A64: Debug code should assert on unexpected situation.

src/a64/lithium-codegen-a64.cc

Index: src/a64/lithium-codegen-a64.cc
diff --git a/src/a64/lithium-codegen-a64.cc b/src/a64/lithium-codegen-a64.cc
index 2bad671197fec3743a3ece7c0d1815a2a90a55d1..00ba56a99c2adb08574ef30e0cd9c787bd527901 100644
--- a/src/a64/lithium-codegen-a64.cc
+++ b/src/a64/lithium-codegen-a64.cc
@@ -3665,8 +3665,7 @@ 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);
   }