/* * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. *
*/
void Block_List::remove(uint i) {
assert(i < _cnt, "index out of bounds");
Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*)));
pop(); // shrink list by one block
}
void Block_List::insert(uint i, Block *b) {
push(b); // grow list by one block
Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*)));
_blocks[i] = b;
}
uint Block::code_alignment() const { // Check for Root block if (_pre_order == 0) return CodeEntryAlignment; // Check for Start block if (_pre_order == 1) return InteriorEntryAlignment; // Check for loop alignment if (has_loop_alignment()) return loop_alignment();
return relocInfo::addr_unit(); // no particular alignment
}
uint Block::compute_loop_alignment() {
Node *h = head(); int unit_sz = relocInfo::addr_unit(); if (h->is_Loop() && h->as_Loop()->is_inner_loop()) { // Pre- and post-loops have low trip count so do not bother with // NOPs for align loop head. The constants are hidden from tuning // but only because my "divide by 4" heuristic surely gets nearly // all possible gain (a "do not align at all" heuristic has a // chance of getting a really tiny gain). if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() ||
h->as_CountedLoop()->is_post_loop())) { return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz;
} // Loops with low backedge frequency should not be aligned.
Node *n = h->in(LoopNode::LoopBackControl)->in(0); if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) { return unit_sz; // Loop does not loop, more often than not!
} return OptoLoopAlignment; // Otherwise align loop head
}
return unit_sz; // no particular alignment
}
// Compute the size of first 'inst_cnt' instructions in this block. // Return the number of instructions left to compute if the block has // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size // exceeds OptoLoopAlignment.
uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt,
PhaseRegAlloc* ra) {
uint last_inst = number_of_nodes(); for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) {
uint inst_size = get_node(j)->size(ra); if( inst_size > 0 ) {
inst_cnt--;
uint sz = sum_size + inst_size; if( sz <= (uint)OptoLoopAlignment ) { // Compute size of instructions which fit into fetch buffer only // since all inst_cnt instructions will not fit even if we align them.
sum_size = sz;
} else { return 0;
}
}
} return inst_cnt;
}
// Return empty status of a block. Empty blocks contain only the head, other // ideal nodes, and an optional trailing goto. int Block::is_Empty() const {
// Root or start block is not considered empty if (head()->is_Root() || head()->is_Start()) { return not_empty;
}
int success_result = completely_empty; int end_idx = number_of_nodes() - 1;
// Check for ending goto if ((end_idx > 0) && (get_node(end_idx)->is_MachGoto())) {
success_result = empty_with_goto;
end_idx--;
}
// Unreachable blocks are considered empty if (is_trivially_unreachable()) { return success_result;
}
// Ideal nodes are allowable in empty blocks: skip them Only MachNodes // turn directly into code, because only MachNodes have non-trivial // emit() functions. while ((end_idx > 0) && !get_node(end_idx)->is_Mach()) {
end_idx--;
}
// No room for any interesting instructions? if (end_idx == 0) { return success_result;
}
return not_empty;
}
// Return true if the block's code implies that it is likely to be // executed infrequently. Check to see if the block ends in a Halt or // a low probability call. bool Block::has_uncommon_code() const {
Node* en = end();
if (en->is_MachGoto())
en = en->in(0); if (en->is_Catch())
en = en->in(0); if (en->is_MachProj() && en->in(0)->is_MachCall()) {
MachCallNode* call = en->in(0)->as_MachCall(); if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { // This is true for slow-path stubs like new_{instance,array}, // slow_arraycopy, complete_monitor_locking, uncommon_trap. // The magic number corresponds to the probability of an uncommon_trap, // even though it is a count not a probability. returntrue;
}
}
int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); return op == Op_Halt;
}
// True if block is low enough frequency or guarded by a test which // mostly does not go here. bool PhaseCFG::is_uncommon(const Block* block) { // Initial blocks must never be moved, so are never uncommon. if (block->head()->is_Root() || block->head()->is_Start()) returnfalse;
// Check for way-low freq if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) returntrue;
// Look for code shape indicating uncommon_trap or slow path if (block->has_uncommon_code()) returntrue;
for( uint i=1; i< block->num_preds(); i++ ) {
Block* guard = get_block_for_node(block->pred(i)); // Check to see if this block follows its guard 1 time out of 10000 // or less. // // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which // we intend to be "uncommon", such as slow-path TLE allocation, // predicted call failure, and uncommon trap triggers. // // Use an epsilon value of 5% to allow for variability in frequency // predictions and floating point calculations. The net effect is // that guard_factor is set to 9500. // // Ignore low-frequency blocks. // The next check is (guard->_freq < 1.e-5 * 9500.). if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) {
uncommon_preds++;
} else {
freq_preds++; if(block->_freq < guard->_freq * guard_factor ) {
uncommon_for_freq_preds++;
}
}
} if( block->num_preds() > 1 && // The block is uncommon if all preds are uncommon or
(uncommon_preds == (block->num_preds()-1) || // it is uncommon for all frequent preds.
uncommon_for_freq_preds == freq_preds) ) { returntrue;
} returnfalse;
}
PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher)
: Phase(CFG)
, _root(root)
, _block_arena(arena)
, _regalloc(NULL)
, _scheduling_for_pressure(false)
, _matcher(matcher)
, _node_to_block_mapping(arena)
, _node_latency(NULL) #ifndef PRODUCT
, _trace_opto_pipelining(C->directive()->TraceOptoPipeliningOption) #endif #ifdef ASSERT
, _raw_oops(arena) #endif
{
ResourceMark rm; // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, // then Match it into a machine-specific Node. Then clone the machine // Node on demand.
