| // Copyright 2008 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: |
| // |
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| // 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. |
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| |
| #ifndef V8_JUMP_TARGET_H_ |
| #define V8_JUMP_TARGET_H_ |
| |
| #include "virtual-frame.h" |
| |
| namespace v8 { namespace internal { |
| |
| // ------------------------------------------------------------------------- |
| // Jump targets |
| // |
| // A jump target is an abstraction of a basic-block entry in generated |
| // code. It collects all the virtual frames reaching the block by |
| // forward jumps and pairs them with labels for the merge code along |
| // all forward-reaching paths. When bound, an expected frame for the |
| // block is determined and code is generated to merge to the expected |
| // frame. For backward jumps, the merge code is generated at the edge |
| // leaving the predecessor block. |
| // |
| // A jump target must have been reached via control flow (either by |
| // jumping, branching, or falling through) at the time it is bound. |
| // In particular, this means that at least one of the control-flow |
| // graph edges reaching the target must be a forward edge. |
| |
| class JumpTarget : public Malloced { // Shadows are dynamically allocated. |
| public: |
| // Forward-only jump targets can only be reached by forward CFG edges. |
| enum Directionality { FORWARD_ONLY, BIDIRECTIONAL }; |
| |
| // Construct a jump target with a given code generator used to generate |
| // code and to provide access to a current frame. |
| explicit JumpTarget(CodeGenerator* cgen, |
| Directionality direction = FORWARD_ONLY); |
| |
| // Construct a jump target without a code generator. A code |
| // generator must be supplied before using the jump target as a |
| // label. This is useful, eg, when break targets are embedded in |
| // AST nodes. |
| JumpTarget(); |
| |
| // Supply a code generator and directionality to an already |
| // constructed jump target. This function expects to be given a |
| // non-null code generator, and to be called only when the code |
| // generator is not yet set. |
| virtual void Initialize(CodeGenerator* cgen, |
| Directionality direction = FORWARD_ONLY); |
| |
| virtual ~JumpTarget() { Unuse(); } |
| |
| // Treat the jump target as a fresh one. The state is reset and |
| // pointed-to virtual frames are deallocated. There should be no |
| // dangling jumps to the target. |
| void Unuse(); |
| |
| // Reset the internal state of this jump target. Pointed-to virtual |
| // frames are not deallocated and dangling jumps to the target are |
| // left dangling. |
| void Reset(); |
| |
| // Accessors. |
| CodeGenerator* code_generator() const { return cgen_; } |
| |
| Label* entry_label() { return &entry_label_; } |
| |
| VirtualFrame* entry_frame() const { return entry_frame_; } |
| void set_entry_frame(VirtualFrame* frame) { |
| entry_frame_ = frame; |
| } |
| |
| void make_bidirectional() { direction_ = BIDIRECTIONAL; } |
| |
| // Predicates testing the state of the encapsulated label. |
| bool is_bound() const { return is_bound_; } |
| bool is_linked() const { return is_linked_; } |
| bool is_unused() const { return !is_bound() && !is_linked(); } |
| |
| // Emit a jump to the target. There must be a current frame at the |
| // jump and there will be no current frame after the jump. |
| virtual void Jump(); |
| void Jump(Result* arg); |
| void Jump(Result* arg0, Result* arg1); |
| void Jump(Result* arg0, Result* arg1, Result* arg2); |
| |
| // Emit a conditional branch to the target. There must be a current |
| // frame at the branch. The current frame will fall through to the |
| // code after the branch. |
| virtual void Branch(Condition cc, Hint hint = no_hint); |
| void Branch(Condition cc, Result* arg, Hint hint = no_hint); |
| void Branch(Condition cc, Result* arg0, Result* arg1, Hint hint = no_hint); |
| void Branch(Condition cc, |
| Result* arg0, |
| Result* arg1, |
| Result* arg2, |
| Hint hint = no_hint); |
| void Branch(Condition cc, |
| Result* arg0, |
| Result* arg1, |
| Result* arg2, |
| Result* arg3, |
| Hint hint = no_hint); |
| |
| // Bind a jump target. If there is no current frame at the binding |
| // site, there must be at least one frame reaching via a forward |
| // jump. |
| // |
| // The number of mergable elements is a number of frame elements |
| // counting from the top down which must be "mergable" (not |
| // constants or copies) in the entry frame at the jump target. |
| // Backward jumps to the target must contain the same constants and |
| // sharing as the entry frame, except for the mergable elements. |
| // |
| // A mergable elements argument of kAllElements indicates that all |
| // frame elements must be mergable. Mergable elements are ignored |
| // completely for forward-only jump targets. |
| virtual void Bind(int mergable_elements = kAllElements); |
| void Bind(Result* arg, int mergable_elements = kAllElements); |
| void Bind(Result* arg0, Result* arg1, int mergable_elements = kAllElements); |
| void Bind(Result* arg0, |
| Result* arg1, |
| Result* arg2, |
| int mergable_elements = kAllElements); |
| void Bind(Result* arg0, |
| Result* arg1, |
| Result* arg2, |
| Result* arg3, |
| int mergable_elements = kAllElements); |
| |
| // Emit a call to a jump target. There must be a current frame at |
| // the call. The frame at the target is the same as the current |
| // frame except for an extra return address on top of it. The frame |
| // after the call is the same as the frame before the call. |
| void Call(); |
| |
| static const int kAllElements = -1; // Not a valid number of elements. |
| |
| protected: |
| // The code generator gives access to its current frame. |
