Revert "Prevent alias from pointing to weak aliases."

This reverts commit r204781.

I will follow up to with msan folks to see what is what they
were trying to do with aliases to weak aliases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204784 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index b0b8bfebee56e7880ac6c4f3c0f759243eca045a..c959f56ef1168c3b85b26a0222c7a50de9dee5c9 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -681,10 +681,6 @@ the aliasee.
 
 The aliasee must be a definition.
 
-Aliases are not allowed to point to aliases with linkages that can be
-overridden. Since they are only a second name, the possibility of the
-intermediate alias being overridden cannot be represented in an object file.
-
 .. _namedmetadatastructure:
 
 Named Metadata

diff --git a/include/llvm/IR/GlobalAlias.h b/include/llvm/IR/GlobalAlias.h
index 2ca481a515f93d773595888f8f0b4bdaa5055b21..81777af38696e69d8da3285098d29f7ad4bbd282 100644 (file)
--- a/include/llvm/IR/GlobalAlias.h
+++ b/include/llvm/IR/GlobalAlias.h
@@ -64,15 +64,23 @@ public:
   Constant *getAliasee() {
     return getOperand(0);
   }
-
-  /// This method tries to ultimately resolve the alias by going through the
-  /// aliasing chain and trying to find the very last global. Returns NULL if a
-  /// cycle was found.
+  /// getAliasedGlobal() - Aliasee can be either global or bitcast of
+  /// global. This method retrives the global for both aliasee flavours.
   GlobalValue *getAliasedGlobal();
   const GlobalValue *getAliasedGlobal() const {
     return const_cast<GlobalAlias *>(this)->getAliasedGlobal();
   }
 
+  /// resolveAliasedGlobal() - This method tries to ultimately resolve the alias
+  /// by going through the aliasing chain and trying to find the very last
+  /// global. Returns NULL if a cycle was found. If stopOnWeak is false, then
+  /// the whole chain aliasing chain is traversed, otherwise - only strong
+  /// aliases.
+  GlobalValue *resolveAliasedGlobal(bool stopOnWeak = true);
+  const GlobalValue *resolveAliasedGlobal(bool stopOnWeak = true) const {
+    return const_cast<GlobalAlias *>(this)->resolveAliasedGlobal(stopOnWeak);
+  }
+
   static bool isValidLinkage(LinkageTypes L) {
     return isExternalLinkage(L) || isLocalLinkage(L) ||
       isWeakLinkage(L) || isLinkOnceLinkage(L);

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 52806235fd2c46aad4d754f9713589fcddcfb9b5..61961d8ca2d5540c0c2575b379fbb367f8f4472d 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1172,7 +1172,7 @@ SDValue SelectionDAG::getGlobalAddress(const GlobalValue *GV, SDLoc DL,
   if (!GVar) {
     // If GV is an alias then use the aliasee for determining thread-localness.
     if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-      GVar = dyn_cast_or_null<GlobalVariable>(GA->getAliasedGlobal());
+      GVar = dyn_cast_or_null<GlobalVariable>(GA->resolveAliasedGlobal(false));
   }
 
   unsigned Opc;

diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 9d215ec96aee7263a59f39411680e5931858d0dc..4b2f012eafb25ee7bdb8c39c7a4153ea03f0017a 100644 (file)
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -688,7 +688,7 @@ void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
     return TheJIT->getOrEmitGlobalVariable(GV);
 
   if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
-    return TheJIT->getPointerToGlobal(GA->getAliasedGlobal());
+    return TheJIT->getPointerToGlobal(GA->resolveAliasedGlobal(false));
 
   // If we have already compiled the function, return a pointer to its body.
   Function *F = cast<Function>(V);

diff --git a/lib/IR/Globals.cpp b/lib/IR/Globals.cpp
index f338dd76aaa8ac2dd2a4a0e68bc94d5d02299ce9..11152d5d6c21c9a941a62a192e0d36414f5abe00 100644 (file)
--- a/lib/IR/Globals.cpp
+++ b/lib/IR/Globals.cpp
@@ -236,10 +236,10 @@ void GlobalAlias::setAliasee(Constant *Aliasee) {
   setOperand(0, Aliasee);
 }
 
