<div dir="ltr">Hi Andy,<div><br></div><div>MCJIT is supposed to support recompilation of a module, and linking multiple modules (thanks for making the latter work! :). So we need to keep external relocations around in case the module they point to is recompiled.</div>
<div><br></div><div>Cheers,</div><div>Lang.</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, May 7, 2014 at 3:56 PM, Kaylor, Andrew <span dir="ltr"><<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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.<br>
<br>
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?<br>
<br>
-Andy<br>
<div class=""><br>
-----Original Message-----<br>
From: <a href="mailto:llvm-commits-bounces@cs.uiuc.edu">llvm-commits-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:llvm-commits-bounces@cs.uiuc.edu">llvm-commits-bounces@cs.uiuc.edu</a>] On Behalf Of Lang Hames<br>
Sent: Wednesday, May 07, 2014 3:34 PM<br>
To: <a href="mailto:llvm-commits@cs.uiuc.edu">llvm-commits@cs.uiuc.edu</a><br>
Subject: [llvm] r208257 - [RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the<br>
<br>
Author: lhames<br>
Date: Wed May 7 17:34:08 2014<br>
New Revision: 208257<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=208257&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=208257&view=rev</a><br>
Log:<br>
[RuntimeDyld] Make RuntimeDyldImpl::resolveExternalSymbols preserve the relocation entries it applies.<br>
<br>
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).<br>
<br>
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.<br>
<br>
Fixes <rdar://problem/16764378><br>
<br>
<br>
Modified:<br>
llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp<br>
<br>
Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=208257&r1=208256&r2=208257&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=208257&r1=208256&r2=208257&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)<br>
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Wed May<br>
</div>+++ 7 17:34:08 2014<br>
<div class="im HOEnZb">@@ -620,6 +620,8 @@ void RuntimeDyldImpl::resolveRelocationL<br>
}<br>
<br>
void RuntimeDyldImpl::resolveExternalSymbols() {<br>
+ StringMap<RelocationList> ProcessedSymbols;<br>
+<br>
while (!ExternalSymbolRelocations.empty()) {<br>
StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();<br>
<br>
@@ -665,8 +667,20 @@ void RuntimeDyldImpl::resolveExternalSym<br>
resolveRelocationList(Relocs, Addr);<br>
}<br>
<br>
+ ProcessedSymbols[i->first()] = i->second;<br>
ExternalSymbolRelocations.erase(i);<br>
}<br>
+<br>
+ // Restore the relocation entries that were consumed in the loop above:<br>
+ //<br>
+ // FIXME: Replace the following loop with:<br>
+ // std::swap(ProcessedSymbols, ExternalSymbolRelocations)<br>
+ // once StringMap has copy and move construction.<br>
+ for (StringMap<RelocationList>::iterator I = ProcessedSymbols.begin(),<br>
+ E = ProcessedSymbols.end();<br>
+ I != E; ++I) {<br>
+ ExternalSymbolRelocations[I->first()] = I->second; }<br>
}<br>
<br>
</div><div class="HOEnZb"><div class="h5"> //===----------------------------------------------------------------------===//<br>
<br>
<br>
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