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loopnode.cpp
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loopnode.cpp
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/*
* Copyright (c) 1998, 2020, 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 "ci/ciMethodData.hpp"
#include "compiler/compileLog.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/c2/barrierSetC2.hpp"
#include "libadt/vectset.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "opto/addnode.hpp"
#include "opto/arraycopynode.hpp"
#include "opto/callnode.hpp"
#include "opto/connode.hpp"
#include "opto/convertnode.hpp"
#include "opto/divnode.hpp"
#include "opto/idealGraphPrinter.hpp"
#include "opto/loopnode.hpp"
#include "opto/movenode.hpp"
#include "opto/mulnode.hpp"
#include "opto/rootnode.hpp"
#include "opto/superword.hpp"
#include "utilities/powerOfTwo.hpp"
//=============================================================================
//--------------------------is_cloop_ind_var-----------------------------------
// Determine if a node is a counted loop induction variable.
// NOTE: The method is declared in "node.hpp".
bool Node::is_cloop_ind_var() const {
return (is_Phi() && !as_Phi()->is_copy() &&
as_Phi()->region()->is_CountedLoop() &&
as_Phi()->region()->as_CountedLoop()->phi() == this);
}
//=============================================================================
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void LoopNode::dump_spec(outputStream *st) const {
if (is_inner_loop()) st->print( "inner " );
if (is_partial_peel_loop()) st->print( "partial_peel " );
if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
}
#endif
//------------------------------is_valid_counted_loop-------------------------
bool LoopNode::is_valid_counted_loop() const {
if (is_CountedLoop()) {
CountedLoopNode* l = as_CountedLoop();
CountedLoopEndNode* le = l->loopexit_or_null();
if (le != NULL &&
le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
Node* phi = l->phi();
Node* exit = le->proj_out_or_null(0 /* false */);
if (exit != NULL && exit->Opcode() == Op_IfFalse &&
phi != NULL && phi->is_Phi() &&
phi->in(LoopNode::LoopBackControl) == l->incr() &&
le->loopnode() == l && le->stride_is_con()) {
return true;
}
}
}
return false;
}
//------------------------------get_early_ctrl---------------------------------
// Compute earliest legal control
Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
uint i;
Node *early;
if (n->in(0) && !n->is_expensive()) {
early = n->in(0);
if (!early->is_CFG()) // Might be a non-CFG multi-def
early = get_ctrl(early); // So treat input as a straight data input
i = 1;
} else {
early = get_ctrl(n->in(1));
i = 2;
}
uint e_d = dom_depth(early);
assert( early, "" );
for (; i < n->req(); i++) {
Node *cin = get_ctrl(n->in(i));
assert( cin, "" );
// Keep deepest dominator depth
uint c_d = dom_depth(cin);
if (c_d > e_d) { // Deeper guy?
early = cin; // Keep deepest found so far
e_d = c_d;
} else if (c_d == e_d && // Same depth?
early != cin) { // If not equal, must use slower algorithm
// If same depth but not equal, one _must_ dominate the other
// and we want the deeper (i.e., dominated) guy.
Node *n1 = early;
Node *n2 = cin;
while (1) {
n1 = idom(n1); // Walk up until break cycle
n2 = idom(n2);
if (n1 == cin || // Walked early up to cin
dom_depth(n2) < c_d)
break; // early is deeper; keep him
if (n2 == early || // Walked cin up to early
dom_depth(n1) < c_d) {
early = cin; // cin is deeper; keep him
break;
}
}
e_d = dom_depth(early); // Reset depth register cache
}
}
// Return earliest legal location
assert(early == find_non_split_ctrl(early), "unexpected early control");
if (n->is_expensive() && !_verify_only && !_verify_me) {
assert(n->in(0), "should have control input");
early = get_early_ctrl_for_expensive(n, early);
}
return early;
}
//------------------------------get_early_ctrl_for_expensive---------------------------------
// Move node up the dominator tree as high as legal while still beneficial
Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
assert(OptimizeExpensiveOps, "optimization off?");
Node* ctl = n->in(0);
assert(ctl->is_CFG(), "expensive input 0 must be cfg");
uint min_dom_depth = dom_depth(earliest);
#ifdef ASSERT
if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
}
#endif
if (dom_depth(ctl) < min_dom_depth) {
return earliest;
}
while (1) {
Node *next = ctl;
// Moving the node out of a loop on the projection of a If
// confuses loop predication. So once we hit a Loop in a If branch
// that doesn't branch to an UNC, we stop. The code that process
// expensive nodes will notice the loop and skip over it to try to
// move the node further up.
