gcm.cpp revision 196:d1605aabd0a1
1/* 2 * Copyright 1997-2008 Sun Microsystems, Inc. All Rights Reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25// Portions of code courtesy of Clifford Click 26 27// Optimization - Graph Style 28 29#include "incls/_precompiled.incl" 30#include "incls/_gcm.cpp.incl" 31 32//----------------------------schedule_node_into_block------------------------- 33// Insert node n into block b. Look for projections of n and make sure they 34// are in b also. 35void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) { 36 // Set basic block of n, Add n to b, 37 _bbs.map(n->_idx, b); 38 b->add_inst(n); 39 40 // After Matching, nearly any old Node may have projections trailing it. 41 // These are usually machine-dependent flags. In any case, they might 42 // float to another block below this one. Move them up. 43 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 44 Node* use = n->fast_out(i); 45 if (use->is_Proj()) { 46 Block* buse = _bbs[use->_idx]; 47 if (buse != b) { // In wrong block? 48 if (buse != NULL) 49 buse->find_remove(use); // Remove from wrong block 50 _bbs.map(use->_idx, b); // Re-insert in this block 51 b->add_inst(use); 52 } 53 } 54 } 55} 56 57 58//------------------------------schedule_pinned_nodes-------------------------- 59// Set the basic block for Nodes pinned into blocks 60void PhaseCFG::schedule_pinned_nodes( VectorSet &visited ) { 61 // Allocate node stack of size C->unique()+8 to avoid frequent realloc 62 GrowableArray <Node *> spstack(C->unique()+8); 63 spstack.push(_root); 64 while ( spstack.is_nonempty() ) { 65 Node *n = spstack.pop(); 66 if( !visited.test_set(n->_idx) ) { // Test node and flag it as visited 67 if( n->pinned() && !_bbs.lookup(n->_idx) ) { // Pinned? Nail it down! 68 Node *input = n->in(0); 69 assert( input, "pinned Node must have Control" ); 70 while( !input->is_block_start() ) 71 input = input->in(0); 72 Block *b = _bbs[input->_idx]; // Basic block of controlling input 73 schedule_node_into_block(n, b); 74 } 75 for( int i = n->req() - 1; i >= 0; --i ) { // For all inputs 76 if( n->in(i) != NULL ) 77 spstack.push(n->in(i)); 78 } 79 } 80 } 81} 82 83#ifdef ASSERT 84// Assert that new input b2 is dominated by all previous inputs. 85// Check this by by seeing that it is dominated by b1, the deepest 86// input observed until b2. 87static void assert_dom(Block* b1, Block* b2, Node* n, Block_Array &bbs) { 88 if (b1 == NULL) return; 89 assert(b1->_dom_depth < b2->_dom_depth, "sanity"); 90 Block* tmp = b2; 91 while (tmp != b1 && tmp != NULL) { 92 tmp = tmp->_idom; 93 } 94 if (tmp != b1) { 95 // Detected an unschedulable graph. Print some nice stuff and die. 96 tty->print_cr("!!! Unschedulable graph !!!"); 97 for (uint j=0; j<n->len(); j++) { // For all inputs 98 Node* inn = n->in(j); // Get input 99 if (inn == NULL) continue; // Ignore NULL, missing inputs 100 Block* inb = bbs[inn->_idx]; 101 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order, 102 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth); 103 inn->dump(); 104 } 105 tty->print("Failing node: "); 106 n->dump(); 107 assert(false, "unscheduable graph"); 108 } 109} 110#endif 111 112static Block* find_deepest_input(Node* n, Block_Array &bbs) { 113 // Find the last input dominated by all other inputs. 114 Block* deepb = NULL; // Deepest block so far 115 int deepb_dom_depth = 0; 116 for (uint k = 0; k < n->len(); k++) { // For all inputs 117 Node* inn = n->in(k); // Get input 118 if (inn == NULL) continue; // Ignore NULL, missing inputs 119 Block* inb = bbs[inn->_idx]; 120 assert(inb != NULL, "must already have scheduled this input"); 121 if (deepb_dom_depth < (int) inb->_dom_depth) { 122 // The new inb must be dominated by the previous deepb. 123 // The various inputs must be linearly ordered in the dom 124 // tree, or else there will not be a unique deepest block. 125 DEBUG_ONLY(assert_dom(deepb, inb, n, bbs)); 126 deepb = inb; // Save deepest block 127 deepb_dom_depth = deepb->_dom_depth; 128 } 129 } 130 assert(deepb != NULL, "must be at least one input to n"); 131 return deepb; 132} 133 134 135//------------------------------schedule_early--------------------------------- 136// Find the earliest Block any instruction can be placed in. Some instructions 137// are pinned into Blocks. Unpinned instructions can appear in last block in 138// which all their inputs occur. 139bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) { 140 // Allocate stack with enough space to avoid frequent realloc 141 Node_Stack nstack(roots.Size() + 8); // (unique >> 1) + 24 from Java2D stats 142 // roots.push(_root); _root will be processed among C->top() inputs 143 roots.push(C->top()); 144 visited.set(C->top()->_idx); 145 146 while (roots.size() != 0) { 147 // Use local variables nstack_top_n & nstack_top_i to cache values 148 // on stack's top. 149 Node *nstack_top_n = roots.pop(); 150 uint nstack_top_i = 0; 151//while_nstack_nonempty: 152 while (true) { 153 // Get parent node and next input's index from stack's top. 154 Node *n = nstack_top_n; 155 uint i = nstack_top_i; 156 157 if (i == 0) { 158 // Special control input processing. 159 // While I am here, go ahead and look for Nodes which are taking control 160 // from a is_block_proj Node. After I inserted RegionNodes to make proper 161 // blocks, the control at a is_block_proj more properly comes from the 162 // Region being controlled by the block_proj Node. 163 const Node *in0 = n->in(0); 164 if (in0 != NULL) { // Control-dependent? 165 const Node *p = in0->is_block_proj(); 166 if (p != NULL && p != n) { // Control from a block projection? 167 // Find trailing Region 168 Block *pb = _bbs[in0->_idx]; // Block-projection already has basic block 169 uint j = 0; 170 if (pb->_num_succs != 1) { // More then 1 successor? 171 // Search for successor 172 uint max = pb->_nodes.size(); 173 assert( max > 1, "" ); 174 uint start = max - pb->_num_succs; 175 // Find which output path belongs to projection 176 for (j = start; j < max; j++) { 177 if( pb->_nodes[j] == in0 ) 178 break; 179 } 180 assert( j < max, "must find" ); 181 // Change control to match head of successor basic block 182 j -= start; 183 } 184 n->set_req(0, pb->_succs[j]->head()); 185 } 186 } else { // n->in(0) == NULL 187 if (n->req() == 1) { // This guy is a constant with NO inputs? 188 n->set_req(0, _root); 189 } 190 } 191 } 192 193 // First, visit all inputs and force them to get a block. If an 194 // input is already in a block we quit following inputs (to avoid 195 // cycles). Instead we put that Node on a worklist to be handled 196 // later (since IT'S inputs may not have a block yet). 197 bool done = true; // Assume all n's inputs will be processed 198 while (i < n->len()) { // For all inputs 199 Node *in = n->in(i); // Get input 200 ++i; 201 if (in == NULL) continue; // Ignore NULL, missing inputs 202 int is_visited = visited.test_set(in->_idx); 203 if (!_bbs.lookup(in->_idx)) { // Missing block selection? 204 if (is_visited) { 205 // assert( !visited.test(in->_idx), "did not schedule early" ); 206 return false; 207 } 208 nstack.push(n, i); // Save parent node and next input's index. 209 nstack_top_n = in; // Process current input now. 210 nstack_top_i = 0; 211 done = false; // Not all n's inputs processed. 212 break; // continue while_nstack_nonempty; 213 } else if (!is_visited) { // Input not yet visited? 214 roots.push(in); // Visit this guy later, using worklist 215 } 216 } 217 if (done) { 218 // All of n's inputs have been processed, complete post-processing. 219 220 // Some instructions are pinned into a block. These include Region, 221 // Phi, Start, Return, and other control-dependent instructions and 222 // any projections which depend on them. 223 if (!n->pinned()) { 224 // Set earliest legal block. 225 _bbs.map(n->_idx, find_deepest_input(n, _bbs)); 226 } 227 228 if (nstack.is_empty()) { 229 // Finished all nodes on stack. 230 // Process next node on the worklist 'roots'. 231 break; 232 } 233 // Get saved parent node and next input's index. 