diff -r 18fd6d87f16f -r bf9503046dd4 src/share/vm/opto/loopTransform.cpp --- a/src/share/vm/opto/loopTransform.cpp Fri Sep 28 14:24:22 2018 +0200 +++ b/src/share/vm/opto/loopTransform.cpp Fri Dec 14 11:22:26 2018 +0100 @@ -1537,13 +1537,20 @@ //------------------------------adjust_limit----------------------------------- // Helper function for add_constraint(). -Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) { +Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl, bool round_up) { // Compute "I :: (limit-offset)/scale" Node *con = new (C) SubINode(rc_limit, offset); register_new_node(con, pre_ctrl); Node *X = new (C) DivINode(0, con, scale); register_new_node(X, pre_ctrl); + // When the absolute value of scale is greater than one, the integer + // division may round limit down so add one to the limit. + if (round_up) { + X = new (C) AddINode(X, _igvn.intcon(1)); + register_new_node(X, pre_ctrl); + } + // Adjust loop limit loop_limit = (stride_con > 0) ? (Node*)(new (C) MinINode(loop_limit, X)) @@ -1584,7 +1591,7 @@ // (upper_limit-offset) may overflow or underflow. // But it is fine since main loop will either have // less iterations or will be skipped in such case. - *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl); + *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl, false); // The underflow limit: low_limit <= scale*I+offset. // For pre-loop compute @@ -1620,7 +1627,8 @@ // max(pre_limit, original_limit) is used in do_range_check(). } // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); - *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl); + *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl, + scale_con > 1 && stride_con > 0); } else { // stride_con*scale_con < 0 // For negative stride*scale pre-loop checks for overflow and @@ -1646,7 +1654,8 @@ Node *plus_one = new (C) AddINode(offset, one); register_new_node( plus_one, pre_ctrl ); // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond); - *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl); + *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl, + scale_con < -1 && stride_con > 0); if (low_limit->get_int() == -max_jint) { if (!RangeLimitCheck) return; @@ -1681,7 +1690,8 @@ // I > (low_limit-(offset+1))/scale // ) - *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl); + *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl, + false); } }