Mercurial > hg > truffle
diff src/share/vm/opto/ifnode.cpp @ 0:a61af66fc99e jdk7-b24
Initial load
author | duke |
---|---|
date | Sat, 01 Dec 2007 00:00:00 +0000 |
parents | |
children | ff5961f4c095 |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/opto/ifnode.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,922 @@ +/* + * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +// Portions of code courtesy of Clifford Click + +// Optimization - Graph Style + +#include "incls/_precompiled.incl" +#include "incls/_ifnode.cpp.incl" + + +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 collaped 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()) && + 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 seperate 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; + for (uint ii = 1; ii < r->req(); ii++) { + if( phi->in(ii) == con1 ) { + req_c++; + } + } + Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1); + Node *phi_c = con1; + uint len = r->req(); + Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1); + 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) ); + } else { + region_x->init_req( i_x, r ->in(i) ); + phi_x ->init_req( i_x++, phi->in(i) ); + } + } + + // Register the new RegionNodes but do not transform them. Cannot + // transform until the entire Region/Phi conglerate has been hacked + // as a single huge transform. + igvn->register_new_node_with_optimizer( region_c ); + igvn->register_new_node_with_optimizer( region_x ); + phi_x = phase->transform( phi_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 (igvn->C, 4) Node(4); + hook->init_req(0, phi_x); + hook->init_req(1, phi_c); + + // 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 (igvn->C, 2) BoolNode(cmp_c,b->_test._test)); + Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test)); + // Make the IfNode + IfNode *iff_c = new (igvn->C, 2) 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 (igvn->C, 2) 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 (igvn->C, 1) IfTrueNode (iff_c)); + Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c)); + Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x)); + Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x)); + + // Merge the TRUE paths + Node *region_s = new (igvn->C, 3) 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 (igvn->C, 3) 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->hash_delete(v); // Have to fixup other Phi users + igvn->_worklist.push(v); + 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 ); + 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 ); + 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); + r->set_req_X(0,NULL,igvn); + + // 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 (igvn->C, 1) 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->is_Add()) { + 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 (gvn->C, 3) AddINode( index, new_add )) : index; + } + Node *new_cmp = (flip == 1) + ? new (gvn->C, 3) CmpUNode( new_add, range ) + : new (gvn->C, 3) 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 (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); + igvn->hash_delete( 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; + + // 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? +} + +//------------------------------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; + + // 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); + 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); + +//------------------------------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 ) { + Node *first_prev_dom = NULL; + + // 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 guarenteed to fail, so just start interpreting there. + // We 'expand' the top 2 range checks to include all post-dominating + // checks. + + // The top 2 range checks seen + Node *prev_chk1 = NULL; + Node *prev_chk2 = NULL; + // Low and high offsets seen so far + jint off_lo = offset1; + jint off_hi = offset1; + + // Scan for the top 2 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 ) { + // Gather expanded bounds + off_lo = MIN2(off_lo,offset2); + off_hi = MAX2(off_hi,offset2); + // Record top 2 range checks + prev_chk2 = prev_chk1; + prev_chk1 = prev_dom; + // If we match the test exactly, then the top test covers + // both our lower and upper bounds. + if( dom->in(1) == in(1) ) + prev_chk2 = prev_chk1; + } + } + prev_dom = dom; + dom = up_one_dom( dom ); + if( !dom ) break; + } + + + // 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 speculative enter the + // interpreter. If we see range-check deopt's, do not widen! + if (!phase->C->allow_range_check_smearing()) return NULL; + + // Constant indices only need to check the upper bound. + // Non-constance indices must check both low and high. + if( index1 ) { + // Didn't find 2 prior covering checks, so cannot remove anything. + if( !prev_chk2 ) return NULL; + // 'Widen' the offsets of the 1st and 2nd covering check + adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); + // Do not call adjust_check twice on the same projection + // as the first call may have transformed the BoolNode to a ConI + if( prev_chk1 != prev_chk2 ) { + adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); + } + // Test is now covered by prior checks, dominate it out + prev_dom = prev_chk2; + } else { + // Didn't find prior covering check, so cannot remove anything. + if( !prev_chk1 ) return NULL; + // 'Widen' the offset of the 1st and only covering check + adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); + // Test is now covered by prior checks, dominate it out + prev_dom = prev_chk1; + } + + + } 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? + + // 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 (phase->C, 1) 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 + + // 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 + igvn->hash_delete(s); // Yank from hash table before edge hacking + 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++ ) { } + s->set_req(l, ctrl_target); + } else { // Else, for control producers, + s->set_req(0, data_target); // Move child to data-target + } + igvn->_worklist.push(s); // Revisit collapsed Phis + } // 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 *IfTrueNode::Identity( PhaseTransform *phase ) { + // Can only optimize if cannot go the other way + const TypeTuple *t = phase->type(in(0))->is_tuple(); + return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) + ? in(0)->in(0) // IfNode control + : this; // no progress +} + +//------------------------------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 (phase->C, 2) 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 (phase->C, 2) 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 (phase->C, 1) IfFalseNode( iff )); + Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); + + igvn->register_new_node_with_optimizer(new_if_f); + igvn->register_new_node_with_optimizer(new_if_t); + igvn->hash_delete(old_if_f); + igvn->hash_delete(old_if_t); + // Flip test, so flip trailing control + igvn->subsume_node(old_if_f, new_if_t); + igvn->subsume_node(old_if_t, new_if_f); + + // Progress + return iff; +} + +//------------------------------Identity--------------------------------------- +// If the test is constant & we match, then we are the input Control +Node *IfFalseNode::Identity( PhaseTransform *phase ) { + // Can only optimize if cannot go the other way + const TypeTuple *t = phase->type(in(0))->is_tuple(); + return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) + ? in(0)->in(0) // IfNode control + : this; // no progress +}