ARM Fixups relative to thumb functions need to have the low bit of the value

set for interworking to work properly. rdar://8755956

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121778 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 319f04cfe7..5bc477d7bc 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -235,12 +235,15 @@ bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
   bool IsPCRel = Emitter.getFixupKindInfo(
     Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
   bool IsResolved = true;
+  bool IsThumb = false;
   if (const MCSymbolRefExpr *A = Target.getSymA()) {
     const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
     if (Sym.isDefined())
       Value += Layout.getSymbolOffset(&getSymbolData(Sym));
     else
       IsResolved = false;
+    if (isThumbFunc(&Sym))
+      IsThumb = true;
   }
   if (const MCSymbolRefExpr *B = Target.getSymB()) {
     const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
@@ -263,6 +266,13 @@ bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
       Value -= Layout.getFragmentOffset(DF) + Fixup.getOffset();
   }
 
+  // ARM fixups based from a thumb function address need to have the low
+  // bit set. The actual value is always at least 16-bit aligned, so the
+  // low bit is normally clear and available for use as an ISA flag for
+  // interworking.
+  if (IsThumb)
+    Value |= 1;
+
   return IsResolved;
 }