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*/
//------------------------------is_loop_exit----------------------------------- // Given an IfNode, return the loop-exiting projection or NULL if both // arms remain in the loop.
Node *IdealLoopTree::is_loop_exit(Node *iff) const { if (iff->outcnt() != 2) return NULL; // Ignore partially dead tests
PhaseIdealLoop *phase = _phase; // Test is an IfNode, has 2 projections. If BOTH are in the loop // we need loop unswitching instead of peeling. if (!is_member(phase->get_loop(iff->raw_out(0)))) return iff->raw_out(0); if (!is_member(phase->get_loop(iff->raw_out(1)))) return iff->raw_out(1); return NULL;
}
//------------------------------record_for_igvn---------------------------- // Put loop body on igvn work list void IdealLoopTree::record_for_igvn() { for (uint i = 0; i < _body.size(); i++) {
Node *n = _body.at(i);
_phase->_igvn._worklist.push(n);
} // put body of outer strip mined loop on igvn work list as well if (_head->is_CountedLoop() && _head->as_Loop()->is_strip_mined()) {
CountedLoopNode* l = _head->as_CountedLoop();
Node* outer_loop = l->outer_loop();
assert(outer_loop != NULL, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop);
Node* outer_loop_tail = l->outer_loop_tail();
assert(outer_loop_tail != NULL, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop_tail);
Node* outer_loop_end = l->outer_loop_end();
assert(outer_loop_end != NULL, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_loop_end);
Node* outer_safepoint = l->outer_safepoint();
assert(outer_safepoint != NULL, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(outer_safepoint);
Node* cle_out = _head->as_CountedLoop()->loopexit()->proj_out(false);
assert(cle_out != NULL, "missing piece of strip mined loop");
_phase->_igvn._worklist.push(cle_out);
}
}
//------------------------------compute_exact_trip_count----------------------- // Compute loop trip count if possible. Do not recalculate trip count for // split loops (pre-main-post) which have their limits and inits behind Opaque node. void IdealLoopTree::compute_trip_count(PhaseIdealLoop* phase) { if (!_head->as_Loop()->is_valid_counted_loop(T_INT)) { return;
}
CountedLoopNode* cl = _head->as_CountedLoop(); // Trip count may become nonexact for iteration split loops since // RCE modifies limits. Note, _trip_count value is not reset since // it is used to limit unrolling of main loop.
cl->set_nonexact_trip_count();
// Loop's test should be part of loop. if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)))) return; // Infinite loop
// Now compute a loop exit count float loop_exit_cnt = 0.0f; if (_child == NULL) { for (uint i = 0; i < _body.size(); i++) {
Node *n = _body[i];
loop_exit_cnt += compute_profile_trip_cnt_helper(n);
}
} else {
ResourceMark rm;
Unique_Node_List wq;
wq.push(back); for (uint i = 0; i < wq.size(); i++) {
Node *n = wq.at(i);
assert(n->is_CFG(), "only control nodes"); if (n != head) { if (n->is_Region()) { for (uint j = 1; j < n->req(); j++) {
wq.push(n->in(j));
}
} else {
loop_exit_cnt += compute_profile_trip_cnt_helper(n);
wq.push(n->in(0));
}
}
}
} if (loop_exit_cnt > 0.0f) {
trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
} else { // No exit count so use
trip_cnt = loop_back_cnt;
}
} else {
head->mark_profile_trip_failed();
} #ifndef PRODUCT if (TraceProfileTripCount) {
tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
} #endif
head->set_profile_trip_cnt(trip_cnt);
}
//---------------------find_invariant----------------------------- // Return nonzero index of invariant operand for an associative // binary operation of (nonconstant) invariant and variant values. // Helper for reassociate_invariants. int IdealLoopTree::find_invariant(Node* n, PhaseIdealLoop *phase) { bool in1_invar = this->is_invariant(n->in(1)); bool in2_invar = this->is_invariant(n->in(2)); if (in1_invar && !in2_invar) return 1; if (!in1_invar && in2_invar) return 2; return 0;
}
//---------------------is_associative----------------------------- // Return TRUE if "n" is an associative binary node. If "base" is // not NULL, "n" must be re-associative with it. bool IdealLoopTree::is_associative(Node* n, Node* base) { int op = n->Opcode(); if (base != NULL) {
assert(is_associative(base), "Base node should be associative"); int base_op = base->Opcode(); if (base_op == Op_AddI || base_op == Op_SubI) { return op == Op_AddI || op == Op_SubI;
} if (base_op == Op_AddL || base_op == Op_SubL) { return op == Op_AddL || op == Op_SubL;
} return op == base_op;
} else { // Integer "add/sub/mul/and/or/xor" operations are associative. return op == Op_AddI || op == Op_AddL
|| op == Op_SubI || op == Op_SubL
|| op == Op_MulI || op == Op_MulL
|| op == Op_AndI || op == Op_AndL
|| op == Op_OrI || op == Op_OrL
|| op == Op_XorI || op == Op_XorL;
}
}
bool is_int = n1->bottom_type()->isa_int() != NULL;
Node* inv1_c = phase->get_ctrl(inv1);
Node* n_inv1; if (neg_inv1) {
Node* zero; if (is_int) {
zero = phase->_igvn.intcon(0);
n_inv1 = new SubINode(zero, inv1);
} else {
zero = phase->_igvn.longcon(0L);
n_inv1 = new SubLNode(zero, inv1);
}
phase->set_ctrl(zero, phase->C->root());
phase->register_new_node(n_inv1, inv1_c);
} else {
n_inv1 = inv1;
}
Node* inv; if (is_int) { if (neg_inv2) {
inv = new SubINode(n_inv1, inv2);
} else {
