8205034: [BACKOUT] Induction variable of over-unrolled loop conflicts with range checks
Summary: Backout fix for JDK-8203915 because it causes SIGILL failures.
Reviewed-by: shade
/*
* Copyright (c) 2011, 2017, 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.
*
*/
#include "precompiled.hpp"
#include "opto/loopnode.hpp"
#include "opto/addnode.hpp"
#include "opto/callnode.hpp"
#include "opto/connode.hpp"
#include "opto/convertnode.hpp"
#include "opto/loopnode.hpp"
#include "opto/matcher.hpp"
#include "opto/mulnode.hpp"
#include "opto/opaquenode.hpp"
#include "opto/rootnode.hpp"
#include "opto/subnode.hpp"
/*
* The general idea of Loop Predication is to insert a predicate on the entry
* path to a loop, and raise a uncommon trap if the check of the condition fails.
* The condition checks are promoted from inside the loop body, and thus
* the checks inside the loop could be eliminated. Currently, loop predication
* optimization has been applied to remove array range check and loop invariant
* checks (such as null checks).
*/
//-------------------------------register_control-------------------------
void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
assert(n->is_CFG(), "must be control node");
_igvn.register_new_node_with_optimizer(n);
loop->_body.push(n);
set_loop(n, loop);
// When called from beautify_loops() idom is not constructed yet.
if (_idom != NULL) {
set_idom(n, pred, dom_depth(pred));
}
}
//------------------------------create_new_if_for_predicate------------------------
// create a new if above the uct_if_pattern for the predicate to be promoted.
//
// before after
// ---------- ----------
// ctrl ctrl
// | |
// | |
// v v
// iff new_iff
// / \ / \
// / \ / \
// v v v v
// uncommon_proj cont_proj if_uct if_cont
// \ | | | |
// \ | | | |
// v v v | v
// rgn loop | iff
// | | / \
// | | / \
// v | v v
// uncommon_trap | uncommon_proj cont_proj
// \ \ | |
// \ \ | |
// v v v v
// rgn loop
// |
// |
// v
// uncommon_trap
//
//
// We will create a region to guard the uct call if there is no one there.
// The true projecttion (if_cont) of the new_iff is returned.
// This code is also used to clone predicates to cloned loops.
ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
Deoptimization::DeoptReason reason,
int opcode) {
assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
IfNode* iff = cont_proj->in(0)->as_If();
ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
Node *rgn = uncommon_proj->unique_ctrl_out();
assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
uint proj_index = 1; // region's edge corresponding to uncommon_proj
if (!rgn->is_Region()) { // create a region to guard the call
assert(rgn->is_Call(), "must be call uct");
CallNode* call = rgn->as_Call();
IdealLoopTree* loop = get_loop(call);
rgn = new RegionNode(1);
rgn->add_req(uncommon_proj);
register_control(rgn, loop, uncommon_proj);
_igvn.replace_input_of(call, 0, rgn);
// When called from beautify_loops() idom is not constructed yet.
if (_idom != NULL) {
set_idom(call, rgn, dom_depth(rgn));
}
for (DUIterator_Fast imax, i = uncommon_proj->fast_outs(imax); i < imax; i++) {
Node* n = uncommon_proj->fast_out(i);
if (n->is_Load() || n->is_Store()) {
_igvn.replace_input_of(n, 0, rgn);
--i; --imax;
}
}
} else {
// Find region's edge corresponding to uncommon_proj
for (; proj_index < rgn->req(); proj_index++)
if (rgn->in(proj_index) == uncommon_proj) break;
assert(proj_index < rgn->req(), "sanity");
}
Node* entry = iff->in(0);
if (new_entry != NULL) {
// Clonning the predicate to new location.
entry = new_entry;
}
// Create new_iff
IdealLoopTree* lp = get_loop(entry);
IfNode* new_iff = NULL;
if (opcode == Op_If) {
new_iff = new IfNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
} else {
assert(opcode == Op_RangeCheck, "no other if variant here");
new_iff = new RangeCheckNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
}
register_control(new_iff, lp, entry);
Node *if_cont = new IfTrueNode(new_iff);
Node *if_uct = new IfFalseNode(new_iff);
if (cont_proj->is_IfFalse()) {
// Swap
Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
}
register_control(if_cont, lp, new_iff);
register_control(if_uct, get_loop(rgn), new_iff);
// if_uct to rgn
_igvn.hash_delete(rgn);
rgn->add_req(if_uct);
// When called from beautify_loops() idom is not constructed yet.