Node *x = new GotoNode(NULL);
x->init_req(0, x);
_goto = matcher.match_tree(x);
assert(_goto != NULL, "");
_goto->set_req(0,_goto);
// Build the CFG in Reverse Post Order
_number_of_blocks = build_cfg();
_root_block = get_block_for_node(_root);
}
// Build a proper looking CFG. Make every block begin with either a StartNode // or a RegionNode. Make every block end with either a Goto, If or Return. // The RootNode both starts and ends it's own block. Do this with a recursive // backwards walk over the control edges.
uint PhaseCFG::build_cfg() {
VectorSet visited;
// Allocate stack with enough space to avoid frequent realloc
Node_Stack nstack(C->live_nodes() >> 1);
nstack.push(_root, 0);
uint sum = 0; // Counter for blocks
while (nstack.is_nonempty()) { // node and in's index from stack's top // 'np' is _root (see above) or RegionNode, StartNode: we push on stack // only nodes which point to the start of basic block (see below).
Node *np = nstack.node(); // idx > 0, except for the first node (_root) pushed on stack // at the beginning when idx == 0. // We will use the condition (idx == 0) later to end the build.
uint idx = nstack.index();
Node *proj = np->in(idx); const Node *x = proj->is_block_proj(); // Does the block end with a proper block-ending Node? One of Return, // If or Goto? (This check should be done for visited nodes also). if (x == NULL) { // Does not end right...
Node *g = _goto->clone(); // Force it to end in a Goto
g->set_req(0, proj);
np->set_req(idx, g);
x = proj = g;
} if (!visited.test_set(x->_idx)) { // Visit this block once // Skip any control-pinned middle'in stuff
Node *p = proj; do {
proj = p; // Update pointer to last Control
p = p->in(0); // Move control forward
} while( !p->is_block_proj() &&
!p->is_block_start() ); // Make the block begin with one of Region or StartNode. if( !p->is_block_start() ) {
RegionNode *r = new RegionNode( 2 );
r->init_req(1, p); // Insert RegionNode in the way
proj->set_req(0, r); // Insert RegionNode in the way
p = r;
} // 'p' now points to the start of this basic block
// Put self in array of basic blocks
Block *bb = new (_block_arena) Block(_block_arena, p);
map_node_to_block(p, bb);
map_node_to_block(x, bb); if( x != p ) { // Only for root is x == p
bb->push_node((Node*)x);
} // Now handle predecessors
++sum; // Count 1 for self block
uint cnt = bb->num_preds(); for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors
Node *prevproj = p->in(i); // Get prior input
assert( !prevproj->is_Con(), "dead input not removed" ); // Check to see if p->in(i) is a "control-dependent" CFG edge - // i.e., it splits at the source (via an IF or SWITCH) and merges // at the destination (via a many-input Region). // This breaks critical edges. The RegionNode to start the block // will be added when <p,i> is pulled off the node stack if ( cnt > 2 ) { // Merging many things?
assert( prevproj== bb->pred(i),""); if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? // Force a block on the control-dependent edge
Node *g = _goto->clone(); // Force it to end in a Goto
g->set_req(0,prevproj);
p->set_req(i,g);
}
}
nstack.push(p, i); // 'p' is RegionNode or StartNode
}
} else { // Post-processing visited nodes
nstack.pop(); // remove node from stack // Check if it the fist node pushed on stack at the beginning. if (idx == 0) break; // end of the build // Find predecessor basic block
Block *pb = get_block_for_node(x); // Insert into nodes array, if not already there if (!has_block(proj)) {
assert( x != proj, "" ); // Map basic block of projection
map_node_to_block(proj, pb);
pb->push_node(proj);
} // Insert self as a child of my predecessor block
pb->_succs.map(pb->_num_succs++, get_block_for_node(np));
assert( pb->get_node(pb->number_of_nodes() - pb->_num_succs)->is_block_proj(), "too many control users, not a CFG?" );
}
} // Return number of basic blocks for all children and self return sum;
}
// Inserts a goto & corresponding basic block between // block[block_no] and its succ_no'th successor block void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { // get block with block_no
assert(block_no < number_of_blocks(), "illegal block number");
Block* in = get_block(block_no); // get successor block succ_no
assert(succ_no < in->_num_succs, "illegal successor number");
Block* out = in->_succs[succ_no]; // Compute frequency of the new block. Do this before inserting // new block in case succ_prob() needs to infer the probability from // surrounding blocks. float freq = in->_freq * in->succ_prob(succ_no); // get ProjNode corresponding to the succ_no'th successor of the in block
ProjNode* proj = in->get_node(in->number_of_nodes() - in->_num_succs + succ_no)->as_Proj(); // create region for basic block
RegionNode* region = new RegionNode(2);
region->init_req(1, proj); // setup corresponding basic block
Block* block = new (_block_arena) Block(_block_arena, region);
map_node_to_block(region, block);
C->regalloc()->set_bad(region->_idx); // add a goto node
Node* gto = _goto->clone(); // get a new goto node
gto->set_req(0, region); // add it to the basic block
block->push_node(gto);
map_node_to_block(gto, block);
C->regalloc()->set_bad(gto->_idx); // hook up successor block
block->_succs.map(block->_num_succs++, out); // remap successor's predecessors if necessary for (uint i = 1; i < out->num_preds(); i++) { if (out->pred(i) == proj) out->head()->set_req(i, gto);
} // remap predecessor's successor to new block
in->_succs.map(succ_no, block); // Set the frequency of the new block
block->_freq = freq; // add new basic block to basic block list
add_block_at(block_no + 1, block); // Update dominator tree information of the new goto block.
block->_idom = in;
block->_dom_depth = in->_dom_depth + 1; if (out->_idom != in) { // The successor block was not immediately dominated by the predecessor // block, so there is no dominator subtree to update. return;
} // Update immediate dominator of the successor block.
out->_idom = block; // Increment the dominator tree depth of the goto block's descendants. These // are found by a depth-first search starting from the successor block. Two // domination properties guarantee that only descendant blocks are visited: // 1) all dominators of a block b must appear in any path from the root to b; // 2) if a block b does not dominate another block b', b cannot dominate any // block reachable from b' either. // The exploration uses header indices as block identifiers, since // Block::_pre_order might not be unique in the context of this function.
ResourceMark rm;
VectorSet descendants;
descendants.set(block->head()->_idx); // The goto block is a descendant of itself.
