From a364f09f185f65c3d23d93a313177ca8da3d7877 Mon Sep 17 00:00:00 2001
From: Dehao Chen <dehao@google.com>
Date: Wed, 19 Apr 2017 20:09:38 +0000
Subject: Using address range map to speedup finding inline stack for address.

Summary:
In the current implementation, to find inline stack for an address incurs expensive linear search in 2 places:

* linear search for the top-level DIE
* recursive linear traverse the DIE tree to find the path to the leaf DIE

In this patch, a map is built from address to its corresponding leaf DIE. The inline stack is built by traversing from the leaf DIE up to the root DIE. This speeds up batch symbolization by ~10X without noticible memory overhead.

Reviewers: dblaikie

Reviewed By: dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32177

llvm-svn: 300742
---
 llvm/lib/DebugInfo/DWARF/DWARFDie.cpp  | 26 --------------
 llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp | 65 +++++++++++++++++++++++++---------
 2 files changed, 48 insertions(+), 43 deletions(-)

(limited to 'llvm/lib/DebugInfo')

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index b88cc636d84..24039eb3520 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -352,32 +352,6 @@ void DWARFDie::dump(raw_ostream &OS, unsigned RecurseDepth,
   }
 }
 
-void DWARFDie::getInlinedChainForAddress(
-    const uint64_t Address, SmallVectorImpl<DWARFDie> &InlinedChain) const {
-  if (isNULL())
-    return;
-  DWARFDie DIE(*this);
-  while (DIE) {
-    // Append current DIE to inlined chain only if it has correct tag
-    // (e.g. it is not a lexical block).
-    if (DIE.isSubroutineDIE())
-      InlinedChain.push_back(DIE);
-
-    // Try to get child which also contains provided address.
-    DWARFDie Child = DIE.getFirstChild();
-    while (Child) {
-      if (Child.addressRangeContainsAddress(Address)) {
-        // Assume there is only one such child.
-        break;
-      }
-      Child = Child.getSibling();
-    }
-    DIE = Child;
-  }
-  // Reverse the obtained chain to make the root of inlined chain last.
-  std::reverse(InlinedChain.begin(), InlinedChain.end());
-}
-
 DWARFDie DWARFDie::getParent() const {
   if (isValid())
     return U->getParent(Die);
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 4ee8e8f46d2..f76b917283c 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -343,36 +343,67 @@ void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
     clearDIEs(true);
 }
 
-DWARFDie
-DWARFUnit::getSubprogramForAddress(uint64_t Address) {
-  extractDIEsIfNeeded(false);
-  for (const DWARFDebugInfoEntry &D : DieArray) {
-    DWARFDie DIE(this, &D);
-    if (DIE.isSubprogramDIE() &&
-        DIE.addressRangeContainsAddress(Address)) {
-      return DIE;
+void DWARFUnit::updateAddressDieMap(DWARFDie Die) {
+  if (Die.isSubroutineDIE()) {
+    for (const auto &R : Die.getAddressRanges()) {
+      // Ignore 0-sized ranges.
+      if (R.first == R.second)
+        continue;
+      auto B = AddrDieMap.upper_bound(R.first);
+      if (B != AddrDieMap.begin() && R.first < (--B)->second.first) {
+        // The range is a sub-range of existing ranges, we need to split the
+        // existing range.
+        if (R.second < B->second.first)
+          AddrDieMap[R.second] = B->second;
+        if (R.first > B->first)
+          AddrDieMap[B->first].first = R.first;
+      }
+      AddrDieMap[R.first] = std::make_pair(R.second, Die);
     }
   }
-  return DWARFDie();
+  // Parent DIEs are added to the AddrDieMap prior to the Children DIEs to
+  // simplify the logic to update AddrDieMap. The child's range will always
+  // be equal or smaller than the parent's range. With this assumption, when
+  // adding one range into the map, it will at most split a range into 3
+  // sub-ranges.
+  for (DWARFDie Child = Die.getFirstChild(); Child; Child = Child.getSibling())
+    updateAddressDieMap(Child);
+}
+
+DWARFDie DWARFUnit::getSubroutineForAddress(uint64_t Address) {
+  extractDIEsIfNeeded(false);
+  if (AddrDieMap.empty())
+    updateAddressDieMap(getUnitDIE());
+  auto R = AddrDieMap.upper_bound(Address);
+  if (R == AddrDieMap.begin())
+    return DWARFDie();
+  // upper_bound's previous item contains Address.
+  --R;
+  if (Address >= R->second.first)
+    return DWARFDie();
+  return R->second.second;
 }
 
 void
 DWARFUnit::getInlinedChainForAddress(uint64_t Address,
                                      SmallVectorImpl<DWARFDie> &InlinedChain) {
-  // First, find a subprogram that contains the given address (the root
+  // First, find the subroutine that contains the given address (the leaf
   // of inlined chain).
-  DWARFDie SubprogramDIE;
+  DWARFDie SubroutineDIE;
   // Try to look for subprogram DIEs in the DWO file.
   parseDWO();
   if (DWO)
-    SubprogramDIE = DWO->getUnit()->getSubprogramForAddress(Address);
+    SubroutineDIE = DWO->getUnit()->getSubroutineForAddress(Address);
   else
-    SubprogramDIE = getSubprogramForAddress(Address);
+    SubroutineDIE = getSubroutineForAddress(Address);
 
-  // Get inlined chain rooted at this subprogram DIE.
-  if (SubprogramDIE)
-    SubprogramDIE.getInlinedChainForAddress(Address, InlinedChain);
-  else
+  if (SubroutineDIE) {
+    while (SubroutineDIE) {
+      if (SubroutineDIE.isSubroutineDIE())
+        InlinedChain.push_back(SubroutineDIE);
+      SubroutineDIE  = SubroutineDIE.getParent();
+    }
+  } else
     InlinedChain.clear();
 }
 
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