if (_idom != NULL) {
Node* ridom = idom(rgn);
Node* nrdom = dom_lca(ridom, new_iff);
set_idom(rgn, nrdom, dom_depth(rgn));
}
// If rgn has phis add new edges which has the same
// value as on original uncommon_proj pass.
assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
bool has_phi = false;
for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
Node* use = rgn->fast_out(i);
if (use->is_Phi() && use->outcnt() > 0) {
assert(use->in(0) == rgn, "");
_igvn.rehash_node_delayed(use);
use->add_req(use->in(proj_index));
has_phi = true;
}
}
assert(!has_phi || rgn->req() > 3, "no phis when region is created");
if (new_entry == NULL) {
// Attach if_cont to iff
_igvn.replace_input_of(iff, 0, if_cont);
if (_idom != NULL) {
set_idom(iff, if_cont, dom_depth(iff));
}
}
return if_cont->as_Proj();
}
//------------------------------create_new_if_for_predicate------------------------
// Create a new if below new_entry for the predicate to be cloned (IGVN optimization)
ProjNode* PhaseIterGVN::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
Deoptimization::DeoptReason reason,
int opcode) {
assert(new_entry != 0, "only used for clone predicate");
assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
IfNode* iff = cont_proj->in(0)->as_If();
ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
Node *rgn = uncommon_proj->unique_ctrl_out();
assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
uint proj_index = 1; // region's edge corresponding to uncommon_proj
if (!rgn->is_Region()) { // create a region to guard the call
assert(rgn->is_Call(), "must be call uct");
CallNode* call = rgn->as_Call();
rgn = new RegionNode(1);
register_new_node_with_optimizer(rgn);
rgn->add_req(uncommon_proj);
replace_input_of(call, 0, rgn);
} else {
// Find region's edge corresponding to uncommon_proj
for (; proj_index < rgn->req(); proj_index++)
if (rgn->in(proj_index) == uncommon_proj) break;
assert(proj_index < rgn->req(), "sanity");
}
// Create new_iff in new location.
IfNode* new_iff = NULL;
if (opcode == Op_If) {
new_iff = new IfNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
} else {
assert(opcode == Op_RangeCheck, "no other if variant here");
new_iff = new RangeCheckNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
}
register_new_node_with_optimizer(new_iff);
Node *if_cont = new IfTrueNode(new_iff);
Node *if_uct = new IfFalseNode(new_iff);
if (cont_proj->is_IfFalse()) {
// Swap
Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
}
register_new_node_with_optimizer(if_cont);
register_new_node_with_optimizer(if_uct);
// if_uct to rgn
hash_delete(rgn);
rgn->add_req(if_uct);
// If rgn has phis add corresponding new edges which has the same
// value as on original uncommon_proj pass.
assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
bool has_phi = false;
for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
Node* use = rgn->fast_out(i);
if (use->is_Phi() && use->outcnt() > 0) {
rehash_node_delayed(use);
use->add_req(use->in(proj_index));
has_phi = true;
}
}
assert(!has_phi || rgn->req() > 3, "no phis when region is created");
return if_cont->as_Proj();
}
//--------------------------clone_predicate-----------------------
ProjNode* PhaseIdealLoop::clone_predicate(ProjNode* predicate_proj, Node* new_entry,
Deoptimization::DeoptReason reason,
PhaseIdealLoop* loop_phase,
PhaseIterGVN* igvn) {
ProjNode* new_predicate_proj;
if (loop_phase != NULL) {
new_predicate_proj = loop_phase->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
} else {
new_predicate_proj = igvn->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
}
IfNode* iff = new_predicate_proj->in(0)->as_If();
Node* ctrl = iff->in(0);
// Match original condition since predicate's projections could be swapped.