inv = new AddINode(n_inv1, inv2);
}
phase->register_new_node(inv, phase->get_early_ctrl(inv)); if (neg_x) { returnnew SubINode(inv, x);
} else { returnnew AddINode(x, inv);
}
} else { if (neg_inv2) {
inv = new SubLNode(n_inv1, inv2);
} else {
inv = new AddLNode(n_inv1, inv2);
}
phase->register_new_node(inv, phase->get_early_ctrl(inv)); if (neg_x) { returnnew SubLNode(inv, x);
} else { returnnew AddLNode(x, inv);
}
}
}
//---------------------reassociate----------------------------- // Reassociate invariant binary expressions with add/sub/mul/ // and/or/xor operators. // For add/sub expressions: see "reassociate_add_sub" // // For mul/and/or/xor expressions: // // inv1 op (x op inv2) => (inv1 op inv2) op x //
Node* IdealLoopTree::reassociate(Node* n1, PhaseIdealLoop *phase) { if (!is_associative(n1) || n1->outcnt() == 0) return NULL; if (is_invariant(n1)) return NULL; // Don't mess with add of constant (igvn moves them to expression tree root.) if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
int inv1_idx = find_invariant(n1, phase); if (!inv1_idx) return NULL;
Node* n2 = n1->in(3 - inv1_idx); if (!is_associative(n2, n1)) return NULL; int inv2_idx = find_invariant(n2, phase); if (!inv2_idx) return NULL;
if (!phase->may_require_nodes(10, 10)) return NULL;
Node* result = NULL; switch (n1->Opcode()) { case Op_AddI: case Op_AddL: case Op_SubI: case Op_SubL:
result = reassociate_add_sub(n1, inv1_idx, inv2_idx, phase); break; case Op_MulI: case Op_MulL: case Op_AndI: case Op_AndL: case Op_OrI: case Op_OrL: case Op_XorI: case Op_XorL: {
Node* inv1 = n1->in(inv1_idx);
Node* inv2 = n2->in(inv2_idx);
Node* x = n2->in(3 - inv2_idx);
Node* inv = n2->clone_with_data_edge(inv1, inv2);
phase->register_new_node(inv, phase->get_early_ctrl(inv));
result = n1->clone_with_data_edge(x, inv); break;
} default:
ShouldNotReachHere();
}
//---------------------reassociate_invariants----------------------------- // Reassociate invariant expressions: void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { for (int i = _body.size() - 1; i >= 0; i--) {
Node *n = _body.at(i); for (int j = 0; j < 5; j++) {
Node* nn = reassociate(n, phase); if (nn == NULL) break;
n = nn; // again
}
}
}
//------------------------------policy_peeling--------------------------------- // Return TRUE if the loop should be peeled, otherwise return FALSE. Peeling // is applicable if we can make a loop-invariant test (usually a null-check) // execute before we enter the loop. When TRUE, the estimated node budget is // also requested. bool IdealLoopTree::policy_peeling(PhaseIdealLoop *phase) {
uint estimate = estimate_peeling(phase);
// Perform actual policy and size estimate for the loop peeling transform, and // return the estimated loop size if peeling is applicable, otherwise return // zero. No node budget is allocated.
uint IdealLoopTree::estimate_peeling(PhaseIdealLoop *phase) {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Peeling does loop cloning which can result in O(N^2) node construction. if (_body.size() > 255) { return 0; // Suppress too large body size.
} // Optimistic estimate that approximates loop body complexity via data and // control flow fan-out (instead of using the more pessimistic: BodySize^2).
uint estimate = est_loop_clone_sz(2);
if (phase->exceeding_node_budget(estimate)) { return 0; // Too large to safely clone.
}
// Check for vectorized loops, any peeling done was already applied. if (_head->is_CountedLoop()) {
CountedLoopNode* cl = _head->as_CountedLoop(); if (cl->is_unroll_only() || cl->trip_count() == 1) { return 0;
}
}
Node* test = tail();
while (test != _head) { // Scan till run off top of loop if (test->is_If()) { // Test?
Node *ctrl = phase->get_ctrl(test->in(1)); if (ctrl->is_top()) { return 0; // Found dead test on live IF? No peeling!
} // Standard IF only has one input value to check for loop invariance.
assert(test->Opcode() == Op_If ||
test->Opcode() == Op_CountedLoopEnd ||
test->Opcode() == Op_LongCountedLoopEnd ||
test->Opcode() == Op_RangeCheck, "Check this code when new subtype is added"); // Condition is not a member of this loop? if (!is_member(phase->get_loop(ctrl)) && is_loop_exit(test)) { return estimate; // Found reason to peel!
}
} // Walk up dominators to loop _head looking for test which is executed on // every path through the loop.
test = phase->idom(test);
} return 0;
}
//------------------------------peeled_dom_test_elim--------------------------- // If we got the effect of peeling, either by actually peeling or by making // a pre-loop which must execute at least once, we can remove all // loop-invariant dominated tests in the main body. void PhaseIdealLoop::peeled_dom_test_elim(IdealLoopTree* loop, Node_List& old_new) { bool progress = true; while (progress) {
progress = false; // Reset for next iteration
Node* prev = loop->_head->in(LoopNode::LoopBackControl); // loop->tail();
Node* test = prev->in(0); while (test != loop->_head) { // Scan till run off top of loop int p_op = prev->Opcode();
assert(test != NULL, "test cannot be NULL");
Node* test_cond = NULL; if ((p_op == Op_IfFalse || p_op == Op_IfTrue) && test->is_If()) {
test_cond = test->in(1);
} if (test_cond != NULL && // Test?
!test_cond->is_Con() && // And not already obvious? // And condition is not a member of this loop?
