Reapply: DebugInfo: Assume an absence of ranges or high_pc on a CU means the CU is empty (devoid of code addresses)

Originally committed in r349333, reverted in r349353.

GCC emitted these unconditionally on/before 4.4/March 2012
Clang emitted these unconditionally on/before 3.5/March 2014

This improves performance when parsing CUs (especially those using split
DWARF) that contain no code ranges (such as the mini CUs that may be
created by ThinLTO importing - though generally they should be/are
avoided, especially for Split DWARF because it produces a lot of very
small CUs, which don't scale well in a bunch of other ways too
(including size)).

The revert was due to a (Google internal) test that had some checked in old
object files missing DW_AT_ranges. That's since been fixed.

llvm-svn: 349968

1 files changed, 0 insertions, 21 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 48900e4b7a2..569512cb8f0 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -581,27 +581,6 @@ void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
   } else
     WithColor::error() << "decoding address ranges: "
                        << toString(CUDIERangesOrError.takeError()) << '\n';
-
-  // This function is usually called if there in no .debug_aranges section
-  // in order to produce a compile unit level set of address ranges that
-  // is accurate. If the DIEs weren't parsed, then we don't want all dies for
-  // all compile units to stay loaded when they weren't needed. So we can end
-  // up parsing the DWARF and then throwing them all away to keep memory usage
-  // down.
-  const bool ClearDIEs = extractDIEsIfNeeded(false) > 1;
-  getUnitDIE().collectChildrenAddressRanges(CURanges);
-
-  // Collect address ranges from DIEs in .dwo if necessary.
-  bool DWOCreated = parseDWO();
-  if (DWO)
-    DWO->collectAddressRanges(CURanges);
-  if (DWOCreated)
-    DWO.reset();
-
-  // Keep memory down by clearing DIEs if this generate function
-  // caused them to be parsed.
-  if (ClearDIEs)
-    clearDIEs(true);
 }
 
 void DWARFUnit::updateAddressDieMap(DWARFDie Die) {