Fix up MCFixup::getAccessVariant to handle unary expressions.

This allows correct relocations to be generated for a symbolic
address that is being adjusted by a negative constant. Since r204294,
such expressions have triggered undefined behavior when LLVM was built
without assertions.

Credit goes to Rafael for this patch; I'm submitting it on his behalf
as he is on vacation this week.

llvm-svn: 206192

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCFixup.cpp b/llvm/lib/MC/MCFixup.cpp
index 8f15db571f3..dab4197b1a4 100644
--- a/llvm/lib/MC/MCFixup.cpp
+++ b/llvm/lib/MC/MCFixup.cpp
@@ -12,7 +12,12 @@ using namespace llvm;
 
 static MCSymbolRefExpr::VariantKind getAccessVariant(const MCExpr *Expr) {
   switch (Expr->getKind()) {
-  case MCExpr::Unary:
+  case MCExpr::Unary: {
+    const MCUnaryExpr *UE = cast<MCUnaryExpr>(Expr);
+    assert(getAccessVariant(UE->getSubExpr()) == MCSymbolRefExpr::VK_None);
+    return MCSymbolRefExpr::VK_None;
+  }
+
   case MCExpr::Target:
     llvm_unreachable("unsupported");