/* * Copyright (c) 2000, 2013, 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 "memory/allocation.inline.hpp" #include "opto/addnode.hpp" #include "opto/cfgnode.hpp" #include "opto/connode.hpp" #include "opto/loopnode.hpp" #include "opto/phaseX.hpp" #include "opto/runtime.hpp" #include "opto/subnode.hpp" // Portions of code courtesy of Clifford Click // Optimization - Graph Style extern int explicit_null_checks_elided; //============================================================================= //------------------------------Value------------------------------------------ // Return a tuple for whichever arm of the IF is reachable const Type *IfNode::Value( PhaseTransform *phase ) const { if( !in(0) ) return Type::TOP; if( phase->type(in(0)) == Type::TOP ) return Type::TOP; const Type *t = phase->type(in(1)); if( t == Type::TOP ) // data is undefined return TypeTuple::IFNEITHER; // unreachable altogether if( t == TypeInt::ZERO ) // zero, or false return TypeTuple::IFFALSE; // only false branch is reachable if( t == TypeInt::ONE ) // 1, or true return TypeTuple::IFTRUE; // only true branch is reachable assert( t == TypeInt::BOOL, "expected boolean type" ); return TypeTuple::IFBOTH; // No progress } const RegMask &IfNode::out_RegMask() const { return RegMask::Empty; } //------------------------------split_if--------------------------------------- // Look for places where we merge constants, then test on the merged value. // If the IF test will be constant folded on the path with the constant, we // win by splitting the IF to before the merge point. static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) { // I could be a lot more general here, but I'm trying to squeeze this // in before the Christmas '98 break so I'm gonna be kinda restrictive // on the patterns I accept. CNC // Look for a compare of a constant and a merged value Node *i1 = iff->in(1); if( !i1->is_Bool() ) return NULL; BoolNode *b = i1->as_Bool(); Node *cmp = b->in(1); if( !cmp->is_Cmp() ) return NULL; i1 = cmp->in(1); if( i1 == NULL || !i1->is_Phi() ) return NULL; PhiNode *phi = i1->as_Phi(); if( phi->is_copy() ) return NULL; Node *con2 = cmp->in(2); if( !con2->is_Con() ) return NULL; // See that the merge point contains some constants Node *con1=NULL; uint i4; for( i4 = 1; i4 < phi->req(); i4++ ) { con1 = phi->in(i4); if( !con1 ) return NULL; // Do not optimize partially collapsed merges if( con1->is_Con() ) break; // Found a constant // Also allow null-vs-not-null checks const TypePtr *tp = igvn->type(con1)->isa_ptr(); if( tp && tp->_ptr == TypePtr::NotNull ) break; } if( i4 >= phi->req() ) return NULL; // Found no constants igvn->C->set_has_split_ifs(true); // Has chance for split-if // Make sure that the compare can be constant folded away Node *cmp2 = cmp->clone(); cmp2->set_req(1,con1); cmp2->set_req(2,con2); const Type *t = cmp2->Value(igvn); // This compare is dead, so whack it! igvn->remove_dead_node(cmp2); if( !t->singleton() ) return NULL; // No intervening control, like a simple Call Node *r = iff->in(0); if( !r->is_Region() ) return NULL; if( phi->region() != r ) return NULL; // No other users of the cmp/bool if (b->outcnt() != 1 || cmp->outcnt() != 1) { //tty->print_cr("many users of cmp/bool"); return NULL; } // Make sure we can determine where all the uses of merged values go for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { Node* u = r->fast_out(j); if( u == r ) continue; if( u == iff ) continue; if( u->outcnt() == 0 ) continue; // use is dead & ignorable if( !u->is_Phi() ) { /* if( u->is_Start() ) { tty->print_cr("Region has inlined start use"); } else { tty->print_cr("Region has odd use"); u->dump(2); }*/ return NULL; } if( u != phi ) { // CNC - do not allow any other merged value //tty->print_cr("Merging another value"); //u->dump(2); return NULL; } // Make sure we can account for all Phi uses for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { Node* v = u->fast_out(k); // User of the phi // CNC - Allow only really simple patterns. // In particular I disallow AddP of the Phi, a fairly common pattern if (v == cmp) continue; // The compare is OK if (v->is_ConstraintCast()) { // If the cast is derived from data flow edges, it may not have a region. // If so, it should be save to split. But I'm not sure whether follow-up code // can deal with this. So skip. if (v->in(0) == NULL) { return NULL; } if (v->in(0)->in(0) == iff) { continue; // CastPP/II of the IfNode is OK } } // Disabled following code because I cannot tell if exactly one // path dominates without a real dominator check. CNC 9/9/1999 //uint vop = v->Opcode(); //if( vop == Op_Phi ) { // Phi from another merge point might be OK // Node *r = v->in(0); // Get controlling