[llvm] r247471 - [MC] Don't crash on division by zero.

[Davide Italiano via llvm-commits]

Author: davide
Date: Fri Sep 11 15:47:35 2015
New Revision: 247471

URL: http://llvm.org/viewvc/llvm-project?rev=247471&view=rev
Log:
[MC] Don't crash on division by zero.

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

Added:
    llvm/trunk/test/MC/ELF/div-by-zero.s
Modified:
    llvm/trunk/lib/MC/MCExpr.cpp

Modified: llvm/trunk/lib/MC/MCExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCExpr.cpp?rev=247471&r1=247470&r2=247471&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCExpr.cpp (original)
+++ llvm/trunk/lib/MC/MCExpr.cpp Fri Sep 11 15:47:35 2015
@@ -739,7 +739,17 @@ bool MCExpr::evaluateAsRelocatableImpl(M
     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;

Added: llvm/trunk/test/MC/ELF/div-by-zero.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/div-by-zero.s?rev=247471&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/div-by-zero.s (added)
+++ llvm/trunk/test/MC/ELF/div-by-zero.s Fri Sep 11 15:47:35 2015
@@ -0,0 +1,6 @@
+// Check that llvm-mc doesn't crash on division by zero.
+// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s 2> %t
+// RUN: FileCheck -input-file %t %s
+
+// CHECK: expected relocatable expression
+.int 1/0