if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
next = idom(ctl->in(1)->in(0));
} else if (ctl->is_Proj()) {
// We only move it up along a projection if the projection is
// the single control projection for its parent: same code path,
// if it's a If with UNC or fallthrough of a call.
Node* parent_ctl = ctl->in(0);
if (parent_ctl == NULL) {
break;
} else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
} else if (parent_ctl->is_If()) {
if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
} else if (ctl->is_CatchProj()) {
if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
break;
}
assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
next = parent_ctl->in(0)->in(0)->in(0);
} else {
// Check if parent control has a single projection (this
// control is the only possible successor of the parent
// control). If so, we can try to move the node above the
// parent control.
int nb_ctl_proj = 0;
for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
Node *p = parent_ctl->fast_out(i);
if (p->is_Proj() && p->is_CFG()) {
nb_ctl_proj++;
if (nb_ctl_proj > 1) {
break;
}
}
}
if (nb_ctl_proj > 1) {
break;
}
assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
}
} else {
next = idom(ctl);
}
if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
break;
}
ctl = next;
}
if (ctl != n->in(0)) {
_igvn.replace_input_of(n, 0, ctl);
_igvn.hash_insert(n);
}
return ctl;
}
//------------------------------set_early_ctrl---------------------------------
// Set earliest legal control
void PhaseIdealLoop::set_early_ctrl( Node *n ) {
Node *early = get_early_ctrl(n);
// Record earliest legal location
set_ctrl(n, early);
}
//------------------------------set_subtree_ctrl-------------------------------
// set missing _ctrl entries on new nodes
void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
// Already set? Get out.
if( _nodes[n->_idx] ) return;
// Recursively set _nodes array to indicate where the Node goes
uint i;
for( i = 0; i < n->req(); ++i ) {
Node *m = n->in(i);
if( m && m != C->root() )
set_subtree_ctrl( m );
}
// Fixup self
set_early_ctrl( n );
}
IdealLoopTree* PhaseIdealLoop::insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift) {
IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
IdealLoopTree* parent = loop->_parent;
IdealLoopTree* sibling = parent->_child;
if (sibling == loop) {
parent->_child = outer_ilt;
} else {
while (sibling->_next != loop) {
sibling = sibling->_next;
}
sibling->_next = outer_ilt;
}
outer_ilt->_next = loop->_next;
outer_ilt->_parent = parent;
outer_ilt->_child = loop;
outer_ilt->_nest = loop->_nest;
loop->_parent = outer_ilt;
loop->_next = NULL;
loop->_nest++;
return outer_ilt;
}
// Create a skeleton strip mined outer loop: a Loop head before the
// inner strip mined loop, a safepoint and an exit condition guarded
// by an opaque node after the inner strip mined loop with a backedge
// to the loop head. The inner strip mined loop is left as it is. Only
// once loop optimizations are over, do we adjust the inner loop exit
// condition to limit its number of iterations, set the outer loop
// exit condition and add Phis to the outer loop head. Some loop
// optimizations that operate on the inner strip mined loop need to be
// aware of the outer strip mined loop: loop unswitching needs to
// clone the outer loop as well as the inner, unrolling needs to only
// clone the inner loop etc. No optimizations need to change the outer
// strip mined loop as it is only a skeleton.
IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
IdealLoopTree* loop, float cl_prob, float le_fcnt,
Node*& entry_control, Node*& iffalse) {
Node* outer_test = _igvn.intcon(0);
set_ctrl(outer_test, C->root());
Node *orig = iffalse;
iffalse = iffalse->clone();
_igvn.register_new_node_with_optimizer(iffalse);
set_idom(iffalse, idom(orig), dom_depth(orig));
IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
Node *outer_ift = new IfTrueNode (outer_le);
Node* outer_iff = orig;
_igvn.replace_input_of(outer_iff, 0, outer_le);
LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
entry_control = outer_l;
IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_l, outer_ift);
set_loop(iffalse, outer_ilt);
// When this code runs, loop bodies have not yet been populated.
const bool body_populated = false;
register_control(outer_le, outer_ilt, iffalse, body_populated);
register_control(outer_ift, outer_ilt, outer_le, body_populated);
set_idom(outer_iff, outer_le, dom_depth(outer_le));
_igvn.register_new_node_with_optimizer(outer_l);
set_loop(outer_l, outer_ilt);
set_idom(outer_l, init_control, dom_depth(init_control)+1);
return outer_ilt;
}
void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
Deoptimization::Reason_loop_limit_check,
Op_If);
Node* iff = new_predicate_proj->in(0);
assert(iff->Opcode() == Op_If, "bad graph shape");
Node* conv = iff->in(1);
assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
Node* opaq = conv->in(1);
assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
bol = _igvn.register_new_node_with_optimizer(bol);
set_subtree_ctrl(bol);
_igvn.replace_input_of(iff, 1, bol);
#ifndef PRODUCT
// report that the loop predication has been actually performed
// for this loop
if (TraceLoopLimitCheck) {
tty->print_cr("Counted Loop Limit Check generated:");
debug_only( bol->dump(2); )
}
#endif
}
Node* PhaseIdealLoop::loop_exit_control(Node* x, IdealLoopTree* loop) {
// Counted loop head must be a good RegionNode with only 3 not NULL
// control input edges: Self, Entry, LoopBack.
if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
return NULL;
}
Node *init_control = x->in(LoopNode::EntryControl);
Node *back_control = x->in(LoopNode::LoopBackControl);
if (init_control == NULL || back_control == NULL) { // Partially dead
return NULL;
}
// Must also check for TOP when looking for a dead loop
if (init_control->is_top() || back_control->is_top()) {
return NULL;
}
// Allow funny placement of Safepoint
if (back_control->Opcode() == Op_SafePoint) {
back_control = back_control->in(TypeFunc::Control);
}
// Controlling test for loop
Node *iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
if (iftrue_op != Op_IfTrue &&
iftrue_op != Op_IfFalse) {
// I have a weird back-control. Probably the loop-exit test is in
// the middle of the loop and I am looking at some trailing control-flow
// merge point. To fix this I would have to partially peel the loop.
return NULL; // Obscure back-control
}
// Get boolean guarding loop-back test
Node *iff = iftrue->in(0);
if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) {
return NULL;
}
return iftrue;
}
Node* PhaseIdealLoop::loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob) {
Node* iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
Node* iff = iftrue->in(0);
BoolNode* test = iff->in(1)->as_Bool();
bt = test->_test._test;
cl_prob = iff->as_If()->_prob;
if (iftrue_op == Op_IfFalse) {
bt = BoolTest(bt).negate();
cl_prob = 1.0 - cl_prob;
}
// Get backedge compare
Node* cmp = test->in(1);
if (!cmp->is_Cmp()) {
return NULL;
}
// Find the trip-counter increment & limit. Limit must be loop invariant.
