LTO: Pass SF_Executable flag through to InputFile::Symbol

Summary:
The linker needs to be able to determine whether a symbol is text or data to
handle the case of a common being overridden by a strong definition in an
archive. If the archive contains a text member of the same name as the common,
that function is discarded. However, if the archive contains a data member of
the same name, that strong definition overrides the common. This is a behavior
of ld.bfd, which the Qualcomm linker also supports in LTO.

Here's a test case to illustrate:

####

cat > 1.c << \!
int blah;
!

cat > 2.c << \!
int blah() {
  return 0;
}
!

cat > 3.c << \!
int blah = 20;
!

clang -c 1.c
clang -c 2.c
clang -c 3.c

ar cr lib.a 2.o 3.o
ld 1.o lib.a -t

####

The correct output is:

1.o
(lib.a)3.o

Thanks to Shankar Easwaran and Hemant Kulkarni for the test case!

Reviewers: mehdi_amini, rafael, pcc, davide

Reviewed By: pcc

Subscribers: davide, llvm-commits, inglorion

Differential Revision: https://reviews.llvm.org/D31901

llvm-svn: 300205

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Object/IRSymtab.cpp b/llvm/lib/Object/IRSymtab.cpp
index 1ef2c4bb730..f78b84b388a 100644
--- a/llvm/lib/Object/IRSymtab.cpp
+++ b/llvm/lib/Object/IRSymtab.cpp
@@ -125,6 +125,8 @@ Error Builder::addSymbol(ModuleSymbolTable::Symbol Msym) {
     Sym.Flags |= 1 << storage::Symbol::FB_global;
   if (Flags & object::BasicSymbolRef::SF_FormatSpecific)
     Sym.Flags |= 1 << storage::Symbol::FB_format_specific;
+  if (Flags & object::BasicSymbolRef::SF_Executable)
+    Sym.Flags |= 1 << storage::Symbol::FB_executable;
 
   Sym.ComdatIndex = -1;
   auto *GV = Msym.dyn_cast<GlobalValue *>();