A64: Debug code should assert on unexpected situation.

R=jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/184533002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19806 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/a64/lithium-codegen-a64.cc

@@ -3732,8 +3732,7 @@ void LCodeGen::DoDeferredMathAbsTagged(LMathAbsTagged* instr,
     Register input = ToRegister(instr->value());
     __ JumpIfSmi(result, &result_ok);
     __ Cmp(input, result);
-    // TODO(all): Shouldn't we assert here?
-    DeoptimizeIf(ne, instr->environment());
+    __ Assert(eq, kUnexpectedValue);
     __ Bind(&result_ok);
   }