Block_List worklist;
worklist.push(out); // Start exploring from the successor block. while (worklist.size() > 0) {
Block* b = worklist.pop(); // The immediate dominator of b is a descendant, hence b is also a // descendant. Even though all predecessors of b might not have been visited // yet, we know that all dominators of b have been already visited (since // they must appear in any path from the goto block to b).
descendants.set(b->head()->_idx);
b->_dom_depth++; for (uint i = 0; i < b->_num_succs; i++) {
Block* s = b->_succs[i]; if (s != get_root_block() &&
!descendants.test(s->head()->_idx) && // Do not search below non-descendant successors, since any block // reachable from them cannot be descendant either.
descendants.test(s->_idom->head()->_idx)) {
worklist.push(s);
}
}
}
}
// Does this block end in a multiway branch that cannot have the default case // flipped for another case? staticbool no_flip_branch(Block *b) { int branch_idx = b->number_of_nodes() - b->_num_succs-1; if (branch_idx < 1) { returnfalse;
}
Node *branch = b->get_node(branch_idx); if (branch->is_Catch()) { returntrue;
} if (branch->is_Mach()) { if (branch->is_MachNullCheck()) { returntrue;
} int iop = branch->as_Mach()->ideal_Opcode(); if (iop == Op_FastLock || iop == Op_FastUnlock) { returntrue;
} // Don't flip if branch has an implicit check. if (branch->as_Mach()->is_TrapBasedCheckNode()) { returntrue;
}
} returnfalse;
}
// Check for NeverBranch at block end. This needs to become a GOTO to the // true target. NeverBranch are treated as a conditional branch that always // goes the same direction for most of the optimizer and are used to give a // fake exit path to infinite loops. At this late stage they need to turn // into Goto's so that when you enter the infinite loop you indeed hang. void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { // Find true target int end_idx = b->end_idx(); int idx = b->get_node(end_idx+1)->as_Proj()->_con;
Block *succ = b->_succs[idx];
Node* gto = _goto->clone(); // get a new goto node
gto->set_req(0, b->head());
Node *bp = b->get_node(end_idx);
b->map_node(gto, end_idx); // Slam over NeverBranch
map_node_to_block(gto, b);
C->regalloc()->set_bad(gto->_idx);
b->pop_node(); // Yank projections
b->pop_node(); // Yank projections
b->_succs.map(0,succ); // Map only successor
b->_num_succs = 1; // remap successor's predecessors if necessary
uint j; for (j = 1; j < succ->num_preds(); j++) { if (succ->pred(j)->in(0) == bp) {
succ->head()->set_req(j, gto);
}
} // Kill alternate exit path
Block* dead = b->_succs[1 - idx]; for (j = 1; j < dead->num_preds(); j++) { if (dead->pred(j)->in(0) == bp) { break;
}
} // Scan through block, yanking dead path from // all regions and phis.
dead->head()->del_req(j); for (int k = 1; dead->get_node(k)->is_Phi(); k++) {
dead->get_node(k)->del_req(j);
}
}
// Helper function to move block bx to the slot following b_index. Return // true if the move is successful, otherwise false bool PhaseCFG::move_to_next(Block* bx, uint b_index) { if (bx == NULL) returnfalse;
// Return false if bx is already scheduled.
uint bx_index = bx->_pre_order; if ((bx_index <= b_index) && (get_block(bx_index) == bx)) { returnfalse;
}
// Find the current index of block bx on the block list
bx_index = b_index + 1; while (bx_index < number_of_blocks() && get_block(bx_index) != bx) {
bx_index++;
}
assert(get_block(bx_index) == bx, "block not found");
// If the previous block conditionally falls into bx, return false, // because moving bx will create an extra jump. for(uint k = 1; k < bx->num_preds(); k++ ) {
Block* pred = get_block_for_node(bx->pred(k)); if (pred == get_block(bx_index - 1)) { if (pred->_num_succs != 1) { returnfalse;
}
}
}
// Reinsert bx just past block 'b'
_blocks.remove(bx_index);
_blocks.insert(b_index + 1, bx); returntrue;
}
// Move empty and uncommon blocks to the end. void PhaseCFG::move_to_end(Block *b, uint i) { int e = b->is_Empty(); if (e != Block::not_empty) { if (e == Block::empty_with_goto) { // Remove the goto, but leave the block.
b->pop_node();
} // Mark this block as a connector block, which will cause it to be // ignored in certain functions such as non_connector_successor().
b->set_connector();
} // Move the empty block to the end, and don't recheck.
_blocks.remove(i);
_blocks.push(b);
}
// Set loop alignment for every block void PhaseCFG::set_loop_alignment() {
uint last = number_of_blocks();
assert(get_block(0) == get_root_block(), "");
for (uint i = 1; i < last; i++) {
Block* block = get_block(i); if (block->head()->is_Loop()) {
block->set_loop_alignment(block);
}
}
}
// Make empty basic blocks to be "connector" blocks, Move uncommon blocks // to the end. void PhaseCFG::remove_empty_blocks() { // Move uncommon blocks to the end
uint last = number_of_blocks();
assert(get_block(0) == get_root_block(), "");
for (uint i = 1; i < last; i++) {
Block* block = get_block(i); if (block->is_connector()) { break;
}
// Check for NeverBranch at block end. This needs to become a GOTO to the // true target. NeverBranch are treated as a conditional branch that // always goes the same direction for most of the optimizer and are used // to give a fake exit path to infinite loops. At this late stage they // need to turn into Goto's so that when you enter the infinite loop you // indeed hang. if (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) {
convert_NeverBranch_to_Goto(block);
}
// Look for uncommon blocks and move to end. if (!C->do_freq_based_layout()) { if (is_uncommon(block)) {
move_to_end(block, i);
last--; // No longer check for being uncommon! if (no_flip_branch(block)) { // Fall-thru case must follow? // Find the fall-thru block
block = get_block(i);
move_to_end(block, i);
last--;
} // backup block counter post-increment
i--;
}
}
}
// Move empty blocks to the end
last = number_of_blocks(); for (uint i = 1; i < last; i++) {
Block* block = get_block(i); if (block->is_Empty() != Block::not_empty) {
move_to_end(block, i);
last--;
i--;
}
} // End of for all blocks
}
Block *PhaseCFG::fixup_trap_based_check(Node *branch, Block *block, int block_pos, Block *bnext) { // Trap based checks must fall through to the successor with // PROB_ALWAYS. // They should be an If with 2 successors.
assert(branch->is_MachIf(), "must be If");
assert(block->_num_succs == 2, "must have 2 successors");
// Get the If node and the projection for the first successor.
