From c45c6d4403c06eaf15de8226c42ba67b03e291db Mon Sep 17 00:00:00 2001
From: Frederic Riss <friss@apple.com>
Date: Wed, 11 Mar 2015 18:45:59 +0000
Subject: [PATCH] [dsymutil] Gather function ranges during DIE selection.

Gather the function ranges [low_pc, high_pc) during DIE selection and
store them along with the offset to apply to them to get the linked
addresses.

This is just the data collection part, it comes with no tests. That
information will be used in multiple followup commits to perform the
relocation of line tables and range sections among other things, and
these commits will add tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231957 91177308-0d34-0410-b5e6-96231b3b80d8
---
 tools/dsymutil/DwarfLinker.cpp | 51 +++++++++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/tools/dsymutil/DwarfLinker.cpp b/tools/dsymutil/DwarfLinker.cpp
index a75643530ca..10abfd34237 100644
--- a/tools/dsymutil/DwarfLinker.cpp
+++ b/tools/dsymutil/DwarfLinker.cpp
@@ -10,6 +10,7 @@
 #include "BinaryHolder.h"
 #include "DebugMap.h"
 #include "dsymutil.h"
+#include "llvm/ADT/IntervalMap.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/DIE.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
@@ -47,6 +48,11 @@ bool error(const Twine &Error, const Twine &Context) {
   return false;
 }
 
+template <typename KeyT, typename ValT>
+using HalfOpenIntervalMap =
+    IntervalMap<KeyT, ValT, IntervalMapImpl::NodeSizer<KeyT, ValT>::LeafSize,
+                IntervalMapHalfOpenInfo<KeyT>>;
+
 /// \brief Stores all information relating to a compile unit, be it in
 /// its original instance in the object file to its brand new cloned
 /// and linked DIE tree.
@@ -61,15 +67,19 @@ public:
     bool InDebugMap;    ///< Was this DIE's entity found in the map?
   };
 
-  CompileUnit(DWARFUnit &OrigUnit) : OrigUnit(OrigUnit) {
+  CompileUnit(DWARFUnit &OrigUnit)
+      : OrigUnit(OrigUnit), RangeAlloc(), Ranges(RangeAlloc) {
     Info.resize(OrigUnit.getNumDIEs());
   }
 
-  // Workaround MSVC not supporting implicit move ops
   CompileUnit(CompileUnit &&RHS)
       : OrigUnit(RHS.OrigUnit), Info(std::move(RHS.Info)),
         CUDie(std::move(RHS.CUDie)), StartOffset(RHS.StartOffset),
-        NextUnitOffset(RHS.NextUnitOffset) {}
+        NextUnitOffset(RHS.NextUnitOffset), RangeAlloc(), Ranges(RangeAlloc) {
+    // The CompileUnit container has been 'reserve()'d with the right
+    // size. We cannot move the IntervalMap anyway.
+    llvm_unreachable("CompileUnits should not be moved.");
+  }
 
   DWARFUnit &getOrigUnit() const { return OrigUnit; }
 
@@ -98,6 +108,10 @@ public:
   /// \brief Apply all fixups recored by noteForwardReference().
   void fixupForwardReferences();
 
+  /// \brief Add a function range [\p LowPC, \p HighPC) that is
+  /// relocatad by applying offset \p PCOffset.
+  void addFunctionRange(uint64_t LowPC, uint64_t HighPC, int64_t PCOffset);
+
 private:
   DWARFUnit &OrigUnit;
   std::vector<DIEInfo> Info;  ///< DIE info indexed by DIE index.
@@ -113,6 +127,12 @@ private:
   /// cloning because for forward refences the target DIE's offset isn't
   /// known you emit the reference attribute.
   std::vector<std::pair<DIE *, DIEInteger *>> ForwardDIEReferences;
+
+  HalfOpenIntervalMap<uint64_t, int64_t>::Allocator RangeAlloc;
+  /// \brief The ranges in that interval map are the PC ranges for
+  /// functions in this unit, associated with the PC offset to apply
+  /// to the addresses to get the linked address.
+  HalfOpenIntervalMap<uint64_t, int64_t> Ranges;
 };
 
 uint64_t CompileUnit::computeNextUnitOffset() {
@@ -136,6 +156,11 @@ void CompileUnit::fixupForwardReferences() {
     Ref.second->setValue(Ref.first->getOffset() + getStartOffset());
 }
 
+void CompileUnit::addFunctionRange(uint64_t LowPC, uint64_t HighPC,
+                                   int64_t PCOffset) {
+  Ranges.insert(LowPC, HighPC, PCOffset);
+}
+
 /// \brief A string table that doesn't need relocations.
 ///
 /// We are doing a final link, no need for a string table that
@@ -942,7 +967,25 @@ unsigned DwarfLinker::shouldKeepSubprogramDIE(
   if (Options.Verbose)
     DIE.dump(outs(), const_cast<DWARFUnit *>(&OrigUnit), 0, 8 /* Indent */);
 
-  return Flags | TF_Keep;
+  Flags |= TF_Keep;
+
+  DWARFFormValue HighPcValue;
+  if (!DIE.getAttributeValue(&OrigUnit, dwarf::DW_AT_high_pc, HighPcValue)) {
+    reportWarning("Function without high_pc. Range will be discarded.\n",
+                  &OrigUnit, &DIE);
+    return Flags;
+  }
+
+  uint64_t HighPc;
+  if (HighPcValue.isFormClass(DWARFFormValue::FC_Address)) {
+    HighPc = *HighPcValue.getAsAddress(&OrigUnit);
+  } else {
+    assert(HighPcValue.isFormClass(DWARFFormValue::FC_Constant));
+    HighPc = LowPc + *HighPcValue.getAsUnsignedConstant();
+  }
+
+  Unit.addFunctionRange(LowPc, HighPc, MyInfo.AddrAdjust);
+  return Flags;
 }
 
 /// \brief Check if a DIE should be kept.
-- 
2.34.1