| CodeGenerator* cgen_; |
| |
| // Used to emit code. |
| MacroAssembler* masm_; |
| |
| // Directionality flag set at initialization time. |
| Directionality direction_; |
| |
| // A list of frames reaching this block via forward jumps. |
| List<VirtualFrame*> reaching_frames_; |
| |
| // A parallel list of labels for merge code. |
| List<Label> merge_labels_; |
| |
| // The frame used on entry to the block and expected at backward |
| // jumps to the block. Set when the jump target is bound, but may |
| // or may not be set for forward-only blocks. |
| VirtualFrame* entry_frame_; |
| |
| // The actual entry label of the block. |
| Label entry_label_; |
| |
| // A target is bound if its Bind member function has been called. |
| // It is linked if it is not bound but its Jump, Branch, or Call |
| // member functions have been called. |
| bool is_bound_; |
| bool is_linked_; |
| |
| private: |
| // Add a virtual frame reaching this labeled block via a forward |
| // jump, and a fresh label for its merge code. |
| void AddReachingFrame(VirtualFrame* frame); |
| |
| // Choose an element from a pair of frame elements to be in the |
| // expected frame. Return null if they are incompatible. |
| FrameElement* Combine(FrameElement* left, FrameElement* right); |
| |
| // Compute a frame to use for entry to this block. Mergable |
| // elements is as described for the Bind function. |
| void ComputeEntryFrame(int mergable_elements); |
| |
| DISALLOW_COPY_AND_ASSIGN(JumpTarget); |
| }; |
| |
| |
| // ------------------------------------------------------------------------- |
| // Break targets |
| // |
| // A break target is a jump target that can be used to break out of a |
| // statement that keeps extra state on the stack (eg, for/in or |
| // try/finally). They know the expected stack height at the target |
| // and will drop state from nested statements as part of merging. |
| // |
| // Break targets are used for return, break, and continue targets. |
| |
| class BreakTarget : public JumpTarget { |
| public: |
| // Construct a break target without a code generator. A code |
| // generator must be supplied before using the break target as a |
| // label. This is useful, eg, when break targets are embedded in AST |
| // nodes. |
| BreakTarget() {} |
| |
| // Supply a code generator, expected expression stack height, and |
| // directionality to an already constructed break target. This |
| // function expects to be given a non-null code generator, and to be |
| // called only when the code generator is not yet set. |
| virtual void Initialize(CodeGenerator* cgen, |
| Directionality direction = FORWARD_ONLY); |
| |
| // Copy the state of this break target to the destination. The |
| // lists of forward-reaching frames and merge-point labels are |
| // copied. All virtual frame pointers are copied, not the |
| // pointed-to frames. The previous state of the destination is |
| // overwritten, without deallocating pointed-to virtual frames. |
| void CopyTo(BreakTarget* destination); |
| |
| // Emit a jump to the target. There must be a current frame at the |
| // jump and there will be no current frame after the jump. |
| virtual void Jump(); |
| |
| // Emit a conditional branch to the target. There must be a current |
| // frame at the branch. The current frame will fall through to the |
| // code after the branch. |
| virtual void Branch(Condition cc, Hint hint = no_hint); |
| |
| // Bind a break target. If there is no current frame at the binding |
| // site, there must be at least one frame reaching via a forward |
| // jump. |
| virtual void Bind(int mergable_elements = kAllElements); |
| |
| // Setter for expected height. |
| void set_expected_height(int expected) { expected_height_ = expected; } |
| |
| private: |
| // The expected height of the expression stack where the target will |
| // be bound, statically known at initialization time. |
| int expected_height_; |
| |
| DISALLOW_COPY_AND_ASSIGN(BreakTarget); |
| }; |
| |
| |
| // ------------------------------------------------------------------------- |
| // Shadow break targets |
| // |
| // A shadow break target represents a break target that is temporarily |
| // shadowed by another one (represented by the original during |
| // shadowing). They are used to catch jumps to labels in certain |
| // contexts, e.g. try blocks. After shadowing ends, the formerly |
| // shadowed target is again represented by the original and the |
| // ShadowTarget can be used as a jump target in its own right, |
| // representing the formerly shadowing target. |
| |
| class ShadowTarget : public BreakTarget { |
| public: |
| // Construct a shadow jump target. After construction the shadow |
| // target object holds the state of the original target, and the |
| // original target is actually a fresh one that intercepts control |
| // flow intended for the shadowed one. |
| explicit ShadowTarget(BreakTarget* shadowed); |
| |
| virtual ~ShadowTarget() { |
| ASSERT(!is_shadowing_); |
| } |
| |
| // End shadowing. After shadowing ends, the original jump target |
| // again gives access to the formerly shadowed target and the shadow |
| // target object gives access to the formerly shadowing target. |
| void StopShadowing(); |
| |
| // During shadowing, the currently shadowing target. After |
| // shadowing, the target that was shadowed. |
| BreakTarget* other_target() const { return other_target_; } |
| |
| private: |
| // During shadowing, the currently shadowing target. After |
| // shadowing, the target that was shadowed. |
| BreakTarget* other_target_; |
| |
| #ifdef DEBUG |
| bool is_shadowing_; |
| #endif |
| |
| DISALLOW_COPY_AND_ASSIGN(ShadowTarget); |
| }; |
| |
| |
| } } // namespace v8::internal |
| |
| #endif // V8_JUMP_TARGET_H_ |