234 nstack_top_n = nstack.node(); 235 nstack_top_i = nstack.index(); 236 nstack.pop(); 237 } // if (done) 238 } // while (true) 239 } // while (roots.size() != 0) 240 return true; 241} 242 243//------------------------------dom_lca---------------------------------------- 244// Find least common ancestor in dominator tree 245// LCA is a current notion of LCA, to be raised above 'this'. 246// As a convenient boundary condition, return 'this' if LCA is NULL. 247// Find the LCA of those two nodes. 248Block* Block::dom_lca(Block* LCA) { 249 if (LCA == NULL || LCA == this) return this; 250 251 Block* anc = this; 252 while (anc->_dom_depth > LCA->_dom_depth) 253 anc = anc->_idom; // Walk up till anc is as high as LCA 254 255 while (LCA->_dom_depth > anc->_dom_depth) 256 LCA = LCA->_idom; // Walk up till LCA is as high as anc 257 258 while (LCA != anc) { // Walk both up till they are the same 259 LCA = LCA->_idom; 260 anc = anc->_idom; 261 } 262 263 return LCA; 264} 265 266//--------------------------raise_LCA_above_use-------------------------------- 267// We are placing a definition, and have been given a def->use edge. 268// The definition must dominate the use, so move the LCA upward in the 269// dominator tree to dominate the use. If the use is a phi, adjust 270// the LCA only with the phi input paths which actually use this def. 271static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, Block_Array &bbs) { 272 Block* buse = bbs[use->_idx]; 273 if (buse == NULL) return LCA; // Unused killing Projs have no use block 274 if (!use->is_Phi()) return buse->dom_lca(LCA); 275 uint pmax = use->req(); // Number of Phi inputs 276 // Why does not this loop just break after finding the matching input to 277 // the Phi? Well...it's like this. I do not have true def-use/use-def 278 // chains. Means I cannot distinguish, from the def-use direction, which 279 // of many use-defs lead from the same use to the same def. That is, this 280 // Phi might have several uses of the same def. Each use appears in a 281 // different predecessor block. But when I enter here, I cannot distinguish 282 // which use-def edge I should find the predecessor block for. So I find 283 // them all. Means I do a little extra work if a Phi uses the same value 284 // more than once. 285 for (uint j=1; j<pmax; j++) { // For all inputs 286 if (use->in(j) == def) { // Found matching input? 287 Block* pred = bbs[buse->pred(j)->_idx]; 288 LCA = pred->dom_lca(LCA); 289 } 290 } 291 return LCA; 292} 293 294//----------------------------raise_LCA_above_marks---------------------------- 295// Return a new LCA that dominates LCA and any of its marked predecessors. 296// Search all my parents up to 'early' (exclusive), looking for predecessors 297// which are marked with the given index. Return the LCA (in the dom tree) 298// of all marked blocks. If there are none marked, return the original 299// LCA. 300static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, 301 Block* early, Block_Array &bbs) { 302 Block_List worklist; 303 worklist.push(LCA); 304 while (worklist.size() > 0) { 305 Block* mid = worklist.pop(); 306 if (mid == early) continue; // stop searching here 307 308 // Test and set the visited bit. 309 if (mid->raise_LCA_visited() == mark) continue; // already visited 310 mid->set_raise_LCA_visited(mark); 311 312 // Don't process the current LCA, otherwise the search may terminate early 313 if (mid != LCA && mid->raise_LCA_mark() == mark) { 314 // Raise the LCA. 315 LCA = mid->dom_lca(LCA); 316 if (LCA == early) break; // stop searching everywhere 317 assert(early->dominates(LCA), "early is high enough"); 318 // Resume searching at that point, skipping intermediate levels. 319 worklist.push(LCA); 320 } else { 321 // Keep searching through this block's predecessors. 322 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) { 323 Block* mid_parent = bbs[ mid->pred(j)->_idx ]; 324 worklist.push(mid_parent); 325 } 326 } 327 } 328 return LCA; 329} 330 331//--------------------------memory_early_block-------------------------------- 332// This is a variation of find_deepest_input, the heart of schedule_early. 333// Find the "early" block for a load, if we considered only memory and 334// address inputs, that is, if other data inputs were ignored. 335// 336// Because a subset of edges are considered, the resulting block will 337// be earlier (at a shallower dom_depth) than the true schedule_early 338// point of the node. We compute this earlier block as a more permissive 339// site for anti-dependency insertion, but only if subsume_loads is enabled. 340static Block* memory_early_block(Node* load, Block* early, Block_Array &bbs) { 341 Node* base; 342 Node* index; 343 Node* store = load->in(MemNode::Memory); 344 load->as_Mach()->memory_inputs(base, index); 345 346 assert(base != NodeSentinel && index != NodeSentinel, 347 "unexpected base/index inputs"); 348 349 Node* mem_inputs[4]; 350 int mem_inputs_length = 0; 351 if (base != NULL) mem_inputs[mem_inputs_length++] = base; 352 if (index != NULL) mem_inputs[mem_inputs_length++] = index; 353 if (store != NULL) mem_inputs[mem_inputs_length++] = store; 354 355 // In the comparision below, add one to account for the control input, 356 // which may be null, but always takes up a spot in the in array. 357 if (mem_inputs_length + 1 < (int) load->req()) { 358 // This "load" has more inputs than just the memory, base and index inputs. 359 // For purposes of checking anti-dependences, we need to start 360 // from the early block of only the address portion of the instruction, 361 // and ignore other blocks that may have factored into the wider 362 // schedule_early calculation. 363 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0); 364 365 Block* deepb = NULL; // Deepest block so far 366 int deepb_dom_depth = 0; 367 for (int i = 0; i < mem_inputs_length; i++) { 368 Block* inb = bbs[mem_inputs[i]->_idx]; 369 if (deepb_dom_depth < (int) inb->_dom_depth) { 370 // The new inb must be dominated by the previous deepb. 371 // The various inputs must be linearly ordered in the dom 372 // tree, or else there will not be a unique deepest block. 373 DEBUG_ONLY(assert_dom(deepb, inb, load, bbs)); 374 deepb = inb; // Save deepest block 375 deepb_dom_depth = deepb->_dom_depth; 376 } 377 } 378 early = deepb; 379 } 380 381 return early; 382} 383 384//--------------------------insert_anti_dependences--------------------------- 385// A load may need to witness memory that nearby stores can overwrite. 386// For each nearby store, either insert an "anti-dependence" edge 387// from the load to the store, or else move LCA upward to force the 388// load to (eventually) be scheduled in a block above the store. 389// 390// Do not add edges to stores on distinct control-flow paths; 391// only add edges to stores which might interfere. 392// 393// Return the (updated) LCA. There will not be any possibly interfering 394// store between the load's "early block" and the updated LCA. 395// Any stores in the updated LCA will have new precedence edges 396// back to the load. The caller is expected to schedule the load 397// in the LCA, in which case the precedence edges will make LCM 398// preserve anti-dependences. The caller may also hoist the load 399// above the LCA, if it is not the early block. 400Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) { 401 assert(load->needs_anti_dependence_check(), "must be a load of some sort"); 402 assert(LCA != NULL, ""); 403 DEBUG_ONLY(Block* LCA_orig = LCA); 404 405 // Compute the alias index. Loads and stores with different alias indices 406 // do not need anti-dependence edges. 407 uint load_alias_idx = C->get_alias_index(load->adr_type()); 408#ifdef ASSERT 409 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 && 410 (PrintOpto || VerifyAliases || 411 PrintMiscellaneous && (WizardMode || Verbose))) { 412 // Load nodes should not consume all of memory. 