assert(predicate_proj->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
Node* opq = new Opaque1Node(igvn->C, predicate_proj->in(0)->in(1)->in(1)->in(1));
igvn->C->add_predicate_opaq(opq);
Node* bol = new Conv2BNode(opq);
if (loop_phase != NULL) {
loop_phase->register_new_node(opq, ctrl);
loop_phase->register_new_node(bol, ctrl);
} else {
igvn->register_new_node_with_optimizer(opq);
igvn->register_new_node_with_optimizer(bol);
}
igvn->hash_delete(iff);
iff->set_req(1, bol);
return new_predicate_proj;
}
//--------------------------clone_loop_predicates-----------------------
// Interface from IGVN
Node* PhaseIterGVN::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
return PhaseIdealLoop::clone_loop_predicates(old_entry, new_entry, clone_limit_check, NULL, this);
}
// Interface from PhaseIdealLoop
Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
return clone_loop_predicates(old_entry, new_entry, clone_limit_check, this, &this->_igvn);
}
// Clone loop predicates to cloned loops (peeled, unswitched, split_if).
Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry,
bool clone_limit_check,
PhaseIdealLoop* loop_phase,
PhaseIterGVN* igvn) {
#ifdef ASSERT
if (new_entry == NULL || !(new_entry->is_Proj() || new_entry->is_Region() || new_entry->is_SafePoint())) {
if (new_entry != NULL)
new_entry->dump();
assert(false, "not IfTrue, IfFalse, Region or SafePoint");
}
#endif
// Search original predicates
Node* entry = old_entry;
ProjNode* limit_check_proj = NULL;
limit_check_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
if (limit_check_proj != NULL) {
entry = entry->in(0)->in(0);
}
if (UseLoopPredicate) {
ProjNode* predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
if (predicate_proj != NULL) { // right pattern that can be used by loop predication
// clone predicate
new_entry = clone_predicate(predicate_proj, new_entry,
Deoptimization::Reason_predicate,
loop_phase, igvn);
assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
if (TraceLoopPredicate) {
tty->print("Loop Predicate cloned: ");
debug_only( new_entry->in(0)->dump(); )
}
}
}
if (limit_check_proj != NULL && clone_limit_check) {
// Clone loop limit check last to insert it before loop.
// Don't clone a limit check which was already finalized
// for this counted loop (only one limit check is needed).
new_entry = clone_predicate(limit_check_proj, new_entry,
Deoptimization::Reason_loop_limit_check,
loop_phase, igvn);
assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone limit check");
if (TraceLoopLimitCheck) {
tty->print("Loop Limit Check cloned: ");
debug_only( new_entry->in(0)->dump(); )
}
}
return new_entry;
}
//--------------------------skip_loop_predicates------------------------------
// Skip related predicates.
Node* PhaseIdealLoop::skip_loop_predicates(Node* entry) {
Node* predicate = NULL;
predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
if (predicate != NULL) {
entry = entry->in(0)->in(0);
}
if (UseLoopPredicate) {
predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
if (predicate != NULL) { // right pattern that can be used by loop predication
IfNode* iff = entry->in(0)->as_If();
ProjNode* uncommon_proj = iff->proj_out(1 - entry->as_Proj()->_con);
Node* rgn = uncommon_proj->unique_ctrl_out();
assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
entry = entry->in(0)->in(0);
while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
uncommon_proj = entry->in(0)->as_If()->proj_out(1 - entry->as_Proj()->_con);
if (uncommon_proj->unique_ctrl_out() != rgn)
break;
entry = entry->in(0)->in(0);
}
}
}
return entry;
}
//--------------------------find_predicate_insertion_point-------------------
// Find a good location to insert a predicate
ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
if (start_c == NULL || !start_c->is_Proj())
return NULL;
if (start_c->as_Proj()->is_uncommon_trap_if_pattern(reason)) {
return start_c->as_Proj();
}
return NULL;
}
//--------------------------find_predicate------------------------------------
// Find a predicate
Node* PhaseIdealLoop::find_predicate(Node* entry) {
Node* predicate = NULL;
predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
if (predicate != NULL) { // right pattern that can be used by loop predication
return entry;
}
if (UseLoopPredicate) {
predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
if (predicate != NULL) { // right pattern that can be used by loop predication
return entry;
}
}
return NULL;
}
//------------------------------Invariance-----------------------------------
// Helper class for loop_predication_impl to compute invariance on the fly and
// clone invariants.
