[turbofan] Handle impossible types (Type::None()) in the backend.

src/compiler/opcodes.h

Index: src/compiler/opcodes.h
diff --git a/src/compiler/opcodes.h b/src/compiler/opcodes.h
index e2964dd7c16d79d810e0055c4338330a39b3e26c..488b172f9816b78627c9f92e4b273ee62cabf98f 100644
--- a/src/compiler/opcodes.h
+++ b/src/compiler/opcodes.h
@@ -376,6 +376,12 @@
   V(ChangeInt32ToInt64)         \
   V(ChangeUint32ToFloat64)      \
   V(ChangeUint32ToUint64)       \
+  V(ImpossibleToBit)            \

[Benedikt Meurer, 2016/07/24 17:23:41]

Hm, why not have a single Impossible machine/common operator, with a
MachineRepresentation parameter? That would also simplify the instruction
selection code.

[Jarin, 2016/07/24 18:15:40]

It just seemed that parametrized machine ops are discouraged. I think I prefer
this explicit way - it is nice when the output representation is obvious from
the opcode.

[Benedikt Meurer, 2016/07/25 03:36:51]

I'd have made this a common operator in the same spirit as Phi/Select that know
their representation. But acknowledge your decision.

+  V(ImpossibleToWord32)         \
+  V(ImpossibleToWord64)         \
+  V(ImpossibleToFloat32)        \
+  V(ImpossibleToFloat64)        \
+  V(ImpossibleToTagged)         \
   V(TruncateFloat64ToFloat32)   \
   V(TruncateInt64ToInt32)       \
   V(RoundFloat64ToInt32)        \