point // if( !r ) return NULL; // Degraded to a copy // // Find exactly one path in (either True or False doms, but not IFF) // int cnt = 0; // for( uint i = 1; i < r->req(); i++ ) // if( r->in(i) && r->in(i)->in(0) == iff ) // cnt++; // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi //} if( !v->is_Call() ) { /* if( v->Opcode() == Op_AddP ) { tty->print_cr("Phi has AddP use"); } else if( v->Opcode() == Op_CastPP ) { tty->print_cr("Phi has CastPP use"); } else if( v->Opcode() == Op_CastII ) { tty->print_cr("Phi has CastII use"); } else { tty->print_cr("Phi has use I cant be bothered with"); } */ } return NULL; /* CNC - Cut out all the fancy acceptance tests // Can we clone this use when doing the transformation? // If all uses are from Phis at this merge or constants, then YES. if( !v->in(0) && v != cmp ) { tty->print_cr("Phi has free-floating use"); v->dump(2); return NULL; } for( uint l = 1; l < v->req(); l++ ) { if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && !v->in(l)->is_Con() ) { tty->print_cr("Phi has use"); v->dump(2); return NULL; } // End of if Phi-use input is neither Phi nor Constant } // End of for all inputs to Phi-use */ } // End of for all uses of Phi } // End of for all uses of Region // Only do this if the IF node is in a sane state if (iff->outcnt() != 2) return NULL; // Got a hit! Do the Mondo Hack! // //ABC a1c def ghi B 1 e h A C a c d f g i // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi // cmp - 2 cmp - 2 cmp - 2 // bool bool_c bool_x // if if_c if_x // T F T F T F // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. // // Split the paths coming into the merge point into 2 separate groups of // merges. On the left will be all the paths feeding constants into the // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi // will fold up into a constant; this will let the Cmp fold up as well as // all the control flow. Below the original IF we have 2 control // dependent regions, 's' and 't'. Now we will merge the two paths // just prior to 's' and 't' from the two IFs. At least 1 path (and quite // likely 2 or more) will promptly constant fold away. PhaseGVN *phase = igvn; // Make a region merging constants and a region merging the rest uint req_c = 0; Node* predicate_proj = NULL; for (uint ii = 1; ii < r->req(); ii++) { if (phi->in(ii) == con1) { req_c++; } Node* proj = PhaseIdealLoop::find_predicate(r->in(ii)); if (proj != NULL) { assert(predicate_proj == NULL, "only one predicate entry expected"); predicate_proj = proj; } } Node* predicate_c = NULL; Node* predicate_x = NULL; bool counted_loop = r->is_CountedLoop(); Node *region_c = new RegionNode(req_c + 1); Node *phi_c = con1; uint len = r->req(); Node *region_x = new RegionNode(len - req_c); Node *phi_x = PhiNode::make_blank(region_x, phi); for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { if (phi->in(i) == con1) { region_c->init_req( i_c++, r ->in(i) ); if (r->in(i) == predicate_proj) predicate_c = predicate_proj; } else { region_x->init_req( i_x, r ->in(i) ); phi_x ->init_req( i_x++, phi->in(i) ); if (r->in(i) == predicate_proj) predicate_x = predicate_proj; } } if (predicate_c != NULL && (req_c > 1)) { assert(predicate_x == NULL, "only one predicate entry expected"); predicate_c = NULL; // Do not clone predicate below merge point } if (predicate_x != NULL && ((len - req_c) > 2)) { assert(predicate_c == NULL, "only one predicate entry expected"); predicate_x = NULL; // Do not clone predicate below merge point } // Register the new RegionNodes but do not transform them. Cannot // transform until the entire Region/Phi conglomerate has been hacked // as a single huge transform. igvn->register_new_node_with_optimizer( region_c ); igvn->register_new_node_with_optimizer( region_x ); // Prevent the untimely death of phi_x. Currently he has no uses. He is // about to get one. If this only use goes away, then phi_x will look dead. // However, he will be picking up some more uses down below. Node *hook = new Node(4); hook->init_req(0, phi_x); hook->init_req(1, phi_c); phi_x = phase->transform( phi_x ); // Make the compare Node *cmp_c = phase->makecon(t); Node *cmp_x = cmp->clone(); cmp_x->set_req(1,phi_x); cmp_x->set_req(2,con2); cmp_x = phase->transform(cmp_x); // Make the bool Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test)); Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test)); // Make the IfNode IfNode *iff_c = new IfNode(region_c,b_c,iff->_prob,iff->_fcnt); igvn->set_type_bottom(iff_c); igvn->_worklist.push(iff_c); hook->init_req(2, iff_c); IfNode *iff_x = new IfNode(region_x,b_x,iff->_prob, iff->_fcnt); igvn->set_type_bottom(iff_x); igvn->_worklist.push(iff_x); hook->init_req(3, iff_x); // Make the