[IRObjectFile] Handle undefined weak symbols in RecordStreamer

[davide]

Summary

Before all the weak symbols were incorrectly reported as defined weak.
This patch extends the RecordStreamer state to include UndefinedWeak.
While I was here, I added a test to ensure we still handle defined weak correctly.
This is an attempt to fix PR30390.

[• rafael]

LGTM. Thanks!

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:
+    case RecordStreamer::DefinedWeak:
       Res |= BasicSymbolRef::SF_Weak;
       Res |= BasicSymbolRef::SF_Global;
       break;
+    case RecordStreamer::UndefinedWeak:
+      Res |= BasicSymbolRef::SF_Weak;
+      Res |= BasicSymbolRef::SF_Undefined;
     }
     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, GlobalWeak, Defined, DefinedGlobal, Used };
+  enum State { NeverSeen, Global, Defined, DefinedGlobal, DefinedWeak, Used,
+               UndefinedWeak};
 
 private:
   StringMap<State> Symbols;
   void markDefined(const MCSymbol &Symbol);
   void markGlobal(const MCSymbol &Symbol, MCSymbolAttr Attribute);
   void markUsed(const MCSymbol &Symbol);
   void visitUsedSymbol(const MCSymbol &Sym) override;
 

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

test/Object/X86/nm-bitcodeweak.test

 ; RUN: llvm-as %s -o=%t1
 ; RUN: llvm-nm %t1 | FileCheck %s
 
+; Check that __libc_blah is reported as defined weak.
 ; 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"
+module asm ".globl blah"
+module asm "blah: ret"

test/Object/X86/nm-undefinedweak.test

+; RUN: llvm-as %s -o=%t1
+; RUN: llvm-nm %t1 | FileCheck %s
+
+; Check that patatino is reported as undefined weak.
+; CHECK: w patatino
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-freebsd11.0"
+
+module asm ".weak patatino"