Vyacheslav Egorov
f496e538f4
This is the next step towards preventing compiler from directly peeking into runtime and instead interact with runtime through a well defined surface. The goal of the refactoring to locate all places where compiler accesses some runtime information and partion those accesses into two categories: - creating objects in the host runtime (e.g. allocating strings, numbers, etc) during compilation; - accessing properties of the target runtime (e.g. offsets of fields) to embed those into the generated code; This change introduces dart::compiler and dart::compiler::target namespaces. All code in the compiler will gradually be moved into dart::compiler namespace. One of the motivations for this change is to be able to prevent access to globally defined host constants like kWordSize by shadowing them in the dart::compiler namespace. The nested namespace dart::compiler::target hosts all information about target runtime that compiler could access, e.g. compiler::target::kWordSize defines word size of the target which will eventually be made different from the host kWordSize (defined by dart::kWordSize). The API for compiler to runtime interaction is placed into compiler_api.h. Note that we still permit runtime to access compiler internals directly - this is not going to be decoupled as part of this work. Issue https://github.com/dart-lang/sdk/issues/31709 Change-Id: If4396d295879391becfa6c38d4802bbff81f5b20 Reviewed-on: https://dart-review.googlesource.com/c/90242 Commit-Queue: Vyacheslav Egorov <vegorov@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com>
67 lines
2.1 KiB
C++
67 lines
2.1 KiB
C++
// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_BITFIELD_H_
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#define RUNTIME_VM_BITFIELD_H_
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#include "platform/assert.h"
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#include "platform/globals.h"
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namespace dart {
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static const uword kUwordOne = 1U;
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// BitField is a template for encoding and decoding a value of type T
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// inside a storage of type S.
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template <typename S, typename T, int position, int size>
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class BitField {
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public:
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static_assert((sizeof(S) * kBitsPerByte) >= (position + size),
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"BitField does not fit into the type.");
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static const intptr_t kNextBit = position + size;
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// Tells whether the provided value fits into the bit field.
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static bool is_valid(T value) {
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return (static_cast<S>(value) & ~((kUwordOne << size) - 1)) == 0;
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}
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// Returns a S mask of the bit field.
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static S mask() { return (kUwordOne << size) - 1; }
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// Returns a S mask of the bit field which can be applied directly to
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// to the raw unshifted bits.
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static S mask_in_place() { return ((kUwordOne << size) - 1) << position; }
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// Returns the shift count needed to right-shift the bit field to
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// the least-significant bits.
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static int shift() { return position; }
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// Returns the size of the bit field.
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static int bitsize() { return size; }
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// Returns an S with the bit field value encoded.
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static S encode(T value) {
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ASSERT(is_valid(value));
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return static_cast<S>(value) << position;
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}
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// Extracts the bit field from the value.
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static T decode(S value) {
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return static_cast<T>((value >> position) & ((kUwordOne << size) - 1));
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}
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// Returns an S with the bit field value encoded based on the
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// original value. Only the bits corresponding to this bit field
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// will be changed.
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static S update(T value, S original) {
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ASSERT(is_valid(value));
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return (static_cast<S>(value) << position) | (~mask_in_place() & original);
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}
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};
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} // namespace dart
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#endif // RUNTIME_VM_BITFIELD_H_
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