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7044738: Loop unroll optimization causes incorrect result

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Take into account memory dependencies when clonning nodes in clone_up_backedge_goo().

Reviewed-by: never
This commit is contained in:
Vladimir Kozlov 2011-06-28 15:24:29 -07:00
parent 565f8579ac
commit b3505a88a4
7 changed files with 211 additions and 13 deletions
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30
hotspot/src/share/vm/opto/loopTransform.cpp
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@ -824,13 +824,23 @@ bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
//------------------------------clone_up_backedge_goo--------------------------
// If Node n lives in the back_ctrl block and cannot float, we clone a private
// version of n in preheader_ctrl block and return that, otherwise return n.
Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
if( get_ctrl(n) != back_ctrl ) return n;
// Only visit once
if (visited.test_set(n->_idx)) {
Node *x = clones.find(n->_idx);
if (x != NULL)
return x;
return n;
}
Node *x = NULL; // If required, a clone of 'n'
// Check for 'n' being pinned in the backedge.
if( n->in(0) && n->in(0) == back_ctrl ) {
assert(clones.find(n->_idx) == NULL, "dead loop");
x = n->clone(); // Clone a copy of 'n' to preheader
clones.push(x, n->_idx);
x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
}
@ -838,10 +848,13 @@ Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ct
// If there are no changes we can just return 'n', otherwise
// we need to clone a private copy and change it.
for( uint i = 1; i < n->req(); i++ ) {
Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
if( g != n->in(i) ) {
if( !x )
if( !x ) {
assert(clones.find(n->_idx) == NULL, "dead loop");
x = n->clone();
clones.push(x, n->_idx);
}
x->set_req(i, g);
}
}
@ -960,6 +973,9 @@ void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_
post_head->set_req(LoopNode::EntryControl, zer_taken);
set_idom(post_head, zer_taken, dd_main_exit);
Arena *a = Thread::current()->resource_area();
VectorSet visited(a);
Node_Stack clones(a, main_head->back_control()->outcnt());
// Step A3: Make the fall-in values to the post-loop come from the
// fall-out values of the main-loop.
for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
@ -968,7 +984,8 @@ void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_
Node *post_phi = old_new[main_phi->_idx];
Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
post_head->init_control(),
main_phi->in(LoopNode::LoopBackControl));
main_phi->in(LoopNode::LoopBackControl),
visited, clones);
_igvn.hash_delete(post_phi);
post_phi->set_req( LoopNode::EntryControl, fallmain );
}
@ -1032,6 +1049,8 @@ void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_
main_head->set_req(LoopNode::EntryControl, min_taken);
set_idom(main_head, min_taken, dd_main_head);
visited.Clear();
clones.clear();
// Step B3: Make the fall-in values to the main-loop come from the
// fall-out values of the pre-loop.
for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
@ -1040,7 +1059,8 @@ void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_
Node *pre_phi = old_new[main_phi->_idx];
Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
main_head->init_control(),
pre_phi->in(LoopNode::LoopBackControl));
pre_phi->in(LoopNode::LoopBackControl),
visited, clones);
_igvn.hash_delete(main_phi);
main_phi->set_req( LoopNode::EntryControl, fallpre );
}