Don't produce relocations for a difference in a section with no symbols.

We were producing a relocation for
----------------
.section foo,bar
La:
Lb:
 .long   La-Lb
--------------

but not for

---------------------
  .section foo,bar
zed:
La:
Lb:
 .long   La-Lb
----------------

This patch handles the case where both fragments are part of the first atom
in a section and there is no corresponding symbol to that atom.

This fixes pr21328.

llvm-svn: 221304

1 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index 7f6d12ce238..577c4b75f97 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -726,6 +726,10 @@ IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
       return false;
   }
 
+  // If they are not in the same section, we can't compute the diff.
+  if (&SecA != &SecB)
+    return false;
+
   const MCFragment *FA = Asm.getSymbolData(SA).getFragment();
 
   // Bail if the symbol has no fragment.
@@ -733,12 +737,7 @@ IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
     return false;
 
   A_Base = FA->getAtom();
-  if (!A_Base)
-    return false;
-
   B_Base = FB.getAtom();
-  if (!B_Base)
-    return false;
 
   // If the atoms are the same, they are guaranteed to have the same address.
   if (A_Base == B_Base)