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comparison src/share/vm/opto/loopTransform.cpp @ 20680:5b8e0f84f00f

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8054478: C2: Incorrectly compiled char[] array access crashes JVM Summary: dead backbranch in main loop results in erroneous array access Reviewed-by: kvn, iveresov
author roland
date Mon, 01 Dec 2014 22:27:00 +0100
parents 9e69e8d1c900
children 7848fc12602b
comparison
equal deleted inserted replaced
20678:97f4214e9a70 20680:5b8e0f84f00f
879 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); 879 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
880 } 880 }
881 return n; 881 return n;
882 } 882 }
883 883
884 bool PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
885 Node* castii = new (C) CastIINode(incr, TypeInt::INT, true);
886 castii->set_req(0, ctrl);
887 register_new_node(castii, ctrl);
888 for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
889 Node* n = incr->fast_out(i);
890 if (n->is_Phi() && n->in(0) == loop) {
891 int nrep = n->replace_edge(incr, castii);
892 return true;
893 }
894 }
895 return false;
896 }
897
884 //------------------------------insert_pre_post_loops-------------------------- 898 //------------------------------insert_pre_post_loops--------------------------
885 // Insert pre and post loops. If peel_only is set, the pre-loop can not have 899 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
886 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no 900 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
887 // alignment. Useful to unroll loops that do no array accesses. 901 // alignment. Useful to unroll loops that do no array accesses.
888 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { 902 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
1076 visited, clones); 1090 visited, clones);
1077 _igvn.hash_delete(main_phi); 1091 _igvn.hash_delete(main_phi);
1078 main_phi->set_req( LoopNode::EntryControl, fallpre ); 1092 main_phi->set_req( LoopNode::EntryControl, fallpre );
1079 } 1093 }
1080 } 1094 }
1095
1096 // Nodes inside the loop may be control dependent on a predicate
1097 // that was moved before the preloop. If the back branch of the main
1098 // or post loops becomes dead, those nodes won't be dependent on the
1099 // test that guards that loop nest anymore which could lead to an
1100 // incorrect array access because it executes independently of the
1101 // test that was guarding the loop nest. We add a special CastII on
1102 // the if branch that enters the loop, between the input induction
1103 // variable value and the induction variable Phi to preserve correct
1104 // dependencies.
1105
1106 // CastII for the post loop:
1107 bool inserted = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
1108 assert(inserted, "no castII inserted");
1109
1110 // CastII for the main loop:
1111 inserted = cast_incr_before_loop(pre_incr, min_taken, main_head);
1112 assert(inserted, "no castII inserted");
1081 1113
1082 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). 1114 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1083 // RCE and alignment may change this later. 1115 // RCE and alignment may change this later.
1084 Node *cmp_end = pre_end->cmp_node(); 1116 Node *cmp_end = pre_end->cmp_node();
1085 assert( cmp_end->in(2) == limit, "" ); 1117 assert( cmp_end->in(2) == limit, "" );