true/false arms Node *iff_c_t = phase->transform(new IfTrueNode (iff_c)); Node *iff_c_f = phase->transform(new IfFalseNode(iff_c)); if (predicate_c != NULL) { assert(predicate_x == NULL, "only one predicate entry expected"); // Clone loop predicates to each path iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop); iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop); } Node *iff_x_t = phase->transform(new IfTrueNode (iff_x)); Node *iff_x_f = phase->transform(new IfFalseNode(iff_x)); if (predicate_x != NULL) { assert(predicate_c == NULL, "only one predicate entry expected"); // Clone loop predicates to each path iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop); iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop); } // Merge the TRUE paths Node *region_s = new RegionNode(3); igvn->_worklist.push(region_s); region_s->init_req(1, iff_c_t); region_s->init_req(2, iff_x_t); igvn->register_new_node_with_optimizer( region_s ); // Merge the FALSE paths Node *region_f = new RegionNode(3); igvn->_worklist.push(region_f); region_f->init_req(1, iff_c_f); region_f->init_req(2, iff_x_f); igvn->register_new_node_with_optimizer( region_f ); igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead cmp->set_req(2,NULL); // Check for all uses of the Phi and give them a new home. // The 'cmp' got cloned, but CastPP/IIs need to be moved. Node *phi_s = NULL; // do not construct unless needed Node *phi_f = NULL; // do not construct unless needed for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { Node* v = phi->last_out(i2);// User of the phi igvn->rehash_node_delayed(v); // Have to fixup other Phi users uint vop = v->Opcode(); Node *proj = NULL; if( vop == Op_Phi ) { // Remote merge point Node *r = v->in(0); for (uint i3 = 1; i3 < r->req(); i3++) if (r->in(i3) && r->in(i3)->in(0) == iff) { proj = r->in(i3); break; } } else if( v->is_ConstraintCast() ) { proj = v->in(0); // Controlling projection } else { assert( 0, "do not know how to handle this guy" ); } Node *proj_path_data, *proj_path_ctrl; if( proj->Opcode() == Op_IfTrue ) { if( phi_s == NULL ) { // Only construct phi_s if needed, otherwise provides // interfering use. phi_s = PhiNode::make_blank(region_s,phi); phi_s->init_req( 1, phi_c ); phi_s->init_req( 2, phi_x ); hook->add_req(phi_s); phi_s = phase->transform(phi_s); } proj_path_data = phi_s; proj_path_ctrl = region_s; } else { if( phi_f == NULL ) { // Only construct phi_f if needed, otherwise provides // interfering use. phi_f = PhiNode::make_blank(region_f,phi); phi_f->init_req( 1, phi_c ); phi_f->init_req( 2, phi_x ); hook->add_req(phi_f); phi_f = phase->transform(phi_f); } proj_path_data = phi_f; proj_path_ctrl = region_f; } // Fixup 'v' for for the split if( vop == Op_Phi ) { // Remote merge point uint i; for( i = 1; i < v->req(); i++ ) if( v->in(i) == phi ) break; v->set_req(i, proj_path_data ); } else if( v->is_ConstraintCast() ) { v->set_req(0, proj_path_ctrl ); v->set_req(1, proj_path_data ); } else ShouldNotReachHere(); } // Now replace the original iff's True/False with region_s/region_t. // This makes the original iff go dead. for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { Node* p = iff->last_out(i3); assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; // Replace p with u igvn->add_users_to_worklist(p); for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { Node* x = p->last_out(l); igvn->hash_delete(x); uint uses_found = 0; for( uint j = 0; j < x->req(); j++ ) { if( x->in(j) == p ) { x->set_req(j, u); uses_found++; } } l -= uses_found; // we deleted 1 or more copies of this edge } igvn->remove_dead_node(p); } // Force the original merge dead igvn->hash_delete(r); // First, remove region's dead users. for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) { Node* u = r->last_out(l); if( u == r ) { r->set_req(0, NULL); } else { assert(u->outcnt() == 0, "only dead users"); igvn->remove_dead_node(u); } l -= 1; } igvn->remove_dead_node(r); // Now remove the bogus extra edges used to keep things alive igvn->remove_dead_node( hook ); // Must return either the original node (now dead) or a new node // (Do not return a top here, since that would break the uniqueness of top.) return new ConINode(TypeInt::ZERO); } //------------------------------is_range_check--------------------------------- // Return 0 if not a range check. Return 1 if a range check and set index and // offset. Return 2 if we had to negate the test. Index is NULL if the check // is versus a constant. int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { Node* b = in(1); if (b == NULL || !b->is_Bool()) return 0; BoolNode* bn = b->as_Bool(); Node* cmp = bn->in(1); if (cmp == NULL) return 0; if (cmp->Opcode() != Op_CmpU) return 