incr = cmp->in(1);
limit = cmp->in(2);
// ---------
// need 'loop()' test to tell if limit is loop invariant
// ---------
if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
Node* tmp = incr; // Then reverse order into the CmpI
incr = limit;
limit = tmp;
bt = BoolTest(bt).commute(); // And commute the exit test
}
if (is_member(loop, get_ctrl(limit))) { // Limit must be loop-invariant
return NULL;
}
if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
return NULL;
}
return cmp;
}
Node* PhaseIdealLoop::loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr) {
if (incr->is_Phi()) {
if (incr->as_Phi()->region() != x || incr->req() != 3) {
return NULL; // Not simple trip counter expression
}
phi_incr = incr;
incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
return NULL;
}
}
return incr;
}
Node* PhaseIdealLoop::loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi) {
assert(incr->Opcode() == Op_AddI || incr->Opcode() == Op_AddL, "caller resp.");
// Get merge point
xphi = incr->in(1);
Node *stride = incr->in(2);
if (!stride->is_Con()) { // Oops, swap these
if (!xphi->is_Con()) { // Is the other guy a constant?
return NULL; // Nope, unknown stride, bail out
}
Node *tmp = xphi; // 'incr' is commutative, so ok to swap
xphi = stride;
stride = tmp;
}
return stride;
}
PhiNode* PhaseIdealLoop::loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop) {
if (!xphi->is_Phi()) {
return NULL; // Too much math on the trip counter
}
if (phi_incr != NULL && phi_incr != xphi) {
return NULL;
}
PhiNode *phi = xphi->as_Phi();
// Phi must be of loop header; backedge must wrap to increment
if (phi->region() != x) {
return NULL;
}
return phi;
}
// Return 0 if it won't overflow, -1 if it must overflow, and 1 otherwise.
static int check_stride_overflow(jint stride_con, const TypeInt* limit_t) {
if (stride_con > 0) {
if (limit_t->_lo > (max_jint - stride_con)) {
return -1;
}
if (limit_t->_hi > (max_jint - stride_con)) {
return 1;
}
} else {
if (limit_t->_hi < (min_jint - stride_con)) {
return -1;
}
if (limit_t->_lo < (min_jint - stride_con)) {
return 1;
}
}
return 0;
}
//------------------------------is_counted_loop--------------------------------
bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
PhaseGVN *gvn = &_igvn;
Node* back_control = loop_exit_control(x, loop);
if (back_control == NULL) {
return false;
}
BoolTest::mask bt = BoolTest::illegal;
float cl_prob = 0;
Node* incr = NULL;
Node* limit = NULL;
Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
if (cmp == NULL || cmp->Opcode() != Op_CmpI) {
return false; // Avoid pointer & float & 64-bit compares
}
// Trip-counter increment must be commutative & associative.
if (incr->Opcode() == Op_CastII) {
incr = incr->in(1);
}
Node* phi_incr = NULL;
incr = loop_iv_incr(incr, x, loop, phi_incr);
if (incr == NULL) {
return false;
}
Node* trunc1 = NULL;
Node* trunc2 = NULL;
const TypeInt* iv_trunc_t = NULL;
Node* orig_incr = incr;
if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
return false; // Funny increment opcode
}
assert(incr->Opcode() == Op_AddI, "wrong increment code");
Node* xphi = NULL;
Node* stride = loop_iv_stride(incr, loop, xphi);
if (stride == NULL) {
return false;
}
if (xphi->Opcode() == Op_CastII) {
xphi = xphi->in(1);
}
// Stride must be constant
int stride_con = stride->get_int();
assert(stride_con != 0, "missed some peephole opt");
PhiNode* phi = loop_iv_phi(xphi, phi_incr, x, loop);
if (phi == NULL ||
(trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
(trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
return false;
}
if (x->in(LoopNode::LoopBackControl)->Opcode() == Op_SafePoint &&
LoopStripMiningIter != 0) {
// Leaving the safepoint on the backedge and creating a
// CountedLoop will confuse optimizations. We can't move the
// safepoint around because its jvm state wouldn't match a new
// location. Give up on that loop.
return false;
}
Node* iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
Node* iff = iftrue->in(0);
BoolNode* test = iff->in(1)->as_Bool();
const TypeInt* limit_t = gvn->type(limit)->is_int();
if (trunc1 != NULL) {
// When there is a truncation, we must be sure that after the truncation
// the trip counter will end up higher than the limit, otherwise we are looking
// at an endless loop. Can happen with range checks.
