--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/opto/split_if.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,536 @@
+/*
+ * Copyright 1999-2006 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.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_split_if.cpp.incl"
+
+
+//------------------------------split_thru_region------------------------------
+// Split Node 'n' through merge point.
+Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
+ uint wins = 0;
+ assert( n->is_CFG(), "" );
+ assert( region->is_Region(), "" );
+ Node *r = new (C, region->req()) RegionNode( region->req() );
+ IdealLoopTree *loop = get_loop( n );
+ for( uint i = 1; i < region->req(); i++ ) {
+ Node *x = n->clone();
+ Node *in0 = n->in(0);
+ if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
+ for( uint j = 1; j < n->req(); j++ ) {
+ Node *in = n->in(j);
+ if( get_ctrl(in) == region )
+ x->set_req( j, in->in(i) );
+ }
+ _igvn.register_new_node_with_optimizer(x);
+ set_loop(x, loop);
+ set_idom(x, x->in(0), dom_depth(x->in(0))+1);
+ r->init_req(i, x);
+ }
+
+ // Record region
+ r->set_req(0,region); // Not a TRUE RegionNode
+ _igvn.register_new_node_with_optimizer(r);
+ set_loop(r, loop);
+ if( !loop->_child )
+ loop->_body.push(r);
+ return r;
+}
+
+//------------------------------split_up---------------------------------------
+// Split block-local op up through the phis to empty the current block
+bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
+ if( n->is_CFG() ) {
+ assert( n->in(0) != blk1, "Lousy candidate for split-if" );
+ return false;
+ }
+ if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
+ return false; // Not block local
+ if( n->is_Phi() ) return false; // Local PHIs are expected
+
+ // Recursively split-up inputs
+ for (uint i = 1; i < n->req(); i++) {
+ if( split_up( n->in(i), blk1, blk2 ) ) {
+ // Got split recursively and self went dead?
+ if (n->outcnt() == 0)
+ _igvn.remove_dead_node(n);
+ return true;
+ }
+ }
+
+ // Check for needing to clone-up a compare. Can't do that, it forces
+ // another (nested) split-if transform. Instead, clone it "down".
+ if( n->is_Cmp() ) {
+ assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
+ // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
+ // sequence can have no other users and it must all reside in the split-if
+ // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
+ // private, per-use versions of the Cmp and Bool are made. These sink to
+ // the CMove block. If the CMove is in the split-if block, then in the
+ // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
+ Node *bol, *cmov;
+ if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
+ (bol = n->unique_out()->as_Bool()) &&
+ (get_ctrl(bol) == blk1 ||
+ get_ctrl(bol) == blk2) &&
+ bol->outcnt() == 1 &&
+ bol->unique_out()->is_CMove() &&
+ (cmov = bol->unique_out()->as_CMove()) &&
+ (get_ctrl(cmov) == blk1 ||
+ get_ctrl(cmov) == blk2) ) ) {
+
+ // Must clone down
+#ifndef PRODUCT
+ if( PrintOpto && VerifyLoopOptimizations ) {
+ tty->print("Cloning down: ");
+ n->dump();
+ }
+#endif
+ // Clone down any block-local BoolNode uses of this CmpNode
+ for (DUIterator i = n->outs(); n->has_out(i); i++) {
+ Node* bol = n->out(i);
+ assert( bol->is_Bool(), "" );
+ if (bol->outcnt() == 1) {
+ Node* use = bol->unique_out();
+ Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
+ if (use_c == blk1 || use_c == blk2) {
+ continue;
+ }
+ }
+ if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
+ // Recursively sink any BoolNode
+#ifndef PRODUCT
+ if( PrintOpto && VerifyLoopOptimizations ) {
+ tty->print("Cloning down: ");
+ bol->dump();
+ }
+#endif
+ for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
+ // Uses are either IfNodes or CMoves
+ Node* iff = bol->last_out(j);
+ assert( iff->in(1) == bol, "" );
+ // Get control block of either the CMove or the If input
+ Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
+ Node *x = bol->clone();
+ register_new_node(x, iff_ctrl);
+ _igvn.hash_delete(iff);
+ iff->set_req(1, x);
+ _igvn._worklist.push(iff);
+ }
+ _igvn.remove_dead_node( bol );
+ --i;
+ }
+ }
+ // Clone down this CmpNode
+ for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
+ Node* bol = n->last_out(j);
+ assert( bol->in(1) == n, "" );
+ Node *x = n->clone();
+ register_new_node(x, get_ctrl(bol));
+ _igvn.hash_delete(bol);
+ bol->set_req(1, x);
+ _igvn._worklist.push(bol);
+ }
+ _igvn.remove_dead_node( n );
+
+ return true;
+ }
+ }
+
+ // See if splitting-up a Store. Any anti-dep loads must go up as
+ // well. An anti-dep load might be in the wrong block, because in
+ // this particular layout/schedule we ignored anti-deps and allow
+ // memory to be alive twice. This only works if we do the same
+ // operations on anti-dep loads as we do their killing stores.
