Revert "[kernel] Change dill representation of doubles"

This reverts commit 6e2536f585 as it
breaks flutter hot_reload test.

Bug: https://github.com/flutter/flutter/issues/17202
Change-Id: I36261a1aec5ec2196c3a02cc0da0dc0833337004
Reviewed-on: https://dart-review.googlesource.com/53460
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>

pkg/kernel/binary.md

@@ -42,8 +42,6 @@ type UInt30 extends UInt {
 
 type UInt32 = big endian 32-bit unsigned integer
 
-type Double = Double-precision floating-point number.
-
 type List<T> {
   UInt length;
   T[length] items;
@@ -713,7 +711,7 @@ type BigIntLiteral extends Expression {
 
 type DoubleLiteral extends Expression {
   Byte tag = 40;
-  Double value;
+  StringReference valueString;
 }
 
 type TrueLiteral extends Expression {
@@ -876,7 +874,7 @@ type IntConstant extends Constant {
 
 type DoubleConstant extends Constant {
   Byte tag = 3;
-  Double value;
+  StringReference value;
 }
 
 type StringConstant extends Constant {

pkg/kernel/lib/binary/ast_from_binary.dart

@@ -97,22 +97,6 @@ class BinaryBuilder {
         readByte();
   }
 
-  final Float64List _doubleBuffer = new Float64List(1);
-  Uint8List _doubleBufferUint8;
-
-  double readDouble() {
-    _doubleBufferUint8 ??= _doubleBuffer.buffer.asUint8List();
-    _doubleBufferUint8[0] = readByte();
-    _doubleBufferUint8[1] = readByte();
-    _doubleBufferUint8[2] = readByte();
-    _doubleBufferUint8[3] = readByte();
-    _doubleBufferUint8[4] = readByte();
-    _doubleBufferUint8[5] = readByte();
-    _doubleBufferUint8[6] = readByte();
-    _doubleBufferUint8[7] = readByte();
-    return _doubleBuffer[0];
-  }
-
   List<int> readByteList() {
     List<int> bytes = new Uint8List(readUInt());
     bytes.setRange(0, bytes.length, _bytes, _byteOffset);
@@ -190,7 +174,7 @@ class BinaryBuilder {
       case ConstantTag.IntConstant:
         return new IntConstant((readExpression() as IntLiteral).value);
       case ConstantTag.DoubleConstant:
-        return new DoubleConstant(readDouble());
+        return new DoubleConstant(double.parse(readStringReference()));
       case ConstantTag.StringConstant:
         return new StringConstant(readStringReference());
       case ConstantTag.MapConstant:
@@ -1351,7 +1335,7 @@ class BinaryBuilder {
       case Tag.BigIntLiteral:
         return new IntLiteral(int.parse(readStringReference()));
       case Tag.DoubleLiteral:
-        return new DoubleLiteral(readDouble());
+        return new DoubleLiteral(double.parse(readStringReference()));
       case Tag.TrueLiteral:
         return new BoolLiteral(true);
       case Tag.FalseLiteral:

pkg/kernel/lib/binary/ast_to_binary.dart

@@ -154,7 +154,7 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
       writeInteger(constant.value);
     } else if (constant is DoubleConstant) {
       writeByte(ConstantTag.DoubleConstant);
-      writeDouble(constant.value);
+      writeStringReference('${constant.value}');
     } else if (constant is StringConstant) {
       writeByte(ConstantTag.StringConstant);
       writeStringReference(constant.value);
@@ -1246,12 +1246,13 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
 
   @override
   void visitDoubleLiteral(DoubleLiteral node) {
-    writeByte(Tag.DoubleLiteral);
     writeDouble(node.value);
   }
 
   writeDouble(double value) {
-    _sink.addDouble(value);
+    // TODO: Pick a better format for double literals.
+    writeByte(Tag.DoubleLiteral);
+    writeStringReference('$value');
   }
 
   @override
@@ -2204,20 +2205,8 @@ class BufferedSink {
   int length = 0;
   int flushedLength = 0;
 
-  Float64List _doubleBuffer = new Float64List(1);
-  Uint8List _doubleBufferUint8;
-
   BufferedSink(this._sink);
 
