[ELF] Implement --keep-unique option

The --keep-unique <symbol> option is taken from gold. The intention is that
<symbol> will be prevented from being folded by ICF. Although not
specifically mentioned in the documentation <symbol> only matches
global symbols, with a warning if the symbol is not found.

The implementation finds the Section defining <symbol> and removes it from
the set of sections considered for ICF.

Differential Revision: https://reviews.llvm.org/D46755

llvm-svn: 332332

1 files changed, 5 insertions, 2 deletions

diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
index 50ca557a634..bc70baf8ba3 100644
--- a/lld/ELF/InputSection.h
+++ b/lld/ELF/InputSection.h
@@ -61,6 +61,9 @@ public:
 
   unsigned Bss : 1;
 
+  // Set for sections that should not be folded by ICF.
+  unsigned KeepUnique : 1;
+
   // These corresponds to the fields in Elf_Shdr.
   uint32_t Alignment;
   uint64_t Flags;
@@ -85,8 +88,8 @@ protected:
               uint64_t Entsize, uint64_t Alignment, uint32_t Type,
               uint32_t Info, uint32_t Link)
       : Name(Name), Repl(this), SectionKind(SectionKind), Live(false),
-        Bss(false), Alignment(Alignment), Flags(Flags), Entsize(Entsize),
-        Type(Type), Link(Link), Info(Info) {}
+        Bss(false), KeepUnique(false), Alignment(Alignment), Flags(Flags),
+        Entsize(Entsize), Type(Type), Link(Link), Info(Info) {}
 };
 
 // This corresponds to a section of an input file.