Optimize one byte string comparisons.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 651 matching lines @@
   M(UnboxFloat32x4)                                                            \
   M(BoxInt32x4)                                                                \
   M(UnboxInt32x4)                                                              \
   M(UnboxInteger)                                                              \
   M(BoxInteger)                                                                \
   M(BinaryMintOp)                                                              \
   M(ShiftMintOp)                                                               \
   M(UnaryMintOp)                                                               \
   M(CheckArrayBound)                                                           \
   M(Constraint)                                                                \
-  M(StringFromCharCode)                                                        \
+  M(StringCharCode)                                                            \
   M(StringInterpolate)                                                         \
   M(InvokeMathCFunction)                                                       \
   M(MergedMath)                                                                \
   M(GuardField)                                                                \
   M(IfThenElse)                                                                \
   M(BinaryFloat32x4Op)                                                         \
   M(Simd32x4Shuffle)                                                           \
   M(Simd32x4ShuffleMix)                                                        \
   M(Simd32x4GetSignMask)                                                       \
   M(Float32x4Constructor)                                                      \
@@ skipping 2974 matching lines @@
   virtual bool MayThrow() const { return false; }
 
  private:
   const intptr_t index_scale_;
   const intptr_t class_id_;
 
   DISALLOW_COPY_AND_ASSIGN(LoadIndexedInstr);
 };
 
 
-class StringFromCharCodeInstr : public TemplateDefinition<1> {
+// Either converts a char-code to a string or a string to a charcode (-1 if
+// string is not of length one).
+class StringCharCodeInstr : public TemplateDefinition<1> {

[Florian Schneider, 2013/12/20 09:29:12]

Why packing two different instructions into one? I'd rather have ToCharCode and
FromCharCode as separate instructions. They don't seem to share much code
anyway.

[srdjan, 2013/12/20 19:48:03]

Split it up in two instructions.

  public:
-  StringFromCharCodeInstr(Value* char_code, intptr_t cid) : cid_(cid) {
-    ASSERT(char_code != NULL);
-    ASSERT(char_code->definition()->IsLoadIndexed() &&
-           (char_code->definition()->AsLoadIndexed()->class_id() ==
-            kOneByteStringCid));
-    SetInputAt(0, char_code);
+  enum Kind {
+    kFromCharCode,
+    kToCharCode,
+  };
+  StringCharCodeInstr(Value* val,
+                      intptr_t cid,
+                      StringCharCodeInstr::Kind kind)
+      : cid_(cid), kind_(kind) {
+    ASSERT(val != NULL);
+    if (kind == kFromCharCode) {
+      ASSERT(val->definition()->IsLoadIndexed() &&
+             (val->definition()->AsLoadIndexed()->class_id() ==
+              kOneByteStringCid));
+    } else {
+      ASSERT(kind == kToCharCode);
+    }
+    SetInputAt(0, val);
   }
 
-  DECLARE_INSTRUCTION(StringFromCharCode)
+  DECLARE_INSTRUCTION(StringCharCode)
   virtual CompileType ComputeType() const;
 
-  Value* char_code() const { return inputs_[0]; }
+  Value* char_code() const {
+    ASSERT(kind_ == kFromCharCode);
+    return inputs_[0];
+  }
+  Value* str() const {
+    ASSERT(kind_ == kToCharCode);
+    return inputs_[0];
+  }
+  StringCharCodeInstr::Kind kind() const { return kind_; }
 
   virtual bool CanDeoptimize() const { return false; }
 
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Effects() const { return EffectSet::None(); }
   virtual EffectSet Dependencies() const { return EffectSet::None(); }
   virtual bool AttributesEqual(Instruction* other) const {
-    return other->AsStringFromCharCode()->cid_ == cid_;
+    return (other->AsStringCharCode()->cid_ == cid_) &&
+        (other->AsStringCharCode()->kind_ == kind_);
   }
 
   virtual bool MayThrow() const { return false; }
 
+  virtual void PrintTo(BufferFormatter* f) const;
+
  private:
   const intptr_t cid_;
+  const Kind kind_;
 
-  DISALLOW_COPY_AND_ASSIGN(StringFromCharCodeInstr);
+  DISALLOW_COPY_AND_ASSIGN(StringCharCodeInstr);
 };
 
 
 class StringInterpolateInstr : public TemplateDefinition<1> {
  public:
   StringInterpolateInstr(Value* value, intptr_t token_pos)
       : token_pos_(token_pos), function_(Function::Handle()) {
     SetInputAt(0, value);
   }
 
@@ skipping 3347 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_