class Invariance : public StackObj {
VectorSet _visited, _invariant;
Node_Stack _stack;
VectorSet _clone_visited;
Node_List _old_new; // map of old to new (clone)
IdealLoopTree* _lpt;
PhaseIdealLoop* _phase;
// Helper function to set up the invariance for invariance computation
// If n is a known invariant, set up directly. Otherwise, look up the
// the possibility to push n onto the stack for further processing.
void visit(Node* use, Node* n) {
if (_lpt->is_invariant(n)) { // known invariant
_invariant.set(n->_idx);
} else if (!n->is_CFG()) {
Node *n_ctrl = _phase->ctrl_or_self(n);
Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
if (_phase->is_dominator(n_ctrl, u_ctrl)) {
_stack.push(n, n->in(0) == NULL ? 1 : 0);
}
}
}
// Compute invariance for "the_node" and (possibly) all its inputs recursively
// on the fly
void compute_invariance(Node* n) {
assert(_visited.test(n->_idx), "must be");
visit(n, n);
while (_stack.is_nonempty()) {
Node* n = _stack.node();
uint idx = _stack.index();
if (idx == n->req()) { // all inputs are processed
_stack.pop();
// n is invariant if it's inputs are all invariant
bool all_inputs_invariant = true;
for (uint i = 0; i < n->req(); i++) {
Node* in = n->in(i);
if (in == NULL) continue;
assert(_visited.test(in->_idx), "must have visited input");
if (!_invariant.test(in->_idx)) { // bad guy
all_inputs_invariant = false;
break;
}
}
if (all_inputs_invariant) {
// If n's control is a predicate that was moved out of the
// loop, it was marked invariant but n is only invariant if
// it depends only on that test. Otherwise, unless that test
// is out of the loop, it's not invariant.
if (n->is_CFG() || n->depends_only_on_test() || n->in(0) == NULL || !_phase->is_member(_lpt, n->in(0))) {
_invariant.set(n->_idx); // I am a invariant too
}
}
} else { // process next input
_stack.set_index(idx + 1);
Node* m = n->in(idx);
if (m != NULL && !_visited.test_set(m->_idx)) {
visit(n, m);
}
}
}
}
// Helper function to set up _old_new map for clone_nodes.
// If n is a known invariant, set up directly ("clone" of n == n).
// Otherwise, push n onto the stack for real cloning.
void clone_visit(Node* n) {
assert(_invariant.test(n->_idx), "must be invariant");
if (_lpt->is_invariant(n)) { // known invariant
_old_new.map(n->_idx, n);
} else { // to be cloned
assert(!n->is_CFG(), "should not see CFG here");
_stack.push(n, n->in(0) == NULL ? 1 : 0);
}
}
// Clone "n" and (possibly) all its inputs recursively
void clone_nodes(Node* n, Node* ctrl) {
clone_visit(n);
while (_stack.is_nonempty()) {
Node* n = _stack.node();
uint idx = _stack.index();
if (idx == n->req()) { // all inputs processed, clone n!
_stack.pop();
// clone invariant node
Node* n_cl = n->clone();
_old_new.map(n->_idx, n_cl);
_phase->register_new_node(n_cl, ctrl);
for (uint i = 0; i < n->req(); i++) {
Node* in = n_cl->in(i);
if (in == NULL) continue;
n_cl->set_req(i, _old_new[in->_idx]);
}
} else { // process next input
_stack.set_index(idx + 1);
Node* m = n->in(idx);
if (m != NULL && !_clone_visited.test_set(m->_idx)) {
clone_visit(m); // visit the input
}
}
}
}
public:
Invariance(Arena* area, IdealLoopTree* lpt) :
_lpt(lpt), _phase(lpt->_phase),
_visited(area), _invariant(area), _stack(area, 10 /* guess */),
_clone_visited(area), _old_new(area)
{
LoopNode* head = _lpt->_head->as_Loop();
Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
if (entry->outcnt() != 1) {
// If a node is pinned between the predicates and the loop
// entry, we won't be able to move any node in the loop that
// depends on it above it in a predicate. Mark all those nodes
// as non loop invariatnt.
