[PATCH] D27959: Use exact vector capacities to store DWARF line tables

[Simon Que via Phabricator via llvm-commits]

sque created this revision.
sque added a reviewer: echristo.
sque added a subscriber: llvm-commits.
Herald added a subscriber: mehdi_amini.

A large binary's DWARF info can contain line tables with thousands of entries. Since dynamically resized vectors don't have exact capacities, there could be a large amount of wasted space. This patch changes the DWARF reader to store the line table rows in vectors with exact capacities.


https://reviews.llvm.org/D27959

Files:
  lib/DebugInfo/DWARF/DWARFDebugLine.cpp


Index: lib/DebugInfo/DWARF/DWARFDebugLine.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -520,6 +520,11 @@
     // rudimentary sequences for address ranges [0x0, 0xsomething).
   }
 
+  // There could be hundreds or thousands of Rows in the line table. The vector
+  // will likely have an internal reserved memory block that is much bigger
+  // than necessary. Reduce the reserved capacity to conserve memroy.
+  Rows.shrink_to_fit();
+
   return end_offset;
 }
 


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