From: Nate Begeman <natebegeman@mac.com>
Date: Wed, 4 Mar 2009 19:10:38 +0000 (+0000)
Subject: Fix a thinko in the JIT where the address of a GV was only recorded in the map
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=66941988de6a295649b33f4c2b0f36a094b2244d;p=oota-llvm.git

Fix a thinko in the JIT where the address of a GV was only recorded in the map
  on failure to resolve it.
Do not abort on failure to resolve an external symbol when using dlsym stubs,
  since the symbol may not be in the JIT's address space.  Just use 0.
Allow dlsym stubs to differentiate between GlobalVars and Functions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66050 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 3fd5be7d16e..633a75ed61c 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -609,12 +609,12 @@ void *JIT::getOrEmitGlobalVariable(const GlobalVariable *GV) {
       return (void*)&__dso_handle;
 #endif
     Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(GV->getName().c_str());
-    if (Ptr == 0) {
+    if (Ptr == 0 && !areDlsymStubsEnabled()) {
       cerr << "Could not resolve external global address: "
            << GV->getName() << "\n";
       abort();
-    addGlobalMapping(GV, Ptr);
     }
+    addGlobalMapping(GV, Ptr);
   } else {
     // GlobalVariable's which are not "constant" will cause trouble in a server
     // situation. It's returned in the same block of memory as code which may
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 5c6236dcaeb..22515f3a82c 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -1348,12 +1348,22 @@ void JIT::updateDlsymStubTable() {
   for (unsigned i = 0; i != GVs.size(); ++i)
     MCE->emitInt32(Offsets[i]);
   
-  // Emit the pointers
-  for (unsigned i = 0; i != GVs.size(); ++i)
+  // Emit the pointers.  Verify that they are at least 2-byte aligned, and set
+  // the low bit to 0 == GV, 1 == Function, so that the client code doing the
+  // relocation can write the relocated pointer at the appropriate place in
+  // the stub.
+  for (unsigned i = 0; i != GVs.size(); ++i) {
+    intptr_t Ptr = (intptr_t)Ptrs[i];
+    assert((Ptr & 1) == 0 && "Stub pointers must be at least 2-byte aligned!");
+    
+    if (isa<Function>(GVs[i]))
+      Ptr |= (intptr_t)1;
+           
     if (sizeof(void *) == 8)
-      MCE->emitInt64((intptr_t)Ptrs[i]);
+      MCE->emitInt64(Ptr);
     else
-      MCE->emitInt32((intptr_t)Ptrs[i]);
+      MCE->emitInt32(Ptr);
+  }
   
   // Emit the strings
   for (unsigned i = 0; i != GVs.size(); ++i)