1/*
2 * Copyright (C) 2009 University of Szeged
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#ifndef AssemblerBufferWithConstantPool_h
28#define AssemblerBufferWithConstantPool_h
29
30#if ENABLE(ASSEMBLER)
31
32#include "AssemblerBuffer.h"
33#include <wtf/SegmentedVector.h>
34
35#define ASSEMBLER_HAS_CONSTANT_POOL 1
36
37namespace JSC {
38
39/*
40    On a constant pool 4 or 8 bytes data can be stored. The values can be
41    constants or addresses. The addresses should be 32 or 64 bits. The constants
42    should be double-precisions float or integer numbers which are hard to be
43    encoded as few machine instructions.
44
45    TODO: The pool is desinged to handle both 32 and 64 bits values, but
46    currently only the 4 bytes constants are implemented and tested.
47
48    The AssemblerBuffer can contain multiple constant pools. Each pool is inserted
49    into the instruction stream - protected by a jump instruction from the
50    execution flow.
51
52    The flush mechanism is called when no space remain to insert the next instruction
53    into the pool. Three values are used to determine when the constant pool itself
54    have to be inserted into the instruction stream (Assembler Buffer):
55
56    - maxPoolSize: size of the constant pool in bytes, this value cannot be
57        larger than the maximum offset of a PC relative memory load
58
59    - barrierSize: size of jump instruction in bytes which protects the
60        constant pool from execution
61
62    - maxInstructionSize: maximum length of a machine instruction in bytes
63
64    There are some callbacks which solve the target architecture specific
65    address handling:
66
67    - TYPE patchConstantPoolLoad(TYPE load, int value):
68        patch the 'load' instruction with the index of the constant in the
69        constant pool and return the patched instruction.
70
71    - void patchConstantPoolLoad(void* loadAddr, void* constPoolAddr):
72        patch the a PC relative load instruction at 'loadAddr' address with the
73        final relative offset. The offset can be computed with help of
74        'constPoolAddr' (the address of the constant pool) and index of the
75        constant (which is stored previously in the load instruction itself).
76
77    - TYPE placeConstantPoolBarrier(int size):
78        return with a constant pool barrier instruction which jumps over the
79        constant pool.
80
81    The 'put*WithConstant*' functions should be used to place a data into the
82    constant pool.
83*/
84
85template <int maxPoolSize, int barrierSize, int maxInstructionSize, class AssemblerType>
86class AssemblerBufferWithConstantPool : public AssemblerBuffer {
87    typedef SegmentedVector<uint32_t, 512> LoadOffsets;
88    using AssemblerBuffer::putIntegral;
89    using AssemblerBuffer::putIntegralUnchecked;
90public:
91    typedef struct {
92        short high;
93        short low;
94    } TwoShorts;
95
96    enum {
97        UniqueConst,
98        ReusableConst,
99        UnusedEntry,
100    };
101
102    AssemblerBufferWithConstantPool()
103        : AssemblerBuffer()
104        , m_numConsts(0)
105        , m_maxDistance(maxPoolSize)
106        , m_lastConstDelta(0)
107    {
108        m_pool = static_cast<uint32_t*>(fastMalloc(maxPoolSize));
109        m_mask = static_cast<char*>(fastMalloc(maxPoolSize / sizeof(uint32_t)));
110    }
111
112    ~AssemblerBufferWithConstantPool()
113    {
114        fastFree(m_mask);
115        fastFree(m_pool);
116    }
117
118    void ensureSpace(int space)
119    {
120        flushIfNoSpaceFor(space);
121        AssemblerBuffer::ensureSpace(space);
122    }
123
124    void ensureSpace(int insnSpace, int constSpace)
125    {
126        flushIfNoSpaceFor(insnSpace, constSpace);
127        AssemblerBuffer::ensureSpace(insnSpace);
128    }
129
130    void ensureSpaceForAnyInstruction(int amount = 1)
131    {
132        flushIfNoSpaceFor(amount * maxInstructionSize, amount * sizeof(uint64_t));
133    }
134
135    bool isAligned(int alignment)
136    {
137        flushIfNoSpaceFor(alignment);
138        return AssemblerBuffer::isAligned(alignment);
139    }
140
141    void putByteUnchecked(int value)
142    {
143        AssemblerBuffer::putByteUnchecked(value);
144        correctDeltas(1);
145    }
146
147    void putByte(int value)
148    {
149        flushIfNoSpaceFor(1);
150        AssemblerBuffer::putByte(value);
151        correctDeltas(1);
152    }
153
154    void putShortUnchecked(int value)
155    {
156        AssemblerBuffer::putShortUnchecked(value);
157        correctDeltas(2);
158    }
159
160    void putShort(int value)
161    {
162        flushIfNoSpaceFor(2);
163        AssemblerBuffer::putShort(value);
164        correctDeltas(2);
165    }
166
167    void putIntUnchecked(int value)
168    {
169        AssemblerBuffer::putIntUnchecked(value);
170        correctDeltas(4);
171    }
172
173    void putInt(int value)
174    {
175        flushIfNoSpaceFor(4);
176        AssemblerBuffer::putInt(value);
177        correctDeltas(4);
178    }
179
180    void putInt64Unchecked(int64_t value)
181    {
182        AssemblerBuffer::putInt64Unchecked(value);
183        correctDeltas(8);
184    }
185
186    void putIntegral(TwoShorts value)
187    {
188        putIntegral(value.high);
189        putIntegral(value.low);
190    }
191
192    void putIntegralUnchecked(TwoShorts value)
193    {
194        putIntegralUnchecked(value.high);
195        putIntegralUnchecked(value.low);
196    }
197
198    void putShortWithConstantInt(uint16_t insn, uint32_t constant, bool isReusable = false)
199    {
200        putIntegralWithConstantInt(insn, constant, isReusable);
201    }
202
203    void putIntWithConstantInt(uint32_t insn, uint32_t constant, bool isReusable = false)
204    {
205        putIntegralWithConstantInt(insn, constant, isReusable);
206    }
207
208    // This flushing mechanism can be called after any unconditional jumps.
