JavaScriptCore-1097.3.tar.gz

[apple/javascriptcore.git] / dfg / DFGCorrectableJumpPoint.h

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+/*
+ * Copyright (C) 2011 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#ifndef DFGCorrectableJumpPoint_h
+#define DFGCorrectableJumpPoint_h
+
+#if ENABLE(DFG_JIT)
+
+#include "LinkBuffer.h"
+#include "MacroAssembler.h"
+
+namespace JSC { namespace DFG {
+
+// This is a type-safe union of MacroAssembler::Jump and CodeLocationJump.
+// Furthermore, it supports the notion of branching (possibly conditionally, but
+// also possibly jumping unconditionally) to an out-of-line patchable jump.
+// Thus it goes through three states:
+//
+// 1) Label of unpatchable branch or jump (i.e. MacroAssembler::Jump).
+// 2) Label of patchable jump (i.e. MacroAssembler::PatchableJump).
+// 3) Corrected post-linking label of patchable jump (i.e. CodeLocationJump).
+//
+// The setting of state (1) corresponds to planting the in-line unpatchable
+// branch or jump. The state transition (1)->(2) corresponds to linking the
+// in-line branch or jump to the out-of-line patchable jump, and recording
+// the latter's label. The state transition (2)->(3) corresponds to recording
+// the out-of-line patchable jump's location after branch compaction has
+// completed.
+//
+// You can also go directly from the first state to the third state, if you
+// wish to use this class for in-line patchable jumps.
+
+class CorrectableJumpPoint {
+public:
+    CorrectableJumpPoint(MacroAssembler::Jump check)
+        : m_codeOffset(check.m_label.m_offset)
+#ifndef NDEBUG
+        , m_mode(InitialJump)
+#endif
+    {
+#if CPU(ARM_THUMB2)
+        m_type = check.m_type;
+        m_condition = check.m_condition;
+#endif
+    }
+    
+    void switchToLateJump(MacroAssembler::PatchableJump check)
+    {
+#ifndef NDEBUG
+        ASSERT(m_mode == InitialJump);
+        m_mode = LateJump;
+#endif
+        // Late jumps should only ever be real jumps.
+#if CPU(ARM_THUMB2)
+        ASSERT(check.m_jump.m_type == ARMv7Assembler::JumpNoConditionFixedSize);
+        ASSERT(check.m_jump.m_condition == ARMv7Assembler::ConditionInvalid);
+        m_type = ARMv7Assembler::JumpNoConditionFixedSize;
+        m_condition = ARMv7Assembler::ConditionInvalid;
+#endif
+        m_codeOffset = check.m_jump.m_label.m_offset;
+    }
+    
+    void correctInitialJump(LinkBuffer& linkBuffer)
+    {
+        ASSERT(m_mode == InitialJump);
+#if CPU(ARM_THUMB2)
+        ASSERT(m_type == ARMv7Assembler::JumpNoConditionFixedSize);
+        ASSERT(m_condition == ARMv7Assembler::ConditionInvalid);
+#endif
+        correctJump(linkBuffer);
+    }
+    
+    void correctLateJump(LinkBuffer& linkBuffer)
+    {
+        ASSERT(m_mode == LateJump);
+        correctJump(linkBuffer);
+    }
+    
+    MacroAssembler::Jump initialJump() const
+    {
+        ASSERT(m_mode == InitialJump);
+        return getJump();
+    }
+    
+    MacroAssembler::Jump lateJump() const
+    {
+        ASSERT(m_mode == LateJump);
+        return getJump();
+    }
+    
+    CodeLocationJump codeLocationForRepatch(CodeBlock*) const;
+    
+private:
+    void correctJump(LinkBuffer& linkBuffer)
+    {
+#ifndef NDEBUG
+        m_mode = CorrectedJump;
+#endif
+        MacroAssembler::Label label;
+        label.m_label.m_offset = m_codeOffset;
+        m_codeOffset = linkBuffer.offsetOf(label);
+    }
+    
+    MacroAssembler::Jump getJump() const
+    {
+        MacroAssembler::Jump jump;
+        jump.m_label.m_offset = m_codeOffset;
+#if CPU(ARM_THUMB2)
+        jump.m_type = m_type;
+        jump.m_condition = m_condition;
+#endif
+        return jump;
+    }
+    
+    unsigned m_codeOffset;
+
+#if CPU(ARM_THUMB2)
+    ARMv7Assembler::JumpType m_type : 8;
+    ARMv7Assembler::Condition m_condition : 8;
+#endif
+
+#ifndef NDEBUG
+    enum Mode {
+        InitialJump,
+        LateJump,
+        CorrectedJump
+    };
+
+    Mode m_mode;
+#endif
+};
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
+#endif // DFGCorrectableJumpPoint_h