Fix IsDeletable() for HStringAdd, HStringCharCodeAt, HStringCharFromCode.

BUG=
R=mstarzinger@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/20241005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15934 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -3718,11 +3718,6 @@ Representation HUnaryMathOperation::RepresentationFromInputs() {
 }
 
 
-HType HStringCharFromCode::CalculateInferredType() {
-  return HType::String();
-}
-
-
 void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
                                           HValue* dominator) {
   ASSERT(side_effect == kChangesNewSpacePromotion);

src/hydrogen-instructions.h

@@ -423,6 +423,24 @@ class HType {
     return IsHeapNumber() || IsString() || IsBoolean() || IsNonPrimitive();
   }
 
+  bool ToStringOrToNumberCanBeObserved(Representation representation) {
+    switch (type_) {
+      case kTaggedPrimitive:  // fallthru
+      case kTaggedNumber:     // fallthru
+      case kSmi:              // fallthru
+      case kHeapNumber:       // fallthru
+      case kString:           // fallthru
+      case kBoolean:
+        return false;
+      case kJSArray:          // fallthru
+      case kJSObject:
+        return true;
+      case kTagged:
+        break;
+    }
+    return !representation.IsSmiOrInteger32() && !representation.IsDouble();
+  }
+
   static HType TypeFromValue(Handle<Object> value);
 
   const char* ToString();
@@ -1126,6 +1144,18 @@ class HValue: public ZoneObject {
     }
   }
 
+  // Returns true conservatively if the program might be able to observe a
+  // ToString() operation on this value.
+  bool ToStringCanBeObserved() const {
+    return type().ToStringOrToNumberCanBeObserved(representation());
+  }
+
+  // Returns true conservatively if the program might be able to observe a
+  // ToNumber() operation on this value.
+  bool ToNumberCanBeObserved() const {
+    return type().ToStringOrToNumberCanBeObserved(representation());
+  }
+
  protected:
   void TryGuaranteeRangeRecursive(RangeEvaluationContext* context);
 
@@ -3320,9 +3350,6 @@ class HPhi: public HValue {
 
   void SimplifyConstantInputs();
 
-  // TODO(titzer): we can't eliminate the receiver for generating backtraces
-  virtual bool IsDeletable() const { return !IsReceiver(); }
-
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {
@@ -3342,6 +3369,9 @@ class HPhi: public HValue {
   int indirect_uses_[Representation::kNumRepresentations];
   int phi_id_;
   InductionVariableData* induction_variable_data_;
+
+  // TODO(titzer): we can't eliminate the receiver for generating backtraces
+  virtual bool IsDeletable() const { return !IsReceiver(); }
 };
 
 
@@ -3653,9 +3683,9 @@ class HBinaryOperation: public HTemplateInstruction<3> {
     observed_input_representation_[1] = Representation::None();
   }
 
-  HValue* context() { return OperandAt(0); }
-  HValue* left() { return OperandAt(1); }
-  HValue* right() { return OperandAt(2); }
+  HValue* context() const { return OperandAt(0); }
+  HValue* left() const { return OperandAt(1); }
+  HValue* right() const { return OperandAt(2); }
 
   // True if switching left and right operands likely generates better code.
   bool AreOperandsBetterSwitched() {
@@ -3909,9 +3939,6 @@ class HBoundsCheck: public HTemplateInstruction<2> {
   virtual Representation RequiredInputRepresentation(int arg_index) {
     return representation();
   }
-  virtual bool IsDeletable() const {
-    return skip_check() && !FLAG_debug_code;
-  }
 
   virtual bool IsRelationTrueInternal(NumericRelation relation,
                                       HValue* related_value,
@@ -3948,6 +3975,11 @@ class HBoundsCheck: public HTemplateInstruction<2> {
   int scale_;
   RangeGuaranteeDirection responsibility_direction_;
   bool allow_equality_;
+
+ private:
+  virtual bool IsDeletable() const {
+    return skip_check() && !FLAG_debug_code;
+  }
 };
 
 
@@ -6451,8 +6483,9 @@ class HStringAdd: public HBinaryOperation {
     SetGVNFlag(kChangesNewSpacePromotion);
   }
 
-  // TODO(svenpanne) Might be safe, but leave it out until we know for sure.
-  //  virtual bool IsDeletable() const { return true; }
+  // No side-effects except possible allocation.
+  // NOTE: this instruction _does not_ call ToString() on its inputs.
+  virtual bool IsDeletable() const { return true; }
 
   const StringAddFlags flags_;
 };
@@ -6477,9 +6510,9 @@ class HStringCharCodeAt: public HTemplateInstruction<3> {
         : Representation::Tagged();
   }
 
-  HValue* context() { return OperandAt(0); }
-  HValue* string() { return OperandAt(1); }
-  HValue* index() { return OperandAt(2); }
+  HValue* context() const { return OperandAt(0); }
+  HValue* string() const { return OperandAt(1); }
+  HValue* index() const { return OperandAt(2); }
 