Unique_Node_List wq;
wq.push(entry);
for (uint next = 0; next < wq.size(); ++next) {
Node *n = wq.at(next);
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
Node* u = n->fast_out(i);
if (!u->is_CFG()) {
Node* c = _phase->get_ctrl(u);
if (_lpt->is_member(_phase->get_loop(c)) || _phase->is_dominator(c, head)) {
_visited.set(u->_idx);
wq.push(u);
}
}
}
}
}
}
// Map old to n for invariance computation and clone
void map_ctrl(Node* old, Node* n) {
assert(old->is_CFG() && n->is_CFG(), "must be");
_old_new.map(old->_idx, n); // "clone" of old is n
_invariant.set(old->_idx); // old is invariant
_clone_visited.set(old->_idx);
}
// Driver function to compute invariance
bool is_invariant(Node* n) {
if (!_visited.test_set(n->_idx))
compute_invariance(n);
return (_invariant.test(n->_idx) != 0);
}
// Driver function to clone invariant
Node* clone(Node* n, Node* ctrl) {
assert(ctrl->is_CFG(), "must be");
assert(_invariant.test(n->_idx), "must be an invariant");
if (!_clone_visited.test(n->_idx))
clone_nodes(n, ctrl);
return _old_new[n->_idx];
}
};
//------------------------------is_range_check_if -----------------------------------
// Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
// Note: this function is particularly designed for loop predication. We require load_range
// and offset to be loop invariant computed on the fly by "invar"
bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
if (!is_loop_exit(iff)) {
return false;
}
if (!iff->in(1)->is_Bool()) {
return false;
}
const BoolNode *bol = iff->in(1)->as_Bool();
if (bol->_test._test != BoolTest::lt) {
return false;
}
if (!bol->in(1)->is_Cmp()) {
return false;
}
const CmpNode *cmp = bol->in(1)->as_Cmp();
if (cmp->Opcode() != Op_CmpU) {
return false;
}
Node* range = cmp->in(2);
if (range->Opcode() != Op_LoadRange && !iff->is_RangeCheck()) {
const TypeInt* tint = phase->_igvn.type(range)->isa_int();
if (tint == NULL || tint->empty() || tint->_lo < 0) {
// Allow predication on positive values that aren't LoadRanges.
// This allows optimization of loops where the length of the
// array is a known value and doesn't need to be loaded back
// from the array.
return false;
}
}
if (!invar.is_invariant(range)) {
return false;
}
Node *iv = _head->as_CountedLoop()->phi();
int scale = 0;
Node *offset = NULL;
if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
return false;
}
if (offset && !invar.is_invariant(offset)) { // offset must be invariant
return false;
}
return true;
}
//------------------------------rc_predicate-----------------------------------
// Create a range check predicate
//
// for (i = init; i < limit; i += stride) {
// a[scale*i+offset]
// }
//
// Compute max(scale*i + offset) for init <= i < limit and build the predicate
// as "max(scale*i + offset) u< a.length".
//
// There are two cases for max(scale*i + offset):
// (1) stride*scale > 0
// max(scale*i + offset) = scale*(limit-stride) + offset
// (2) stride*scale < 0
// max(scale*i + offset) = scale*init + offset
BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
int scale, Node* offset,
Node* init, Node* limit, jint stride,
Node* range, bool upper, bool &overflow) {
jint con_limit = (limit != NULL && limit->is_Con()) ? limit->get_int() : 0;
jint con_init = init->is_Con() ? init->get_int() : 0;
jint con_offset = offset->is_Con() ? offset->get_int() : 0;
stringStream* predString = NULL;
if (TraceLoopPredicate) {
predString = new stringStream();
predString->print("rc_predicate ");
}
overflow = false;
Node* max_idx_expr = NULL;
const TypeInt* idx_type = TypeInt::INT;
if ((stride > 0) == (scale > 0) == upper) {
if (TraceLoopPredicate) {
