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1 // Copyright 2008 the V8 project authors. All rights reserved. | |
2 // Redistribution and use in source and binary forms, with or without | |
3 // modification, are permitted provided that the following conditions are | |
4 // met: | |
5 // | |
6 // * Redistributions of source code must retain the above copyright | |
7 // notice, this list of conditions and the following disclaimer. | |
8 // * Redistributions in binary form must reproduce the above | |
9 // copyright notice, this list of conditions and the following | |
10 // disclaimer in the documentation and/or other materials provided | |
11 // with the distribution. | |
12 // * Neither the name of Google Inc. nor the names of its | |
13 // contributors may be used to endorse or promote products derived | |
14 // from this software without specific prior written permission. | |
15 // | |
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
27 | |
28 #include "v8.h" | |
29 | |
30 #include "codegen-inl.h" | |
31 #include "register-allocator-inl.h" | |
32 | |
33 namespace v8 { namespace internal { | |
34 | |
35 // ------------------------------------------------------------------------- | |
36 // JumpTarget implementation. | |
37 | |
38 #define __ ACCESS_MASM(masm_) | |
39 | |
40 void JumpTarget::DoJump() { | |
41 ASSERT(cgen_ != NULL); | |
42 ASSERT(cgen_->has_valid_frame()); | |
43 // Live non-frame registers are not allowed at unconditional jumps | |
44 // because we have no way of invalidating the corresponding results | |
45 // which are still live in the C++ code. | |
46 ASSERT(cgen_->HasValidEntryRegisters()); | |
47 | |
48 if (is_bound()) { | |
49 // Backward jump. There is an expected frame to merge to. | |
50 ASSERT(direction_ == BIDIRECTIONAL); | |
51 cgen_->frame()->MergeTo(entry_frame_); | |
52 cgen_->DeleteFrame(); | |
53 __ jmp(&entry_label_); | |
54 } else { | |
55 // Forward jump. The current frame is added to the end of the list | |
56 // of frames reaching the target block and a jump to the merge code | |
57 // is emitted. | |
58 AddReachingFrame(cgen_->frame()); | |
59 RegisterFile empty; | |
60 cgen_->SetFrame(NULL, &empty); | |
61 __ jmp(&merge_labels_.last()); | |
62 } | |
63 | |
64 is_linked_ = !is_bound_; | |
65 } | |
66 | |
67 | |
68 void JumpTarget::DoBranch(Condition cc, Hint hint) { | |
69 ASSERT(cgen_ != NULL); | |
70 ASSERT(cgen_->has_valid_frame()); | |
71 | |
72 if (is_bound()) { | |
73 ASSERT(direction_ == BIDIRECTIONAL); | |
74 // Backward branch. We have an expected frame to merge to on the | |
75 // backward edge. | |
76 | |
77 // Swap the current frame for a copy (we do the swapping to get | |
78 // the off-frame registers off the fall through) to use for the | |
79 // branch. | |
80 VirtualFrame* fall_through_frame = cgen_->frame(); | |
81 VirtualFrame* branch_frame = new VirtualFrame(fall_through_frame); | |
82 RegisterFile non_frame_registers = RegisterAllocator::Reserved(); | |
83 cgen_->SetFrame(branch_frame, &non_frame_registers); | |
84 | |
85 // Check if we can avoid merge code. | |
86 cgen_->frame()->PrepareMergeTo(entry_frame_); | |
87 if (cgen_->frame()->Equals(entry_frame_)) { | |
88 // Branch right in to the block. | |
89 cgen_->DeleteFrame(); | |
90 __ j(cc, &entry_label_, hint); | |
91 cgen_->SetFrame(fall_through_frame, &non_frame_registers); | |
92 return; | |
93 } | |
94 | |
95 // Check if we can reuse existing merge code. | |
96 for (int i = 0; i < reaching_frames_.length(); i++) { | |
97 if (reaching_frames_[i] != NULL && | |
98 cgen_->frame()->Equals(reaching_frames_[i])) { | |
99 // Branch to the merge code. | |
100 cgen_->DeleteFrame(); | |
101 __ j(cc, &merge_labels_[i], hint); | |
102 cgen_->SetFrame(fall_through_frame, &non_frame_registers); | |
103 return; | |
104 } | |
105 } | |
106 | |
107 // To emit the merge code here, we negate the condition and branch | |
108 // around the merge code on the fall through path. | |
109 Label original_fall_through; | |
110 __ j(NegateCondition(cc), &original_fall_through, NegateHint(hint)); | |
111 cgen_->frame()->MergeTo(entry_frame_); | |
112 cgen_->DeleteFrame(); | |
113 __ jmp(&entry_label_); | |
114 cgen_->SetFrame(fall_through_frame, &non_frame_registers); | |
115 __ bind(&original_fall_through); | |
116 | |
117 } else { | |
118 // Forward branch. A copy of the current frame is added to the end | |
