[PATCH] [Core] Do not reclaim absolute atoms in resolver

[Davide Italiano]

Hi ruiu, shankarke, Bigcheese,

After discussion with Rui, he explained me the Resolver shouldn't reclaim absolute atoms at all.
This was found out while testing --gc-sections for the GNU driver, which cause lld to crash because of reclaim of absolute atoms.
The patch proposed is supposed to fix the problem.
I modified an existing test rather than adding a new one. Let me know if it's fine for you.

http://reviews.llvm.org/D7823

Files:
  lib/Core/Resolver.cpp
  test/core/absolute-basic.objtxt

Index: lib/Core/Resolver.cpp
===================================================================
--- lib/Core/Resolver.cpp
+++ lib/Core/Resolver.cpp
@@ -383,11 +383,16 @@

   // Some type of references prevent referring atoms to be dead-striped.
   // Make a reverse map of such references before traversing the graph.
-  for (const Atom *atom : _atoms)
+  // While traversing the list of atoms, mark AbsoluteAtoms as live
+  // in order to avoid reclaim.
+  for (const Atom *atom : _atoms) {
     if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(atom))
       for (const Reference *ref : *defAtom)
         if (isBackref(ref))
           _reverseRef[ref->target()].insert(atom);
+    if (const AbsoluteAtom *absAtom = dyn_cast<AbsoluteAtom>(atom))
+      markLive(absAtom);
+  }

   // By default, shared libraries are built with all globals as dead strip roots
   if (_context.globalsAreDeadStripRoots())
Index: test/core/absolute-basic.objtxt
===================================================================
--- test/core/absolute-basic.objtxt
+++ test/core/absolute-basic.objtxt
@@ -1,4 +1,4 @@
-# RUN: lld -core %s | FileCheck %s
+# RUN: lld -core --dead-strip %s | FileCheck %s

 #
 # Test that absolute symbols are parsed and preserved

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