413 // Reporting a bottom type indicates a bug in adlc. 414 // If some particular type of node validly consumes all of memory, 415 // sharpen the preceding "if" to exclude it, so we can catch bugs here. 416 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory."); 417 load->dump(2); 418 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, ""); 419 } 420#endif 421 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp), 422 "String compare is only known 'load' that does not conflict with any stores"); 423 424 if (!C->alias_type(load_alias_idx)->is_rewritable()) { 425 // It is impossible to spoil this load by putting stores before it, 426 // because we know that the stores will never update the value 427 // which 'load' must witness. 428 return LCA; 429 } 430 431 node_idx_t load_index = load->_idx; 432 433 // Note the earliest legal placement of 'load', as determined by 434 // by the unique point in the dom tree where all memory effects 435 // and other inputs are first available. (Computed by schedule_early.) 436 // For normal loads, 'early' is the shallowest place (dom graph wise) 437 // to look for anti-deps between this load and any store. 438 Block* early = _bbs[load_index]; 439 440 // If we are subsuming loads, compute an "early" block that only considers 441 // memory or address inputs. This block may be different than the 442 // schedule_early block in that it could be at an even shallower depth in the 443 // dominator tree, and allow for a broader discovery of anti-dependences. 444 if (C->subsume_loads()) { 445 early = memory_early_block(load, early, _bbs); 446 } 447 448 ResourceArea *area = Thread::current()->resource_area(); 449 Node_List worklist_mem(area); // prior memory state to store 450 Node_List worklist_store(area); // possible-def to explore 451 Node_List worklist_visited(area); // visited mergemem nodes 452 Node_List non_early_stores(area); // all relevant stores outside of early 453 bool must_raise_LCA = false; 454 455#ifdef TRACK_PHI_INPUTS 456 // %%% This extra checking fails because MergeMem nodes are not GVNed. 457 // Provide "phi_inputs" to check if every input to a PhiNode is from the 458 // original memory state. This indicates a PhiNode for which should not 459 // prevent the load from sinking. For such a block, set_raise_LCA_mark 460 // may be overly conservative. 461 // Mechanism: count inputs seen for each Phi encountered in worklist_store. 462 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0)); 463#endif 464 465 // 'load' uses some memory state; look for users of the same state. 466 // Recurse through MergeMem nodes to the stores that use them. 467 468 // Each of these stores is a possible definition of memory 469 // that 'load' needs to use. We need to force 'load' 470 // to occur before each such store. When the store is in 471 // the same block as 'load', we insert an anti-dependence 472 // edge load->store. 473 474 // The relevant stores "nearby" the load consist of a tree rooted 475 // at initial_mem, with internal nodes of type MergeMem. 476 // Therefore, the branches visited by the worklist are of this form: 477 // initial_mem -> (MergeMem ->)* store 478 // The anti-dependence constraints apply only to the fringe of this tree. 479 480 Node* initial_mem = load->in(MemNode::Memory); 481 worklist_store.push(initial_mem); 482 worklist_visited.push(initial_mem); 483 worklist_mem.push(NULL); 484 while (worklist_store.size() > 0) { 485 // Examine a nearby store to see if it might interfere with our load. 486 Node* mem = worklist_mem.pop(); 487 Node* store = worklist_store.pop(); 488 uint op = store->Opcode(); 489 490 // MergeMems do not directly have anti-deps. 491 // Treat them as internal nodes in a forward tree of memory states, 492 // the leaves of which are each a 'possible-def'. 493 if (store == initial_mem // root (exclusive) of tree we are searching 494 || op == Op_MergeMem // internal node of tree we are searching 495 ) { 496 mem = store; // It's not a possibly interfering store. 497 if (store == initial_mem) 498 initial_mem = NULL; // only process initial memory once 499 500 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { 501 store = mem->fast_out(i); 502 if (store->is_MergeMem()) { 503 // Be sure we don't get into combinatorial problems. 504 // (Allow phis to be repeated; they can merge two relevant states.) 505 uint j = worklist_visited.size(); 506 for (; j > 0; j--) { 507 if (worklist_visited.at(j-1) == store) break; 508 } 509 if (j > 0) continue; // already on work list; do not repeat 510 worklist_visited.push(store); 511 } 512 worklist_mem.push(mem); 513 worklist_store.push(store); 514 } 515 continue; 516 } 517 518 if (op == Op_MachProj || op == Op_Catch) continue; 519 if (store->needs_anti_dependence_check()) continue; // not really a store 520 521 // Compute the alias index. Loads and stores with different alias 522 // indices do not need anti-dependence edges. Wide MemBar's are 523 // anti-dependent on everything (except immutable memories). 524 const TypePtr* adr_type = store->adr_type(); 525 if (!C->can_alias(adr_type, load_alias_idx)) continue; 526 527 // Most slow-path runtime calls do NOT modify Java memory, but 528 // they can block and so write Raw memory. 529 if (store->is_Mach()) { 530 MachNode* mstore = store->as_Mach(); 531 if (load_alias_idx != Compile::AliasIdxRaw) { 532 // Check for call into the runtime using the Java calling 533 // convention (and from there into a wrapper); it has no 534 // _method. Can't do this optimization for Native calls because 535 // they CAN write to Java memory. 536 if (mstore->ideal_Opcode() == Op_CallStaticJava) { 537 assert(mstore->is_MachSafePoint(), ""); 538 MachSafePointNode* ms = (MachSafePointNode*) mstore; 539 assert(ms->is_MachCallJava(), ""); 540 MachCallJavaNode* mcj = (MachCallJavaNode*) ms; 541 if (mcj->_method == NULL) { 542 // These runtime calls do not write to Java visible memory 543 // (other than Raw) and so do not require anti-dependence edges. 544 continue; 545 } 546 } 547 // Same for SafePoints: they read/write Raw but only read otherwise. 548 // This is basically a workaround for SafePoints only defining control 549 // instead of control + memory. 550 if (mstore->ideal_Opcode() == Op_SafePoint) 551 continue; 552 } else { 553 // Some raw memory, such as the load of "top" at an allocation, 554 // can be control dependent on the previous safepoint. See 555 // comments in GraphKit::allocate_heap() about control input. 556 // Inserting an anti-dep between such a safepoint and a use 557 // creates a cycle, and will cause a subsequent failure in 558 // local scheduling. (BugId 4919904) 559 // (%%% How can a control input be a safepoint and not a projection??) 560 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore) 561 continue; 562 } 563 } 564 565 // Identify a block that the current load must be above, 566 // or else observe that 'store' is all the way up in the 567 // earliest legal block for 'load'. In the latter case, 568 // immediately insert an anti-dependence edge. 569 Block* store_block = _bbs[store->_idx]; 570 assert(store_block != NULL, "unused killing projections skipped above"); 571 572 if (store->is_Phi()) { 573 // 'load' uses memory which is one (or more) of the Phi's inputs. 574 // It must be scheduled not before the Phi, but rather before 575 // each of the relevant Phi inputs. 576 // 577 // Instead of finding the LCA of all inputs to a Phi that match 'mem', 578 // we mark each corresponding predecessor block and do a combined 579 // hoisting operation later (raise_LCA_above_marks). 580 // 581 // Do not assert(store_block != early, "Phi merging memory after access") 582 // PhiNode may be at start of block 'early' with backedge to 'early' 583 DEBUG_ONLY(bool found_match = false); 584 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) { 585 if (store->in(j) == mem) { // Found matching input? 