!loop->is_member(get_loop(get_ctrl(test_cond)))) { // Walk loop body looking for instances of this test for (uint i = 0; i < loop->_body.size(); i++) {
Node* n = loop->_body.at(i); // Check against cached test condition because dominated_by() // replaces the test condition with a constant. if (n->is_If() && n->in(1) == test_cond) { // IfNode was dominated by version in peeled loop body
progress = true;
dominated_by(old_new[prev->_idx]->as_IfProj(), n->as_If());
}
}
}
prev = test;
test = idom(test);
} // End of scan tests in loop
} // End of while (progress)
}
//------------------------------do_peeling------------------------------------- // Peel the first iteration of the given loop. // Step 1: Clone the loop body. The clone becomes the peeled iteration. // The pre-loop illegally has 2 control users (old & new loops). // Step 2: Make the old-loop fall-in edges point to the peeled iteration. // Do this by making the old-loop fall-in edges act as if they came // around the loopback from the prior iteration (follow the old-loop // backedges) and then map to the new peeled iteration. This leaves // the pre-loop with only 1 user (the new peeled iteration), but the // peeled-loop backedge has 2 users. // Step 3: Cut the backedge on the clone (so its not a loop) and remove the // extra backedge user. // // orig // // stmt1 // | // v // loop predicate // | // v // loop<----+ // | | // stmt2 | // | | // v | // if ^ // / \ | // / \ | // v v | // false true | // / \ | // / ----+ // | // v // exit // // // after clone loop // // stmt1 // | // v // loop predicate // / \ // clone / \ orig // / \ // / \ // v v // +---->loop clone loop<----+ // | | | | // | stmt2 clone stmt2 | // | | | | // | v v | // ^ if clone If ^ // | / \ / \ | // | / \ / \ | // | v v v v | // | true false false true | // | / \ / \ | // +---- \ / ----+ // \ / // 1v v2 // region // | // v // exit // // // after peel and predicate move // // stmt1 // | // v // loop predicate // / // / // clone / orig // / // / +----------+ // / | | // / | | // / | | // v v | // TOP-->loop clone loop<----+ | // | | | | // stmt2 clone stmt2 | | // | | | ^ // v v | | // if clone If ^ | // / \ / \ | | // / \ / \ | | // v v v v | | // true false false true | | // | \ / \ | | // | \ / ----+ ^ // | \ / | // | 1v v2 | // v region | // | | | // | v | // | exit | // | | // +--------------->-----------------+ // // // final graph // // stmt1 // | // v // loop predicate // | // v // stmt2 clone // | // v // if clone // / | // / | // v v // false true // | | // | v // | initialized skeleton predicates // | | // | v // | loop<----+ // | | | // | stmt2 | // | | | // | v | // v if ^ // | / \ | // | / \ | // | v v | // | false true | // | | \ | // v v --+ // region // | // v // exit // void PhaseIdealLoop::do_peeling(IdealLoopTree *loop, Node_List &old_new) {
C->set_major_progress(); // Peeling a 'main' loop in a pre/main/post situation obfuscates the // 'pre' loop from the main and the 'pre' can no longer have its // iterations adjusted. Therefore, we need to declare this loop as // no longer a 'main' loop; it will need new pre and post loops before // we can do further RCE. #ifndef PRODUCT if (TraceLoopOpts) {
tty->print("Peel ");
loop->dump_head();
} #endif
LoopNode* head = loop->_head->as_Loop(); bool counted_loop = head->is_CountedLoop(); if (counted_loop) {
CountedLoopNode *cl = head->as_CountedLoop();
assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
cl->set_trip_count(cl->trip_count() - 1); if (cl->is_main_loop()) {
cl->set_normal_loop(); #ifndef PRODUCT if (PrintOpto && VerifyLoopOptimizations) {
tty->print("Peeling a 'main' loop; resetting to 'normal' ");
loop->dump_head();
} #endif
}
}
Node* entry = head->in(LoopNode::EntryControl);
// Step 1: Clone the loop body. The clone becomes the peeled iteration. // The pre-loop illegally has 2 control users (old & new loops). const uint idx_before_clone = Compile::current()->unique();
LoopNode* outer_loop_head = head->skip_strip_mined();
clone_loop(loop, old_new, dom_depth(outer_loop_head), ControlAroundStripMined);
// Step 2: Make the old-loop fall-in edges point to the peeled iteration. // Do this by making the old-loop fall-in edges act as if they came // around the loopback from the prior iteration (follow the old-loop // backedges) and then map to the new peeled iteration. This leaves // the pre-loop with only 1 user (the new peeled iteration), but the // peeled-loop backedge has 2 users.
Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
_igvn.hash_delete(outer_loop_head);
outer_loop_head->set_req(LoopNode::EntryControl, new_entry); for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
Node* old = head->fast_out(j); if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; if (!new_exit_value) // Backedge value is ALSO loop invariant? // Then loop body backedge value remains the same.
new_exit_value = old->in(LoopNode::LoopBackControl);
_igvn.hash_delete(old);
old->set_req(LoopNode::EntryControl, new_exit_value);
}
}
// Step 3: Cut the backedge on the clone (so its not a loop) and remove the // extra backedge user.
Node* new_head = old_new[head->_idx];
_igvn.hash_delete(new_head);
new_head->set_req(LoopNode::LoopBackControl, C->top()); for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
Node* use = new_head->fast_out(j2); if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
_igvn.hash_delete(use);
use->set_req(LoopNode::LoopBackControl, C->top());
}
}
// Step 4: Correct dom-depth info. Set to loop-head depth.
// Now force out all loop-invariant dominating tests. The optimizer // finds some, but we _know_ they are all useless.
peeled_dom_test_elim(loop,old_new);
loop->record_for_igvn();
}
//------------------------------policy_maximally_unroll------------------------ // Calculate the exact loop trip-count and return TRUE if loop can be fully, // i.e. maximally, unrolled, otherwise return FALSE. When TRUE, the estimated // node budget is also requested. bool IdealLoopTree::policy_maximally_unroll(PhaseIdealLoop* phase) const {
CountedLoopNode* cl = _head->as_CountedLoop();
assert(cl->is_normal_loop(), ""); if (!cl->is_valid_counted_loop(T_INT)) { returnfalse; // Malformed counted loop.