MachIfNode *iff = block->get_node(block->number_of_nodes()-3)->as_MachIf();
ProjNode *proj0 = block->get_node(block->number_of_nodes()-2)->as_Proj();
ProjNode *proj1 = block->get_node(block->number_of_nodes()-1)->as_Proj();
ProjNode *projt = (proj0->Opcode() == Op_IfTrue) ? proj0 : proj1;
ProjNode *projf = (proj0->Opcode() == Op_IfFalse) ? proj0 : proj1;
// Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0");
assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1");
ProjNode *proj_always;
ProjNode *proj_never; // We must negate the branch if the implicit check doesn't follow // the branch's TRUE path. Then, the new TRUE branch target will // be the old FALSE branch target. if (iff->_prob <= 2*PROB_NEVER) { // There are small rounding errors.
proj_never = projt;
proj_always = projf;
} else { // We must negate the branch if the trap doesn't follow the // branch's TRUE path. Then, the new TRUE branch target will // be the old FALSE branch target.
proj_never = projf;
proj_always = projt;
iff->negate();
}
assert(iff->_prob <= 2*PROB_NEVER, "Trap based checks are expected to trap never!"); // Map the successors properly
block->_succs.map(0, get_block_for_node(proj_never ->raw_out(0))); // The target of the trap.
block->_succs.map(1, get_block_for_node(proj_always->raw_out(0))); // The fall through target.
// Place the fall through block after this block.
Block *bs1 = block->non_connector_successor(1); if (bs1 != bnext && move_to_next(bs1, block_pos)) {
bnext = bs1;
} // If the fall through block still is not the next block, insert a goto. if (bs1 != bnext) {
insert_goto_at(block_pos, 1);
} return bnext;
}
// Fix up the final control flow for basic blocks. void PhaseCFG::fixup_flow() { // Fixup final control flow for the blocks. Remove jump-to-next // block. If neither arm of an IF follows the conditional branch, we // have to add a second jump after the conditional. We place the // TRUE branch target in succs[0] for both GOTOs and IFs. for (uint i = 0; i < number_of_blocks(); i++) {
Block* block = get_block(i);
block->_pre_order = i; // turn pre-order into block-index
// Connector blocks need no further processing. if (block->is_connector()) {
assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end"); continue;
}
assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors");
// Check for multi-way branches where I cannot negate the test to // exchange the true and false targets. if (no_flip_branch(block)) { // Find fall through case - if must fall into its target. // Get the index of the branch's first successor. int branch_idx = block->number_of_nodes() - block->_num_succs;
// The branch is 1 before the branch's first successor.
Node *branch = block->get_node(branch_idx-1);
// Handle no-flip branches which have implicit checks and which require // special block ordering and individual semantics of the 'fall through // case'. if ((TrapBasedNullChecks || TrapBasedRangeChecks) &&
branch->is_Mach() && branch->as_Mach()->is_TrapBasedCheckNode()) {
bnext = fixup_trap_based_check(branch, block, i, bnext);
} else { // Else, default handling for no-flip branches for (uint j2 = 0; j2 < block->_num_succs; j2++) { const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj(); if (p->_con == 0) { // successor j2 is fall through case if (block->non_connector_successor(j2) != bnext) { // but it is not the next block => insert a goto
insert_goto_at(i, j2);
} // Put taken branch in slot 0 if (j2 == 0 && block->_num_succs == 2) { // Flip targets in succs map
Block *tbs0 = block->_succs[0];
Block *tbs1 = block->_succs[1];
block->_succs.map(0, tbs1);
block->_succs.map(1, tbs0);
} break;
}
}
}
// Remove all CatchProjs for (uint j = 0; j < block->_num_succs; j++) {
block->pop_node();
}
} elseif (block->_num_succs == 1) { // Block ends in a Goto? if (bnext == bs0) { // We fall into next block; remove the Goto
block->pop_node();
}
} elseif(block->_num_succs == 2) { // Block ends in a If? // Get opcode of 1st projection (matches _succs[0]) // Note: Since this basic block has 2 exits, the last 2 nodes must // be projections (in any order), the 3rd last node must be // the IfNode (we have excluded other 2-way exits such as // CatchNodes already).
MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach();
ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj();
ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj();
// Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0");
assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1");
Block* bs1 = block->non_connector_successor(1);
// Check for neither successor block following the current // block ending in a conditional. If so, move one of the // successors after the current one, provided that the // successor was previously unscheduled, but moveable // (i.e., all paths to it involve a branch). if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) { // Choose the more common successor based on the probability // of the conditional branch.
Block* bx = bs0;
Block* by = bs1;
// _prob is the probability of taking the true path. Make // p the probability of taking successor #1. float p = iff->as_MachIf()->_prob; if (proj0->Opcode() == Op_IfTrue) {
p = 1.0 - p;
}
// Prefer successor #1 if p > 0.5 if (p > PROB_FAIR) {
bx = bs1;
by = bs0;
}
// Attempt the more common successor first if (move_to_next(bx, i)) {
bnext = bx;
} elseif (move_to_next(by, i)) {
bnext = by;
}
}
// Check for conditional branching the wrong way. Negate // conditional, if needed, so it falls into the following block // and branches to the not-following block.