if (limit->is_Con()) {
predString->print("(%d ", con_limit);
} else {
predString->print("(limit ");
}
predString->print("- %d) ", stride);
}
// Check if (limit - stride) may overflow
const TypeInt* limit_type = _igvn.type(limit)->isa_int();
jint limit_lo = limit_type->_lo;
jint limit_hi = limit_type->_hi;
if ((stride > 0 && (java_subtract(limit_lo, stride) < limit_lo)) ||
(stride < 0 && (java_subtract(limit_hi, stride) > limit_hi))) {
// No overflow possible
ConINode* con_stride = _igvn.intcon(stride);
set_ctrl(con_stride, C->root());
max_idx_expr = new SubINode(limit, con_stride);
idx_type = TypeInt::make(limit_lo - stride, limit_hi - stride, limit_type->_widen);
} else {
// May overflow
overflow = true;
limit = new ConvI2LNode(limit);
register_new_node(limit, ctrl);
ConLNode* con_stride = _igvn.longcon(stride);
set_ctrl(con_stride, C->root());
max_idx_expr = new SubLNode(limit, con_stride);
}
register_new_node(max_idx_expr, ctrl);
} else {
if (TraceLoopPredicate) {
if (init->is_Con()) {
predString->print("%d ", con_init);
} else {
predString->print("init ");
}
}
idx_type = _igvn.type(init)->isa_int();
max_idx_expr = init;
}
if (scale != 1) {
ConNode* con_scale = _igvn.intcon(scale);
set_ctrl(con_scale, C->root());
if (TraceLoopPredicate) {
predString->print("* %d ", scale);
}
// Check if (scale * max_idx_expr) may overflow
const TypeInt* scale_type = TypeInt::make(scale);
MulINode* mul = new MulINode(max_idx_expr, con_scale);
idx_type = (TypeInt*)mul->mul_ring(idx_type, scale_type);
if (overflow || TypeInt::INT->higher_equal(idx_type)) {
// May overflow
mul->destruct();
if (!overflow) {
max_idx_expr = new ConvI2LNode(max_idx_expr);
register_new_node(max_idx_expr, ctrl);
}
overflow = true;
con_scale = _igvn.longcon(scale);
set_ctrl(con_scale, C->root());
max_idx_expr = new MulLNode(max_idx_expr, con_scale);
} else {
// No overflow possible
max_idx_expr = mul;
}
register_new_node(max_idx_expr, ctrl);
}
if (offset && (!offset->is_Con() || con_offset != 0)){
if (TraceLoopPredicate) {
if (offset->is_Con()) {
predString->print("+ %d ", con_offset);
} else {
predString->print("+ offset");
}
}
// Check if (max_idx_expr + offset) may overflow
const TypeInt* offset_type = _igvn.type(offset)->isa_int();
jint lo = java_add(idx_type->_lo, offset_type->_lo);
jint hi = java_add(idx_type->_hi, offset_type->_hi);
if (overflow || (lo > hi) ||
((idx_type->_lo & offset_type->_lo) < 0 && lo >= 0) ||
((~(idx_type->_hi | offset_type->_hi)) < 0 && hi < 0)) {
// May overflow
if (!overflow) {
max_idx_expr = new ConvI2LNode(max_idx_expr);
register_new_node(max_idx_expr, ctrl);
}
overflow = true;
offset = new ConvI2LNode(offset);
register_new_node(offset, ctrl);
max_idx_expr = new AddLNode(max_idx_expr, offset);
} else {
// No overflow possible
max_idx_expr = new AddINode(max_idx_expr, offset);
}
register_new_node(max_idx_expr, ctrl);
}
CmpNode* cmp = NULL;
if (overflow) {
// Integer expressions may overflow, do long comparison
range = new ConvI2LNode(range);
register_new_node(range, ctrl);
cmp = new CmpULNode(max_idx_expr, range);
} else {
cmp = new CmpUNode(max_idx_expr, range);
}
register_new_node(cmp, ctrl);
BoolNode* bol = new BoolNode(cmp, BoolTest::lt);
register_new_node(bol, ctrl);
if (TraceLoopPredicate) {
predString->print_cr("<u range");
tty->print("%s", predString->as_string());
}
return bol;
}
// After pre/main/post loops are created, we'll put a copy of some
// range checks between the pre and main loop to validate the initial
// value of the induction variable for the main loop. Make a copy of
// the predicates here with an opaque node as a place holder for the
// initial value.