+ if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
+ // Get store's memory slice
+ int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
+
+ // Get memory-phi anti-dep loads will be using
+ Node *memphi = n->in(MemNode::Memory);
+ assert( memphi->is_Phi(), "" );
+ // Hoist any anti-dep load to the splitting block;
+ // it will then "split-up".
+ for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
+ Node *load = memphi->fast_out(i);
+ if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
+ set_ctrl(load,blk1);
+ }
+ }
+
+ // Found some other Node; must clone it up
+#ifndef PRODUCT
+ if( PrintOpto && VerifyLoopOptimizations ) {
+ tty->print("Cloning up: ");
+ n->dump();
+ }
+#endif
+
+ // Now actually split-up this guy. One copy per control path merging.
+ Node *phi = PhiNode::make_blank(blk1, n);
+ for( uint j = 1; j < blk1->req(); j++ ) {
+ Node *x = n->clone();
+ if( n->in(0) && n->in(0) == blk1 )
+ x->set_req( 0, blk1->in(j) );
+ for( uint i = 1; i < n->req(); i++ ) {
+ Node *m = n->in(i);
+ if( get_ctrl(m) == blk1 ) {
+ assert( m->in(0) == blk1, "" );
+ x->set_req( i, m->in(j) );
+ }
+ }
+ register_new_node( x, blk1->in(j) );
+ phi->init_req( j, x );
+ }
+ // Announce phi to optimizer
+ register_new_node(phi, blk1);
+
+ // Remove cloned-up value from optimizer; use phi instead
+ _igvn.hash_delete(n);
+ _igvn.subsume_node( n, phi );
+
+ // (There used to be a self-recursive call to split_up() here,
+ // but it is not needed. All necessary forward walking is done
+ // by do_split_if() below.)
+
+ return true;
+}
+
+//------------------------------register_new_node------------------------------
+void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
+ _igvn.register_new_node_with_optimizer(n);
+ set_ctrl(n, blk);
+ IdealLoopTree *loop = get_loop(blk);
+ if( !loop->_child )
+ loop->_body.push(n);
+}
+
+//------------------------------small_cache------------------------------------
+struct small_cache : public Dict {
+
+ small_cache() : Dict( cmpkey, hashptr ) {}
+ Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
+ void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
+};
+
+//------------------------------spinup-----------------------------------------
+// "Spin up" the dominator tree, starting at the use site and stopping when we
+// find the post-dominating point.
+
+// We must be at the merge point which post-dominates 'new_false' and
+// 'new_true'. Figure out which edges into the RegionNode eventually lead up
+// to false and which to true. Put in a PhiNode to merge values; plug in
+// the appropriate false-arm or true-arm values. If some path leads to the
+// original IF, then insert a Phi recursively.
+Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
+ if (use_blk->is_top()) // Handle dead uses
+ return use_blk;
+ Node *prior_n = (Node*)0xdeadbeef;
+ Node *n = use_blk; // Get path input
+ assert( use_blk != iff_dom, "" );
+ // Here's the "spinup" the dominator tree loop. Do a cache-check
+ // along the way, in case we've come this way before.
+ while( n != iff_dom ) { // Found post-dominating point?
+ prior_n = n;
+ n = idom(n); // Search higher
+ Node *s = cache->probe( prior_n ); // Check cache
+ if( s ) return s; // Cache hit!
+ }
+
+ Node *phi_post;
+ if( prior_n == new_false || prior_n == new_true ) {
+ phi_post = def->clone();
+ phi_post->set_req(0, prior_n );
+ register_new_node(phi_post, prior_n);
+ } else {
+ // This method handles both control uses (looking for Regions) or data
+ // uses (looking for Phis). If looking for a control use, then we need
+ // to insert a Region instead of a Phi; however Regions always exist
+ // previously (the hash_find_insert below would always hit) so we can
+ // return the existing Region.
+ if( def->is_CFG() ) {
+ phi_post = prior_n; // If looking for CFG, return prior
+ } else {
+ assert( def->is_Phi(), "" );
+ assert( prior_n->is_Region(), "must be a post-dominating merge point" );
+
+ // Need a Phi here
+ phi_post = PhiNode::make_blank(prior_n, def);
+ // Search for both true and false on all paths till find one.
+ for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
+ phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
+ Node *t = _igvn.hash_find_insert(phi_post);
+ if( t ) { // See if we already have this one
+ // phi_post will not be used, so kill it
+ _igvn.remove_dead_node(phi_post);
+ phi_post->destruct();
+ phi_post = t;
+ } else {
+ register_new_node( phi_post, prior_n );
+ }
+ }
+ }
+
+ // Update cache everywhere
+ prior_n = (Node*)0xdeadbeef; // Reset IDOM walk
+ n = use_blk; // Get path input
+ // Spin-up the idom tree again, basically doing path-compression.