// Example:
// int i = 0;
// while (true)
// sum + = array[i];
// i++;
// i = i && 0x7fff;
// }
//
// If the array is shorter than 0x8000 this exits through a AIOOB
// - Counted loop transformation is ok
// If the array is longer then this is an endless loop
// - No transformation can be done.
const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
if (limit_t->_hi > incr_t->_hi) {
// if the limit can have a higher value than the increment (before the phi)
return false;
}
}
Node *init_trip = phi->in(LoopNode::EntryControl);
// If iv trunc type is smaller than int, check for possible wrap.
if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
assert(trunc1 != NULL, "must have found some truncation");
// Get a better type for the phi (filtered thru if's)
const TypeInt* phi_ft = filtered_type(phi);
// Can iv take on a value that will wrap?
//
// Ensure iv's limit is not within "stride" of the wrap value.
//
// Example for "short" type
// Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
// If the stride is +10, then the last value of the induction
// variable before the increment (phi_ft->_hi) must be
// <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
// ensure no truncation occurs after the increment.
if (stride_con > 0) {
if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
iv_trunc_t->_lo > phi_ft->_lo) {
return false; // truncation may occur
}
} else if (stride_con < 0) {
if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
iv_trunc_t->_hi < phi_ft->_hi) {
return false; // truncation may occur
}
}
// No possibility of wrap so truncation can be discarded
// Promote iv type to Int
} else {
assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
}
// If the condition is inverted and we will be rolling
// through MININT to MAXINT, then bail out.
if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
// Odd stride
(bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
// Count down loop rolls through MAXINT
((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
// Count up loop rolls through MININT
((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
return false; // Bail out
}
const TypeInt* init_t = gvn->type(init_trip)->is_int();
if (stride_con > 0) {
jlong init_p = (jlong)init_t->_lo + stride_con;
if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
return false; // cyclic loop or this loop trips only once
} else {
jlong init_p = (jlong)init_t->_hi + stride_con;
if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
return false; // cyclic loop or this loop trips only once
}
if (phi_incr != NULL && bt != BoolTest::ne) {
// check if there is a possiblity of IV overflowing after the first increment
if (stride_con > 0) {
if (init_t->_hi > max_jint - stride_con) {
return false;
}
} else {
if (init_t->_lo < min_jint - stride_con) {
return false;
}
}
}
// =================================================
// ---- SUCCESS! Found A Trip-Counted Loop! -----
//
assert(x->Opcode() == Op_Loop, "regular loops only");
C->print_method(PHASE_BEFORE_CLOOPS, 3);
Node *hook = new Node(6);
// ===================================================
// Generate loop limit check to avoid integer overflow
// in cases like next (cyclic loops):
//
// for (i=0; i <= max_jint; i++) {}
// for (i=0; i < max_jint; i+=2) {}
//
//
// Limit check predicate depends on the loop test:
//
// for(;i != limit; i++) --> limit <= (max_jint)
// for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1)
// for(;i <= limit; i+=stride) --> limit <= (max_jint - stride )
//
// Check if limit is excluded to do more precise int overflow check.
bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
// If compare points directly to the phi we need to adjust
// the compare so that it points to the incr. Limit have
// to be adjusted to keep trip count the same and the
// adjusted limit should be checked for int overflow.
