Initial (stub) port of jump targets to the ARM platform....

src/jump-target-arm.h

+// 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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+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
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+//       with the distribution.
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+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
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+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_JUMP_TARGET_ARM_H_
+#define V8_JUMP_TARGET_ARM_H_
+
+#include "virtual-frame-arm.h"
+
+namespace v8 { namespace internal {
+
+// -------------------------------------------------------------------------

[Erik Corry, 2008/11/07 11:55:10]

Almost everything in this file looks architecture independent - should be
factored out at some point.

+// Jump targets
+//
+// A jump target is an abstraction of a control-flow target in generated
+// code.  It encapsulates an assembler label and an expected virtual frame
+// layout at that label.  The first time control flow reaches the target,
+// either via jumping or branching or by binding the target, the expected
+// frame is set.  If control flow subsequently reaches the target, code may
+// be emitted to ensure that the current frame matches the expected frame.
+//
+// A jump target must have been reached via control flow (either by jumping,
+// branching, or falling through) when 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 and must be compiled before any backward
+// edges.
+
+class JumpTarget : public ZoneObject {  // Shadows are dynamically allocated.
+ public:
+  // 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);
+
+  // 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 jump targets are embedded in AST nodes.
+  JumpTarget();
+
+  virtual ~JumpTarget() { delete expected_frame_; }
+
+  // Supply a code generator.  This function expects to be given a non-null
+  // code generator, and to be called only when the code generator is not
+  // yet set.
+  void set_code_generator(CodeGenerator* cgen);
+
+  // Accessors.
+  CodeGenerator* code_generator() const { return code_generator_; }
+
+  Label* label() { return &label_; }
+
+  VirtualFrame* expected_frame() const { return expected_frame_; }
+  void set_expected_frame(VirtualFrame* frame) {
+    expected_frame_ = frame;
+  }
+
+  // Predicates testing the state of the encapsulated label.
+  bool is_bound() const { return label_.is_bound(); }
+  bool is_linked() const { return label_.is_linked(); }
+  bool is_unused() const { return label_.is_unused(); }
+
+  // Treat the jump target as a fresh one---the label is unused and the
+  // expected frame if any is reset.
+  void Unuse() {
+    label_.Unuse();
+    delete expected_frame_;
+    expected_frame_ = NULL;
+  }
+
+  // Emit a jump to the target.  If there is no expected frame, the code
+  // generator's current frame becomes the expected one.  If there is
+  // already an expected frame, code may be emitted to merge the current
+  // frame to the expected one.  After the jump, the code generate has no
+  // current frame (because control flow does not fall through from a jump).
+  // A new current frame can be picked up by, eg, binding a jump target with
+  // an expected frame.
+  void Jump();
+
+  // Emit a conditional branch to the target.  If there is no expected
+  // frame, a clone of the code generator's current frame becomes the
+  // expected one.  If there is already an expected frame, code may be
+  // emitted to merge the current frame to the expected one.
+  void Branch(Condition cc);
+
+  // Bind a jump target.  If there is no expected frame and there is a
+  // current frame (ie, control flow is falling through to the target), then
+  // a clone of the current frame becomes the expected one.  If there is a
+  // current frame and an expected one (eg, control flow is falling through
+  // to a target that has already been reached via a jump or branch), then
+  // code may be emitted to merge the frames.  A jump target that already
+  // has an expected frame can be bound even if there is no current
+  // frame---in that case, the new current frame is picked up from the jump
+  // target.
+  void Bind();
+
+ protected:
+  // The encapsulated assembler label.
+  Label label_;
+
+  // The expected frame where the label is bound, or NULL.
+  VirtualFrame* expected_frame_;
+
+ private:
+  // The code generator gives access to the current frame.
+  CodeGenerator* code_generator_;
+
+  // Used to emit code.
+  MacroAssembler* masm_;
+};
+
+
+// -------------------------------------------------------------------------
+// Shadow jump targets
+//
+// Shadow jump targets represent a jump 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 JumpTarget {
+ public:
+  // Construct a shadow a jump target.  After construction, the original
+  // jump target shadows the former target, which is hidden as the
+  // newly-constructed shadow target.
+  explicit ShadowTarget(JumpTarget* original);
+
+  virtual ~ShadowTarget() {
+    ASSERT(!is_shadowing_);
+  }
+
+  // End shadowing.  After shadowing ends, the original jump target 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.
+  JumpTarget* original_target() const { return original_target_; }
+
+ private:
+  // During shadowing, the currently shadowing target.  After shadowing, the
+  // target that was shadowed.
+  JumpTarget* original_target_;
+
+  // During shadowing, the saved state of the shadowed target's label.
+  int original_pos_;
+
+  // During shadowing, the saved state of the shadowed target's expected
+  // frame.
+  VirtualFrame* original_expected_frame_;
+
+#ifdef DEBUG
+  bool is_shadowing_;
+#endif
+};
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_JUMP_TARGET_ARM_H_