} if (!cl->has_exact_trip_count()) { returnfalse; // Trip count is not exact.
}
uint trip_count = cl->trip_count(); // Note, max_juint is used to indicate unknown trip count.
assert(trip_count > 1, "one iteration loop should be optimized out already");
assert(trip_count < max_juint, "exact trip_count should be less than max_juint.");
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Allow the unrolled body to get larger than the standard loop size limit.
uint unroll_limit = (uint)LoopUnrollLimit * 4;
assert((intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); if (trip_count > unroll_limit || _body.size() > unroll_limit) { returnfalse;
}
if (new_body_size == UINT_MAX) { // Check for bad estimate (overflow). returnfalse;
}
// Fully unroll a loop with few iterations, regardless of other conditions, // since the following (general) loop optimizations will split such loop in // any case (into pre-main-post). if (trip_count <= 3) { return phase->may_require_nodes(new_body_size);
}
// Reject if unrolling will result in too much node construction. if (new_body_size > unroll_limit || phase->exceeding_node_budget(new_body_size)) { returnfalse;
}
// Do not unroll a loop with String intrinsics code. // String intrinsics are large and have loops. for (uint k = 0; k < _body.size(); k++) {
Node* n = _body.at(k); switch (n->Opcode()) { case Op_StrComp: case Op_StrEquals: case Op_StrIndexOf: case Op_StrIndexOfChar: case Op_EncodeISOArray: case Op_AryEq: case Op_CountPositives: { returnfalse;
} #if INCLUDE_RTM_OPT case Op_FastLock: case Op_FastUnlock: { // Don't unroll RTM locking code because it is large. if (UseRTMLocking) { returnfalse;
}
} #endif
} // switch
}
return phase->may_require_nodes(new_body_size);
}
//------------------------------policy_unroll---------------------------------- // Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll if // the loop is a counted loop and the loop body is small enough. When TRUE, // the estimated node budget is also requested. bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
if (!cl->is_valid_counted_loop(T_INT)) { returnfalse; // Malformed counted loop
}
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Protect against over-unrolling. // After split at least one iteration will be executed in pre-loop. if (cl->trip_count() <= (cl->is_normal_loop() ? 2u : 1u)) { returnfalse;
}
_local_loop_unroll_limit = LoopUnrollLimit;
_local_loop_unroll_factor = 4; int future_unroll_cnt = cl->unrolled_count() * 2; if (!cl->is_vectorized_loop()) { if (future_unroll_cnt > LoopMaxUnroll) returnfalse;
} else { // obey user constraints on vector mapped loops with additional unrolling applied int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1; if ((future_unroll_cnt / unroll_constraint) > LoopMaxUnroll) returnfalse;
}
constint stride_con = cl->stride_con();
// Check for initial stride being a small enough constant constint initial_stride_sz = MAX2(1<<2, Matcher::max_vector_size(T_BYTE) / 2); // Maximum stride size should protect against overflow, when doubling stride unroll_count times constint max_stride_size = MIN2<int>(max_jint / 2 - 2, initial_stride_sz * future_unroll_cnt); // No abs() use; abs(min_jint) = min_jint if (stride_con < -max_stride_size || stride_con > max_stride_size) returnfalse;
// Don't unroll if the next round of unrolling would push us // over the expected trip count of the loop. One is subtracted // from the expected trip count because the pre-loop normally // executes 1 iteration. if (UnrollLimitForProfileCheck > 0 &&
cl->profile_trip_cnt() != COUNT_UNKNOWN &&
future_unroll_cnt > UnrollLimitForProfileCheck &&
(float)future_unroll_cnt > cl->profile_trip_cnt() - 1.0) { returnfalse;
}
bool should_unroll = true;
// When unroll count is greater than LoopUnrollMin, don't unroll if: // the residual iterations are more than 10% of the trip count // and rounds of "unroll,optimize" are not making significant progress // Progress defined as current size less than 20% larger than previous size. if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
future_unroll_cnt > LoopUnrollMin &&
is_residual_iters_large(future_unroll_cnt, cl) &&
1.2 * cl->node_count_before_unroll() < (double)_body.size()) { if ((cl->slp_max_unroll() == 0) && !is_residual_iters_large(cl->unrolled_count(), cl)) { // cl->slp_max_unroll() = 0 means that the previous slp analysis never passed. // slp analysis may fail due to the loop IR is too complicated especially during the early stage // of loop unrolling analysis. But after several rounds of loop unrolling and other optimizations, // it's possible that the loop IR becomes simple enough to pass the slp analysis. // So we don't return immediately in hoping that the next slp analysis can succeed.
should_unroll = false;
future_unroll_cnt = cl->unrolled_count();
} else { returnfalse;
}
}
Node *init_n = cl->init_trip();
Node *limit_n = cl->limit(); if (limit_n == NULL) returnfalse; // We will dereference it below.