Node* adjusted_limit = limit;
if (phi_incr != NULL) {
stride_m += stride_con;
}
Node *init_control = x->in(LoopNode::EntryControl);
int sov = check_stride_overflow(stride_m, limit_t);
// If sov==0, limit's type always satisfies the condition, for
// example, when it is an array length.
if (sov != 0) {
if (sov < 0) {
return false; // Bailout: integer overflow is certain.
}
// Generate loop's limit check.
// Loop limit check predicate should be near the loop.
ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
if (!limit_check_proj) {
// The limit check predicate is not generated if this method trapped here before.
#ifdef ASSERT
if (TraceLoopLimitCheck) {
tty->print("missing loop limit check:");
loop->dump_head();
x->dump(1);
}
#endif
return false;
}
IfNode* check_iff = limit_check_proj->in(0)->as_If();
if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
return false;
}
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
bol = new BoolNode(cmp_limit, BoolTest::le);
} else {
cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
bol = new BoolNode(cmp_limit, BoolTest::ge);
}
insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
}
// Now we need to canonicalize loop condition.
if (bt == BoolTest::ne) {
assert(stride_con == 1 || stride_con == -1, "simple increment only");
if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
// 'ne' can be replaced with 'lt' only when init < limit.
bt = BoolTest::lt;
} else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
// 'ne' can be replaced with 'gt' only when init > limit.
bt = BoolTest::gt;
} else {
ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
if (!limit_check_proj) {
// The limit check predicate is not generated if this method trapped here before.
#ifdef ASSERT
if (TraceLoopLimitCheck) {
tty->print("missing loop limit check:");
loop->dump_head();
x->dump(1);
}
#endif
return false;
}
IfNode* check_iff = limit_check_proj->in(0)->as_If();
if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
!is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
return false;
}
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = new CmpINode(init_trip, limit);
bol = new BoolNode(cmp_limit, BoolTest::lt);
} else {
cmp_limit = new CmpINode(init_trip, limit);
bol = new BoolNode(cmp_limit, BoolTest::gt);
}
insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
if (stride_con > 0) {
// 'ne' can be replaced with 'lt' only when init < limit.
bt = BoolTest::lt;
} else if (stride_con < 0) {
// 'ne' can be replaced with 'gt' only when init > limit.
bt = BoolTest::gt;
}
}
}
if (phi_incr != NULL) {
// If compare points directly to the phi we need to adjust
// the compare so that it points to the incr. Limit have
// to be adjusted to keep trip count the same and we
// should avoid int overflow.
//
// i = init; do {} while(i++ < limit);
// is converted to
// i = init; do {} while(++i < limit+1);
//
adjusted_limit = gvn->transform(new AddINode(limit, stride));
}
if (incl_limit) {
// The limit check guaranties that 'limit <= (max_jint - stride)' so
// we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
//
Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
adjusted_limit = gvn->transform(new AddINode(adjusted_limit, one));
if (bt == BoolTest::le)
bt = BoolTest::lt;
else if (bt == BoolTest::ge)
bt = BoolTest::gt;
else
ShouldNotReachHere();
}
set_subtree_ctrl(adjusted_limit);
if (LoopStripMiningIter == 0) {
// Check for SafePoint on backedge and remove
Node *sfpt = x->in(LoopNode::LoopBackControl);
if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
lazy_replace( sfpt, iftrue );
if (loop->_safepts != NULL) {
loop->_safepts->yank(sfpt);
}
loop->_tail = iftrue;
}
}
// Build a canonical trip test.
