Add DoubleTestOp instruction

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 1fe4377941f990987729271f0acee23ef76ad06c..aac9677fb84b432f1d0997b86e946a7ae23ee792 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -497,6 +497,7 @@ class EmbeddedArray<T, 0> {
   M(UnboxedConstant)                                                           \
   M(CheckEitherNonSmi)                                                         \
   M(BinaryDoubleOp)                                                            \
+  M(DoubleTestOp)                                                             \
   M(MathUnary)                                                                 \
   M(MathMinMax)                                                                \
   M(Box)                                                                       \
@@ -5343,6 +5344,54 @@ class BinaryDoubleOpInstr : public TemplateDefinition<2, NoThrow, Pure> {
 };
 
 
+class DoubleTestOpInstr : public TemplateDefinition<1, NoThrow, Pure> {

[Florian Schneider, 2016/10/18 16:03:23]

Can you make this inherit from ComparisonInstr?

This would allow even better code for branches like if (x.isNaN) {...}

It should work like for TestCidsInstr (which also takes only one input), where
we override InputCount() to return 1.

There is a TODO there to make ComparisonInstr more general, and allow 1 or 2
inputs.

[zra, 2016/10/18 17:20:40]

Are there any other cases where we use an inlined getter for a comparison that I
could crib from? Otherwise, I think I'll probably punt on this for now.

[Florian Schneider, 2016/10/18 20:34:20]

I'm not aware of any. It should be straight-forward following the pattern used
for TestCidsInstr. Basically, you only need to add a EmitBranchCode method,
which branches to true- or false-label directly.

I'm ok with doing this as a separate CL.

[zra, 2016/10/18 22:36:32]

Does the inliner magically know that it can take a ComparisonInstr and use its
EmitBranchCode directly? Or is there extra wiring-up that needs to be done?

+ public:
+  DoubleTestOpInstr(MethodRecognizer::Kind op_kind,
+                    Value* d,
+                    intptr_t deopt_id,
+                    TokenPosition token_pos)
+      : TemplateDefinition(deopt_id),
+        op_kind_(op_kind),
+        token_pos_(token_pos) {
+    SetInputAt(0, d);
+  }
+
+  Value* value() const { return inputs_[0]; }
+
+  MethodRecognizer::Kind op_kind() const { return op_kind_; }
+
+  virtual TokenPosition token_pos() const { return token_pos_; }
+
+  virtual bool CanDeoptimize() const { return false; }
+
+  virtual Representation RequiredInputRepresentation(intptr_t idx) const {
+    ASSERT(idx == 0);
+    return kUnboxedDouble;
+  }
+
+  virtual intptr_t DeoptimizationTarget() const {
+    // Direct access since this instruction cannot deoptimize, and the deopt-id
+    // was inherited from another instruction that could deoptimize.
+    return GetDeoptId();
+  }
+
+  PRINT_OPERANDS_TO_SUPPORT
+
+  DECLARE_INSTRUCTION(DoubleTestOp)
+  virtual CompileType ComputeType() const;
+
+  virtual Definition* Canonicalize(FlowGraph* flow_graph);
+
+  virtual bool AttributesEqual(Instruction* other) const { return true; }
+
+ private:
+  const MethodRecognizer::Kind op_kind_;
+  const TokenPosition token_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(DoubleTestOpInstr);
+};
+
+
 class BinaryFloat32x4OpInstr : public TemplateDefinition<2, NoThrow, Pure> {
  public:
   BinaryFloat32x4OpInstr(Token::Kind op_kind,