   DECLARE_CONCRETE_INSTRUCTION(StringCharCodeAt)
 
@@ -6490,9 +6523,9 @@ class HStringCharCodeAt: public HTemplateInstruction<3> {
     return new(zone) Range(0, String::kMaxUtf16CodeUnit);
   }
 
-  // TODO(svenpanne) Might be safe, but leave it out until we know for sure.
-  // private:
-  //  virtual bool IsDeletable() const { return true; }
+ private:
+  // No side effects: runtime function assumes string + number inputs.
+  virtual bool IsDeletable() const { return true; }
 };
 
 
@@ -6507,10 +6540,10 @@ class HStringCharFromCode: public HTemplateInstruction<2> {
         ? Representation::Tagged()
         : Representation::Integer32();
   }
-  virtual HType CalculateInferredType();
+  virtual HType CalculateInferredType() { return HType::String(); }
 
-  HValue* context() { return OperandAt(0); }
-  HValue* value() { return OperandAt(1); }
+  HValue* context() const { return OperandAt(0); }
+  HValue* value() const { return OperandAt(1); }
 
   virtual bool DataEquals(HValue* other) { return true; }
 
@@ -6525,8 +6558,9 @@ class HStringCharFromCode: public HTemplateInstruction<2> {
     SetGVNFlag(kChangesNewSpacePromotion);
   }
 
-  // TODO(svenpanne) Might be safe, but leave it out until we know for sure.
-  // virtual bool IsDeletable() const { return true; }
+  virtual bool IsDeletable() const {
+    return !value()->ToNumberCanBeObserved();
+  }
 };
 
 

test/mjsunit/compiler/dead-string-add-warm.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+function dead1(a, b) {
+    var x = "a" + "b";
+    return a; // x, "a", and "b" are dead code
+}
+
+function dead2(a, b) {
+    var x = "0" + a;
+    var y = "0" + b;
+    return a; // x and y are both dead
+}
+
+function dead3(a, b) {
+    a = a ? "1" : "0";
+    b = b ? "1" : "0";
+    var x = a + "0";
+    var y = b + "0";
+    return a; // x and y are both dead
+}
+
+function run() {
+  assertEquals(33, dead1(33, 32));
+  assertEquals(33, dead2(33, 32));
+  assertEquals("1", dead3(33, 32));
+
+  assertEquals(31, dead1(31, 30));
+  assertEquals(31, dead2(31, 30));
+  assertEquals("1", dead3(31, 32));
+
+  assertEquals(0, dead1(0, 30));
+  assertEquals(0, dead2(0, 30));
+  assertEquals("0", dead3(0, 32));
+
+  assertEquals(true, dead1(true, 0));
+  assertEquals(true, dead2(true, 0));
+  assertEquals("1", dead3(true, 0));
+
+  assertEquals("true", dead1("true", 0));
+  assertEquals("true", dead2("true", 0));
+  assertEquals("1", dead3("true", 0));
+}
+
+run();
+run();
+%OptimizeFunctionOnNextCall(dead1);
+%OptimizeFunctionOnNextCall(dead2);
+%OptimizeFunctionOnNextCall(dead3);
+run();

test/mjsunit/compiler/dead-string-add.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+function dead1(a, b) {
+    var x = "a" + "b";
+    return a; // x, "a", and "b" are dead code
+}
+
+function dead2(a, b) {
+    var x = a + "0";
+    var y = b + "0";
+    return a; // x and y are both dead
+}
+
+function dead3(a, b) {
+    a = a ? "1" : "0";
+    b = b ? "1" : "0";
+    var x = a + "0";
+    var y = b + "0";
+    return a; // x and y are both dead
+}
+
+assertEquals(33, dead1(33, 32));
+assertEquals(33, dead2(33, 32));
+assertEquals("1", dead3(33, 32));
+
+assertEquals(31, dead1(31, 30));
+assertEquals(31, dead2(31, 30));
+assertEquals("1", dead3(31, 32));
+
+assertEquals(0, dead1(0, 30));
+assertEquals(0, dead2(0, 30));
+assertEquals("0", dead3(0, 32));
+
+assertEquals(true, dead1(true, 0));
+assertEquals(true, dead2(true, 0));
+assertEquals("1", dead3(true, 0));
+
+assertEquals("true", dead1("true", 0));
+assertEquals("true", dead2("true", 0));
+assertEquals("1", dead3("true", 0));