-  void addDouble(double d) {
-    _doubleBufferUint8 ??= _doubleBuffer.buffer.asUint8List();
-    _doubleBuffer[0] = d;
-    addByte4(_doubleBufferUint8[0], _doubleBufferUint8[1],
-        _doubleBufferUint8[2], _doubleBufferUint8[3]);
-    addByte4(_doubleBufferUint8[4], _doubleBufferUint8[5],
-        _doubleBufferUint8[6], _doubleBufferUint8[7]);
-  }
-
   void addByte(int byte) {
     _buffer[length++] = byte;
     if (length == SIZE) {

pkg/kernel/lib/binary/tag.dart

@@ -135,7 +135,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h.
-  static const int BinaryFormatVersion = 5;
+  static const int BinaryFormatVersion = 4;
 }
 
 abstract class ConstantTag {

runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc

@@ -1548,7 +1548,7 @@ void StreamingScopeBuilder::VisitExpression() {
       builder_->ReadUInt();  // read value.
       return;
     case kDoubleLiteral:
-      builder_->ReadDouble();  // read value.
+      builder_->SkipStringReference();  // read index into string table.
       return;
     case kTrueLiteral:
       return;
@@ -3542,7 +3542,8 @@ void StreamingConstantEvaluator::EvaluateIntLiteral(bool is_negative) {
 }
 
 void StreamingConstantEvaluator::EvaluateDoubleLiteral() {
-  result_ = Double::New(builder_->ReadDouble(), Heap::kOld);  // read value.
+  result_ = Double::New(H.DartString(builder_->ReadStringReference()),
+                        Heap::kOld);  // read string reference.
   result_ = H.Canonicalize(result_);
 }
 
@@ -6021,10 +6022,6 @@ uint32_t KernelReaderHelper::PeekUInt() {
   return reader_.ReadUInt();
 }
 
-double KernelReaderHelper::ReadDouble() {
-  return reader_.ReadDouble();
-}
-
 uint32_t KernelReaderHelper::PeekListLength() {
   AlternativeReadingScope alt(&reader_);
   return reader_.ReadListLength();
@@ -6492,7 +6489,7 @@ void KernelReaderHelper::SkipExpression() {
       ReadUInt();  // read value.
       return;
     case kDoubleLiteral:
-      ReadDouble();  // read value.
+      SkipStringReference();  // read index into string table.
       return;
     case kTrueLiteral:
       return;
@@ -8985,7 +8982,8 @@ Fragment StreamingFlowGraphBuilder::BuildDoubleLiteral(
   if (position != NULL) *position = TokenPosition::kNoSource;
 
   Double& constant = Double::ZoneHandle(
-      Z, Double::NewCanonical(ReadDouble()));  // read double.
+      Z, Double::NewCanonical(
+             H.DartString(ReadStringReference())));  // read string reference.
   return Constant(constant);
 }
 
@@ -10819,7 +10817,8 @@ const Array& ConstantHelper::ReadConstantTable() {
         break;
       }
       case kDoubleConstant: {
-        temp_instance_ = Double::New(builder_.ReadDouble(), Heap::kOld);
+        temp_instance_ = Double::New(
+            H.DartString(builder_.ReadStringReference()), Heap::kOld);
         temp_instance_ = H.Canonicalize(temp_instance_);
         break;
       }

runtime/vm/compiler/frontend/kernel_binary_flowgraph.h

@@ -1040,7 +1040,6 @@ class KernelReaderHelper {
   uint32_t ReadUInt();
   uint32_t ReadUInt32();
   uint32_t PeekUInt();
-  double ReadDouble();
   uint32_t PeekListLength();
   StringIndex ReadStringReference();
   NameIndex ReadCanonicalNameReference();

runtime/vm/kernel_binary.h

@@ -19,7 +19,7 @@ namespace kernel {
 // Keep in sync with package:kernel/lib/binary/tag.dart.
 
 static const uint32_t kMagicProgramFile = 0x90ABCDEFu;
-static const uint32_t kBinaryFormatVersion = 5;
+static const uint32_t kBinaryFormatVersion = 4;
 
 // Keep in sync with package:kernel/lib/binary/tag.dart
 #define KERNEL_TAG_LIST(V)                                                     \
@@ -213,14 +213,6 @@ class Reader : public ValueObject {
     return value;
   }
 
-  double ReadDouble() {
-    ASSERT((size_ >= 8) && (offset_ >= 0) && (offset_ <= size_ - 8));
-    double value = ReadUnaligned(
-        reinterpret_cast<const double*>(&this->buffer()[offset_]));
-    offset_ += 8;
-    return value;
-  }
-
   uint32_t ReadUInt() {
     ASSERT((size_ >= 1) && (offset_ >= 0) && (offset_ <= size_ - 1));
 

runtime/vm/kernel_loader.cc

@@ -82,7 +82,8 @@ class SimpleExpressionConverter {
         return true;
       case kDoubleLiteral:
         simple_value_ = &Double::ZoneHandle(
-            Z, Double::New(builder_->ReadDouble(), Heap::kOld));  // read value.
+            Z, Double::New(H.DartString(builder_->ReadStringReference()),
+                           Heap::kOld));  // read string reference.
         *simple_value_ = H.Canonicalize(*simple_value_);
         return true;
       case kTrueLiteral: