[IRObjectFile] Propagate .weak attribute correctly in symbols

[davide]

Summary

This should fix PR28256, see https://llvm.org/bugs/show_bug.cgi?id=28256 for reference.

[• rafael]

Lgtm.

We should also add support for weak undefined, but that can be a followup
patch.

Cheers,
Rafael

[davide]

In D21616#465015, @rafael wrote:

Lgtm.

We should also add support for weak undefined, but that can be a followup
patch.

Sure thing. Thanks for your review, Rafael.

lib/Object/IRObjectFile.cpp

case RecordStreamer::DefinedGlobal:
       break;
     case RecordStreamer::Defined:
       break;
     case RecordStreamer::Global:
     case RecordStreamer::Used:
       Res |= BasicSymbolRef::SF_Undefined;
       Res |= BasicSymbolRef::SF_Global;
       break;
+    case RecordStreamer::GlobalWeak:
+      Res |= BasicSymbolRef::SF_Weak;
+      Res |= BasicSymbolRef::SF_Global;
     }
     AsmUndefinedRefs(Key, BasicSymbolRef::Flags(Res));
   }
 }
 
 IRObjectFile::~IRObjectFile() {
  }
 

lib/Object/RecordStreamer.h

 #ifndef LLVM_LIB_OBJECT_RECORDSTREAMER_H
 #define LLVM_LIB_OBJECT_RECORDSTREAMER_H
 
 #include "llvm/MC/MCStreamer.h"
 
 namespace llvm {
 class RecordStreamer : public MCStreamer {
 public:
-  enum State { NeverSeen, Global, Defined, DefinedGlobal, Used };
+  enum State { NeverSeen, Global, GlobalWeak, Defined, DefinedGlobal, Used };
 
 private:
   StringMap<State> Symbols;
   void markDefined(const MCSymbol &Symbol);
-  void markGlobal(const MCSymbol &Symbol);
+  void markGlobal(const MCSymbol &Symbol, MCSymbolAttr Attribute);
   void markUsed(const MCSymbol &Symbol);
   void visitUsedSymbol(const MCSymbol &Sym) override;
 
 public:
   typedef StringMap<State>::const_iterator const_iterator;
   const_iterator begin();
   const_iterator end();
   RecordStreamer(MCContext &Context);

lib/Object/RecordStreamer.cpp

void RecordStreamer::markDefined(const MCSymbol &Symbol) {
   case Global:
     S = DefinedGlobal;
     break;
   case NeverSeen:
   case Defined:
   case Used:
     S = Defined;
     break;
+  case GlobalWeak:
+    break;
   }
 }
 
-void RecordStreamer::markGlobal(const MCSymbol &Symbol) {
+void RecordStreamer::markGlobal(const MCSymbol &Symbol,
+                                MCSymbolAttr Attribute) {
   State &S = Symbols[Symbol.getName()];
   switch (S) {
   case DefinedGlobal:
   case Defined:
-    S = DefinedGlobal;
+    S = (Attribute == MCSA_Weak) ? GlobalWeak : DefinedGlobal;
     break;
 
   case NeverSeen:
   case Global:
   case Used:
-    S = Global;
+    S = (Attribute == MCSA_Weak) ? GlobalWeak : Global;
+    break;
+  case GlobalWeak:
     break;
   }
 }
 
 void RecordStreamer::markUsed(const MCSymbol &Symbol) {
   State &S = Symbols[Symbol.getName()];
   switch (S) {
   case DefinedGlobal:
   case Defined:
   case Global:
+  case GlobalWeak:
     break;
 
   case NeverSeen:
   case Used:
     S = Used;
     break;
   }
 }

 void RecordStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
   markDefined(*Symbol);
   MCStreamer::EmitAssignment(Symbol, Value);
 }
 
 bool RecordStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
                                          MCSymbolAttr Attribute) {
   if (Attribute == MCSA_Global || Attribute == MCSA_Weak)
-    markGlobal(*Symbol);
+    markGlobal(*Symbol, Attribute);
   return true;
 }
 
 void RecordStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
                                   uint64_t Size, unsigned ByteAlignment) {
   markDefined(*Symbol);
 }
 
 void RecordStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment) {
   markDefined(*Symbol);
 }

test/Object/X86/nm-bitcodeweak.test

 ; RUN: llvm-as %s -o=%t1
 ; RUN: llvm-nm %t1 | FileCheck %s
 
-; CHECK: T __libc_blah
+; CHECK: W __libc_blah
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-freebsd11.0"
 
 module asm ".weak __libc_blah"
 module asm ".equ __libc_blah, blah"