ProjNode* PhaseIdealLoop::insert_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
ProjNode* proj, ProjNode *predicate_proj,
ProjNode* upper_bound_proj,
int scale, Node* offset,
Node* init, Node* limit, jint stride,
Node* rng, bool &overflow) {
assert(proj->_con && predicate_proj->_con, "not a range check?");
Node* opaque_init = new Opaque1Node(C, init);
register_new_node(opaque_init, upper_bound_proj);
BoolNode* bol = rc_predicate(loop, upper_bound_proj, scale, offset, opaque_init, limit, stride, rng, (stride > 0) != (scale > 0), overflow);
Node* opaque_bol = new Opaque4Node(C, bol, _igvn.intcon(1)); // This will go away once loop opts are over
register_new_node(opaque_bol, upper_bound_proj);
ProjNode* new_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate, overflow ? Op_If : iff->Opcode());
_igvn.replace_input_of(new_proj->in(0), 1, opaque_bol);
assert(opaque_init->outcnt() > 0, "should be used");
return new_proj;
}
//------------------------------ loop_predication_impl--------------------------
// Insert loop predicates for null checks and range checks
bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
if (!UseLoopPredicate) return false;
if (!loop->_head->is_Loop()) {
// Could be a simple region when irreducible loops are present.
return false;
}
LoopNode* head = loop->_head->as_Loop();
if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
// do nothing for infinite loops
return false;
}
if (head->is_OuterStripMinedLoop()) {
return false;
}
CountedLoopNode *cl = NULL;
if (head->is_valid_counted_loop()) {
cl = head->as_CountedLoop();
// do nothing for iteration-splitted loops
if (!cl->is_normal_loop()) return false;
// Avoid RCE if Counted loop's test is '!='.
BoolTest::mask bt = cl->loopexit()->test_trip();
if (bt != BoolTest::lt && bt != BoolTest::gt)
cl = NULL;
}
Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
ProjNode *predicate_proj = NULL;
// Loop limit check predicate should be near the loop.
predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
if (predicate_proj != NULL)
entry = predicate_proj->in(0)->in(0);
predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
if (!predicate_proj) {
#ifndef PRODUCT
if (TraceLoopPredicate) {
tty->print("missing predicate:");
loop->dump_head();
head->dump(1);
}
#endif
return false;
}
ConNode* zero = _igvn.intcon(0);
set_ctrl(zero, C->root());
ResourceArea *area = Thread::current()->resource_area();
Invariance invar(area, loop);
// Create list of if-projs such that a newer proj dominates all older
// projs in the list, and they all dominate loop->tail()
Node_List if_proj_list(area);
Node *current_proj = loop->tail(); //start from tail
while (current_proj != head) {
if (loop == get_loop(current_proj) && // still in the loop ?
current_proj->is_Proj() && // is a projection ?
(current_proj->in(0)->Opcode() == Op_If ||
current_proj->in(0)->Opcode() == Op_RangeCheck)) { // is a if projection ?
if_proj_list.push(current_proj);
}
current_proj = idom(current_proj);
}
bool hoisted = false; // true if at least one proj is promoted
while (if_proj_list.size() > 0) {
// Following are changed to nonnull when a predicate can be hoisted
ProjNode* new_predicate_proj = NULL;
ProjNode* proj = if_proj_list.pop()->as_Proj();
IfNode* iff = proj->in(0)->as_If();
if (!proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
if (loop->is_loop_exit(iff)) {
// stop processing the remaining projs in the list because the execution of them
// depends on the condition of "iff" (iff->in(1)).
break;
} else {
// Both arms are inside the loop. There are two cases:
// (1) there is one backward branch. In this case, any remaining proj
// in the if_proj list post-dominates "iff". So, the condition of "iff"
// does not determine the execution the remining projs directly, and we
// can safely continue.
// (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
// does not dominate loop->tail(), so it can not be in the if_proj list.
continue;
}
}
Node* test = iff->in(1);
if (!test->is_Bool()){ //Conv2B, ...