119 // of the list of frames reaching the target block and a branch to | |
120 // the merge code is emitted. | |
121 AddReachingFrame(new VirtualFrame(cgen_->frame())); | |
122 __ j(cc, &merge_labels_.last(), hint); | |
123 is_linked_ = true; | |
124 } | |
125 } | |
126 | |
127 | |
128 void JumpTarget::Call() { | |
129 // Call is used to push the address of the catch block on the stack as | |
130 // a return address when compiling try/catch and try/finally. We | |
131 // fully spill the frame before making the call. The expected frame | |
132 // at the label (which should be the only one) is the spilled current | |
133 // frame plus an in-memory return address. The "fall-through" frame | |
134 // at the return site is the spilled current frame. | |
135 ASSERT(cgen_ != NULL); | |
136 ASSERT(cgen_->has_valid_frame()); | |
137 // There are no non-frame references across the call. | |
138 ASSERT(cgen_->HasValidEntryRegisters()); | |
139 ASSERT(!is_linked()); | |
140 | |
141 cgen_->frame()->SpillAll(); | |
142 VirtualFrame* target_frame = new VirtualFrame(cgen_->frame()); | |
143 target_frame->Adjust(1); | |
144 AddReachingFrame(target_frame); | |
145 __ call(&merge_labels_.last()); | |
146 | |
147 is_linked_ = !is_bound_; | |
148 } | |
149 | |
150 | |
151 void JumpTarget::DoBind(int mergable_elements) { | |
152 ASSERT(cgen_ != NULL); | |
153 ASSERT(!is_bound()); | |
154 | |
155 // Live non-frame registers are not allowed at the start of a basic | |
156 // block. | |
157 ASSERT(!cgen_->has_valid_frame() || cgen_->HasValidEntryRegisters()); | |
158 | |
159 if (direction_ == FORWARD_ONLY) { | |
160 // A simple case: no forward jumps and no possible backward jumps. | |
161 if (!is_linked()) { | |
162 // The stack pointer can be floating above the top of the | |
163 // virtual frame before the bind. Afterward, it should not. | |
164 ASSERT(cgen_->has_valid_frame()); | |
165 VirtualFrame* frame = cgen_->frame(); | |
166 int difference = | |
167 frame->stack_pointer_ - (frame->elements_.length() - 1); | |
168 if (difference > 0) { | |
169 frame->stack_pointer_ -= difference; | |
170 __ add(Operand(esp), Immediate(difference * kPointerSize)); | |
171 } | |
172 | |
173 is_bound_ = true; | |
174 return; | |
175 } | |
176 | |
177 // Another simple case: no fall through, a single forward jump, | |
178 // and no possible backward jumps. | |
179 if (!cgen_->has_valid_frame() && reaching_frames_.length() == 1) { | |
180 // Pick up the only reaching frame, take ownership of it, and | |
181 // use it for the block about to be emitted. | |
182 VirtualFrame* frame = reaching_frames_[0]; | |
183 RegisterFile reserved = RegisterAllocator::Reserved(); | |
184 cgen_->SetFrame(frame, &reserved); | |
185 reaching_frames_[0] = NULL; | |
186 __ bind(&merge_labels_[0]); | |
187 | |
188 // The stack pointer can be floating above the top of the | |
189 // virtual frame before the bind. Afterward, it should not. | |
190 int difference = | |
191 frame->stack_pointer_ - (frame->elements_.length() - 1); | |
192 if (difference > 0) { | |
193 frame->stack_pointer_ -= difference; | |
194 __ add(Operand(esp), Immediate(difference * kPointerSize)); | |
195 } | |
196 | |
197 is_linked_ = false; | |
198 is_bound_ = true; | |
199 return; | |
200 } | |
201 } | |
202 | |
203 // If there is a current frame, record it as the fall-through. It | |
204 // is owned by the reaching frames for now. | |
205 bool had_fall_through = false; | |
206 if (cgen_->has_valid_frame()) { | |
207 had_fall_through = true; | |
208 AddReachingFrame(cgen_->frame()); | |
209 RegisterFile empty; | |
210 cgen_->SetFrame(NULL, &empty); | |
211 } | |
212 | |
213 // Compute the frame to use for entry to the block. | |
214 ComputeEntryFrame(mergable_elements); | |
215 | |
216 // Some moves required to merge to an expected frame require purely | |
217 // frame state changes, and do not require any code generation. | |
218 // Perform those first to increase the possibility of finding equal | |
219 // frames below. | |
220 for (int i = 0; i < reaching_frames_.length(); i++) { | |
221 if (reaching_frames_[i] != NULL) { | |
222 reaching_frames_[i]->PrepareMergeTo(entry_frame_); | |
223 } | |
224 } | |
225 | |
226 if (is_linked()) { | |
227 // There were forward jumps. Handle merging the reaching frames | |
228 // to the entry frame. | |
229 | |