0; Node* l = cmp->in(1); Node* r = cmp->in(2); int flip_test = 1; if (bn->_test._test == BoolTest::le) { l = cmp->in(2); r = cmp->in(1); flip_test = 2; } else if (bn->_test._test != BoolTest::lt) { return 0; } if (l->is_top()) return 0; // Top input means dead test if (r->Opcode() != Op_LoadRange) return 0; // We have recognized one of these forms: // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... // Make sure it's a real range check by requiring an uncommon trap // along the OOB path. Otherwise, it's possible that the user wrote // something which optimized to look like a range check but behaves // in some other way. Node* iftrap = proj_out(flip_test == 2 ? true : false); bool found_trap = false; if (iftrap != NULL) { Node* u = iftrap->unique_ctrl_out(); if (u != NULL) { // It could be a merge point (Region) for uncommon trap. if (u->is_Region()) { Node* c = u->unique_ctrl_out(); if (c != NULL) { iftrap = u; u = c; } } if (u->in(0) == iftrap && u->is_CallStaticJava()) { int req = u->as_CallStaticJava()->uncommon_trap_request(); if (Deoptimization::trap_request_reason(req) == Deoptimization::Reason_range_check) { found_trap = true; } } } } if (!found_trap) return 0; // sorry, no cigar // Look for index+offset form Node* ind = l; jint off = 0; if (l->is_top()) { return 0; } else if (l->Opcode() == Op_AddI) { if ((off = l->in(1)->find_int_con(0)) != 0) { ind = l->in(2); } else if ((off = l->in(2)->find_int_con(0)) != 0) { ind = l->in(1); } } else if ((off = l->find_int_con(-1)) >= 0) { // constant offset with no variable index ind = NULL; } else { // variable index with no constant offset (or dead negative index) off = 0; } // Return all the values: index = ind; offset = off; range = r; return flip_test; } //------------------------------adjust_check----------------------------------- // Adjust (widen) a prior range check static void adjust_check(Node* proj, Node* range, Node* index, int flip, jint off_lo, PhaseIterGVN* igvn) { PhaseGVN *gvn = igvn; // Break apart the old check Node *iff = proj->in(0); Node *bol = iff->in(1); if( bol->is_top() ) return; // In case a partially dead range check appears // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) if( !bol->is_Bool() ) return; Node *cmp = bol->in(1); // Compute a new check Node *new_add = gvn->intcon(off_lo); if( index ) { new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index; } Node *new_cmp = (flip == 1) ? new CmpUNode( new_add, range ) : new CmpUNode( range, new_add ); new_cmp = gvn->transform(new_cmp); // See if no need to adjust the existing check if( new_cmp == cmp ) return; // Else, adjust existing check Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); igvn->rehash_node_delayed( iff ); iff->set_req_X( 1, new_bol, igvn ); } //------------------------------up_one_dom------------------------------------- // Walk up the dominator tree one step. Return NULL at root or true // complex merges. Skips through small diamonds. Node* IfNode::up_one_dom(Node *curr, bool linear_only) { Node *dom = curr->in(0); if( !dom ) // Found a Region degraded to a copy? return curr->nonnull_req(); // Skip thru it if( curr != dom ) // Normal walk up one step? return dom; // Use linear_only if we are still parsing, since we cannot // trust the regions to be fully filled in. if (linear_only) return NULL; if( dom->is_Root() ) return NULL; // Else hit a Region. Check for a loop header if( dom->is_Loop() ) return dom->in(1); // Skip up thru loops // Check for small diamonds Node *din1, *din2, *din3, *din4; if( dom->req() == 3 && // 2-path merge point (din1 = dom ->in(1)) && // Left path exists (din2 = dom ->in(2)) && // Right path exists (din3 = din1->in(0)) && // Left path up one (din4 = din2->in(0)) ) { // Right path up one if( din3->is_Call() && // Handle a slow-path call on either arm (din3 = din3->in(0)) ) din3 = din3->in(0); if( din4->is_Call() && // Handle a slow-path call on either arm (din4 = din4->in(0)) ) din4 = din4->in(0); if( din3 == din4 && din3->is_If() ) return din3; // Skip around diamonds } // Give up the search at true merges return NULL; // Dead loop? Or hit root? } //------------------------------filtered_int_type-------------------------------- // Return a possibly more restrictive type for val based on condition control flow for an if const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) { assert(if_proj && (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection"); if (if_proj->in(0) && if_proj->in(0)->is_If()) { IfNode* iff = if_proj->in(0)->as_If(); if (iff->in(1) && iff->in(1)->is_Bool()) { BoolNode* bol = iff->in(1)->as_Bool(); if (bol->in(1) && bol->in(1)->is_Cmp()) { const CmpNode* cmp = bol->in(1)->as_Cmp(); if (cmp->in(1) == val) { const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int(); if (cmp2_t != NULL) { jint lo = cmp2_t->_lo; jint hi = cmp2_t->_hi; BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate(); switch (msk) { case BoolTest::ne: // Can't refine type return NULL; case BoolTest::eq: return cmp2_t; case BoolTest::lt: lo = TypeInt::INT->_lo; if (hi - 1 < hi) { hi = hi - 1; } break; case BoolTest::le: lo = TypeInt::INT->_lo; break; case BoolTest::gt: if (lo + 1 > lo) { lo = lo + 1; } hi = TypeInt::INT->_hi; break; case BoolTest::ge: // lo unchanged hi = TypeInt::INT->_hi; break; } const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen); return rtn_t; } } } } } return NULL; } //------------------------------fold_compares---------------------------- // See if a pair of CmpIs can be converted into a CmpU. In some cases // the direction of this if is determined by the preceding if so it // can be eliminate entirely. Given an if testing (CmpI n c) check // for an immediately control dependent if that is testing (CmpI n c2) // and has one projection leading to this if and the other projection // leading to a region that merges one of this ifs control // projections. // // If // / | // / | // / | // If | // /\ | // / \ | // / \ | // / Region // Node* IfNode::fold_compares(PhaseGVN* phase) { if (Opcode() != Op_If) return NULL; Node* this_cmp = in(1)->in(1); if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI && this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) { Node* ctrl = in(0); BoolNode* this_bool = in(1)->as_Bool(); Node* n = this_cmp->in(1); int hi = this_cmp->in(2)->get_int(); if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 && ctrl->in(0)->is_If() && ctrl->in(0)->outcnt() == 2 && ctrl->in(0)->in(1)->is_Bool() && ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI && ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() && ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() && ctrl->in(0)->in(1)->in(1)->in(1) == n) { IfNode* dom_iff = ctrl->in(0)->as_If(); Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con); if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() && this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) { // Identify which proj goes to the region and which continues on RegionNode* region = otherproj->unique_out()->as_Region(); Node* success = NULL; Node* fail = NULL; for (int i = 0; i < 2; i++) { Node* proj = proj_out(i); if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) { success = proj; } else if (fail == NULL) { fail = proj; } else { success = fail = NULL; } } if (success != NULL && fail != NULL && !region->has_phi()) { int lo = dom_iff->in(1)->in(1)->in(2)->get_int(); BoolNode* dom_bool = dom_iff->in(1)->as_Bool(); Node* dom_cmp = dom_bool->in(1); const TypeInt* failtype = filtered_int_type(phase, n, ctrl); if (failtype != NULL) { const TypeInt* type2 = filtered_int_type(phase, n, fail); if (type2 != NULL) { failtype = failtype->join(type2)->is_int(); } else { failtype = NULL; } } if (failtype != NULL && dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) { int bound = failtype->_hi - failtype->_lo + 1; if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) { // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi) BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge; Node* adjusted = phase->transform(new SubINode(n, phase->intcon(failtype->_lo))); Node* newcmp = phase->transform(new CmpUNode(adjusted, phase->intcon(bound))); Node* newbool = phase->transform(new BoolNode(newcmp, cond)); phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con)); phase->hash_delete(this); set_req(1, newbool); return this; } if (failtype->_lo > failtype->_hi) { // previous if determines the result of this if so // replace Bool with constant phase->hash_delete(this); set_req(1, phase->intcon(success->as_Proj()->_con)); return this; } } } } } } return NULL; } //------------------------------remove_useless_bool---------------------------- // Check for people making a useless boolean: things like // if( (x < y ? true : false) ) { ... } // Replace with if( x < y ) { ... } static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { Node *i1 = iff->in(1); if( !i1->is_Bool() ) return NULL; BoolNode *bol = i1->as_Bool(); Node *cmp = bol->in(1); if( cmp->Opcode() != Op_CmpI ) return NULL; // Must be comparing against a bool const Type *cmp2_t = phase->type( cmp->in(2) ); if( cmp2_t != TypeInt::ZERO && cmp2_t != TypeInt::ONE ) return NULL; // Find a prior merge point merging the boolean i1 = cmp->in(1); if( !i1->is_Phi() ) return NULL; PhiNode *phi = i1->as_Phi(); if( phase->type( phi ) != TypeInt::BOOL ) return NULL; // Check for diamond pattern int true_path = phi->is_diamond_phi(); if( true_path == 0 ) return NULL; // Make sure that iff and the control of the phi are different. This // should really only happen for dead control flow since it requires // an illegal cycle. if (phi->in(0)->in(1)->in(0) == iff) return NULL; // phi->region->if_proj->ifnode->bool->cmp BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); // Now get the 'sense' of the test correct so we can plug in // either iff2->in(1) or its complement. int flip = 0; if( bol->_test._test == BoolTest::ne ) flip = 1-flip; else if( bol->_test._test != BoolTest::eq ) return NULL; if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; const Type *phi1_t = phase->type( phi->in(1) ); const Type *phi2_t = phase->type( phi->in(2) ); // Check for Phi(0,1) and flip if( phi1_t == TypeInt::ZERO ) { if( phi2_t != TypeInt::ONE ) return NULL; flip = 1-flip; } else { // Check for Phi(1,0) if( phi1_t != TypeInt::ONE ) return NULL; if( phi2_t != TypeInt::ZERO ) return NULL; } if( true_path == 2 ) { flip = 1-flip; } Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); assert(new_bol != iff->in(1), "must make progress"); iff->set_req(1, new_bol); // Intervening diamond probably goes dead phase->C->set_major_progress(); return iff; } static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); struct RangeCheck { Node* ctl; jint off; }; //------------------------------Ideal------------------------------------------ // Return a node which is more "ideal" than the current node. Strip out // control copies Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { if (remove_dead_region(phase, can_reshape)) return this; // No Def-Use info? if (!can_reshape) return NULL; PhaseIterGVN *igvn = phase->is_IterGVN(); // Don't bother trying to transform a dead if if (in(0)->is_top()) return NULL; // Don't bother trying to transform an if with a dead test if (in(1)->is_top()) return NULL; // Another variation of a dead test if (in(1)->is_Con()) return NULL; // Another variation of a dead if if (outcnt() < 2) return NULL; // Canonicalize the test. Node* idt_if = idealize_test(phase, this); if (idt_if != NULL) return idt_if; // Try to split the IF Node *s = split_if(this, igvn); if (s != NULL) return s; // Check for people making a useless boolean: things like // if( (x < y ? true : false) ) { ... } // Replace with if( x < y ) { ... } Node *bol2 = remove_useless_bool(this, phase); if( bol2 ) return bol2; // Setup to scan up the CFG looking for a dominating test Node *dom = in(0); Node *prev_dom = this; // Check for range-check vs other kinds of tests Node *index1, *range1; jint offset1; int flip1 = is_range_check(range1, index1, offset1); if( flip1 ) { // Try to remove extra range checks. All 'up_one_dom' gives up at merges // so all checks we inspect post-dominate the top-most check we find. // If we are going to fail the current check and we reach the top check // then we are guaranteed to fail, so just start interpreting there. // We 'expand' the top 3 range checks to include all post-dominating // checks. // The top 3 range checks seen const int NRC =3; RangeCheck prev_checks[NRC]; int nb_checks = 0; // Low and high offsets seen so far jint off_lo = offset1; jint off_hi = offset1; bool found_immediate_dominator = false; // Scan for the top checks and collect range of offsets for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit if (dom->Opcode() == Op_If && // Not same opcode? prev_dom->in(0) == dom) { // One path of test does dominate? if (dom == this) return NULL; // dead loop // See if this is a range check Node *index2, *range2; jint offset2; int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); // See if this is a _matching_ range check, checking against // the same array bounds. if (flip2 == flip1 && range2 == range1 && index2 == index1 && dom->outcnt() == 2) { if (nb_checks == 0 && dom->in(1) == in(1)) { // Found an immediately dominating test at the same offset. // This kind of back-to-back test can be eliminated locally, // and there is no need to search further for dominating tests. assert(offset2 == offset1, "Same test but different offsets"); found_immediate_dominator = true; break; } // Gather expanded bounds off_lo = MIN2(off_lo,offset2); off_hi = MAX2(off_hi,offset2); // Record top NRC range checks prev_checks[nb_checks%NRC].ctl = prev_dom; prev_checks[nb_checks%NRC].off = offset2; nb_checks++; } } prev_dom = dom; dom = up_one_dom(dom); if (!dom) break; } if (!found_immediate_dominator) { // Attempt to widen the dominating range check to cover some later // ones. Since range checks "fail" by uncommon-trapping to the // interpreter, widening a check can make us speculatively enter // the interpreter. If we see range-check deopt's, do not widen! if (!phase->C->allow_range_check_smearing()) return NULL; // Didn't find prior covering check, so cannot remove anything. if (nb_checks == 0) { return NULL; } // Constant indices only need to check the upper bound. // Non-constant indices must check both low and high. int chk0 = (nb_checks - 1) % NRC; if (index1) { if (nb_checks == 1) { return NULL; } else { // If the top range check's constant is the min or max of // all constants we widen the next one to cover the whole // range of constants. RangeCheck rc0 = prev_checks[chk0]; int chk1 = (nb_checks - 2) % NRC; RangeCheck rc1 = prev_checks[chk1]; if (rc0.off == off_lo) { adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); prev_dom = rc1.ctl; } else if (rc0.off == off_hi) { adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); prev_dom = rc1.ctl; } else { // If the top test's constant is not the min or max of all // constants, we need 3 range checks. We must leave the // top test unchanged because widening it would allow the // accesses it protects to successfully read/write out of // bounds. if (nb_checks == 2) { return NULL; } int chk2 = (nb_checks - 3) % NRC; RangeCheck rc2 = prev_checks[chk2]; // The top range check a+i covers interval: -a <= i < length-a // The second range check b+i covers interval: -b <= i < length-b if (rc1.off <= rc0.off) { // if b <= a, we change the second range check to: // -min_of_all_constants <= i < length-min_of_all_constants // Together top and second range checks now cover: // -min_of_all_constants <= i < length-a // which is more restrictive than -b <= i < length-b: // -b <= -min_of_all_constants <= i < length-a <= length-b // The third check is then changed to: // -max_of_all_constants <= i < length-max_of_all_constants // so 2nd and 3rd checks restrict allowed values of i to: // -min_of_all_constants <= i < length-max_of_all_constants adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn); adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn); } else { // if b > a, we change the second range check to: // -max_of_all_constants <= i < length-max_of_all_constants // Together top and second range checks now cover: // -a <= i < length-max_of_all_constants // which is more restrictive than -b <= i < length-b: // -b < -a <= i < length-max_of_all_constants <= length-b // The third check is then changed to: // -max_of_all_constants <= i < length-max_of_all_constants // so 2nd and 3rd checks restrict allowed values of i to: // -min_of_all_constants <= i < length-max_of_all_constants adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn); adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn); } prev_dom = rc2.ctl; } } } else { RangeCheck rc0 = prev_checks[chk0]; // 'Widen' the offset of the 1st and only covering check adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn); // Test is now covered by prior checks, dominate it out prev_dom = rc0.ctl; } } } else { // Scan for an equivalent test Node *cmp; int dist = 0; // Cutoff limit for search int op = Opcode(); if( op == Op_If && (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { if( cmp->in(2) != NULL && // make sure cmp is not already dead cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { dist = 64; // Limit for null-pointer scans } else { dist = 4; // Do not bother for random pointer tests } } else { dist = 4; // Limit for random junky scans } // Normal equivalent-test check. if( !dom ) return NULL; // Dead loop? Node* result = fold_compares(phase); if (result != NULL) { return result; } // Search up the dominator tree for an If with an identical test while( dom->Opcode() != op || // Not same opcode? dom->in(1) != in(1) || // Not same input 1? (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? prev_dom->in(0) != dom ) { // One path of test does not dominate? if( dist < 0 ) return NULL; dist--; prev_dom = dom; dom = up_one_dom( dom ); if( !dom ) return NULL; } // Check that we did not follow a loop back to ourselves if( this == dom ) return NULL; if( dist > 2 ) // Add to count of NULL checks elided explicit_null_checks_elided++; } // End of Else scan for an equivalent test // Hit! Remove this IF #ifndef PRODUCT if( TraceIterativeGVN ) { tty->print(" Removing IfNode: "); this->dump(); } if( VerifyOpto && !phase->allow_progress() ) { // Found an equivalent dominating test, // we can not guarantee reaching a fix-point for these during iterativeGVN // since intervening nodes may not change. return NULL; } #endif // Replace dominated IfNode dominated_by( prev_dom, igvn ); // Must return either the original node (now dead) or a new node // (Do not return a top here, since that would break the uniqueness of top.) return new ConINode(TypeInt::ZERO); } //------------------------------dominated_by----------------------------------- void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { igvn->hash_delete(this); // Remove self to prevent spurious V-N Node *idom = in(0); // Need opcode to decide which way 'this' test goes int prev_op = prev_dom->Opcode(); Node *top = igvn->C->top(); // Shortcut to top // Loop predicates may have depending checks which should not // be skipped. For example, range check predicate has two checks // for lower and upper bounds. ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj(); if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate)) prev_dom = idom; // Now walk the current IfNode's projections. // Loop ends when 'this' has no more uses. for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { Node *ifp = last_out(i); // Get IfTrue/IfFalse igvn->add_users_to_worklist(ifp); // Check which projection it is and set target. // Data-target is either the dominating projection of the same type // or TOP if the dominating projection is of opposite type. // Data-target will be used as the new control edge for the non-CFG // nodes like Casts and Loads. Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top; // Control-target is just the If's immediate dominator or TOP. Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top; // For each child of an IfTrue/IfFalse projection, reroute. // Loop ends when projection has no more uses. for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse if( !s->depends_only_on_test() ) { // Find the control input matching this def-use edge. // For Regions it may not be in slot 0. uint l; for( l = 0; s->in(l) != ifp; l++ ) { } igvn->replace_input_of(s, l, ctrl_target); } else { // Else, for control producers, igvn->replace_input_of(s, 0, data_target); // Move child to data-target } } // End for each child of a projection igvn->remove_dead_node(ifp); } // End for each IfTrue/IfFalse child of If // Kill the IfNode igvn->remove_dead_node(this); } //------------------------------Identity--------------------------------------- // If the test is constant & we match, then we are the input Control Node *IfProjNode::Identity(PhaseTransform *phase) { // Can only optimize if cannot go the other way const TypeTuple *t = phase->type(in(0))->is_tuple(); if (t == TypeTuple::IFNEITHER || // kill dead branch first otherwise the IfNode's control will // have 2 control uses (the IfNode that doesn't go away because // it still has uses and this branch of the // If). Node::has_special_unique_user() will cause this node to // be reprocessed once the dead branch is killed. (always_taken(t) && in(0)->outcnt() == 1)) { // IfNode control return in(0)->in(0); } // no progress return this; } //------------------------------dump_spec-------------------------------------- #ifndef PRODUCT void IfNode::dump_spec(outputStream *st) const { st->print("P=%f, C=%f",_prob,_fcnt); } #endif //------------------------------idealize_test---------------------------------- // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as // needed. static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { assert(iff->in(0) != NULL, "If must be live"); if (iff->outcnt() != 2) return NULL; // Malformed projections. Node* old_if_f = iff->proj_out(false); Node* old_if_t = iff->proj_out(true); // CountedLoopEnds want the back-control test to be TRUE, irregardless of // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition // happens in count-down loops if (iff->is_CountedLoopEnd()) return NULL; if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests BoolNode *b = iff->in(1)->as_Bool(); BoolTest bt = b->_test; // Test already in good order? if( bt.is_canonical() ) return NULL; // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and // cloning the IfNode. Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) ); if( !new_b->is_Bool() ) return NULL; b = new_b->as_Bool(); PhaseIterGVN *igvn = phase->is_IterGVN(); assert( igvn, "Test is not canonical in parser?" ); // The IF node never really changes, but it needs to be cloned iff = new IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); Node *prior = igvn->hash_find_insert(iff); if( prior ) { igvn->remove_dead_node(iff); iff = (IfNode*)prior; } else { // Cannot call transform on it just yet igvn->set_type_bottom(iff); } igvn->_worklist.push(iff); // Now handle projections. Cloning not required. Node* new_if_f = (Node*)(new IfFalseNode( iff )); Node* new_if_t = (Node*)(new IfTrueNode ( iff )); igvn->register_new_node_with_optimizer(new_if_f); igvn->register_new_node_with_optimizer(new_if_t); // Flip test, so flip trailing control igvn->replace_node(old_if_f, new_if_t); igvn->replace_node(old_if_t, new_if_f); // Progress return iff; }