// Non-constant bounds. // Protect against over-unrolling when init or/and limit are not constant // (so that trip_count's init value is maxint) but iv range is known. if (init_n == NULL || !init_n->is_Con() || !limit_n->is_Con()) {
Node* phi = cl->phi(); if (phi != NULL) {
assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); int next_stride = stride_con * 2; // stride after this unroll if (next_stride > 0) { if (iv_type->_lo > max_jint - next_stride || // overflow
iv_type->_lo + next_stride > iv_type->_hi) { returnfalse; // over-unrolling
}
} elseif (next_stride < 0) { if (iv_type->_hi < min_jint - next_stride || // overflow
iv_type->_hi + next_stride < iv_type->_lo) { returnfalse; // over-unrolling
}
}
}
}
// After unroll limit will be adjusted: new_limit = limit-stride. // Bailout if adjustment overflow. const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int(); if ((stride_con > 0 && ((min_jint + stride_con) > limit_type->_hi)) ||
(stride_con < 0 && ((max_jint + stride_con) < limit_type->_lo))) returnfalse; // overflow
// Rudimentary cost model to estimate loop unrolling // factor. // Adjust body_size to determine if we unroll or not
uint body_size = _body.size(); // Key test to unroll loop in CRC32 java code int xors_in_loop = 0; // Also count ModL, DivL and MulL which expand mightly for (uint k = 0; k < _body.size(); k++) {
Node* n = _body.at(k); switch (n->Opcode()) { case Op_XorI: xors_in_loop++; break; // CRC32 java code case Op_ModL: body_size += 30; break; case Op_DivL: body_size += 30; break; case Op_MulL: body_size += 10; break; case Op_RoundF: case Op_RoundD: {
body_size += Matcher::scalar_op_pre_select_sz_estimate(n->Opcode(), n->bottom_type()->basic_type());
} break; case Op_CountTrailingZerosV: case Op_CountLeadingZerosV: case Op_ReverseV: case Op_RoundVF: case Op_RoundVD: case Op_VectorCastD2X: case Op_VectorCastF2X: case Op_PopCountVI: case Op_PopCountVL: { const TypeVect* vt = n->bottom_type()->is_vect();
body_size += Matcher::vector_op_pre_select_sz_estimate(n->Opcode(), vt->element_basic_type(), vt->length());
} break; case Op_StrComp: case Op_StrEquals: case Op_StrIndexOf: case Op_StrIndexOfChar: case Op_EncodeISOArray: case Op_AryEq: case Op_CountPositives: { // Do not unroll a loop with String intrinsics code. // String intrinsics are large and have loops. returnfalse;
} #if INCLUDE_RTM_OPT case Op_FastLock: case Op_FastUnlock: { // Don't unroll RTM locking code because it is large. if (UseRTMLocking) { returnfalse;
}
} #endif
} // switch
}
if (UseSuperWord) { if (!cl->is_reduction_loop()) {
phase->mark_reductions(this);
}
// Only attempt slp analysis when user controls do not prohibit it if (!cl->range_checks_present() && (LoopMaxUnroll > _local_loop_unroll_factor)) { // Once policy_slp_analysis succeeds, mark the loop with the // maximal unroll factor so that we minimize analysis passes if (future_unroll_cnt >= _local_loop_unroll_factor) {
policy_unroll_slp_analysis(cl, phase, future_unroll_cnt);
}
}
}
int slp_max_unroll_factor = cl->slp_max_unroll(); if ((LoopMaxUnroll < slp_max_unroll_factor) && FLAG_IS_DEFAULT(LoopMaxUnroll) && UseSubwordForMaxVector) {
LoopMaxUnroll = slp_max_unroll_factor;
}
uint estimate = est_loop_clone_sz(2);
if (cl->has_passed_slp()) { if (slp_max_unroll_factor >= future_unroll_cnt) { return should_unroll && phase->may_require_nodes(estimate);
} returnfalse; // Loop too big.
}
// Check for being too big if (body_size > (uint)_local_loop_unroll_limit) { if ((cl->is_subword_loop() || xors_in_loop >= 4) && body_size < 4u * LoopUnrollLimit) { return should_unroll && phase->may_require_nodes(estimate);
} returnfalse; // Loop too big.
}
if (cl->is_unroll_only()) { if (TraceSuperWordLoopUnrollAnalysis) {
tty->print_cr("policy_unroll passed vector loop(vlen=%d, factor=%d)\n",
slp_max_unroll_factor, future_unroll_cnt);
}
}
// Unroll once! (Each trip will soon do double iterations) return should_unroll && phase->may_require_nodes(estimate);
}
void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_cnt) {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// Enable this functionality target by target as needed if (SuperWordLoopUnrollAnalysis) { if (!cl->was_slp_analyzed()) {
SuperWord sw(phase);
sw.transform_loop(this, false);
// If the loop is slp canonical analyze it if (sw.early_return() == false) {
sw.unrolling_analysis(_local_loop_unroll_factor);
}
}
if (cl->has_passed_slp()) { int slp_max_unroll_factor = cl->slp_max_unroll(); if (slp_max_unroll_factor >= future_unroll_cnt) { int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor; if (new_limit > LoopUnrollLimit) { if (TraceSuperWordLoopUnrollAnalysis) {
tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit);
}
_local_loop_unroll_limit = new_limit;
}
}
}
}
}
//------------------------------policy_range_check----------------------------- // Return TRUE or FALSE if the loop should be range-check-eliminated or not. // When TRUE, the estimated node budget is also requested. // // We will actually perform iteration-splitting, a more powerful form of RCE. bool IdealLoopTree::policy_range_check(PhaseIdealLoop* phase, bool provisional, BasicType bt) const { if (!provisional && !RangeCheckElimination) returnfalse;
// If nodes are depleted, some transform has miscalculated its needs.
assert(provisional || !phase->exceeding_node_budget(), "sanity");
if (_head->is_CountedLoop()) {
CountedLoopNode *cl = _head->as_CountedLoop(); // If we unrolled with no intention of doing RCE and we later changed our // minds, we got no pre-loop. Either we need to make a new pre-loop, or we // have to disallow RCE. if (cl->is_main_no_pre_loop()) returnfalse; // Disallowed for now.
// check for vectorized loops, some opts are no longer needed // RCE needs pre/main/post loops. Don't apply it on a single iteration loop. if (cl->is_unroll_only() || (cl->is_normal_loop() && cl->trip_count() == 1)) returnfalse;
} else {
assert(provisional, "no long counted loop expected");
}
BaseCountedLoopNode* cl = _head->as_BaseCountedLoop();
Node *trip_counter = cl->phi();
assert(!cl->is_LongCountedLoop() || bt == T_LONG, "only long range checks in long counted loops");
assert(cl->is_valid_counted_loop(cl->bt()), "only for well formed loops");
// Check loop body for tests of trip-counter plus loop-invariant vs // loop-invariant. for (uint i = 0; i < _body.size(); i++) {
Node *iff = _body[i]; if (iff->Opcode() == Op_If ||
iff->Opcode() == Op_RangeCheck) { // Test?