-static GlobalValue *getAliaseeGV(GlobalAlias *GA) {
-  Constant *C = GA->getAliasee();
-  assert(C && "Must alias something");
-
+GlobalValue *GlobalAlias::getAliasedGlobal() {
+  Constant *C = getAliasee();
+  if (C == 0) return 0;
+  
   if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
     return GV;
 
@@ -248,23 +248,30 @@ static GlobalValue *getAliaseeGV(GlobalAlias *GA) {
           CE->getOpcode() == Instruction::AddrSpaceCast ||
           CE->getOpcode() == Instruction::GetElementPtr) &&
          "Unsupported aliasee");
-
+  
   return cast<GlobalValue>(CE->getOperand(0));
 }
 
-GlobalValue *GlobalAlias::getAliasedGlobal() {
+GlobalValue *GlobalAlias::resolveAliasedGlobal(bool stopOnWeak) {
   SmallPtrSet<GlobalValue*, 3> Visited;
 
-  GlobalAlias *GA = this;
+  // Check if we need to stop early.
+  if (stopOnWeak && mayBeOverridden())
+    return this;
+
+  GlobalValue *GV = getAliasedGlobal();
+  Visited.insert(GV);
+
+  // Iterate over aliasing chain, stopping on weak alias if necessary.
+  while (GlobalAlias *GA = dyn_cast<GlobalAlias>(GV)) {
+    if (stopOnWeak && GA->mayBeOverridden())
+      break;
+
+    GV = GA->getAliasedGlobal();
 
-  for (;;) {
-    GlobalValue *GV = getAliaseeGV(GA);
     if (!Visited.insert(GV))
       return 0;
-
-    // Iterate over aliasing chain.
-    GA = dyn_cast<GlobalAlias>(GV);
-    if (!GA)
-      return GV;
   }
+
+  return GV;
 }

diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index f5c8ac623b135ecfe590158f6aa6e58cc0cfb8a7..50c6ae204e93549f699e621aaa8bfa2e36010846 100644 (file)
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -502,14 +502,10 @@ void Verifier::visitGlobalAlias(const GlobalAlias &GA) {
     }
   }
   Assert1(!GV->isDeclaration(), "Alias must point to a definition", &GA);
-  if (const GlobalAlias *GAAliasee = dyn_cast<GlobalAlias>(GV)) {
-    Assert1(!GAAliasee->mayBeOverridden(), "Alias cannot point to a weak alias",
-            &GA);
-  }
 
-  const GlobalValue *AG = GA.getAliasedGlobal();
-  Assert1(AG, "Aliasing chain should end with function or global variable",
-          &GA);
+  const GlobalValue* Resolved = GA.resolveAliasedGlobal(/*stopOnWeak*/ false);
+  Assert1(Resolved,
+          "Aliasing chain should end with function or global variable", &GA);
 
   visitGlobalValue(GA);
 }

diff --git a/lib/Target/PowerPC/PPCAsmPrinter.cpp b/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 9ce8ea911cf0ee64a4cadb5a4d2ac316838a4efc..daf90c86ef92c0df896d36e6b66990cabb21ec59 100644 (file)
--- a/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -381,8 +381,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue =
-          GAlias ? GAlias->getAliasedGlobal() : GValue;
+      const GlobalValue *RealGValue = GAlias ?
+        GAlias->resolveAliasedGlobal(false) : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
       IsExternal = GVar && !GVar->hasInitializer();
@@ -428,8 +428,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     else if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue =
-          GAlias ? GAlias->getAliasedGlobal() : GValue;
+      const GlobalValue *RealGValue = GAlias ?
+        GAlias->resolveAliasedGlobal(false) : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
     
@@ -463,8 +463,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue =
-          GAlias ? GAlias->getAliasedGlobal() : GValue;
+      const GlobalValue *RealGValue = GAlias ?
+        GAlias->resolveAliasedGlobal(false) : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
       IsExternal = GVar && !GVar->hasInitializer();

diff --git a/lib/Target/PowerPC/PPCFastISel.cpp b/lib/Target/PowerPC/PPCFastISel.cpp
index dd45683032ab7cfc5e1d9101eb0a602134df3292..4753160e0913c3e2f0a73bd5ed7522729060274c 100644 (file)
--- a/lib/Target/PowerPC/PPCFastISel.cpp
+++ b/lib/Target/PowerPC/PPCFastISel.cpp
@@ -1863,7 +1863,7 @@ unsigned PPCFastISel::PPCMaterializeGV(const GlobalValue *GV, MVT VT) {
   if (!GVar) {
     // If GV is an alias, use the aliasee for determining thread-locality.
     if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-      GVar = dyn_cast_or_null<GlobalVariable>(GA->getAliasedGlobal());
+      GVar = dyn_cast_or_null<GlobalVariable>(GA->resolveAliasedGlobal(false));
   }
 