586 DEBUG_ONLY(found_match = true); 587 Block* pred_block = _bbs[store_block->pred(j)->_idx]; 588 if (pred_block != early) { 589 // If any predecessor of the Phi matches the load's "early block", 590 // we do not need a precedence edge between the Phi and 'load' 591 // since the load will be forced into a block preceeding the Phi. 592 pred_block->set_raise_LCA_mark(load_index); 593 assert(!LCA_orig->dominates(pred_block) || 594 early->dominates(pred_block), "early is high enough"); 595 must_raise_LCA = true; 596 } 597 } 598 } 599 assert(found_match, "no worklist bug"); 600#ifdef TRACK_PHI_INPUTS 601#ifdef ASSERT 602 // This assert asks about correct handling of PhiNodes, which may not 603 // have all input edges directly from 'mem'. See BugId 4621264 604 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1; 605 // Increment by exactly one even if there are multiple copies of 'mem' 606 // coming into the phi, because we will run this block several times 607 // if there are several copies of 'mem'. (That's how DU iterators work.) 608 phi_inputs.at_put(store->_idx, num_mem_inputs); 609 assert(PhiNode::Input + num_mem_inputs < store->req(), 610 "Expect at least one phi input will not be from original memory state"); 611#endif //ASSERT 612#endif //TRACK_PHI_INPUTS 613 } else if (store_block != early) { 614 // 'store' is between the current LCA and earliest possible block. 615 // Label its block, and decide later on how to raise the LCA 616 // to include the effect on LCA of this store. 617 // If this store's block gets chosen as the raised LCA, we 618 // will find him on the non_early_stores list and stick him 619 // with a precedence edge. 620 // (But, don't bother if LCA is already raised all the way.) 621 if (LCA != early) { 622 store_block->set_raise_LCA_mark(load_index); 623 must_raise_LCA = true; 624 non_early_stores.push(store); 625 } 626 } else { 627 // Found a possibly-interfering store in the load's 'early' block. 628 // This means 'load' cannot sink at all in the dominator tree. 629 // Add an anti-dep edge, and squeeze 'load' into the highest block. 630 assert(store != load->in(0), "dependence cycle found"); 631 if (verify) { 632 assert(store->find_edge(load) != -1, "missing precedence edge"); 633 } else { 634 store->add_prec(load); 635 } 636 LCA = early; 637 // This turns off the process of gathering non_early_stores. 638 } 639 } 640 // (Worklist is now empty; all nearby stores have been visited.) 641 642 // Finished if 'load' must be scheduled in its 'early' block. 643 // If we found any stores there, they have already been given 644 // precedence edges. 645 if (LCA == early) return LCA; 646 647 // We get here only if there are no possibly-interfering stores 648 // in the load's 'early' block. Move LCA up above all predecessors 649 // which contain stores we have noted. 650 // 651 // The raised LCA block can be a home to such interfering stores, 652 // but its predecessors must not contain any such stores. 653 // 654 // The raised LCA will be a lower bound for placing the load, 655 // preventing the load from sinking past any block containing 656 // a store that may invalidate the memory state required by 'load'. 657 if (must_raise_LCA) 658 LCA = raise_LCA_above_marks(LCA, load->_idx, early, _bbs); 659 if (LCA == early) return LCA; 660 661 // Insert anti-dependence edges from 'load' to each store 662 // in the non-early LCA block. 663 // Mine the non_early_stores list for such stores. 664 if (LCA->raise_LCA_mark() == load_index) { 665 while (non_early_stores.size() > 0) { 666 Node* store = non_early_stores.pop(); 667 Block* store_block = _bbs[store->_idx]; 668 if (store_block == LCA) { 669 // add anti_dependence from store to load in its own block 670 assert(store != load->in(0), "dependence cycle found"); 671 if (verify) { 672 assert(store->find_edge(load) != -1, "missing precedence edge"); 673 } else { 674 store->add_prec(load); 675 } 676 } else { 677 assert(store_block->raise_LCA_mark() == load_index, "block was marked"); 678 // Any other stores we found must be either inside the new LCA 679 // or else outside the original LCA. In the latter case, they 680 // did not interfere with any use of 'load'. 681 assert(LCA->dominates(store_block) 682 || !LCA_orig->dominates(store_block), "no stray stores"); 683 } 684 } 685 } 686 687 // Return the highest block containing stores; any stores 688 // within that block have been given anti-dependence edges. 689 return LCA; 690} 691 692// This class is used to iterate backwards over the nodes in the graph. 693 694class Node_Backward_Iterator { 695 696private: 697 Node_Backward_Iterator(); 698 699public: 700 // Constructor for the iterator 701 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs); 702 703 // Postincrement operator to iterate over the nodes 704 Node *next(); 705 706private: 707 VectorSet &_visited; 708 Node_List &_stack; 709 Block_Array &_bbs; 710}; 711 712// Constructor for the Node_Backward_Iterator 713Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs ) 714 : _visited(visited), _stack(stack), _bbs(bbs) { 715 // The stack should contain exactly the root 716 stack.clear(); 717 stack.push(root); 718 719 // Clear the visited bits 720 visited.Clear(); 721} 722 723// Iterator for the Node_Backward_Iterator 724Node *Node_Backward_Iterator::next() { 725 726 // If the _stack is empty, then just return NULL: finished. 727 if ( !_stack.size() ) 728 return NULL; 729 730 // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been 731 // made stateless, so I do not need to record the index 'i' on my _stack. 732 // Instead I visit all users each time, scanning for unvisited users. 733 // I visit unvisited not-anti-dependence users first, then anti-dependent 734 // children next. 735 Node *self = _stack.pop(); 736 737 // I cycle here when I am entering a deeper level of recursion. 738 // The key variable 'self' was set prior to jumping here. 739 while( 1 ) { 740 741 _visited.set(self->_idx); 742 743 // Now schedule all uses as late as possible. 744 uint src = self->is_Proj() ? self->in(0)->_idx : self->_idx; 745 uint src_rpo = _bbs[src]->_rpo; 746 747 // Schedule all nodes in a post-order visit 748 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any 749 750 // Scan for unvisited nodes 751 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) { 752 // For all uses, schedule late 753 Node* n = self->fast_out(i); // Use 754 755 // Skip already visited children 756 if ( _visited.test(n->_idx) ) 757 continue; 758 759 // do not traverse backward control edges 760 Node *use = n->is_Proj() ? n->in(0) : n; 761 uint use_rpo = _bbs[use->_idx]->_rpo; 762 763 if ( use_rpo < src_rpo ) 764 continue; 765 766 // Phi nodes always precede uses in a basic block 767 if ( use_rpo == src_rpo && use->is_Phi() ) 768 continue; 769 770 unvisited = n; // Found unvisited 771 772 // Check for possible-anti-dependent 773 if( !n->needs_anti_dependence_check() ) 774 break; // Not visited, not anti-dep; schedule it NOW 775 } 776 777 // Did I find an unvisited not-anti-dependent Node? 778 if ( !unvisited ) 779 break; // All done with children; post-visit 'self' 780 781 // Visit the unvisited Node. Contains the obvious push to 782 // indicate I'm entering a deeper level of recursion. I push the 783 // old state onto the _stack and set a new state and loop (recurse). 784 _stack.push(self); 785 self = unvisited; 786 } // End recursion loop 787 788 return self; 789} 790 791//------------------------------ComputeLatenciesBackwards---------------------- 792// Compute the latency of all the instructions. 793void PhaseCFG::ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack) { 794#ifndef PRODUCT 795 if (trace_opto_pipelining()) 796 tty->print("\n#---- ComputeLatenciesBackwards ----\n"); 797#endif 798 799 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs); 800 Node *n; 801 802 // Walk over all the nodes from last to first 803 while (n = iter.next()) { 804 // Set the latency for the definitions of this instruction 805 partial_latency_of_defs(n); 806 } 807} // end ComputeLatenciesBackwards 808 809//------------------------------partial_latency_of_defs------------------------ 810// Compute the latency impact of this node on all defs. This computes 811// a number that increases as we approach the beginning of the routine. 