Correctly produce R_X86_64_32 or R_X86_64_32S.

With this patch in

movq    $foo, foo(%rip)
foo:
.long   foo

We produce a R_X86_64_32S for the first relocation and R_X86_64_32 for the
second one.

llvm-svn: 115134
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index 02a5575..689aabc 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -28,6 +28,7 @@
 #include <vector>
 using namespace llvm;
 
+// FIXME: this has been copied from (or to) X86AsmBackend.cpp
 static unsigned getFixupKindLog2Size(unsigned Kind) {
   switch (Kind) {
   default: llvm_unreachable("invalid fixup kind!");
@@ -38,6 +39,7 @@
   case X86::reloc_pcrel_4byte:
   case X86::reloc_riprel_4byte:
   case X86::reloc_riprel_4byte_movq_load:
+  case X86::reloc_signed_4byte:
   case FK_Data_4: return 2;
   case FK_Data_8: return 3;
   }