// Check for the next block being in succs[0]. We are going to branch // to succs[0], so we want the fall-thru case as the next block in // succs[1]. if (bnext == bs0) { // Fall-thru case in succs[0], should be in succs[1], so flip targets in _succs map
Block* tbs0 = block->_succs[0];
Block* tbs1 = block->_succs[1];
block->_succs.map(0, tbs1);
block->_succs.map(1, tbs0); // Flip projection for each target
swap(proj0, proj1);
} elseif(bnext != bs1) { // Need a double-branch // The existing conditional branch need not change. // Add a unconditional branch to the false target. // Alas, it must appear in its own block and adding a // block this late in the game is complicated. Sigh.
insert_goto_at(i, 1);
}
// Make sure we TRUE branch to the target if (proj0->Opcode() == Op_IfFalse) {
iff->as_MachIf()->negate();
}
} else { // Multi-exit block, e.g. a switch statement // But we don't need to do anything here
}
} // End of for all blocks
}
void PhaseCFG::remove_unreachable_blocks() {
ResourceMark rm;
Block_List unreachable; // Initialize worklist of unreachable blocks to be removed. for (uint i = 0; i < number_of_blocks(); i++) {
Block* block = get_block(i);
assert(block->_pre_order == i, "Block::pre_order does not match block index"); if (block->is_trivially_unreachable()) {
unreachable.push(block);
}
} // Now remove all blocks that are transitively unreachable. while (unreachable.size() > 0) {
Block* dead = unreachable.pop(); // When this code runs (after PhaseCFG::fixup_flow()), Block::_pre_order // does not contain pre-order but block-list indices. Ensure they stay // contiguous by decrementing _pre_order for all elements after 'dead'. // Block::_rpo does not contain valid reverse post-order indices anymore // (they are invalidated by block insertions in PhaseCFG::fixup_flow()), // so there is no need to update them. for (uint i = dead->_pre_order + 1; i < number_of_blocks(); i++) {
get_block(i)->_pre_order--;
}
_blocks.remove(dead->_pre_order);
_number_of_blocks--; // Update the successors' predecessor list and push new unreachable blocks. for (uint i = 0; i < dead->_num_succs; i++) {
Block* succ = dead->_succs[i];
Node* head = succ->head(); for (int j = head->req() - 1; j >= 1; j--) { if (get_block_for_node(head->in(j)) == dead) {
head->del_req(j);
}
} if (succ->is_trivially_unreachable()) {
unreachable.push(succ);
}
}
}
}
// postalloc_expand: Expand nodes after register allocation. // // postalloc_expand has to be called after register allocation, just // before output (i.e. scheduling). It only gets called if // Matcher::require_postalloc_expand is true. // // Background: // // Nodes that are expandend (one compound node requiring several // assembler instructions to be implemented split into two or more // non-compound nodes) after register allocation are not as nice as // the ones expanded before register allocation - they don't // participate in optimizations as global code motion. But after // register allocation we can expand nodes that use registers which // are not spillable or registers that are not allocated, because the // old compound node is simply replaced (in its location in the basic // block) by a new subgraph which does not contain compound nodes any // more. The scheduler called during output can later on process these // non-compound nodes. // // Implementation: // // Nodes requiring postalloc expand are specified in the ad file by using // a postalloc_expand statement instead of ins_encode. A postalloc_expand // contains a single call to an encoding, as does an ins_encode // statement. Instead of an emit() function a postalloc_expand() function // is generated that doesn't emit assembler but creates a new // subgraph. The code below calls this postalloc_expand function for each // node with the appropriate attribute. This function returns the new // nodes generated in an array passed in the call. The old node, // potential MachTemps before and potential Projs after it then get // disconnected and replaced by the new nodes. The instruction // generating the result has to be the last one in the array. In // general it is assumed that Projs after the node expanded are // kills. These kills are not required any more after expanding as // there are now explicitly visible def-use chains and the Projs are // removed. This does not hold for calls: They do not only have // kill-Projs but also Projs defining values. Therefore Projs after // the node expanded are removed for all but for calls. If a node is // to be reused, it must be added to the nodes list returned, and it // will be added again. // // Implementing the postalloc_expand function for a node in an enc_class // is rather tedious. It requires knowledge about many node details, as // the nodes and the subgraph must be hand crafted. To simplify this, // adlc generates some utility variables into the postalloc_expand function, // e.g., holding the operands as specified by the postalloc_expand encoding // specification, e.g.: // * unsigned idx_<par_name> holding the index of the node in the ins // * Node *n_<par_name> holding the node loaded from the ins // * MachOpnd *op_<par_name> holding the corresponding operand // // The ordering of operands can not be determined by looking at a // rule. Especially if a match rule matches several different trees, // several nodes are generated from one instruct specification with // different operand orderings. In this case the adlc generated // variables are the only way to access the ins and operands // deterministically. // // If assigning a register to a node that contains an oop, don't // forget to call ra_->set_oop() for the node. void PhaseCFG::postalloc_expand(PhaseRegAlloc* _ra) {
GrowableArray <Node *> new_nodes(32); // Array with new nodes filled by postalloc_expand function of node.
GrowableArray <Node *> remove(32);
GrowableArray <Node *> succs(32); unsignedint max_idx = C->unique(); // Remember to distinguish new from old nodes.
DEBUG_ONLY(bool foundNode = false);
// for all blocks for (uint i = 0; i < number_of_blocks(); i++) {
Block *b = _blocks[i]; // For all instructions in the current block. for (uint j = 0; j < b->number_of_nodes(); j++) {
Node *n = b->get_node(j); if (n->is_Mach() && n->as_Mach()->requires_postalloc_expand()) { #ifdef ASSERT if (TracePostallocExpand) { if (!foundNode) {
foundNode = true;
tty->print("POSTALLOC EXPANDING %d %s\n", C->compile_id(),
C->method() ? C->method()->name()->as_utf8() : C->stub_name());
}
tty->print(" postalloc expanding "); n->dump(); if (Verbose) {
tty->print(" with ins:\n"); for (uint k = 0; k < n->len(); ++k) { if (n->in(k)) { tty->print(" "); n->in(k)->dump(); }
}
}
} #endif
new_nodes.clear(); // Collect nodes that have to be removed from the block later on.