continue;
}
BoolNode* bol = test->as_Bool();
if (invar.is_invariant(bol)) {
// Invariant test
new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
Deoptimization::Reason_predicate,
iff->Opcode());
Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
// Negate test if necessary
bool negated = false;
if (proj->_con != predicate_proj->_con) {
new_predicate_bol = new BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
register_new_node(new_predicate_bol, ctrl);
negated = true;
}
IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
_igvn.hash_delete(new_predicate_iff);
new_predicate_iff->set_req(1, new_predicate_bol);
#ifndef PRODUCT
if (TraceLoopPredicate) {
tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
loop->dump_head();
} else if (TraceLoopOpts) {
tty->print("Predicate IC ");
loop->dump_head();
}
#endif
} else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
// Range check for counted loops
const Node* cmp = bol->in(1)->as_Cmp();
Node* idx = cmp->in(1);
assert(!invar.is_invariant(idx), "index is variant");
Node* rng = cmp->in(2);
assert(rng->Opcode() == Op_LoadRange || iff->is_RangeCheck() || _igvn.type(rng)->is_int()->_lo >= 0, "must be");
assert(invar.is_invariant(rng), "range must be invariant");
int scale = 1;
Node* offset = zero;
bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
assert(ok, "must be index expression");
Node* init = cl->init_trip();
// Limit is not exact.
// Calculate exact limit here.
// Note, counted loop's test is '<' or '>'.
Node* limit = exact_limit(loop);
int stride = cl->stride()->get_int();
// Build if's for the upper and lower bound tests. The
// lower_bound test will dominate the upper bound test and all
// cloned or created nodes will use the lower bound test as
// their declared control.
// Perform cloning to keep Invariance state correct since the
// late schedule will place invariant things in the loop.
Node *ctrl = predicate_proj->in(0)->as_If()->in(0);
rng = invar.clone(rng, ctrl);
if (offset && offset != zero) {
assert(invar.is_invariant(offset), "offset must be loop invariant");
offset = invar.clone(offset, ctrl);
}
// If predicate expressions may overflow in the integer range, longs are used.
bool overflow = false;
// Test the lower bound
BoolNode* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false, overflow);
// Negate test if necessary
bool negated = false;
if (proj->_con != predicate_proj->_con) {
lower_bound_bol = new BoolNode(lower_bound_bol->in(1), lower_bound_bol->_test.negate());
register_new_node(lower_bound_bol, ctrl);
negated = true;
}
ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate, overflow ? Op_If : iff->Opcode());
IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
_igvn.hash_delete(lower_bound_iff);
lower_bound_iff->set_req(1, lower_bound_bol);
if (TraceLoopPredicate) tty->print_cr("lower bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
// Test the upper bound
BoolNode* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true, overflow);
negated = false;
if (proj->_con != predicate_proj->_con) {
upper_bound_bol = new BoolNode(upper_bound_bol->in(1), upper_bound_bol->_test.negate());
register_new_node(upper_bound_bol, ctrl);
negated = true;
}
ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate, overflow ? Op_If : iff->Opcode());
assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
_igvn.hash_delete(upper_bound_iff);
upper_bound_iff->set_req(1, upper_bound_bol);
if (TraceLoopPredicate) tty->print_cr("upper bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
// Fall through into rest of the clean up code which will move
// any dependent nodes onto the upper bound test.
new_predicate_proj = upper_bound_proj;
if (iff->is_RangeCheck()) {
new_predicate_proj = insert_skeleton_predicate(iff, loop, proj, predicate_proj, upper_bound_proj, scale, offset, init, limit, stride, rng, overflow);
}
#ifndef PRODUCT
if (TraceLoopOpts && !TraceLoopPredicate) {
tty->print("Predicate RC ");
loop->dump_head();
}
#endif
} else {
// Loop variant check (for example, range check in non-counted loop)
// with uncommon trap.
continue;
}
assert(new_predicate_proj != NULL, "sanity");
// Success - attach condition (new_predicate_bol) to predicate if
invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
// Eliminate the old If in the loop body
dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
hoisted = true;
C->set_major_progress();
} // end while
#ifndef PRODUCT
// report that the loop predication has been actually performed
// for this loop
if (TraceLoopPredicate && hoisted) {
tty->print("Loop Predication Performed:");
loop->dump_head();
}
#endif
head->verify_strip_mined(1);
return hoisted;
}
//------------------------------loop_predication--------------------------------
// driver routine for loop predication optimization
bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
bool hoisted = false;
// Recursively promote predicates
if (_child) {
hoisted = _child->loop_predication( phase);
}
// self
if (!_irreducible && !tail()->is_top()) {
hoisted |= phase->loop_predication_impl(this);
}
if (_next) { //sibling
hoisted |= _next->loop_predication( phase);
}
return hoisted;
}