[ORC] Get rid of ObjectLinkingLayer::Plugin::getSyntheticSymbolDependencies.

Instead, when a MaterializationResponsibility contains an initializer symbol,
the Platform classes (MachO, COFF, ELFNix) will now add a defined symbol with
the same name to an arbitary block within the initializer sections, and then
add keep-alive edges from that symbol to all other init section blocks.
ObjectLinkingLayer is updated to automatically discard symbols where the
corresponding MaterializationResponsibility entry has the
MaterializationSideEffecstsOnly flag. This change simplifies both the
ObjectLinkingLayer::Plugin interface and the dependence tracking algorithm,
which no longer needs a special case for "synthetic"
(MaterializationSideEffectsOnly) symbols.

1 files changed, 9 insertions, 10 deletions

diff --git a/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp b/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
index 19d8307..25ab154 100644
--- a/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
@@ -275,24 +275,22 @@ public:
 
       // First check that there aren't any missing symbols.
       size_t NumMaterializationSideEffectsOnlySymbols = 0;
-      SymbolNameVector ExtraSymbols;
       SymbolNameVector MissingSymbols;
-      for (auto &KV : MR->getSymbols()) {
+      for (auto &[Sym, Flags] : MR->getSymbols()) {
 
-        auto I = InternedResult.find(KV.first);
+        auto I = InternedResult.find(Sym);
 
         // If this is a materialization-side-effects only symbol then bump
-        // the counter and make sure it's *not* defined, otherwise make
-        // sure that it is defined.
-        if (KV.second.hasMaterializationSideEffectsOnly()) {
+        // the counter and remove in from the result, otherwise make sure that
+        // it's defined.
+        if (Flags.hasMaterializationSideEffectsOnly()) {
           ++NumMaterializationSideEffectsOnlySymbols;
-          if (I != InternedResult.end())
-            ExtraSymbols.push_back(KV.first);
+          InternedResult.erase(Sym);
           continue;
         } else if (I == InternedResult.end())
-          MissingSymbols.push_back(KV.first);
+          MissingSymbols.push_back(Sym);
         else if (Layer.OverrideObjectFlags)
-          I->second.setFlags(KV.second);
+          I->second.setFlags(Flags);
       }
 
       // If there were missing symbols then report the error.
@@ -303,6 +301,7 @@ public:
 
       // If there are more definitions than expected, add them to the
       // ExtraSymbols vector.
+      SymbolNameVector ExtraSymbols;
       if (InternedResult.size() >
           MR->getSymbols().size() - NumMaterializationSideEffectsOnlySymbols) {
         for (auto &KV : InternedResult)