812void PhaseCFG::partial_latency_of_defs(Node *n) { 813 // Set the latency for this instruction 814#ifndef PRODUCT 815 if (trace_opto_pipelining()) { 816 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", 817 n->_idx, _node_latency.at_grow(n->_idx)); 818 dump(); 819 } 820#endif 821 822 if (n->is_Proj()) 823 n = n->in(0); 824 825 if (n->is_Root()) 826 return; 827 828 uint nlen = n->len(); 829 uint use_latency = _node_latency.at_grow(n->_idx); 830 uint use_pre_order = _bbs[n->_idx]->_pre_order; 831 832 for ( uint j=0; j<nlen; j++ ) { 833 Node *def = n->in(j); 834 835 if (!def || def == n) 836 continue; 837 838 // Walk backwards thru projections 839 if (def->is_Proj()) 840 def = def->in(0); 841 842#ifndef PRODUCT 843 if (trace_opto_pipelining()) { 844 tty->print("# in(%2d): ", j); 845 def->dump(); 846 } 847#endif 848 849 // If the defining block is not known, assume it is ok 850 Block *def_block = _bbs[def->_idx]; 851 uint def_pre_order = def_block ? def_block->_pre_order : 0; 852 853 if ( (use_pre_order < def_pre_order) || 854 (use_pre_order == def_pre_order && n->is_Phi()) ) 855 continue; 856 857 uint delta_latency = n->latency(j); 858 uint current_latency = delta_latency + use_latency; 859 860 if (_node_latency.at_grow(def->_idx) < current_latency) { 861 _node_latency.at_put_grow(def->_idx, current_latency); 862 } 863 864#ifndef PRODUCT 865 if (trace_opto_pipelining()) { 866 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, node_latency[%d] = %d", 867 use_latency, j, delta_latency, current_latency, def->_idx, 868 _node_latency.at_grow(def->_idx)); 869 } 870#endif 871 } 872} 873 874//------------------------------latency_from_use------------------------------- 875// Compute the latency of a specific use 876int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) { 877 // If self-reference, return no latency 878 if (use == n || use->is_Root()) 879 return 0; 880 881 uint def_pre_order = _bbs[def->_idx]->_pre_order; 882 uint latency = 0; 883 884 // If the use is not a projection, then it is simple... 885 if (!use->is_Proj()) { 886#ifndef PRODUCT 887 if (trace_opto_pipelining()) { 888 tty->print("# out(): "); 889 use->dump(); 890 } 891#endif 892 893 uint use_pre_order = _bbs[use->_idx]->_pre_order; 894 895 if (use_pre_order < def_pre_order) 896 return 0; 897 898 if (use_pre_order == def_pre_order && use->is_Phi()) 899 return 0; 900 901 uint nlen = use->len(); 902 uint nl = _node_latency.at_grow(use->_idx); 903 904 for ( uint j=0; j<nlen; j++ ) { 905 if (use->in(j) == n) { 906 // Change this if we want local latencies 907 uint ul = use->latency(j); 908 uint l = ul + nl; 909 if (latency < l) latency = l; 910#ifndef PRODUCT 911 if (trace_opto_pipelining()) { 912 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d", 913 nl, j, ul, l, latency); 914 } 915#endif 916 } 917 } 918 } else { 919 // This is a projection, just grab the latency of the use(s) 920 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) { 921 uint l = latency_from_use(use, def, use->fast_out(j)); 922 if (latency < l) latency = l; 923 } 924 } 925 926 return latency; 927} 928 929//------------------------------latency_from_uses------------------------------ 930// Compute the latency of this instruction relative to all of it's uses. 931// This computes a number that increases as we approach the beginning of the 932// routine. 933void PhaseCFG::latency_from_uses(Node *n) { 934 // Set the latency for this instruction 935#ifndef PRODUCT 936 if (trace_opto_pipelining()) { 937 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", 938 n->_idx, _node_latency.at_grow(n->_idx)); 939 dump(); 940 } 941#endif 942 uint latency=0; 943 const Node *def = n->is_Proj() ? n->in(0): n; 944 945 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { 946 uint l = latency_from_use(n, def, n->fast_out(i)); 947 948 if (latency < l) latency = l; 949 } 950 951 _node_latency.at_put_grow(n->_idx, latency); 952} 953 954//------------------------------hoist_to_cheaper_block------------------------- 955// Pick a block for node self, between early and LCA, that is a cheaper 956// alternative to LCA. 957Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) { 958 const double delta = 1+PROB_UNLIKELY_MAG(4); 959 Block* least = LCA; 960 double least_freq = least->_freq; 961 uint target = _node_latency.at_grow(self->_idx); 962 uint start_latency = _node_latency.at_grow(LCA->_nodes[0]->_idx); 963 uint end_latency = _node_latency.at_grow(LCA->_nodes[LCA->end_idx()]->_idx); 964 bool in_latency = (target <= start_latency); 965 const Block* root_block = _bbs[_root->_idx]; 966 967 // Turn off latency scheduling if scheduling is just plain off 968 if (!C->do_scheduling()) 969 in_latency = true; 970 971 // Do not hoist (to cover latency) instructions which target a 972 // single register. Hoisting stretches the live range of the 973 // single register and may force spilling. 974 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL; 975 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty()) 976 in_latency = true; 977 978#ifndef PRODUCT 979 if (trace_opto_pipelining()) { 980 tty->print("# Find cheaper block for latency %d: ", 981 _node_latency.at_grow(self->_idx)); 982 self->dump(); 983 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g", 984 LCA->_pre_order, 985 LCA->_nodes[0]->_idx, 986 start_latency, 987 LCA->_nodes[LCA->end_idx()]->_idx, 988 end_latency, 989 least_freq); 990 } 991#endif 992 993 // Walk up the dominator tree from LCA (Lowest common ancestor) to 994 // the earliest legal location. Capture the least execution frequency. 995 while (LCA != early) { 996 LCA = LCA->_idom; // Follow up the dominator tree 997 998 if (LCA == NULL) { 999 // Bailout without retry 1000 C->record_method_not_compilable("late schedule failed: LCA == NULL"); 1001 return least; 1002 } 1003 1004 // Don't hoist machine instructions to the root basic block 1005 if (mach && LCA == root_block) 1006 break; 1007 1008 uint start_lat = _node_latency.at_grow(LCA->_nodes[0]->_idx); 1009 uint end_idx = LCA->end_idx(); 1010 uint end_lat = _node_latency.at_grow(LCA->_nodes[end_idx]->_idx); 1011 double LCA_freq = LCA->_freq; 1012#ifndef PRODUCT 1013 if (trace_opto_pipelining()) { 1014 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g", 1015 LCA->_pre_order, LCA->_nodes[0]->_idx, start_lat, end_idx, end_lat, LCA_freq); 1016 } 1017#endif 1018 if (LCA_freq < least_freq || // Better Frequency 1019 ( !in_latency && // No block containing latency 1020 LCA_freq < least_freq * delta && // No worse frequency 1021 target >= end_lat && // within latency range 1022 !self->is_iteratively_computed() ) // But don't hoist IV increments 1023 // because they may end up above other uses of their phi forcing 1024 // their result register to be different from their input. 1025 ) { 1026 least = LCA; // Found cheaper block 1027 least_freq = LCA_freq; 1028 start_latency = start_lat; 1029 end_latency = end_lat; 1030 if (target <= start_lat) 1031 in_latency = true; 1032 } 1033 } 1034 1035#ifndef PRODUCT 1036 if (trace_opto_pipelining()) { 1037 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g", 1038 least->_pre_order, start_latency, least_freq); 1039 } 1040#endif 1041 1042 // See if the latency needs to be updated 1043 if (target < end_latency) { 1044#ifndef PRODUCT 1045 if (trace_opto_pipelining()) { 1046 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency); 1047 } 1048#endif 1049 _node_latency.at_put_grow(self->_idx, end_latency); 1050 partial_latency_of_defs(self); 1051 } 1052 1053 return least; 1054} 1055 1056 1057//------------------------------schedule_late----------------------------------- 1058// Now schedule all codes as LATE as possible. This is the LCA in the 1059// dominator tree of all USES of a value. Pick the block with the least 1060// loop nesting depth that is lowest in the dominator tree. 1061extern const char must_clone[]; 1062void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) { 1063#ifndef PRODUCT 1064 if (trace_opto_pipelining()) 1065 tty->print("\n#---- schedule_late ----\n"); 1066#endif 1067 1068 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs); 1069 Node *self; 1070 1071 // Walk over all the nodes from last to first 1072 while (self = iter.next()) { 1073 Block* early = _bbs[self->_idx]; // Earliest legal placement 1074 1075 if (self->is_top()) { 1076 // Top node goes in bb #2 with other constants. 