230 // Loop over the (non-null) reaching frames and process any that | |
231 // need merge code. Iterate backwards through the list to handle | |
232 // the fall-through frame first. Set frames that will be | |
233 // processed after 'i' to NULL if we want to avoid processing | |
234 // them. | |
235 for (int i = reaching_frames_.length() - 1; i >= 0; i--) { | |
236 VirtualFrame* frame = reaching_frames_[i]; | |
237 | |
238 if (frame != NULL) { | |
239 // Does the frame (probably) need merge code? | |
240 if (!frame->Equals(entry_frame_)) { | |
241 // We could have a valid frame as the fall through to the | |
242 // binding site or as the fall through from a previous merge | |
243 // code block. Jump around the code we are about to | |
244 // generate. | |
245 if (cgen_->has_valid_frame()) { | |
246 cgen_->DeleteFrame(); | |
247 __ jmp(&entry_label_); | |
248 } | |
249 // Pick up the frame for this block. Assume ownership if | |
250 // there cannot be backward jumps. | |
251 RegisterFile reserved = RegisterAllocator::Reserved(); | |
252 if (direction_ == BIDIRECTIONAL) { | |
253 cgen_->SetFrame(new VirtualFrame(frame), &reserved); | |
254 } else { | |
255 cgen_->SetFrame(frame, &reserved); | |
256 reaching_frames_[i] = NULL; | |
257 } | |
258 __ bind(&merge_labels_[i]); | |
259 | |
260 // Loop over the remaining (non-null) reaching frames, | |
261 // looking for any that can share merge code with this one. | |
262 for (int j = 0; j < i; j++) { | |
263 VirtualFrame* other = reaching_frames_[j]; | |
264 if (other != NULL && other->Equals(cgen_->frame())) { | |
265 // Set the reaching frame element to null to avoid | |
266 // processing it later, and then bind its entry label. | |
267 delete other; | |
268 reaching_frames_[j] = NULL; | |
269 __ bind(&merge_labels_[j]); | |
270 } | |
271 } | |
272 | |
273 // Emit the merge code. | |
274 cgen_->frame()->MergeTo(entry_frame_); | |
275 } else if (i == reaching_frames_.length() - 1 && had_fall_through) { | |
276 // If this is the fall through frame, and it didn't need | |
277 // merge code, we need to pick up the frame so we can jump | |
278 // around subsequent merge blocks if necessary. | |
279 RegisterFile reserved = RegisterAllocator::Reserved(); | |
280 cgen_->SetFrame(frame, &reserved); | |
281 reaching_frames_[i] = NULL; | |
282 } | |
283 } | |
284 } | |
285 | |
286 // The code generator may not have a current frame if there was no | |
287 // fall through and none of the reaching frames needed merging. | |
288 // In that case, clone the entry frame as the current frame. | |
289 if (!cgen_->has_valid_frame()) { | |
290 RegisterFile reserved_registers = RegisterAllocator::Reserved(); | |
291 cgen_->SetFrame(new VirtualFrame(entry_frame_), &reserved_registers); | |
292 } | |
293 | |
294 // There is certainly a current frame equal to the entry frame. | |
295 // Bind the entry frame label. | |
296 __ bind(&entry_label_); | |
297 | |
298 // There may be unprocessed reaching frames that did not need | |
299 // merge code. They will have unbound merge labels. Bind their | |
300 // merge labels to be the same as the entry label and deallocate | |
301 // them. | |
302 for (int i = 0; i < reaching_frames_.length(); i++) { | |
303 if (!merge_labels_[i].is_bound()) { | |
304 delete reaching_frames_[i]; | |
305 reaching_frames_[i] = NULL; | |
306 __ bind(&merge_labels_[i]); | |
307 } | |
308 } | |
309 | |
310 // There are non-NULL reaching frames with bound labels for each | |
311 // merge block, but only on backward targets. | |
312 } else { | |
313 // There were no forward jumps. There must be a current frame and | |
314 // this must be a bidirectional target. | |
315 ASSERT(reaching_frames_.length() == 1); | |
316 ASSERT(reaching_frames_[0] != NULL); | |
317 ASSERT(direction_ == BIDIRECTIONAL); | |
318 | |
319 // Use a copy of the reaching frame so the original can be saved | |
320 // for possible reuse as a backward merge block. | |
321 RegisterFile reserved = RegisterAllocator::Reserved(); | |
322 cgen_->SetFrame(new VirtualFrame(reaching_frames_[0]), &reserved); | |
323 __ bind(&merge_labels_[0]); | |
324 cgen_->frame()->MergeTo(entry_frame_); | |
325 __ bind(&entry_label_); | |
326 } | |
327 | |
328 is_linked_ = false; | |
329 is_bound_ = true; | |
330 } | |
331 | |
332 #undef __ | |
333 | |
334 | |
335 } } // namespace v8::internal | |
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