// Copyright 2014 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef V8_COMPILER_FRAME_H_ #define V8_COMPILER_FRAME_H_ #include "src/base/bits.h" #include "src/codegen/aligned-slot-allocator.h" #include "src/execution/frame-constants.h" #include "src/utils/bit-vector.h" namespace v8 { namespace internal { namespace compiler { class CallDescriptor; // Collects the spill slot and other frame slot requirements for a compiled // function. Frames are usually populated by the register allocator and are used // by Linkage to generate code for the prologue and epilogue to compiled // code. Frame objects must be considered immutable once they've been // instantiated and the basic information about the frame has been collected // into them. Mutable state associated with the frame is stored separately in // FrameAccessState. // // Frames are divided up into four regions. // - The first is the fixed header, which always has a constant size and can be // predicted before code generation begins depending on the type of code being // generated. // - The second is the region for spill slots, which is immediately below the // fixed header and grows as the register allocator needs to spill to the // stack and asks the frame for more space. // - The third region, which contains the callee-saved registers must be // reserved after register allocation, since its size can only be precisely // determined after register allocation once the number of used callee-saved // register is certain. // - The fourth region is a scratch area for return values from other functions // called, if multiple returns cannot all be passed in registers. This region // Must be last in a stack frame, so that it is positioned immediately below // the stack frame of a callee to store to. // // The frame region immediately below the fixed header contains spill slots // starting at slot 4 for JSFunctions. The callee-saved frame region below that // starts at 4+spill_slot_count_. Callee stack slots correspond to // parameters that are accessible through negative slot ids. // // Every slot of a caller or callee frame is accessible by the register // allocator and gap resolver with a SpillSlotOperand containing its // corresponding slot id. // // Below an example JSFunction Frame with slot ids, frame regions and contents: // // slot JS frame // +-----------------+-------------------------------- // -n-1 | parameter n | ^ // |- - - - - - - - -| | // -n | parameter n-1 | Caller // ... | ... | frame slots // -2 | parameter 1 | (slot < 0) // |- - - - - - - - -| | // -1 | parameter 0 | v // -----+-----------------+-------------------------------- // 0 | return addr | ^ ^ // |- - - - - - - - -| | | // 1 | saved frame ptr | Fixed | // |- - - - - - - - -| Header <-- frame ptr | // 2 |Context/Frm. Type| | | // |- - - - - - - - -| | | // 3 | [JSFunction] | v | // +-----------------+---- | // 4 | spill 1 | ^ Callee // |- - - - - - - - -| | frame slots // ... | ... | Spill slots (slot >= 0) // |- - - - - - - - -| | | // m+3 | spill m | v | // +-----------------+---- | // m+4 | callee-saved 1 | ^ | // |- - - - - - - - -| | | // | ... | Callee-saved | // |- - - - - - - - -| | | // m+r+3 | callee-saved r | v | // +-----------------+---- | // m+r+4 | return 0 | ^ | // |- - - - - - - - -| | | // | ... | Return | // |- - - - - - - - -| | | // | return q-1 | v v // -----+-----------------+----- <-- stack ptr ------------- // class V8_EXPORT_PRIVATE Frame : public ZoneObject { … }; // Represents an offset from either the stack pointer or frame pointer. class FrameOffset { … }; // Encapsulates the mutable state maintained during code generation about the // current function's frame. class FrameAccessState : public ZoneObject { … }; } // namespace compiler } // namespace internal } // namespace v8 #endif // V8_COMPILER_FRAME_H_
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