1077 // It must be special-cased, because it has no out edges. 1078 early->add_inst(self); 1079 continue; 1080 } 1081 1082 // No uses, just terminate 1083 if (self->outcnt() == 0) { 1084 assert(self->Opcode() == Op_MachProj, "sanity"); 1085 continue; // Must be a dead machine projection 1086 } 1087 1088 // If node is pinned in the block, then no scheduling can be done. 1089 if( self->pinned() ) // Pinned in block? 1090 continue; 1091 1092 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL; 1093 if (mach) { 1094 switch (mach->ideal_Opcode()) { 1095 case Op_CreateEx: 1096 // Don't move exception creation 1097 early->add_inst(self); 1098 continue; 1099 break; 1100 case Op_CheckCastPP: 1101 // Don't move CheckCastPP nodes away from their input, if the input 1102 // is a rawptr (5071820). 1103 Node *def = self->in(1); 1104 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) { 1105 early->add_inst(self); 1106 continue; 1107 } 1108 break; 1109 } 1110 } 1111 1112 // Gather LCA of all uses 1113 Block *LCA = NULL; 1114 { 1115 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) { 1116 // For all uses, find LCA 1117 Node* use = self->fast_out(i); 1118 LCA = raise_LCA_above_use(LCA, use, self, _bbs); 1119 } 1120 } // (Hide defs of imax, i from rest of block.) 1121 1122 // Place temps in the block of their use. This isn't a 1123 // requirement for correctness but it reduces useless 1124 // interference between temps and other nodes. 1125 if (mach != NULL && mach->is_MachTemp()) { 1126 _bbs.map(self->_idx, LCA); 1127 LCA->add_inst(self); 1128 continue; 1129 } 1130 1131 // Check if 'self' could be anti-dependent on memory 1132 if (self->needs_anti_dependence_check()) { 1133 // Hoist LCA above possible-defs and insert anti-dependences to 1134 // defs in new LCA block. 1135 LCA = insert_anti_dependences(LCA, self); 1136 } 1137 1138 if (early->_dom_depth > LCA->_dom_depth) { 1139 // Somehow the LCA has moved above the earliest legal point. 1140 // (One way this can happen is via memory_early_block.) 1141 if (C->subsume_loads() == true && !C->failing()) { 1142 // Retry with subsume_loads == false 1143 // If this is the first failure, the sentinel string will "stick" 1144 // to the Compile object, and the C2Compiler will see it and retry. 1145 C->record_failure(C2Compiler::retry_no_subsuming_loads()); 1146 } else { 1147 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth) 1148 C->record_method_not_compilable("late schedule failed: incorrect graph"); 1149 } 1150 return; 1151 } 1152 1153 // If there is no opportunity to hoist, then we're done. 1154 bool try_to_hoist = (LCA != early); 1155 1156 // Must clone guys stay next to use; no hoisting allowed. 1157 // Also cannot hoist guys that alter memory or are otherwise not 1158 // allocatable (hoisting can make a value live longer, leading to 1159 // anti and output dependency problems which are normally resolved 1160 // by the register allocator giving everyone a different register). 1161 if (mach != NULL && must_clone[mach->ideal_Opcode()]) 1162 try_to_hoist = false; 1163 1164 Block* late = NULL; 1165 if (try_to_hoist) { 1166 // Now find the block with the least execution frequency. 1167 // Start at the latest schedule and work up to the earliest schedule 1168 // in the dominator tree. Thus the Node will dominate all its uses. 1169 late = hoist_to_cheaper_block(LCA, early, self); 1170 } else { 1171 // Just use the LCA of the uses. 1172 late = LCA; 1173 } 1174 1175 // Put the node into target block 1176 schedule_node_into_block(self, late); 1177 1178#ifdef ASSERT 1179 if (self->needs_anti_dependence_check()) { 1180 // since precedence edges are only inserted when we're sure they 1181 // are needed make sure that after placement in a block we don't 1182 // need any new precedence edges. 1183 verify_anti_dependences(late, self); 1184 } 1185#endif 1186 } // Loop until all nodes have been visited 1187 1188} // end ScheduleLate 1189 1190//------------------------------GlobalCodeMotion------------------------------- 1191void PhaseCFG::GlobalCodeMotion( Matcher &matcher, uint unique, Node_List &proj_list ) { 1192 ResourceMark rm; 1193 1194#ifndef PRODUCT 1195 if (trace_opto_pipelining()) { 1196 tty->print("\n---- Start GlobalCodeMotion ----\n"); 1197 } 1198#endif 1199 1200 // Initialize the bbs.map for things on the proj_list 1201 uint i; 1202 for( i=0; i < proj_list.size(); i++ ) 1203 _bbs.map(proj_list[i]->_idx, NULL); 1204 1205 // Set the basic block for Nodes pinned into blocks 1206 Arena *a = Thread::current()->resource_area(); 1207 VectorSet visited(a); 1208 schedule_pinned_nodes( visited ); 1209 1210 // Find the earliest Block any instruction can be placed in. Some 1211 // instructions are pinned into Blocks. Unpinned instructions can 1212 // appear in last block in which all their inputs occur. 1213 visited.Clear(); 1214 Node_List stack(a); 1215 stack.map( (unique >> 1) + 16, NULL); // Pre-grow the list 1216 if (!schedule_early(visited, stack)) { 1217 // Bailout without retry 1218 C->record_method_not_compilable("early schedule failed"); 1219 return; 1220 } 1221 1222 // Build Def-Use edges. 1223 proj_list.push(_root); // Add real root as another root 1224 proj_list.pop(); 1225 1226 // Compute the latency information (via backwards walk) for all the 1227 // instructions in the graph 1228 GrowableArray<uint> node_latency; 1229 _node_latency = node_latency; 1230 1231 if( C->do_scheduling() ) 1232 ComputeLatenciesBackwards(visited, stack); 1233 1234 // Now schedule all codes as LATE as possible. This is the LCA in the 1235 // dominator tree of all USES of a value. Pick the block with the least 1236 // loop nesting depth that is lowest in the dominator tree. 1237 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() ) 1238 schedule_late(visited, stack); 1239 if( C->failing() ) { 1240 // schedule_late fails only when graph is incorrect. 1241 assert(!VerifyGraphEdges, "verification should have failed"); 1242 return; 1243 } 1244 1245 unique = C->unique(); 1246 1247#ifndef PRODUCT 1248 if (trace_opto_pipelining()) { 1249 tty->print("\n---- Detect implicit null checks ----\n"); 1250 } 1251#endif 1252 1253 // Detect implicit-null-check opportunities. Basically, find NULL checks 1254 // with suitable memory ops nearby. Use the memory op to do the NULL check. 1255 // I can generate a memory op if there is not one nearby. 1256 if (C->is_method_compilation()) { 1257 // Don't do it for natives, adapters, or runtime stubs 1258 int allowed_reasons = 0; 1259 // ...and don't do it when there have been too many traps, globally. 1260 for (int reason = (int)Deoptimization::Reason_none+1; 1261 reason < Compile::trapHistLength; reason++) { 1262 assert(reason < BitsPerInt, "recode bit map"); 1263 if (!C->too_many_traps((Deoptimization::DeoptReason) reason)) 1264 allowed_reasons |= nth_bit(reason); 1265 } 1266 // By reversing the loop direction we get a very minor gain on mpegaudio. 1267 // Feel free to revert to a forward loop for clarity. 1268 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) { 1269 for( int i= matcher._null_check_tests.size()-2; i>=0; i-=2 ) { 1270 Node *proj = matcher._null_check_tests[i ]; 1271 Node *val = matcher._null_check_tests[i+1]; 1272 _bbs[proj->_idx]->implicit_null_check(this, proj, val, allowed_reasons); 1273 // The implicit_null_check will only perform the transformation 1274 // if the null branch is truly uncommon, *and* it leads to an 1275 // uncommon trap. Combined with the too_many_traps guards 1276 // above, this prevents SEGV storms reported in 6366351, 1277 // by recompiling offending methods without this optimization. 1278 } 1279 } 1280 1281#ifndef PRODUCT 1282 if (trace_opto_pipelining()) { 1283 tty->print("\n---- Start Local Scheduling ----\n"); 1284 } 1285#endif 1286 1287 // Schedule locally. Right now a simple topological sort. 1288 // Later, do a real latency aware scheduler. 