it into two functions (one for debug_loc,
the other for debug_loc.dwo).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205382 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 39 insertions, 12 deletions

diff --git a/lib/CodeGen/AsmPrinter/DIE.cpp b/lib/CodeGen/AsmPrinter/DIE.cpp
index cea9df14df..26e8f2da85 100644
--- a/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -560,7 +560,7 @@ unsigned DIELocList::SizeOf(AsmPrinter *AP, dwarf::Form Form) const {
 ///
 void DIELocList::EmitValue(AsmPrinter *AP, dwarf::Form Form) const {
   DwarfDebug *DD = AP->getDwarfDebug();
-  MCSymbol *Label = AP->GetTempSymbol("debug_loc", Index);
+  MCSymbol *Label = DD->getDebugLocEntries()[Index].Label;
 
   if (AP->MAI->doesDwarfUseRelocationsAcrossSections() && !DD->useSplitDwarf())
     AP->EmitSectionOffset(Label, DD->getDebugLocSym());
diff --git a/lib/CodeGen/AsmPrinter/DIEHash.cpp b/lib/CodeGen/AsmPrinter/DIEHash.cpp
index 9756054b28..74beec1c95 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.cpp
+++ b/lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -284,9 +284,10 @@ void DIEHash::hashBlockData(const SmallVectorImpl<DIEValue *> &Values) {
 // Hash the contents of a loclistptr class.
 void DIEHash::hashLocList(const DIELocList &LocList) {
   HashingByteStreamer Streamer(*this);
+  DwarfDebug &DD = *AP->getDwarfDebug();
   for (const auto &Entry :
-       AP->getDwarfDebug()->getDebugLocEntries()[LocList.getValue()])
-    AP->getDwarfDebug()->emitDebugLocEntry(Streamer, Entry);
+       DD.getDebugLocEntries()[LocList.getValue()].List)
+    DD.emitDebugLocEntry(Streamer, Entry);
 }
 
 // Hash an individual attribute \param Attr based on the type of attribute and
diff --git a/lib/CodeGen/AsmPrinter/DebugLocList.h b/lib/CodeGen/AsmPrinter/DebugLocList.h
new file mode 100644
index 0000000000..7a51c7bd5b
--- /dev/null
+++ b/lib/CodeGen/AsmPrinter/DebugLocList.h
@@ -0,0 +1,23 @@
+//===--- lib/CodeGen/DebugLocList.h - DWARF debug_loc list ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CODEGEN_ASMPRINTER_DEBUGLOCLIST_H__
+#define CODEGEN_ASMPRINTER_DEBUGLOCLIST_H__
+
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/ADT/SmallVector.h"
+#include "DebugLocEntry.h"
+
+namespace llvm {
+struct DebugLocList {
+  MCSymbol *Label;
+  SmallVector<DebugLocEntry, 4> List;
+};
+}
+#endif
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 7770cee1b3..1b99ba61d3 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1271,7 +1271,11 @@ DwarfDebug::collectVariableInfo(SmallPtrSet<const MDNode *, 16> &Processed) {
     // Handle multiple DBG_VALUE instructions describing one variable.
     RegVar->setDotDebugLocOffset(DotDebugLocEntries.size());
 
-    SmallVector<DebugLocEntry, 4> DebugLoc;
+    DotDebugLocEntries.resize(DotDebugLocEntries.size() + 1);
+    DebugLocList &LocList = DotDebugLocEntries.back();
+    LocList.Label =
+        Asm->GetTempSymbol("debug_loc", DotDebugLocEntries.size() - 1);
+    SmallVector<DebugLocEntry, 4> &DebugLoc = LocList.List;
     for (SmallVectorImpl<const MachineInstr *>::const_iterator
              HI = History.begin(),
              HE = History.end();
@@ -1313,7 +1317,6 @@ DwarfDebug::collectVariableInfo(SmallPtrSet<const MDNode *, 16> &Processed) {
       if (DebugLoc.empty() || !DebugLoc.back().Merge(Loc))
         DebugLoc.push_back(std::move(Loc));
     }
-    DotDebugLocEntries.push_back(std::move(DebugLoc));
   }
 
   // Collect info for variables that were optimized out.
@@ -2406,10 +2409,9 @@ void DwarfDebug::emitDebugLoc() {
       useSplitDwarf() ? Asm->getObjFileLowering().getDwarfLocDWOSection()
                       : Asm->getObjFileLowering().getDwarfLocSection());
   unsigned char Size = Asm->getDataLayout().getPointerSize();
-  unsigned index = 0;
   for (const auto &DebugLoc : DotDebugLocEntries) {
-    Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_loc", index));
-    for (const auto &Entry : DebugLoc) {
+    Asm->OutStreamer.EmitLabel(DebugLoc.Label);
+    for (const auto &Entry : DebugLoc.List) {
       // Set up the range. This range is relative to the entry point of the
       // compile unit. This is a hard coded 0 for low_pc when we're emitting
       // ranges, or the DW_AT_low_pc on the compile unit otherwise.
@@ -2440,7 +2442,6 @@ void DwarfDebug::emitDebugLoc() {
       Asm->OutStreamer.EmitIntValue(0, Size);
       Asm->OutStreamer.EmitIntValue(0, Size);
     }
-    ++index;
   }
 }
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index fcac25d520..424595070d 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -17,6 +17,7 @@
 #include "AsmPrinterHandler.h"
 #include "DIE.h"
 #include "DebugLocEntry.h"
+#include "DebugLocList.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
@@ -288,8 +289,9 @@ class DwarfDebug : public AsmPrinterHandler {
   // Collection of abstract variables.
   DenseMap<const MDNode *, DbgVariable *> AbstractVariables;
 
-  // Collection of DebugLocEntry.
-  SmallVector<SmallVector<DebugLocEntry, 4>, 4> DotDebugLocEntries;
+  // Collection of DebugLocEntry. Stored in a linked list so that DIELocLists
+  // can refer to them in spite of insertions into this list.
+  SmallVector<DebugLocList, 4> DotDebugLocEntries;
 
   // Collection of subprogram DIEs that are marked (at the end of the module)
   // as DW_AT_inline.
@@ -686,7 +688,7 @@ public:
   const DwarfCompileUnit *getPrevCU() const { return PrevCU; }
 
   /// Returns the entries for the .debug_loc section.
-  const SmallVectorImpl<SmallVector<DebugLocEntry, 4>> &
+  const SmallVectorImpl<DebugLocList> &
   getDebugLocEntries() const {
     return DotDebugLocEntries;
   }