[MC] Don't crash on division by zero.

Differential Revision:	http://reviews.llvm.org/D12776

llvm-svn: 247471

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index a30ceecc952..90cd7fa07b1 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -739,7 +739,17 @@ bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
     case MCBinaryExpr::AShr: Result = LHS >> RHS; break;
     case MCBinaryExpr::Add:  Result = LHS + RHS; break;
     case MCBinaryExpr::And:  Result = LHS & RHS; break;
-    case MCBinaryExpr::Div:  Result = LHS / RHS; break;
+    case MCBinaryExpr::Div: {
+      // Handle division by zero. gas just emits a warning and keeps going,
+      // we try to be stricter.
+      // FIXME: Currently the caller of this function has no way to understand
+      // we're bailing out because of 'division by zero'. Therefore, it will
+      // emit a 'expected relocatable expression' error. It would be nice to
+      // change this code to emit a better diagnostic.
+      if (RHS == 0)
+        return false;
+      Result = LHS / RHS; break;
+    }
     case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
     case MCBinaryExpr::GT:   Result = LHS > RHS; break;
     case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;