[Orc] Fix common symbol support in ORC.

Common symbol support in ORC was broken in r270716 when the symbol resolution
rules in RuntimeDyld were changed. With the switch to lazily materialized
symbols in r277386, common symbols can be supported by having
RuntimeDyld::emitCommonSymbols search for (but not materialize!) definitions
elsewhere in the logical dylib.

This patch adds the 'Common' flag to JITSymbolFlags, and the necessary check
to RuntimeDyld::emitCommonSymbols.

llvm-svn: 277397

4 files changed, 37 insertions, 4 deletions

diff --git a/llvm/include/llvm/ExecutionEngine/JITSymbolFlags.h b/llvm/include/llvm/ExecutionEngine/JITSymbolFlags.h
index 7e1d57dabc8..ba76695c953 100644
--- a/llvm/include/llvm/ExecutionEngine/JITSymbolFlags.h
+++ b/llvm/include/llvm/ExecutionEngine/JITSymbolFlags.h
@@ -23,7 +23,8 @@ namespace llvm {
 enum class JITSymbolFlags : char {
   None = 0,
   Weak = 1U << 0,
-  Exported = 1U << 1
+  Common = 1U << 1,
+  Exported = 1U << 2
 };
 
 inline JITSymbolFlags operator|(JITSymbolFlags LHS, JITSymbolFlags RHS) {
@@ -59,6 +60,10 @@ public:
     return (Flags & JITSymbolFlags::Weak) == JITSymbolFlags::Weak;
   }
 
+  bool isCommon() const {
+    return (Flags & JITSymbolFlags::Common) == JITSymbolFlags::Common;
+  }
+
   bool isExported() const {
     return (Flags & JITSymbolFlags::Exported) == JITSymbolFlags::Exported;
   }
@@ -67,6 +72,8 @@ public:
     JITSymbolFlags Flags = JITSymbolFlags::None;
     if (GV.hasWeakLinkage())
       Flags |= JITSymbolFlags::Weak;
+    if (GV.hasCommonLinkage())
+      Flags |= JITSymbolFlags::Common;
     if (!GV.hasLocalLinkage() && !GV.hasHiddenVisibility())
       Flags |= JITSymbolFlags::Exported;
     return Flags;
@@ -77,6 +84,8 @@ public:
     JITSymbolFlags Flags = JITSymbolFlags::None;
     if (Symbol.getFlags() & object::BasicSymbolRef::SF_Weak)
       Flags |= JITSymbolFlags::Weak;
+    if (Symbol.getFlags() & object::BasicSymbolRef::SF_Common)
+      Flags |= JITSymbolFlags::Common;
     if (Symbol.getFlags() & object::BasicSymbolRef::SF_Exported)
       Flags |= JITSymbolFlags::Exported;
     return Flags;
diff --git a/llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h b/llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h
index 1435c86326e..0e8b5ca5976 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h
@@ -122,10 +122,10 @@ private:
       RTDyld.setProcessAllSections(PFC->ProcessAllSections);
       PFC->RTDyld = &RTDyld;
 
+      this->Finalized = true;
       PFC->Finalizer(PFC->Handle, RTDyld, std::move(PFC->Objects),
                      [&]() {
                        this->updateSymbolTable(RTDyld);
-                       this->Finalized = true;
                      });
 
       // Release resources.
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 1e0903349ef..1b40329eb19 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -584,13 +584,19 @@ Error RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
       return NameOrErr.takeError();
 
     // Skip common symbols already elsewhere.
-    if (GlobalSymbolTable.count(Name) ||
-        Resolver.findSymbolInLogicalDylib(Name)) {
+    if (GlobalSymbolTable.count(Name)) {
       DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
                    << "'\n");
       continue;
     }
 
+    if (auto Sym = Resolver.findSymbolInLogicalDylib(Name)) {
+      if (!Sym.isCommon()) {
+        DEBUG(dbgs() << "\tSkipping common symbol '" << Name
+                     << "' in favor of stronger definition.\n");
+        continue;
+      }
+    }
     uint32_t Align = Sym.getAlignment();
     uint64_t Size = Sym.getCommonSize();
 
diff --git a/llvm/test/ExecutionEngine/OrcLazy/common-symbols.ll b/llvm/test/ExecutionEngine/OrcLazy/common-symbols.ll
new file mode 100644
index 00000000000..ece490ae8c8
--- /dev/null
+++ b/llvm/test/ExecutionEngine/OrcLazy/common-symbols.ll
@@ -0,0 +1,18 @@
+; RUN: lli -jit-kind=orc-lazy %s | FileCheck %s
+;
+; CHECK: 7
+
+@x = common global i32 0, align 4
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+
+define i32 @main() {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  store i32 7, i32* @x, align 4
+  %0 = load i32, i32* @x, align 4
+  %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 %0)
+  ret i32 0
+}
+
+declare i32 @printf(i8*, ...)