test/mjsunit/compiler/dead-string-char-code-at.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+var S1 = "string1";
+var S2 = "@@string2";
+
+function dead1(a, b) {
+    var x = %StringCharCodeAt(a, 4);
+    return a; // x is dead code
+}
+
+function dead2(a, b) {
+    var x = %StringCharCodeAt(a, 3);
+    var y = %StringCharCodeAt(b, 1);
+    return a; // x and y are both dead
+}
+
+function dead3(a, b) {
+    a = a ? "11" : "12";
+    b = b ? "13" : "14";
+    var x = %StringCharCodeAt(a, 2);
+    var y = %StringCharCodeAt(b, 0);
+    return a; // x and y are both dead
+}
+
+function test() {
+  var S3 = S1 + S2;
+
+  assertEquals(S1, dead1(S1, S2));
+  assertEquals(S1, dead2(S1, S2));
+  assertEquals("11", dead3(S1, S2));
+
+  assertEquals(S2, dead1(S2, 677));
+  assertEquals(S2, dead2(S2, S3));
+  assertEquals("11", dead3(S2, S3));
+
+  assertEquals(S3, dead1(S3, 399));
+  assertEquals(S3, dead2(S3, "false"));
+  assertEquals("12", dead3(0, 32));
+
+  assertEquals(S3, dead1(S3, 0));
+  assertEquals(S3, dead2(S3, S1));
+  assertEquals("11", dead3(S3, 0));
+
+  assertEquals("true", dead1("true", 0));
+  assertEquals("true", dead2("true", S3));
+  assertEquals("11", dead3("true", 0));
+}
+
+test();
+test();
+%OptimizeFunctionOnNextCall(dead1);
+%OptimizeFunctionOnNextCall(dead2);
+%OptimizeFunctionOnNextCall(dead3);
+test();

test/mjsunit/compiler/dead-string-char-code-at2.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+var S1 = "string1";
+var S2 = "@@string2";
+
+function dead1(a, b) {
+    var x = %_StringCharCodeAt(a, 4);
+    return a; // x is dead code
+}
+
+function dead2(a, b) {
+    var x = %_StringCharCodeAt(a, 3);
+    var y = %_StringCharCodeAt(b, 1);
+    return a; // x and y are both dead
+}
+
+function dead3(a, b) {
+    a = a ? "11" : "12";
+    b = b ? "13" : "14";
+    var x = %_StringCharCodeAt(a, 2);
+    var y = %_StringCharCodeAt(b, 0);
+    return a; // x and y are both dead
+}
+
+function test() {
+  var S3 = S1 + S2;
+
+  assertEquals(S1, dead1(S1, S2));
+  assertEquals(S1, dead2(S1, S2));
+  assertEquals("11", dead3(S1, S2));
+
+  assertEquals(S2, dead1(S2, 677));
+  assertEquals(S2, dead2(S2, S3));
+  assertEquals("11", dead3(S2, S3));
+
+  assertEquals(S3, dead1(S3, 399));
+  assertEquals(S3, dead2(S3, "false"));
+  assertEquals("12", dead3(0, 32));
+
+  assertEquals(S3, dead1(S3, 0));
+  assertEquals(S3, dead2(S3, S1));
+  assertEquals("11", dead3(S3, 0));
+
+  assertEquals("true", dead1("true", 0));
+  assertEquals("true", dead2("true", S3));
+  assertEquals("11", dead3("true", 0));
+}
+
+test();
+test();
+%OptimizeFunctionOnNextCall(dead1);
+%OptimizeFunctionOnNextCall(dead2);
+%OptimizeFunctionOnNextCall(dead3);
+test();

test/mjsunit/compiler/dead-string-char-from-code.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+function dead1(a, b) {
+    var x = %_StringCharFromCode(a);
+    return a; // x is dead code
+}
+
+function dead2(a, b) {
+    var x = %_StringCharFromCode(a);
+    var y = %_StringCharFromCode(b);
+    return a; // x and y are both dead
+}
+
+function dead3(a, b) {
+    a = a ? 11 : 12;
+    b = b ? 13 : 14;
+    var x = %_StringCharFromCode(a);
+    var y = %_StringCharFromCode(b);
+    return a; // x and y are both dead
+}
+
+function test() {
+    assertEquals(33, dead1(33, 32));
+    assertEquals(33, dead2(33, 32));
+    assertEquals(11, dead3(33, 32));
+
+    assertEquals(31, dead1(31, 30));
+    assertEquals(31, dead2(31, 30));
+    assertEquals(11, dead3(31, 32));
+
+    assertEquals(0, dead1(0, 30));
+    assertEquals(0, dead2(0, 30));
+    assertEquals(12, dead3(0, 32));
+
+    assertEquals(true, dead1(true, 0));
+    assertEquals(true, dead2(true, 0));
+    assertEquals(11, dead3(true, 0));
+
+    assertEquals("true", dead1("true", 0));
+    assertEquals("true", dead2("true", 0));
+    assertEquals(11, dead3("true", 0));
+}
+
+test();
+test();
+%OptimizeFunctionOnNextCall(dead1);
+%OptimizeFunctionOnNextCall(dead2);
+%OptimizeFunctionOnNextCall(dead3);
+test();