uint req = n->req();
remove.clear(); for (uint k = 0; k < req; ++k) { if (n->in(k) && n->in(k)->is_MachTemp()) {
remove.push(n->in(k)); // MachTemps which are inputs to the old node have to be removed.
n->in(k)->del_req(0);
j--;
}
}
// Check whether we can allocate enough nodes. We set a fix limit for // the size of postalloc expands with this.
uint unique_limit = C->unique() + 40; if (unique_limit >= _ra->node_regs_max_index()) {
Compile::current()->record_failure("out of nodes in postalloc expand"); return;
}
// Emit (i.e. generate new nodes).
n->as_Mach()->postalloc_expand(&new_nodes, _ra);
assert(C->unique() < unique_limit, "You allocated too many nodes in your postalloc expand.");
// Disconnect the inputs of the old node. // // We reuse MachSpillCopy nodes. If we need to expand them, there // are many, so reusing pays off. If reused, the node already // has the new ins. n must be the last node on new_nodes list. if (!n->is_MachSpillCopy()) { for (int k = req - 1; k >= 0; --k) {
n->del_req(k);
}
}
#ifdef ASSERT // Check that all nodes have proper operands. for (int k = 0; k < new_nodes.length(); ++k) { if (new_nodes.at(k)->_idx < max_idx || !new_nodes.at(k)->is_Mach()) continue; // old node, Proj ...
MachNode *m = new_nodes.at(k)->as_Mach(); for (unsignedint l = 0; l < m->num_opnds(); ++l) { if (MachOper::notAnOper(m->_opnds[l])) {
outputStream *os = tty;
os->print("Node %s ", m->Name());
os->print("has invalid opnd %d: %p\n", l, m->_opnds[l]);
assert(0, "Invalid operands, see inline trace in hs_err_pid file.");
}
}
} #endif
// Collect succs of old node in remove (for projections) and in succs (for // all other nodes) do _not_ collect projections in remove (but in succs) // in case the node is a call. We need the projections for calls as they are // associated with registers (i.e. they are defs).
succs.clear(); for (DUIterator k = n->outs(); n->has_out(k); k++) { if (n->out(k)->is_Proj() && !n->is_MachCall() && !n->is_MachBranch()) {
remove.push(n->out(k));
} else {
succs.push(n->out(k));
}
} // Replace old node n as input of its succs by last of the new nodes. for (int k = 0; k < succs.length(); ++k) {
Node *succ = succs.at(k); for (uint l = 0; l < succ->req(); ++l) { if (succ->in(l) == n) {
succ->set_req(l, new_nodes.at(new_nodes.length() - 1));
}
} for (uint l = succ->req(); l < succ->len(); ++l) { if (succ->in(l) == n) {
succ->set_prec(l, new_nodes.at(new_nodes.length() - 1));
}
}
}
// Index of old node in block.
uint index = b->find_node(n); // Insert new nodes into block and map them in nodes->blocks array // and remember last node in n2.
Node *n2 = NULL; for (int k = 0; k < new_nodes.length(); ++k) {
n2 = new_nodes.at(k);
b->insert_node(n2, ++index);
map_node_to_block(n2, b);
}
// Add old node n to remove and remove them all from block.
remove.push(n);
j--; #ifdef ASSERT if (TracePostallocExpand && Verbose) {
tty->print(" removing:\n"); for (int k = 0; k < remove.length(); ++k) {
tty->print(" "); remove.at(k)->dump();
}
tty->print(" inserting:\n"); for (int k = 0; k < new_nodes.length(); ++k) {
tty->print(" "); new_nodes.at(k)->dump();
}
} #endif for (int k = 0; k < remove.length(); ++k) { if (b->contains(remove.at(k))) {
b->find_remove(remove.at(k));
} else {
assert(remove.at(k)->is_Proj() && (remove.at(k)->in(0)->is_MachBranch()), "");
}
} // If anything has been inserted (n2 != NULL), continue after last node inserted. // This does not always work. Some postalloc expands don't insert any nodes, if they // do optimizations (e.g., max(x,x)). In this case we decrement j accordingly.
j = n2 ? b->find_node(n2) : j;
}
}
}
// Do not visit this block again if( visited.test_set(x->_idx) ) return;
// Skip through this block const Node *p = x; do {
p = p->in(0); // Move control forward
assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
} while( !p->is_block_start() );
// Recursively visit for (uint i = 1; i < p->req(); i++) {
_dump_cfg(p->in(i), visited);
}
// Dump the block
get_block_for_node(p)->dump(this);
}
void PhaseCFG::dump( ) const {
tty->print("\n--- CFG --- %d BBs\n", number_of_blocks()); if (_blocks.size()) { // Did we do basic-block layout? for (uint i = 0; i < number_of_blocks(); i++) { const Block* block = get_block(i);
block->dump(this);
}
} else { // Else do it with a DFS
VectorSet visited(_block_arena);
_dump_cfg(_root,visited);
}
}
void PhaseCFG::dump_headers() { for (uint i = 0; i < number_of_blocks(); i++) {
Block* block = get_block(i); if (block != NULL) {
block->dump_head(this);
}
}
} #endif// !PRODUCT
#ifdef ASSERT void PhaseCFG::verify_memory_writer_placement(const Block* b, const Node* n) const { if (!n->is_memory_writer()) { return;
}
CFGLoop* home_or_ancestor = find_block_for_node(n->in(0))->_loop; bool found = false; do { if (b->_loop == home_or_ancestor) {
found = true; break;
}
home_or_ancestor = home_or_ancestor->parent();
} while (home_or_ancestor != NULL);
assert(found, "block b is not in n's home loop or an ancestor of it");
}
void PhaseCFG::verify_dominator_tree() const { for (uint i = 0; i < number_of_blocks(); i++) {
Block* block = get_block(i);
assert(block->_dom_depth <= number_of_blocks(), "unexpected dominator tree depth"); if (block == get_root_block()) {
assert(block->_dom_depth == 1, "unexpected root dominator tree depth"); // The root block does not have an immediate dominator, stop checking. continue;
}
assert(block->_idom != nullptr, "non-root blocks must have immediate dominators");
assert(block->_dom_depth == block->_idom->_dom_depth + 1, "the dominator tree depth of a node must succeed that of its immediate dominator");
assert(block->num_preds() > 2 || block->_idom == get_block_for_node(block->pred(1)), "the immediate dominator of a single-predecessor block must be the predecessor");
}
}
void PhaseCFG::verify() const { // Verify sane CFG for (uint i = 0; i < number_of_blocks(); i++) {
Block* block = get_block(i);
uint cnt = block->number_of_nodes();
uint j; for (j = 0; j < cnt; j++) {
Node *n = block->get_node(j);
assert(get_block_for_node(n) == block, ""); if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) {
assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block");
}
verify_memory_writer_placement(block, n); if (n->needs_anti_dependence_check()) {
verify_anti_dependences(block, n);
} for (uint k = 0; k < n->req(); k++) {
Node *def = n->in(k); if (def && def != n) {
Block* def_block = get_block_for_node(def);
assert(def_block || def->is_Con(), "must have block; constants for debug info ok"); // Verify that all definitions dominate their uses (except for virtual // instructions merging multiple definitions).