// Comparing trip+off vs limit
Node *bol = iff->in(1); if (bol->req() != 2) { continue; // dead constant test
} if (!bol->is_Bool()) {
assert(bol->Opcode() == Op_Conv2B, "predicate check only"); continue;
} if (bol->as_Bool()->_test._test == BoolTest::ne) { continue; // not RC
}
Node *cmp = bol->in(1);
if (provisional) { // Try to pattern match with either cmp inputs, do not check // whether one of the inputs is loop independent as it may not // have had a chance to be hoisted yet. if (!phase->is_scaled_iv_plus_offset(cmp->in(1), trip_counter, bt, NULL, NULL) &&
!phase->is_scaled_iv_plus_offset(cmp->in(2), trip_counter, bt, NULL, NULL)) { continue;
}
} else {
Node *rc_exp = cmp->in(1);
Node *limit = cmp->in(2);
Node *limit_c = phase->get_ctrl(limit); if (limit_c == phase->C->top()) { returnfalse; // Found dead test on live IF? No RCE!
} if (is_member(phase->get_loop(limit_c))) { // Compare might have operands swapped; commute them
rc_exp = cmp->in(2);
limit = cmp->in(1);
limit_c = phase->get_ctrl(limit); if (is_member(phase->get_loop(limit_c))) { continue; // Both inputs are loop varying; cannot RCE
}
}
if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, bt, NULL, NULL)) { continue;
}
} // Found a test like 'trip+off vs limit'. Test is an IfNode, has two (2) // projections. If BOTH are in the loop we need loop unswitching instead // of iteration splitting. if (is_loop_exit(iff)) { // Found valid reason to split iterations (if there is room). // NOTE: Usually a gross overestimate. // Long range checks cause the loop to be transformed in a loop nest which only causes a fixed number of nodes // to be added return provisional || bt == T_LONG || phase->may_require_nodes(est_loop_clone_sz(2));
}
} // End of is IF
}
returnfalse;
}
//------------------------------policy_peel_only------------------------------- // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful // for unrolling loops with NO array accesses. bool IdealLoopTree::policy_peel_only(PhaseIdealLoop *phase) const {
// If nodes are depleted, some transform has miscalculated its needs.
assert(!phase->exceeding_node_budget(), "sanity");
// check for vectorized loops, any peeling done was already applied if (_head->is_CountedLoop() && _head->as_CountedLoop()->is_unroll_only()) { returnfalse;
}
for (uint i = 0; i < _body.size(); i++) { if (_body[i]->is_Mem()) { returnfalse;
}
} // No memory accesses at all! returntrue;
}
//------------------------------clone_up_backedge_goo-------------------------- // If Node n lives in the back_ctrl block and cannot float, we clone a private // version of n in preheader_ctrl block and return that, otherwise return n.
Node *PhaseIdealLoop::clone_up_backedge_goo(Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones) { if (get_ctrl(n) != back_ctrl) return n;
// Only visit once if (visited.test_set(n->_idx)) {
Node *x = clones.find(n->_idx); return (x != NULL) ? x : n;
}
Node *x = NULL; // If required, a clone of 'n' // Check for 'n' being pinned in the backedge. if (n->in(0) && n->in(0) == back_ctrl) {
assert(clones.find(n->_idx) == NULL, "dead loop");
x = n->clone(); // Clone a copy of 'n' to preheader
clones.push(x, n->_idx);
x->set_req(0, preheader_ctrl); // Fix x's control input to preheader
}
// Recursive fixup any other input edges into x. // If there are no changes we can just return 'n', otherwise // we need to clone a private copy and change it. for (uint i = 1; i < n->req(); i++) {
Node *g = clone_up_backedge_goo(back_ctrl, preheader_ctrl, n->in(i), visited, clones); if (g != n->in(i)) { if (!x) {
assert(clones.find(n->_idx) == NULL, "dead loop");
x = n->clone();
clones.push(x, n->_idx);
}
x->set_req(i, g);
}
} if (x) { // x can legally float to pre-header location
register_new_node(x, preheader_ctrl); return x;
} else { // raise n to cover LCA of uses
set_ctrl(n, find_non_split_ctrl(back_ctrl->in(0)));
} return n;
}
Node* PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
Node* castii = new CastIINode(incr, TypeInt::INT, ConstraintCastNode::UnconditionalDependency);
castii->set_req(0, ctrl);
register_new_node(castii, ctrl); for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
Node* n = incr->fast_out(i); if (n->is_Phi() && n->in(0) == loop) { int nrep = n->replace_edge(incr, castii, &_igvn); return castii;
}
} return NULL;
}
#ifdef ASSERT void PhaseIdealLoop::ensure_zero_trip_guard_proj(Node* node, bool is_main_loop) {
assert(node->is_IfProj(), "must be the zero trip guard If node");
Node* zer_bol = node->in(0)->in(1);
assert(zer_bol != NULL && zer_bol->is_Bool(), "must be Bool");
Node* zer_cmp = zer_bol->in(1);
assert(zer_cmp != NULL && zer_cmp->Opcode() == Op_CmpI, "must be CmpI"); // For the main loop, the opaque node is the second input to zer_cmp, for the post loop it's the first input node
Node* zer_opaq = zer_cmp->in(is_main_loop ? 2 : 1);
assert(zer_opaq != NULL && zer_opaq->Opcode() == Op_OpaqueZeroTripGuard, "must be OpaqueZeroTripGuard");
} #endif
// Make a copy of the skeleton range check predicates before the main // loop and set the initial value of loop as input. After unrolling, // the range of values for the induction variable in the main loop can // fall outside the allowed range of values by the array access (main // loop is never executed). When that happens, range check // CastII/ConvI2L nodes cause some data paths to die. For consistency, // the control paths must die too but the range checks were removed by // predication. The range checks that we add here guarantee that they do. void PhaseIdealLoop::copy_skeleton_predicates_to_main_loop_helper(Node* predicate, Node* init, Node* stride,
