[lld] r329044 - Use OffsetMap in getSectionPiece.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Mon Apr  2 21:06:14 2018
New Revision: 329044

URL: http://llvm.org/viewvc/llvm-project?rev=329044&view=rev
Log:
Use OffsetMap in getSectionPiece.

OffsetMap maps to a SectionPiece index, but we were not taking
advantage of that in getSectionPiece.

With this patch both getOffset and getSectionPiece use OffsetMap and
the binary search is moved to findSectionPiece.

Modified:
    lld/trunk/ELF/InputSection.cpp

Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=329044&r1=329043&r2=329044&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Mon Apr  2 21:06:14 2018
@@ -939,18 +939,29 @@ static It fastUpperBound(It First, It La
 }
 
 // Do binary search to get a section piece at a given input offset.
-SectionPiece *MergeInputSection::getSectionPiece(uint64_t Offset) {
-  if (Data.size() <= Offset)
-    fatal(toString(this) + ": entry is past the end of the section");
+static SectionPiece *findSectionPiece(MergeInputSection *Sec, uint64_t Offset) {
+  if (Sec->Data.size() <= Offset)
+    fatal(toString(Sec) + ": entry is past the end of the section");
 
   // Find the element this offset points to.
   auto I = fastUpperBound(
-      Pieces.begin(), Pieces.end(), Offset,
+      Sec->Pieces.begin(), Sec->Pieces.end(), Offset,
       [](const uint64_t &A, const SectionPiece &B) { return A < B.InputOff; });
   --I;
   return &*I;
 }
 
+SectionPiece *MergeInputSection::getSectionPiece(uint64_t Offset) {
+  // Find a piece starting at a given offset.
+  auto It = OffsetMap.find(Offset);
+  if (It != OffsetMap.end())
+    return &Pieces[It->second];
+
+  // If Offset is not at beginning of a section piece, it is not in the map.
+  // In that case we need to search from the original section piece vector.
+  return findSectionPiece(this, Offset);
+}
+
 // Returns the offset in an output section for a given input offset.
 // Because contents of a mergeable section is not contiguous in output,
 // it is not just an addition to a base output offset.
@@ -965,7 +976,8 @@ uint64_t MergeInputSection::getOffset(ui
 
   // If Offset is not at beginning of a section piece, it is not in the map.
   // In that case we need to search from the original section piece vector.
-  const SectionPiece &Piece = *getSectionPiece(Offset);
+  const SectionPiece &Piece =
+      *findSectionPiece(const_cast<MergeInputSection *>(this), Offset);
   if (!Piece.Live)
     return 0;