Use 0 as sh_link when we don't have a dynamic symbol table.

It doesn't make sense to link from an alloc section to a non alloc
one as we were doing.

This matches the behavior of both gold and bfd.

llvm-svn: 315584

lld/ELF/SyntheticSections.cpp

@@ -1284,8 +1284,10 @@ template <class ELFT> unsigned RelocationSection<ELFT>::getRelocOffset() {
 }
 
 template <class ELFT> void RelocationSection<ELFT>::finalizeContents() {
-  this->Link = InX::DynSymTab ? InX::DynSymTab->getParent()->SectionIndex
-                              : InX::SymTab->getParent()->SectionIndex;
+  // If all relocations are *RELATIVE they don't refer to any
+  // dynamic symbol and we don't need a dynamic symbol table. If that
+  // is the case, just use 0 as the link.
+  this->Link = InX::DynSymTab ? InX::DynSymTab->getParent()->SectionIndex : 0;
 
   // Set required output section properties.
   getParent()->Link = this->Link;

lld/test/ELF/aarch64-gnu-ifunc.s

@@ -15,7 +15,7 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0x158
 // CHECK-NEXT:  Size: 48
-// CHECK-NEXT:  Link: 6
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: 0
 // CHECK-NEXT:  AddressAlignment: 8
 // CHECK-NEXT:  EntrySize: 24

lld/test/ELF/gnu-ifunc-i386.s

@@ -15,7 +15,7 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0xD4
 // CHECK-NEXT:  Size: 16
-// CHECK-NEXT:  Link: 6
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: 0
 // CHECK-NEXT:  AddressAlignment: 4
 // CHECK-NEXT:  EntrySize: 8

lld/test/ELF/gnu-ifunc.s

@@ -15,7 +15,7 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0x158
 // CHECK-NEXT:  Size: 48
-// CHECK-NEXT:  Link: 6
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: 0
 // CHECK-NEXT:  AddressAlignment: 8
 // CHECK-NEXT:  EntrySize: 24