209    void flushWithoutBarrier(bool isForced = false)
210    {
211        // Flush if constant pool is more than 60% full to avoid overuse of this function.
212        if (isForced || 5 * static_cast<uint32_t>(m_numConsts) > 3 * maxPoolSize / sizeof(uint32_t))
213            flushConstantPool(false);
214    }
215
216    uint32_t* poolAddress()
217    {
218        return m_pool;
219    }
220
221    int sizeOfConstantPool()
222    {
223        return m_numConsts;
224    }
225
226    void flushConstantPool(bool useBarrier = true)
227    {
228        if (!m_numConsts)
229            return;
230        int alignPool = (codeSize() + (useBarrier ? barrierSize : 0)) & (sizeof(uint64_t) - 1);
231
232        if (alignPool)
233            alignPool = sizeof(uint64_t) - alignPool;
234
235        // Callback to protect the constant pool from execution
236        if (useBarrier)
237            putIntegral(AssemblerType::placeConstantPoolBarrier(m_numConsts * sizeof(uint32_t) + alignPool));
238
239        if (alignPool) {
240            if (alignPool & 1)
241                AssemblerBuffer::putByte(AssemblerType::padForAlign8);
242            if (alignPool & 2)
243                AssemblerBuffer::putShort(AssemblerType::padForAlign16);
244            if (alignPool & 4)
245                AssemblerBuffer::putInt(AssemblerType::padForAlign32);
246        }
247
248        int constPoolOffset = codeSize();
249        append(reinterpret_cast<char*>(m_pool), m_numConsts * sizeof(uint32_t));
250
251        // Patch each PC relative load
252        for (LoadOffsets::Iterator iter = m_loadOffsets.begin(); iter != m_loadOffsets.end(); ++iter) {
253            void* loadAddr = reinterpret_cast<char*>(data()) + *iter;
254            AssemblerType::patchConstantPoolLoad(loadAddr, reinterpret_cast<char*>(data()) + constPoolOffset);
255        }
256
257        m_loadOffsets.clear();
258        m_numConsts = 0;
259    }
260
261private:
262    void correctDeltas(int insnSize)
263    {
264        m_maxDistance -= insnSize;
265        m_lastConstDelta -= insnSize;
266        if (m_lastConstDelta < 0)
267            m_lastConstDelta = 0;
268    }
269
270    void correctDeltas(int insnSize, int constSize)
271    {
272        correctDeltas(insnSize);
273
274        m_maxDistance -= m_lastConstDelta;
275        m_lastConstDelta = constSize;
276    }
277
278    template<typename IntegralType>
279    void putIntegralWithConstantInt(IntegralType insn, uint32_t constant, bool isReusable)
280    {
281        if (!m_numConsts)
282            m_maxDistance = maxPoolSize;
283        flushIfNoSpaceFor(sizeof(IntegralType), 4);
284
285        m_loadOffsets.append(codeSize());
286        if (isReusable) {
287            for (int i = 0; i < m_numConsts; ++i) {
288                if (m_mask[i] == ReusableConst && m_pool[i] == constant) {
289                    putIntegral(static_cast<IntegralType>(AssemblerType::patchConstantPoolLoad(insn, i)));
290                    correctDeltas(sizeof(IntegralType));
291                    return;
292                }
293            }
294        }
295
296        m_pool[m_numConsts] = constant;
297        m_mask[m_numConsts] = static_cast<char>(isReusable ? ReusableConst : UniqueConst);
298
299        putIntegral(static_cast<IntegralType>(AssemblerType::patchConstantPoolLoad(insn, m_numConsts)));
300        ++m_numConsts;
301
302        correctDeltas(sizeof(IntegralType), 4);
303    }
304
305    void flushIfNoSpaceFor(int nextInsnSize)
306    {
307        if (m_numConsts == 0)
308            return;
309        int lastConstDelta = m_lastConstDelta > nextInsnSize ? m_lastConstDelta - nextInsnSize : 0;
310        if ((m_maxDistance < nextInsnSize + lastConstDelta + barrierSize + (int)sizeof(uint32_t)))
311            flushConstantPool();
312    }
313
314    void flushIfNoSpaceFor(int nextInsnSize, int nextConstSize)
315    {
316        if (m_numConsts == 0)
317            return;
318        if ((m_maxDistance < nextInsnSize + m_lastConstDelta + nextConstSize + barrierSize + (int)sizeof(uint32_t)) ||
319            (m_numConsts * sizeof(uint32_t) + nextConstSize >= maxPoolSize))
320            flushConstantPool();
321    }
322
323    uint32_t* m_pool;
324    char* m_mask;
325    LoadOffsets m_loadOffsets;
326
327    int m_numConsts;
328    int m_maxDistance;
329    int m_lastConstDelta;
330};
331
332} // namespace JSC
333
334#endif // ENABLE(ASSEMBLER)
335
336#endif // AssemblerBufferWithConstantPool_h
337