[PATCH] [ELF] Set up initial live symbol(s) to avoid incorrect reclaim of atoms

[Davide Italiano]

Hi ruiu, shankarke, Bigcheese, kledzik,

If no initial live symbols are set up, and deadStrip() == true, the Resolver ends up reclaiming all the symbols that aren't absolute. This is wrong.
This patch fixes the issue by setting entrySymbolName() as live, and this allows us to self-host lld when --gc-sections is enabled.
There are still quite a few problems with --gc-sections (quite a few tests failing), so the option can't be enabled by default.

P.S. This particular change depends on --gc-section so can't be tested easily. I would like to commit it as is and start looking at the test failures. I'll eventually add an unit test for this when --gc-sections will be enabled.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7926

Files:
  lib/ReaderWriter/ELF/ELFLinkingContext.cpp

Index: lib/ReaderWriter/ELF/ELFLinkingContext.cpp
===================================================================
--- lib/ReaderWriter/ELF/ELFLinkingContext.cpp
+++ lib/ReaderWriter/ELF/ELFLinkingContext.cpp
@@ -106,6 +106,11 @@
     _writer = createWriterELF(this->targetHandler());
     break;
   }
+
+  // If -dead_strip, set up initial live symbols.
+  if (deadStrip())
+    // Entry point is live.
+    addDeadStripRoot(entrySymbolName());
   return true;
 }

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D7926.20812.patch
Type: text/x-patch
Size: 469 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150227/07366741/attachment.bin>