assert(n->is_Root() || n->is_Region() || n->is_Phi() || n->is_MachMerge() ||
def_block->dominates(block), "uses must be dominated by definitions"); // Verify that instructions in the block are in correct order. // Uses must follow their definition if they are at the same block. // Mostly done to check that MachSpillCopy nodes are placed correctly // when CreateEx node is moved in build_ifg_physical(). if (def_block == block && !(block->head()->is_Loop() && n->is_Phi()) && // See (+++) comment in reg_split.cpp
!(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) { bool is_loop = false; if (n->is_Phi()) { for (uint l = 1; l < def->req(); l++) { if (n == def->in(l)) {
is_loop = true; break; // Some kind of loop
}
}
}
assert(is_loop || block->find_node(def) < j, "uses must follow definitions");
}
}
} if (n->is_Proj()) {
assert(j >= 1, "a projection cannot be the first instruction in a block");
Node* pred = block->get_node(j - 1);
Node* parent = n->in(0);
assert(parent != NULL, "projections must have a parent");
assert(pred == parent || (pred->is_Proj() && pred->in(0) == parent), "projections must follow their parents or other sibling projections");
}
}
j = block->end_idx();
Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj();
assert(bp, "last instruction must be a block proj");
assert(bp == block->get_node(j), "wrong number of successors for this block"); if (bp->is_Catch()) { while (block->get_node(--j)->is_MachProj()) {
;
}
assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call");
} elseif (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) {
assert(block->_num_succs == 2, "Conditional branch must have two targets");
}
}
verify_dominator_tree();
} #endif// ASSERT
void UnionFind::reset( uint max ) { // Force the Union-Find mapping to be at least this large
extend(max,0); // Initialize to be the ID mapping. for( uint i=0; i<max; i++ ) map(i,i);
}
// Straight out of Tarjan's union-find algorithm
uint UnionFind::Find_compress( uint idx ) {
uint cur = idx;
uint next = lookup(cur); while( next != cur ) { // Scan chain of equivalences
assert( next < cur, "always union smaller" );
cur = next; // until find a fixed-point
next = lookup(cur);
} // Core of union-find algorithm: update chain of // equivalences to be equal to the root. while( idx != next ) {
uint tmp = lookup(idx);
map(idx, next);
idx = tmp;
} return idx;
}
// Like Find above, but no path compress, so bad asymptotic behavior
uint UnionFind::Find_const( uint idx ) const { if( idx == 0 ) return idx; // Ignore the zero idx // Off the end? This can happen during debugging dumps // when data structures have not finished being updated. if( idx >= _max ) return idx;
uint next = lookup(idx); while( next != idx ) { // Scan chain of equivalences
idx = next; // until find a fixed-point
next = lookup(idx);
} return next;
}
// The trace of connector blocks goes at the end; // we only expect one such trace if (b0->is_connector() != b1->is_connector()) { return b1->is_connector() ? -1 : 1;
}
// Pull more frequently executed blocks to the beginning float freq0 = b0->_freq; float freq1 = b1->_freq; if (freq0 != freq1) { return freq0 > freq1 ? -1 : 1;
}
int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo;
return diff;
}
// Find edges of interest, i.e, those which can fall through. Presumes that // edges which don't fall through are of low frequency and can be generally // ignored. Initialize the list of traces. void PhaseBlockLayout::find_edges() { // Walk the blocks, creating edges and Traces
uint i;
Trace *tr = NULL; for (i = 0; i < _cfg.number_of_blocks(); i++) {
Block* b = _cfg.get_block(i);
tr = new Trace(b, next, prev);
traces[tr->id()] = tr;
// All connector blocks should be at the end of the list if (b->is_connector()) break;
// If this block and the next one have a one-to-one successor // predecessor relationship, simply append the next block int nfallthru = b->num_fall_throughs(); while (nfallthru == 1 &&
b->succ_fall_through(0)) {
Block *n = b->_succs[0];
// Skip over single-entry connector blocks, we don't want to // add them to the trace. while (n->is_connector() && n->num_preds() == 1) {
n = n->_succs[0];
}
// We see a merge point, so stop search for the next block if (n->num_preds() != 1) break;
i++;
assert(n == _cfg.get_block(i), "expecting next block");
tr->append(n);
uf->map(n->_pre_order, tr->id());
traces[n->_pre_order] = NULL;
nfallthru = b->num_fall_throughs();
b = n;
}
if (nfallthru > 0) { // Create a CFGEdge for each outgoing // edge that could be a fall-through. for (uint j = 0; j < b->_num_succs; j++ ) { if (b->succ_fall_through(j)) {
Block *target = b->non_connector_successor(j); float freq = b->_freq * b->succ_prob(j); int from_pct = (int) ((100 * freq) / b->_freq); int to_pct = (int) ((100 * freq) / target->_freq);
edges->append(new CFGEdge(b, target, freq, from_pct, to_pct));
}
}
}
}
// Group connector blocks into one trace for (i++; i < _cfg.number_of_blocks(); i++) {
Block *b = _cfg.get_block(i);
assert(b->is_connector(), "connector blocks at the end");
tr->append(b);
uf->map(b->_pre_order, tr->id());
traces[b->_pre_order] = NULL;
}
}
// Union two traces together in uf, and null out the trace in the list void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) {
uint old_id = old_trace->id();
uint updated_id = updated_trace->id();
uint lo_id = updated_id;
uint hi_id = old_id;
// If from is greater than to, swap values to meet // UnionFind guarantee. if (updated_id > old_id) {
lo_id = old_id;
hi_id = updated_id;
// Fix up the trace ids
traces[lo_id] = traces[updated_id];
updated_trace->set_id(lo_id);
}
// Union the lower with the higher and remove the pointer // to the higher.