   // FIXME: We don't yet handle the complexity of TLS.

diff --git a/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index 0e75bb45757528d8b7a84a7275d94ac834d7e61f..5b09588e0f9dbedb40ca084f54ace550c12386ef 100644 (file)
--- a/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -1413,8 +1413,8 @@ SDNode *PPCDAGToDAGISel::Select(SDNode *N) {
     if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(GA)) {
       const GlobalValue *GValue = G->getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue =
-          GAlias ? GAlias->getAliasedGlobal() : GValue;
+      const GlobalValue *RealGValue = GAlias ?
+        GAlias->resolveAliasedGlobal(false) : GValue;
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
       assert((GVar || isa<Function>(RealGValue)) &&
              "Unexpected global value subclass!");

diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index fe3c870c980a16aebdbf9c635230c270857f08dc..f8a58ec2922c26d627f26ea582ee23fbe3382a33 100644 (file)
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -129,7 +129,7 @@ TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
   // If GV is an alias then use the aliasee for determining
   // thread-localness.
   if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-    GV = GA->getAliasedGlobal();
+    GV = GA->resolveAliasedGlobal(false);
   const GlobalVariable *Var = cast<GlobalVariable>(GV);
 
   bool isLocal = Var->hasLocalLinkage();

diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index 9c57f0d1f195125e01349621a97bb4cc90751051..c3e002082dd09f284fec7ed31e50ccacac4e7d17 100644 (file)
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -363,7 +363,7 @@ bool X86FastISel::handleConstantAddresses(const Value *V, X86AddressMode &AM) {
     // it works...).
     if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
       if (const GlobalVariable *GVar =
-              dyn_cast_or_null<GlobalVariable>(GA->getAliasedGlobal()))
+            dyn_cast_or_null<GlobalVariable>(GA->resolveAliasedGlobal(false)))
         if (GVar->isThreadLocal())
           return false;
 

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 630fba01519497c0323ab222ee1fd1ad59cd6bbe..ec923ba7aa276f6fac573b04725bbcf570bacc35 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -8509,7 +8509,7 @@ X86TargetLowering::LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const {
     // If GV is an alias then use the aliasee for determining
     // thread-localness.
     if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-      GV = GA->getAliasedGlobal();
+      GV = GA->resolveAliasedGlobal(false);
     SDLoc dl(GA);
     SDValue Chain = DAG.getEntryNode();
 

diff --git a/lib/Target/XCore/XCoreISelLowering.cpp b/lib/Target/XCore/XCoreISelLowering.cpp
index 1b74013ac18bbf0f2e2b7415dc008b66828cd101..079e886457bcf0059abf12fa24df97b110e5ee19 100644 (file)
--- a/lib/Target/XCore/XCoreISelLowering.cpp
+++ b/lib/Target/XCore/XCoreISelLowering.cpp
@@ -277,7 +277,7 @@ getGlobalAddressWrapper(SDValue GA, const GlobalValue *GV,
   const GlobalValue *UnderlyingGV = GV;
   // If GV is an alias then use the aliasee to determine the wrapper type
   if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-    UnderlyingGV = GA->getAliasedGlobal();
+    UnderlyingGV = GA->resolveAliasedGlobal();
   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(UnderlyingGV)) {
     if (  ( GVar->isConstant() &&
             UnderlyingGV->isLocalLinkage(GV->getLinkage()) )

diff --git a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index df1549d405ce4e6259146547246edb27c63f91e7..0249df1c6d8378d9d5f23d33072de966c0a9a197 100644 (file)
--- a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -554,7 +554,8 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
     ++i;
     // Don't stop on weak.  We assume people aren't playing games with the
     // instrumentedness of overridden weak aliases.
-    if (Function *F = dyn_cast<Function>(GA->getAliasedGlobal())) {
+    if (Function *F = dyn_cast<Function>(
+            GA->resolveAliasedGlobal(/*stopOnWeak=*/false))) {
       bool GAInst = isInstrumented(GA), FInst = isInstrumented(F);
       if (GAInst && FInst) {
         addGlobalNamePrefix(GA);