1289 int *ready_cnt = NEW_RESOURCE_ARRAY(int,C->unique()); 1290 memset( ready_cnt, -1, C->unique() * sizeof(int) ); 1291 visited.Clear(); 1292 for (i = 0; i < _num_blocks; i++) { 1293 if (!_blocks[i]->schedule_local(this, matcher, ready_cnt, visited)) { 1294 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) { 1295 C->record_method_not_compilable("local schedule failed"); 1296 } 1297 return; 1298 } 1299 } 1300 1301 // If we inserted any instructions between a Call and his CatchNode, 1302 // clone the instructions on all paths below the Catch. 1303 for( i=0; i < _num_blocks; i++ ) 1304 _blocks[i]->call_catch_cleanup(_bbs); 1305 1306#ifndef PRODUCT 1307 if (trace_opto_pipelining()) { 1308 tty->print("\n---- After GlobalCodeMotion ----\n"); 1309 for (uint i = 0; i < _num_blocks; i++) { 1310 _blocks[i]->dump(); 1311 } 1312 } 1313#endif 1314} 1315 1316 1317//------------------------------Estimate_Block_Frequency----------------------- 1318// Estimate block frequencies based on IfNode probabilities. 1319void PhaseCFG::Estimate_Block_Frequency() { 1320 int cnts = C->method() ? C->method()->interpreter_invocation_count() : 1; 1321 // Most of our algorithms will die horribly if frequency can become 1322 // negative so make sure cnts is a sane value. 1323 if( cnts <= 0 ) cnts = 1; 1324 float f = (float)cnts/(float)FreqCountInvocations; 1325 1326 // Create the loop tree and calculate loop depth. 1327 _root_loop = create_loop_tree(); 1328 _root_loop->compute_loop_depth(0); 1329 1330 // Compute block frequency of each block, relative to a single loop entry. 1331 _root_loop->compute_freq(); 1332 1333 // Adjust all frequencies to be relative to a single method entry 1334 _root_loop->_freq = f * 1.0; 1335 _root_loop->scale_freq(); 1336 1337 // force paths ending at uncommon traps to be infrequent 1338 Block_List worklist; 1339 Block* root_blk = _blocks[0]; 1340 for (uint i = 0; i < root_blk->num_preds(); i++) { 1341 Block *pb = _bbs[root_blk->pred(i)->_idx]; 1342 if (pb->has_uncommon_code()) { 1343 worklist.push(pb); 1344 } 1345 } 1346 while (worklist.size() > 0) { 1347 Block* uct = worklist.pop(); 1348 uct->_freq = PROB_MIN; 1349 for (uint i = 0; i < uct->num_preds(); i++) { 1350 Block *pb = _bbs[uct->pred(i)->_idx]; 1351 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) { 1352 worklist.push(pb); 1353 } 1354 } 1355 } 1356 1357#ifndef PRODUCT 1358 if (PrintCFGBlockFreq) { 1359 tty->print_cr("CFG Block Frequencies"); 1360 _root_loop->dump_tree(); 1361 if (Verbose) { 1362 tty->print_cr("PhaseCFG dump"); 1363 dump(); 1364 tty->print_cr("Node dump"); 1365 _root->dump(99999); 1366 } 1367 } 1368#endif 1369} 1370 1371//----------------------------create_loop_tree-------------------------------- 1372// Create a loop tree from the CFG 1373CFGLoop* PhaseCFG::create_loop_tree() { 1374 1375#ifdef ASSERT 1376 assert( _blocks[0] == _broot, "" ); 1377 for (uint i = 0; i < _num_blocks; i++ ) { 1378 Block *b = _blocks[i]; 1379 // Check that _loop field are clear...we could clear them if not. 1380 assert(b->_loop == NULL, "clear _loop expected"); 1381 // Sanity check that the RPO numbering is reflected in the _blocks array. 1382 // It doesn't have to be for the loop tree to be built, but if it is not, 1383 // then the blocks have been reordered since dom graph building...which 1384 // may question the RPO numbering 1385 assert(b->_rpo == i, "unexpected reverse post order number"); 1386 } 1387#endif 1388 1389 int idct = 0; 1390 CFGLoop* root_loop = new CFGLoop(idct++); 1391 1392 Block_List worklist; 1393 1394 // Assign blocks to loops 1395 for(uint i = _num_blocks - 1; i > 0; i-- ) { // skip Root block 1396 Block *b = _blocks[i]; 1397 1398 if (b->head()->is_Loop()) { 1399 Block* loop_head = b; 1400 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors"); 1401 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl); 1402 Block* tail = _bbs[tail_n->_idx]; 1403 1404 // Defensively filter out Loop nodes for non-single-entry loops. 1405 // For all reasonable loops, the head occurs before the tail in RPO. 1406 if (i <= tail->_rpo) { 1407 1408 // The tail and (recursive) predecessors of the tail 1409 // are made members of a new loop. 1410 1411 assert(worklist.size() == 0, "nonempty worklist"); 1412 CFGLoop* nloop = new CFGLoop(idct++); 1413 assert(loop_head->_loop == NULL, "just checking"); 1414 loop_head->_loop = nloop; 1415 // Add to nloop so push_pred() will skip over inner loops 1416 nloop->add_member(loop_head); 1417 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, _bbs); 1418 1419 while (worklist.size() > 0) { 1420 Block* member = worklist.pop(); 1421 if (member != loop_head) { 1422 for (uint j = 1; j < member->num_preds(); j++) { 1423 nloop->push_pred(member, j, worklist, _bbs); 1424 } 1425 } 1426 } 1427 } 1428 } 1429 } 1430 1431 // Create a member list for each loop consisting 1432 // of both blocks and (immediate child) loops. 1433 for (uint i = 0; i < _num_blocks; i++) { 1434 Block *b = _blocks[i]; 1435 CFGLoop* lp = b->_loop; 1436 if (lp == NULL) { 1437 // Not assigned to a loop. Add it to the method's pseudo loop. 1438 b->_loop = root_loop; 1439 lp = root_loop; 1440 } 1441 if (lp == root_loop || b != lp->head()) { // loop heads are already members 1442 lp->add_member(b); 1443 } 1444 if (lp != root_loop) { 1445 if (lp->parent() == NULL) { 1446 // Not a nested loop. Make it a child of the method's pseudo loop. 1447 root_loop->add_nested_loop(lp); 1448 } 1449 if (b == lp->head()) { 1450 // Add nested loop to member list of parent loop. 1451 lp->parent()->add_member(lp); 1452 } 1453 } 1454 } 1455 1456 return root_loop; 1457} 1458 1459//------------------------------push_pred-------------------------------------- 1460void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk) { 1461 Node* pred_n = blk->pred(i); 1462 Block* pred = node_to_blk[pred_n->_idx]; 1463 CFGLoop *pred_loop = pred->_loop; 1464 if (pred_loop == NULL) { 1465 // Filter out blocks for non-single-entry loops. 1466 // For all reasonable loops, the head occurs before the tail in RPO. 1467 if (pred->_rpo > head()->_rpo) { 1468 pred->_loop = this; 1469 worklist.push(pred); 1470 } 1471 } else if (pred_loop != this) { 1472 // Nested loop. 1473 while (pred_loop->_parent != NULL && pred_loop->_parent != this) { 1474 pred_loop = pred_loop->_parent; 1475 } 1476 // Make pred's loop be a child 1477 if (pred_loop->_parent == NULL) { 1478 add_nested_loop(pred_loop); 1479 // Continue with loop entry predecessor. 1480 Block* pred_head = pred_loop->head(); 1481 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors"); 1482 assert(pred_head != head(), "loop head in only one loop"); 1483 push_pred(pred_head, LoopNode::EntryControl, worklist, node_to_blk); 1484 } else { 1485 assert(pred_loop->_parent == this && _parent == NULL, "just checking"); 1486 } 1487 } 1488} 1489 1490//------------------------------add_nested_loop-------------------------------- 1491// Make cl a child of the current loop in the loop tree. 1492void CFGLoop::add_nested_loop(CFGLoop* cl) { 1493 assert(_parent == NULL, "no parent yet"); 1494 assert(cl != this, "not my own parent"); 1495 cl->_parent = this; 1496 CFGLoop* ch = _child; 1497 if (ch == NULL) { 1498 _child = cl; 1499 } else { 1500 while (ch->_sibling != NULL) { ch = ch->_sibling; } 1501 ch->_sibling = cl; 1502 } 1503} 1504 1505//------------------------------compute_loop_depth----------------------------- 1506// Store the loop depth in each CFGLoop object. 1507// Recursively walk the children to do the same for them. 1508void CFGLoop::compute_loop_depth(int depth) { 1509 _depth = depth; 1510 CFGLoop* ch = _child; 1511 while (ch != NULL) { 1512 ch->compute_loop_depth(depth + 1); 1513 ch = ch->_sibling; 1514 } 1515} 1516 1517//------------------------------compute_freq----------------------------------- 1518// Compute the frequency of each block and loop, relative to a single entry 1519// into the dominating loop head. 1520void CFGLoop::compute_freq() { 1521 // Bottom up traversal of loop tree (visit inner loops first.) 