IdealLoopTree* outer_loop, LoopNode* outer_main_head,
uint dd_main_head, const uint idx_before_pre_post, const uint idx_after_post_before_pre, Node* zero_trip_guard_proj_main,
Node* zero_trip_guard_proj_post, const Node_List &old_new) { if (predicate != NULL) { #ifdef ASSERT
ensure_zero_trip_guard_proj(zero_trip_guard_proj_main, true);
ensure_zero_trip_guard_proj(zero_trip_guard_proj_post, false); #endif
IfNode* iff = predicate->in(0)->as_If();
ProjNode* uncommon_proj = iff->proj_out(1 - predicate->as_Proj()->_con);
Node* rgn = uncommon_proj->unique_ctrl_out();
assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
assert(iff->in(1)->in(1)->Opcode() == Op_Opaque1, "unexpected predicate shape");
predicate = iff->in(0);
Node* current_proj = outer_main_head->in(LoopNode::EntryControl);
Node* prev_proj = current_proj;
Node* opaque_init = new OpaqueLoopInitNode(C, init);
register_new_node(opaque_init, outer_main_head->in(LoopNode::EntryControl));
Node* opaque_stride = new OpaqueLoopStrideNode(C, stride);
register_new_node(opaque_stride, outer_main_head->in(LoopNode::EntryControl));
while (predicate != NULL && predicate->is_Proj() && predicate->in(0)->is_If()) {
iff = predicate->in(0)->as_If();
uncommon_proj = iff->proj_out(1 - predicate->as_Proj()->_con); if (uncommon_proj->unique_ctrl_out() != rgn) break; if (iff->in(1)->Opcode() == Op_Opaque4) {
assert(skeleton_predicate_has_opaque(iff), "unexpected"); // Clone the skeleton predicate twice and initialize one with the initial // value of the loop induction variable. Leave the other predicate // to be initialized when increasing the stride during loop unrolling.
prev_proj = clone_skeleton_predicate_and_initialize(iff, opaque_init, NULL, predicate, uncommon_proj,
current_proj, outer_loop, prev_proj);
assert(skeleton_predicate_has_opaque(prev_proj->in(0)->as_If()), "");
// Rewire any control inputs from the cloned skeleton predicates down to the main and post loop for data nodes that are part of the // main loop (and were cloned to the pre and post loop). for (DUIterator i = predicate->outs(); predicate->has_out(i); i++) {
Node* loop_node = predicate->out(i);
Node* pre_loop_node = old_new[loop_node->_idx]; // Change the control if 'loop_node' is part of the main loop. If there is an old->new mapping and the index of // 'pre_loop_node' is greater than idx_before_pre_post, then we know that 'loop_node' was cloned and is part of // the main loop (and 'pre_loop_node' is part of the pre loop). if (!loop_node->is_CFG() && (pre_loop_node != NULL && pre_loop_node->_idx > idx_after_post_before_pre)) { // 'loop_node' is a data node and part of the main loop. Rewire the control to the projection of the zero-trip guard if node // of the main loop that is immediately preceding the cloned predicates.
_igvn.replace_input_of(loop_node, 0, zero_trip_guard_proj_main);
--i;
} elseif (loop_node->_idx > idx_before_pre_post && loop_node->_idx < idx_after_post_before_pre) { // 'loop_node' is a data node and part of the post loop. Rewire the control to the projection of the zero-trip guard if node // of the post loop that is immediately preceding the post loop header node (there are no cloned predicates for the post loop).
assert(pre_loop_node == NULL, "a node belonging to the post loop should not have an old_new mapping at this stage");
_igvn.replace_input_of(loop_node, 0, zero_trip_guard_proj_post);
--i;
}
}
// Remove the skeleton predicate from the pre-loop
_igvn.replace_input_of(iff, 1, _igvn.intcon(1));
}
predicate = predicate->in(0)->in(0);
}
_igvn.replace_input_of(outer_main_head, LoopNode::EntryControl, prev_proj);
set_idom(outer_main_head, prev_proj, dd_main_head);
}
}
staticbool skeleton_follow_inputs(Node* n) { int op = n->Opcode(); return (n->is_Bool() ||
n->is_Cmp() ||
op == Op_AndL ||
op == Op_OrL ||
op == Op_RShiftL ||
op == Op_LShiftL ||
op == Op_LShiftI ||
op == Op_AddL ||
op == Op_AddI ||
op == Op_MulL ||
op == Op_MulI ||
op == Op_SubL ||
op == Op_SubI ||
op == Op_ConvI2L ||
op == Op_CastII);
}
bool PhaseIdealLoop::skeleton_predicate_has_opaque(IfNode* iff) {
uint init;
uint stride;
count_opaque_loop_nodes(iff->in(1)->in(1), init, stride); #ifdef ASSERT
ResourceMark rm;
Unique_Node_List wq;
wq.clear();
wq.push(iff->in(1)->in(1));
uint verif_init = 0;
uint verif_stride = 0; for (uint i = 0; i < wq.size(); i++) {
Node* n = wq.at(i); int op = n->Opcode(); if (!n->is_CFG()) { if (n->Opcode() == Op_OpaqueLoopInit) {
verif_init++;
} elseif (n->Opcode() == Op_OpaqueLoopStride) {
verif_stride++;
} else { for (uint j = 1; j < n->req(); j++) {
Node* m = n->in(j); if (m != NULL) {
wq.push(m);
}
}
}
}
}
assert(init == verif_init && stride == verif_stride, "missed opaque node"); #endif
assert(stride == 0 || init != 0, "init should be there every time stride is"); return init != 0;
}
void PhaseIdealLoop::count_opaque_loop_nodes(Node* n, uint& init, uint& stride) {
init = 0;
stride = 0;
ResourceMark rm;
Unique_Node_List wq;
wq.push(n); for (uint i = 0; i < wq.size(); i++) {
Node* n = wq.at(i); if (skeleton_follow_inputs(n)) { for (uint j = 1; j < n->req(); j++) {
Node* m = n->in(j); if (m != NULL) {
wq.push(m);
}
} continue;
} if (n->Opcode() == Op_OpaqueLoopInit) {
init++;
} elseif (n->Opcode() == Op_OpaqueLoopStride) {
stride++;
}
}
}
// Clone the skeleton predicate bool for a main or unswitched loop: // Main loop: Set new_init and new_stride nodes as new inputs. // Unswitched loop: new_init and new_stride are both NULL. Clone OpaqueLoopInit and OpaqueLoopStride instead.
