ELF: Exclude dead symbols from -Map output.

This was previously erroring out if one of the dead symbols was a
TLS symbol and we were able to discard all TLS sections.

Differential Revision: https://reviews.llvm.org/D35397

llvm-svn: 307984

lld/ELF/MapFile.cpp

@@ -55,7 +55,7 @@ template <class ELFT> std::vector<DefinedRegular *> getSymbols() {
     for (SymbolBody *B : File->getSymbols())
       if (B->File == File && !B->isSection())
         if (auto *Sym = dyn_cast<DefinedRegular>(B))
-          if (Sym->Section)
+          if (Sym->Section && Sym->Section->Live)
             V.push_back(Sym);
   return V;
 }

lld/test/ELF/map-gc-sections.s

@@ -0,0 +1,9 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld %t.o -o %t -Map=- --gc-sections | FileCheck %s
+
+.section .tbss,"awT",@nobits
+// CHECK-NOT: foo
+.globl foo
+foo:
+.align 8
+.long 0