1522 // Set loop head frequency to 1.0, then transitively 1523 // compute frequency for all successors in the loop, 1524 // as well as for each exit edge. Inner loops are 1525 // treated as single blocks with loop exit targets 1526 // as the successor blocks. 1527 1528 // Nested loops first 1529 CFGLoop* ch = _child; 1530 while (ch != NULL) { 1531 ch->compute_freq(); 1532 ch = ch->_sibling; 1533 } 1534 assert (_members.length() > 0, "no empty loops"); 1535 Block* hd = head(); 1536 hd->_freq = 1.0f; 1537 for (int i = 0; i < _members.length(); i++) { 1538 CFGElement* s = _members.at(i); 1539 float freq = s->_freq; 1540 if (s->is_block()) { 1541 Block* b = s->as_Block(); 1542 for (uint j = 0; j < b->_num_succs; j++) { 1543 Block* sb = b->_succs[j]; 1544 update_succ_freq(sb, freq * b->succ_prob(j)); 1545 } 1546 } else { 1547 CFGLoop* lp = s->as_CFGLoop(); 1548 assert(lp->_parent == this, "immediate child"); 1549 for (int k = 0; k < lp->_exits.length(); k++) { 1550 Block* eb = lp->_exits.at(k).get_target(); 1551 float prob = lp->_exits.at(k).get_prob(); 1552 update_succ_freq(eb, freq * prob); 1553 } 1554 } 1555 } 1556 1557#if 0 1558 // Raise frequency of the loop backedge block, in an effort 1559 // to keep it empty. Skip the method level "loop". 1560 if (_parent != NULL) { 1561 CFGElement* s = _members.at(_members.length() - 1); 1562 if (s->is_block()) { 1563 Block* bk = s->as_Block(); 1564 if (bk->_num_succs == 1 && bk->_succs[0] == hd) { 1565 // almost any value >= 1.0f works 1566 // FIXME: raw constant 1567 bk->_freq = 1.05f; 1568 } 1569 } 1570 } 1571#endif 1572 1573 // For all loops other than the outer, "method" loop, 1574 // sum and normalize the exit probability. The "method" loop 1575 // should keep the initial exit probability of 1, so that 1576 // inner blocks do not get erroneously scaled. 1577 if (_depth != 0) { 1578 // Total the exit probabilities for this loop. 1579 float exits_sum = 0.0f; 1580 for (int i = 0; i < _exits.length(); i++) { 1581 exits_sum += _exits.at(i).get_prob(); 1582 } 1583 1584 // Normalize the exit probabilities. Until now, the 1585 // probabilities estimate the possibility of exit per 1586 // a single loop iteration; afterward, they estimate 1587 // the probability of exit per loop entry. 1588 for (int i = 0; i < _exits.length(); i++) { 1589 Block* et = _exits.at(i).get_target(); 1590 float new_prob = _exits.at(i).get_prob() / exits_sum; 1591 BlockProbPair bpp(et, new_prob); 1592 _exits.at_put(i, bpp); 1593 } 1594 1595 // Save the total, but guard against unreasoable probability, 1596 // as the value is used to estimate the loop trip count. 1597 // An infinite trip count would blur relative block 1598 // frequencies. 1599 if (exits_sum > 1.0f) exits_sum = 1.0; 1600 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN; 1601 _exit_prob = exits_sum; 1602 } 1603} 1604 1605//------------------------------succ_prob------------------------------------- 1606// Determine the probability of reaching successor 'i' from the receiver block. 1607float Block::succ_prob(uint i) { 1608 int eidx = end_idx(); 1609 Node *n = _nodes[eidx]; // Get ending Node 1610 int op = n->is_Mach() ? n->as_Mach()->ideal_Opcode() : n->Opcode(); 1611 1612 // Switch on branch type 1613 switch( op ) { 1614 case Op_CountedLoopEnd: 1615 case Op_If: { 1616 assert (i < 2, "just checking"); 1617 // Conditionals pass on only part of their frequency 1618 float prob = n->as_MachIf()->_prob; 1619 assert(prob >= 0.0 && prob <= 1.0, "out of range probability"); 1620 // If succ[i] is the FALSE branch, invert path info 1621 if( _nodes[i + eidx + 1]->Opcode() == Op_IfFalse ) { 1622 return 1.0f - prob; // not taken 1623 } else { 1624 return prob; // taken 1625 } 1626 } 1627 1628 case Op_Jump: 1629 // Divide the frequency between all successors evenly 1630 return 1.0f/_num_succs; 1631 1632 case Op_Catch: { 1633 const CatchProjNode *ci = _nodes[i + eidx + 1]->as_CatchProj(); 1634 if (ci->_con == CatchProjNode::fall_through_index) { 1635 // Fall-thru path gets the lion's share. 1636 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs; 1637 } else { 1638 // Presume exceptional paths are equally unlikely 1639 return PROB_UNLIKELY_MAG(5); 1640 } 1641 } 1642 1643 case Op_Root: 1644 case Op_Goto: 1645 // Pass frequency straight thru to target 1646 return 1.0f; 1647 1648 case Op_NeverBranch: 1649 return 0.0f; 1650 1651 case Op_TailCall: 1652 case Op_TailJump: 1653 case Op_Return: 1654 case Op_Halt: 1655 case Op_Rethrow: 1656 // Do not push out freq to root block 1657 return 0.0f; 1658 1659 default: 1660 ShouldNotReachHere(); 1661 } 1662 1663 return 0.0f; 1664} 1665 1666//------------------------------update_succ_freq------------------------------- 1667// Update the appropriate frequency associated with block 'b', a succesor of 1668// a block in this loop. 1669void CFGLoop::update_succ_freq(Block* b, float freq) { 1670 if (b->_loop == this) { 1671 if (b == head()) { 1672 // back branch within the loop 1673 // Do nothing now, the loop carried frequency will be 1674 // adjust later in scale_freq(). 1675 } else { 1676 // simple branch within the loop 1677 b->_freq += freq; 1678 } 1679 } else if (!in_loop_nest(b)) { 1680 // branch is exit from this loop 1681 BlockProbPair bpp(b, freq); 1682 _exits.append(bpp); 1683 } else { 1684 // branch into nested loop 1685 CFGLoop* ch = b->_loop; 1686 ch->_freq += freq; 1687 } 1688} 1689 1690//------------------------------in_loop_nest----------------------------------- 1691// Determine if block b is in the receiver's loop nest. 1692bool CFGLoop::in_loop_nest(Block* b) { 1693 int depth = _depth; 1694 CFGLoop* b_loop = b->_loop; 1695 int b_depth = b_loop->_depth; 1696 if (depth == b_depth) { 1697 return true; 1698 } 1699 while (b_depth > depth) { 1700 b_loop = b_loop->_parent; 1701 b_depth = b_loop->_depth; 1702 } 1703 return b_loop == this; 1704} 1705 1706//------------------------------scale_freq------------------------------------- 1707// Scale frequency of loops and blocks by trip counts from outer loops 1708// Do a top down traversal of loop tree (visit outer loops first.) 1709void CFGLoop::scale_freq() { 1710 float loop_freq = _freq * trip_count(); 1711 for (int i = 0; i < _members.length(); i++) { 1712 CFGElement* s = _members.at(i); 1713 s->_freq *= loop_freq; 1714 } 1715 CFGLoop* ch = _child; 1716 while (ch != NULL) { 1717 ch->scale_freq(); 1718 ch = ch->_sibling; 1719 } 1720} 1721 1722#ifndef PRODUCT 1723//------------------------------dump_tree-------------------------------------- 1724void CFGLoop::dump_tree() const { 1725 dump(); 1726 if (_child != NULL) _child->dump_tree(); 1727 if (_sibling != NULL) _sibling->dump_tree(); 1728} 1729 1730//------------------------------dump------------------------------------------- 1731void CFGLoop::dump() const { 1732 for (int i = 0; i < _depth; i++) tty->print(" "); 1733 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n", 1734 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq); 1735 for (int i = 0; i < _depth; i++) tty->print(" "); 1736 tty->print(" members:", _id); 1737 int k = 0; 1738 for (int i = 0; i < _members.length(); i++) { 1739 if (k++ >= 6) { 1740 tty->print("\n "); 1741 for (int j = 0; j < _depth+1; j++) tty->print(" "); 1742 k = 0; 1743 } 1744 CFGElement *s = _members.at(i); 1745 if (s->is_block()) { 1746 Block *b = s->as_Block(); 1747 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq); 1748 } else { 1749 CFGLoop* lp = s->as_CFGLoop(); 1750 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq); 1751 } 1752 } 1753 tty->print("\n"); 1754 for (int i = 0; i < _depth; i++) tty->print(" "); 1755 tty->print(" exits: "); 1756 k = 0; 1757 for (int i = 0; i < _exits.length(); i++) { 1758 if (k++ >= 7) { 1759 tty->print("\n "); 1760 for (int j = 0; j < _depth+1; j++) tty->print(" "); 1761 k = 0; 1762 } 1763 Block *blk = _exits.at(i).get_target(); 1764 float prob = _exits.at(i).get_prob(); 1765 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100)); 1766 } 1767 tty->print("\n"); 1768} 1769#endif 1770