// Clone code, as old values may be in use.
incr = incr->clone();
incr->set_req(1,phi);
incr->set_req(2,stride);
incr = _igvn.register_new_node_with_optimizer(incr);
set_early_ctrl( incr );
_igvn.rehash_node_delayed(phi);
phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
// If phi type is more restrictive than Int, raise to
// Int to prevent (almost) infinite recursion in igvn
// which can only handle integer types for constants or minint..maxint.
if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
nphi = _igvn.register_new_node_with_optimizer(nphi);
set_ctrl(nphi, get_ctrl(phi));
_igvn.replace_node(phi, nphi);
phi = nphi->as_Phi();
}
cmp = cmp->clone();
cmp->set_req(1,incr);
cmp->set_req(2, adjusted_limit);
cmp = _igvn.register_new_node_with_optimizer(cmp);
set_ctrl(cmp, iff->in(0));
test = test->clone()->as_Bool();
(*(BoolTest*)&test->_test)._test = bt;
test->set_req(1,cmp);
_igvn.register_new_node_with_optimizer(test);
set_ctrl(test, iff->in(0));
// Replace the old IfNode with a new LoopEndNode
Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
IfNode *le = lex->as_If();
uint dd = dom_depth(iff);
set_idom(le, le->in(0), dd); // Update dominance for loop exit
set_loop(le, loop);
// Get the loop-exit control
Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
// Need to swap loop-exit and loop-back control?
if (iftrue_op == Op_IfFalse) {
Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
loop->_tail = back_control = ift2;
set_loop(ift2, loop);
set_loop(iff2, get_loop(iffalse));
// Lazy update of 'get_ctrl' mechanism.
lazy_replace(iffalse, iff2);
lazy_replace(iftrue, ift2);
// Swap names
iffalse = iff2;
iftrue = ift2;
} else {
_igvn.rehash_node_delayed(iffalse);
_igvn.rehash_node_delayed(iftrue);
iffalse->set_req_X( 0, le, &_igvn );
iftrue ->set_req_X( 0, le, &_igvn );
}
set_idom(iftrue, le, dd+1);
set_idom(iffalse, le, dd+1);
assert(iff->outcnt() == 0, "should be dead now");
lazy_replace( iff, le ); // fix 'get_ctrl'
Node *sfpt2 = le->in(0);
Node* entry_control = init_control;
bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
IdealLoopTree* outer_ilt = NULL;
if (strip_mine_loop) {
outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
cl_prob, le->_fcnt, entry_control,
iffalse);
}
// Now setup a new CountedLoopNode to replace the existing LoopNode
CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
// The following assert is approximately true, and defines the intention
// of can_be_counted_loop. It fails, however, because phase->type
// is not yet initialized for this loop and its parts.
//assert(l->can_be_counted_loop(this), "sanity");
_igvn.register_new_node_with_optimizer(l);
set_loop(l, loop);
loop->_head = l;
// Fix all data nodes placed at the old loop head.
// Uses the lazy-update mechanism of 'get_ctrl'.
lazy_replace( x, l );
set_idom(l, entry_control, dom_depth(entry_control) + 1);
if (LoopStripMiningIter == 0 || strip_mine_loop) {
// Check for immediately preceding SafePoint and remove
if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
if (strip_mine_loop) {
Node* outer_le = outer_ilt->_tail->in(0);
Node* sfpt = sfpt2->clone();
sfpt->set_req(0, iffalse);
outer_le->set_req(0, sfpt);
// When this code runs, loop bodies have not yet been populated.
const bool body_populated = false;
register_control(sfpt, outer_ilt, iffalse, body_populated);
set_idom(outer_le, sfpt, dom_depth(sfpt));
}
lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
if (loop->_safepts != NULL) {
loop->_safepts->yank(sfpt2);
}
}
}
// Free up intermediate goo
_igvn.remove_dead_node(hook);
#ifdef ASSERT
assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
#endif
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Counted ");
loop->dump_head();
}
#endif
C->print_method(PHASE_AFTER_CLOOPS, 3);
// Capture bounds of the loop in the induction variable Phi before
// subsequent transformation (iteration splitting) obscures the
// bounds
l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
if (strip_mine_loop) {
l->mark_strip_mined();
l->verify_strip_mined(1);
outer_ilt->_head->as_Loop()->verify_strip_mined(1);
loop = outer_ilt;
}
return true;
}