diff --git a/test/CodeGen/X86/dllexport-x86_64.ll b/test/CodeGen/X86/dllexport-x86_64.ll
index a38c2d8f8abe1f0a2da41fa8a89ade561ade5d12..1fadfec2543f9926c3956eb26bc42f5a68481ff2 100644 (file)
--- a/test/CodeGen/X86/dllexport-x86_64.ll
+++ b/test/CodeGen/X86/dllexport-x86_64.ll
@@ -65,7 +65,7 @@ define weak_odr dllexport void @weak1() {
 @alias2 = dllexport alias void()* @f1
 
 ; CHECK: .globl alias3
-; CHECK: alias3 = notExported
+; CHECK: alias3 = alias
 @alias3 = dllexport alias void()* @alias
 
 ; CHECK: .weak weak_alias

diff --git a/test/CodeGen/X86/dllexport.ll b/test/CodeGen/X86/dllexport.ll
index 1b34d238693941541acd07833a49b24d47e7af43..7f0dadb6a2ee79d93f71f3f05a6ece5aa682e271 100644 (file)
--- a/test/CodeGen/X86/dllexport.ll
+++ b/test/CodeGen/X86/dllexport.ll
@@ -80,7 +80,7 @@ define weak_odr dllexport void @weak1() {
 @alias2 = dllexport alias void()* @f1
 
 ; CHECK: .globl _alias3
-; CHECK: _alias3 = _notExported
+; CHECK: _alias3 = _alias
 @alias3 = dllexport alias void()* @alias
 
 ; CHECK: .weak _weak_alias

diff --git a/test/Feature/aliases.ll b/test/Feature/aliases.ll
index 7fe9d0b374ec59e658f1132f21ab81a6d9203b10..7ffa5f2601361a21057c5dd434918852ccd71c39 100644 (file)
--- a/test/Feature/aliases.ll
+++ b/test/Feature/aliases.ll
@@ -14,7 +14,7 @@
 define i32 @foo_f() {
   ret i32 0
 }
-@bar_f = alias weak_odr %FunTy* @foo_f
+@bar_f = alias weak %FunTy* @foo_f
 @bar_ff = alias i32()* @bar_f
 
 @bar_i = alias internal i32* @bar

diff --git a/test/Transforms/GlobalOpt/alias-resolve.ll b/test/Transforms/GlobalOpt/alias-resolve.ll
index 2d5a956d14b1266467f49f7f005478dafe9ba4b0..64e3d88af8aa721d1d9f18bab91d8fb85fe4a06d 100644 (file)
--- a/test/Transforms/GlobalOpt/alias-resolve.ll
+++ b/test/Transforms/GlobalOpt/alias-resolve.ll
@@ -1,17 +1,14 @@
 ; RUN: opt < %s -globalopt -S | FileCheck %s
 
 @foo1 = alias void ()* @foo2
-; CHECK: @foo1 = alias void ()* @bar2
+; CHECK: @foo1 = alias void ()* @foo2
 
-@foo2 = alias void()* @bar1
-; CHECK: @foo2 = alias void ()* @bar2
+@foo2 = alias weak void()* @bar1
+; CHECK: @foo2 = alias weak void ()* @bar2
 
 @bar1  = alias void ()* @bar2
 ; CHECK: @bar1 = alias void ()* @bar2
 
-@weak1 = alias weak void ()* @bar2
-; CHECK: @weak1 = alias weak void ()* @bar2
-
 define void @bar2() {
   ret void
 }
@@ -20,16 +17,14 @@ define void @bar2() {
 define void @baz() {
 entry:
          call void @foo1()
-; CHECK: call void @bar2()
+; CHECK: call void @foo2()
 
          call void @foo2()
-; CHECK: call void @bar2()
+; CHECK: call void @foo2()
 
          call void @bar1()
 ; CHECK: call void @bar2()
 
-         call void @weak1()
-; CHECK: call void @weak1()
          ret void
 }