uf->Union(lo_id, hi_id);
traces[hi_id] = NULL;
}
// Append traces together via the most frequently executed edges void PhaseBlockLayout::grow_traces() { // Order the edges, and drive the growth of Traces via the most // frequently executed edges.
edges->sort(edge_order); for (int i = 0; i < edges->length(); i++) {
CFGEdge *e = edges->at(i);
// If the edge in question can join two traces at their ends, // append one trace to the other. if (src_trace->last_block() == src_block) { if (src_trace == targ_trace) {
e->set_state(CFGEdge::interior); if (targ_trace->backedge(e)) { // Reset i to catch any newly eligible edge // (Or we could remember the first "open" edge, and reset there)
i = 0;
}
} elseif (targ_trace->first_block() == targ_block) {
e->set_state(CFGEdge::connected);
src_trace->append(targ_trace);
union_traces(src_trace, targ_trace);
}
}
}
}
// Embed one trace into another, if the fork or join points are sufficiently // balanced. void PhaseBlockLayout::merge_traces(bool fall_thru_only) { // Walk the edge list a another time, looking at unprocessed edges. // Fold in diamonds for (int i = 0; i < edges->length(); i++) {
CFGEdge *e = edges->at(i);
if (e->state() != CFGEdge::open) continue; if (fall_thru_only) { if (e->infrequent()) continue;
}
if (src_trace == targ_trace) { // This may be a loop, but we can't do much about it.
e->set_state(CFGEdge::interior); continue;
}
if (fall_thru_only) { // If the edge links the middle of two traces, we can't do anything. // Mark the edge and continue. if (!src_at_tail & !targ_at_start) { continue;
}
// Don't grow traces along backedges? if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) { continue;
}
// If both ends of the edge are available, why didn't we handle it earlier?
assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier.");
if (targ_at_start) { // Insert the "targ" trace in the "src" trace if the insertion point // is a two way branch. // Better profitability check possible, but may not be worth it. // Someday, see if the this "fork" has an associated "join"; // then make a policy on merging this trace at the fork or join. // For example, other things being equal, it may be better to place this // trace at the join point if the "src" trace ends in a two-way, but // the insertion point is one-way.
assert(src_block->num_fall_throughs() == 2, "unexpected diamond");
e->set_state(CFGEdge::connected);
src_trace->insert_after(src_block, targ_trace);
union_traces(src_trace, targ_trace);
} elseif (src_at_tail) { if (src_trace != trace(_cfg.get_root_block())) {
e->set_state(CFGEdge::connected);
targ_trace->insert_before(targ_block, src_trace);
union_traces(targ_trace, src_trace);
}
}
} elseif (e->state() == CFGEdge::open) { // Append traces, even without a fall-thru connection. // But leave root entry at the beginning of the block list. if (targ_trace != trace(_cfg.get_root_block())) {
e->set_state(CFGEdge::connected);
src_trace->append(targ_trace);
union_traces(src_trace, targ_trace);
}
}
}
}
// Order the sequence of the traces in some desirable way void PhaseBlockLayout::reorder_traces(int count) {
ResourceArea *area = Thread::current()->resource_area();
Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count);
Block_List worklist; int new_count = 0;
// Compact the traces. for (int i = 0; i < count; i++) {
Trace *tr = traces[i]; if (tr != NULL) {
new_traces[new_count++] = tr;
}
}
// The entry block should be first on the new trace list.
Trace *tr = trace(_cfg.get_root_block());
assert(tr == new_traces[0], "entry trace misplaced");
// Sort the new trace list by frequency
qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order);
// Collect all blocks from existing Traces
_cfg.clear_blocks(); for (int i = 0; i < new_count; i++) {
Trace *tr = new_traces[i]; if (tr != NULL) { // push blocks onto the CFG list for (Block* b = tr->first_block(); b != NULL; b = tr->next(b)) {
_cfg.add_block(b);
}
}
}
}
// Order basic blocks based on frequency
PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg)
: Phase(BlockLayout)
, _cfg(cfg) {
ResourceMark rm;
ResourceArea *area = Thread::current()->resource_area();
// List of traces int size = _cfg.number_of_blocks() + 1;
traces = NEW_ARENA_ARRAY(area, Trace *, size);
memset(traces, 0, size*sizeof(Trace*));
next = NEW_ARENA_ARRAY(area, Block *, size);
memset(next, 0, size*sizeof(Block *));
prev = NEW_ARENA_ARRAY(area, Block *, size);
memset(prev , 0, size*sizeof(Block *));
// List of edges
edges = new GrowableArray<CFGEdge*>;
// Mapping block index --> block_trace
uf = new UnionFind(size);
uf->reset(size);
// Find edges and create traces.
find_edges();
// Grow traces at their ends via most frequent edges.
grow_traces();
// Merge one trace into another, but only at fall-through points. // This may make diamonds and other related shapes in a trace.
merge_traces(true);
// Run merge again, allowing two traces to be catenated, even if
--> --------------------
--> maximum size reached
--> --------------------
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