Node* PhaseIdealLoop::clone_skeleton_predicate_bool(Node* iff, Node* new_init, Node* new_stride, Node* control) {
Node_Stack to_clone(2);
to_clone.push(iff->in(1), 1);
uint current = C->unique();
Node* result = NULL; bool is_unswitched_loop = new_init == NULL && new_stride == NULL;
assert(new_init != NULL || is_unswitched_loop, "new_init must be set when new_stride is non-null"); // Look for the opaque node to replace with the new value // and clone everything in between. We keep the Opaque4 node // so the duplicated predicates are eliminated once loop // opts are over: they are here only to keep the IR graph // consistent. do {
Node* n = to_clone.node();
uint i = to_clone.index();
Node* m = n->in(i); if (skeleton_follow_inputs(m)) {
to_clone.push(m, 1); continue;
} if (m->is_Opaque1()) { if (n->_idx < current) {
n = n->clone();
register_new_node(n, control);
} int op = m->Opcode(); if (op == Op_OpaqueLoopInit) { if (is_unswitched_loop && m->_idx < current && new_init == NULL) {
new_init = m->clone();
register_new_node(new_init, control);
}
n->set_req(i, new_init);
} else {
assert(op == Op_OpaqueLoopStride, "unexpected opaque node"); if (is_unswitched_loop && m->_idx < current && new_stride == NULL) {
new_stride = m->clone();
register_new_node(new_stride, control);
} if (new_stride != NULL) {
n->set_req(i, new_stride);
}
}
to_clone.set_node(n);
} while (true) {
Node* cur = to_clone.node();
uint j = to_clone.index(); if (j+1 < cur->req()) {
to_clone.set_index(j+1); break;
}
to_clone.pop(); if (to_clone.size() == 0) {
result = cur; break;
}
Node* next = to_clone.node();
j = to_clone.index(); if (next->in(j) != cur) {
assert(cur->_idx >= current || next->in(j)->Opcode() == Op_Opaque1, "new node or Opaque1 being replaced"); if (next->_idx < current) {
next = next->clone();
register_new_node(next, control);
to_clone.set_node(next);
}
next->set_req(j, cur);
}
}
} while (result == NULL);
assert(result->_idx >= current, "new node expected");
assert(!is_unswitched_loop || new_init != NULL, "new_init must always be found and cloned"); return result;
}
// Clone a skeleton predicate for the main loop. new_init and new_stride are set as new inputs. Since the predicates cannot fail at runtime, // Halt nodes are inserted instead of uncommon traps.
Node* PhaseIdealLoop::clone_skeleton_predicate_and_initialize(Node* iff, Node* new_init, Node* new_stride, Node* predicate, Node* uncommon_proj,
Node* control, IdealLoopTree* outer_loop, Node* input_proj) {
Node* result = clone_skeleton_predicate_bool(iff, new_init, new_stride, control);
Node* proj = predicate->clone();
Node* other_proj = uncommon_proj->clone();
Node* new_iff = iff->clone();
new_iff->set_req(1, result);
proj->set_req(0, new_iff);
other_proj->set_req(0, new_iff);
Node* frame = new ParmNode(C->start(), TypeFunc::FramePtr);
register_new_node(frame, C->start()); // It's impossible for the predicate to fail at runtime. Use an Halt node.
Node* halt = new HaltNode(other_proj, frame, "duplicated predicate failed which is impossible");
_igvn.add_input_to(C->root(), halt);
new_iff->set_req(0, input_proj);
//------------------------------insert_pre_post_loops-------------------------- // Insert pre and post loops. If peel_only is set, the pre-loop can not have // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no // alignment. Useful to unroll loops that do no array accesses. void PhaseIdealLoop::insert_pre_post_loops(IdealLoopTree *loop, Node_List &old_new, bool peel_only) {
#ifndef PRODUCT if (TraceLoopOpts) { if (peel_only)
tty->print("PeelMainPost "); else
tty->print("PreMainPost ");
loop->dump_head();
} #endif
C->set_major_progress();
// Find common pieces of the loop being guarded with pre & post loops
CountedLoopNode *main_head = loop->_head->as_CountedLoop();
assert(main_head->is_normal_loop(), "");
CountedLoopEndNode *main_end = main_head->loopexit();
assert(main_end->outcnt() == 2, "1 true, 1 false path only");
// Need only 1 user of 'bol' because I will be hacking the loop bounds.
Node *bol = main_end->in(CountedLoopEndNode::TestValue); if (bol->outcnt() != 1) {
bol = bol->clone();
register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
_igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
} // Need only 1 user of 'cmp' because I will be hacking the loop bounds. if (cmp->outcnt() != 1) {
cmp = cmp->clone();
register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
_igvn.replace_input_of(bol, 1, cmp);
}
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