[llvm] r208257 - [RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the

[Kaylor, Andrew]

The discarding of processed relocations was an intentional choice.  The relocation map can take up a pretty fair amount of memory, particularly in the case where you have a large number of modules that reference one another.  Keeping the relocation map around will cause memory bloat issues for some clients.

My thinking was that once a module was finalized you can't remap its sections anymore.  Do you have a use case where this is an unacceptable limitation?

-Andy

-----Original Message-----
From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Lang Hames
Sent: Wednesday, May 07, 2014 3:34 PM
To: llvm-commits at cs.uiuc.edu
Subject: [llvm] r208257 - [RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the

Author: lhames
Date: Wed May  7 17:34:08 2014
New Revision: 208257

URL: http://llvm.org/viewvc/llvm-project?rev=208257&view=rev
Log:
[RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the relocation entries it applies.

Prior to this patch, RuntimeDyldImpl::resolveExternalSymbols discarded relocations for external symbols once they had been applied. This causes issues if the client calls MCJIT::finalizeLoadedModules more than once, and updates the location of any symbols in between (e.g. by calling MCJIT::mapSectionAddress).

No test case yet: None of our in-tree memory managers support moving sections around. I'll have to hack up a dummy memory manager before I can write a unit test.

Fixes <rdar://problem/16764378>


Modified:
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=208257&r1=208256&r2=208257&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Wed May  
+++ 7 17:34:08 2014
@@ -620,6 +620,8 @@ void RuntimeDyldImpl::resolveRelocationL
 }
 
 void RuntimeDyldImpl::resolveExternalSymbols() {
+  StringMap<RelocationList> ProcessedSymbols;
+
   while (!ExternalSymbolRelocations.empty()) {
     StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();
 
@@ -665,8 +667,20 @@ void RuntimeDyldImpl::resolveExternalSym
       resolveRelocationList(Relocs, Addr);
     }
 
+    ProcessedSymbols[i->first()] = i->second;
     ExternalSymbolRelocations.erase(i);
   }
+
+  // Restore the relocation entries that were consumed in the loop above:
+  //
+  // FIXME: Replace the following loop with:
+  //           std::swap(ProcessedSymbols, ExternalSymbolRelocations)
+  //        once StringMap has copy and move construction.
+  for (StringMap<RelocationList>::iterator I = ProcessedSymbols.begin(),
+                                           E = ProcessedSymbols.end();
+       I != E; ++I) {
+    ExternalSymbolRelocations[I->first()] = I->second;  }
 }
 
 //===----------------------------------------------------------------------===//


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