+ // Insert cache entries along the way, so that if we ever hit this
+ // point in the IDOM tree again we'll stop immediately on a cache hit.
+ while( n != iff_dom ) { // Found post-dominating point?
+ prior_n = n;
+ n = idom(n); // Search higher
+ cache->lru_insert( prior_n, phi_post ); // Fill cache
+ } // End of while not gone high enough
+
+ return phi_post;
+}
+
+//------------------------------find_use_block---------------------------------
+// Find the block a USE is in. Normally USE's are in the same block as the
+// using instruction. For Phi-USE's, the USE is in the predecessor block
+// along the corresponding path.
+Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
+ // CFG uses are their own block
+ if( use->is_CFG() )
+ return use;
+
+ if( use->is_Phi() ) { // Phi uses in prior block
+ // Grab the first Phi use; there may be many.
+ // Each will be handled as a seperate iteration of
+ // the "while( phi->outcnt() )" loop.
+ uint j;
+ for( j = 1; j < use->req(); j++ )
+ if( use->in(j) == def )
+ break;
+ assert( j < use->req(), "def should be among use's inputs" );
+ return use->in(0)->in(j);
+ }
+ // Normal (non-phi) use
+ Node *use_blk = get_ctrl(use);
+ // Some uses are directly attached to the old (and going away)
+ // false and true branches.
+ if( use_blk == old_false ) {
+ use_blk = new_false;
+ set_ctrl(use, new_false);
+ }
+ if( use_blk == old_true ) {
+ use_blk = new_true;
+ set_ctrl(use, new_true);
+ }
+
+ if (use_blk == NULL) { // He's dead, Jim
+ _igvn.hash_delete(use);
+ _igvn.subsume_node(use, C->top());
+ }
+
+ return use_blk;
+}
+
+//------------------------------handle_use-------------------------------------
+// Handle uses of the merge point. Basically, split-if makes the merge point
+// go away so all uses of the merge point must go away as well. Most block
+// local uses have already been split-up, through the merge point. Uses from
+// far below the merge point can't always be split up (e.g., phi-uses are
+// pinned) and it makes too much stuff live. Instead we use a path-based
+// solution to move uses down.
+//
+// If the use is along the pre-split-CFG true branch, then the new use will
+// be from the post-split-CFG true merge point. Vice-versa for the false
+// path. Some uses will be along both paths; then we sink the use to the
+// post-dominating location; we may need to insert a Phi there.
+void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
+
+ Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
+ if( !use_blk ) return; // He's dead, Jim
+
+ // Walk up the dominator tree until I hit either the old IfFalse, the old
+ // IfTrue or the old If. Insert Phis where needed.
+ Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
+
+ // Found where this USE goes. Re-point him.
+ uint i;
+ for( i = 0; i < use->req(); i++ )
+ if( use->in(i) == def )
+ break;
+ assert( i < use->req(), "def should be among use's inputs" );
+ _igvn.hash_delete(use);
+ use->set_req(i, new_def);
+ _igvn._worklist.push(use);
+}
+
+//------------------------------do_split_if------------------------------------
+// Found an If getting its condition-code input from a Phi in the same block.
+// Split thru the Region.
+void PhaseIdealLoop::do_split_if( Node *iff ) {
+#ifndef PRODUCT
+ if( PrintOpto && VerifyLoopOptimizations )
+ tty->print_cr("Split-if");
+#endif
+ C->set_major_progress();
+ Node *region = iff->in(0);
+ Node *region_dom = idom(region);
+
+ // We are going to clone this test (and the control flow with it) up through
+ // the incoming merge point. We need to empty the current basic block.
+ // Clone any instructions which must be in this block up through the merge
+ // point.
+ DUIterator i, j;
+ bool progress = true;
+ while (progress) {
+ progress = false;
+ for (i = region->outs(); region->has_out(i); i++) {
+ Node* n = region->out(i);
+ if( n == region ) continue;
+ // The IF to be split is OK.
+ if( n == iff ) continue;
+ if( !n->is_Phi() ) { // Found pinned memory op or such
+ if (split_up(n, region, iff)) {
+ i = region->refresh_out_pos(i);
+ progress = true;
+ }
+ continue;
+ }
+ assert( n->in(0) == region, "" );
+
+ // Recursively split up all users of a Phi
+ for (j = n->outs(); n->has_out(j); j++) {
+ Node* m = n->out(j);
+ // If m is dead, throw it away, and declare progress
+ if (_nodes[m->_idx] == NULL) {
+ _igvn.remove_dead_node(m);
+ // fall through
+ }
+ else if (m != iff && split_up(m, region, iff)) {
+ // fall through
+ } else {
+ continue;
+ }
+ // Something unpredictable changed.
+ // Tell the iterators to refresh themselves, and rerun the loop.
+ i = region->refresh_out_pos(i);
+ j = region->refresh_out_pos(j);
+ progress = true;
+ }
+ }
+ }
+
+ // Now we have no instructions in the block containing the IF.
+ // Split the IF.
+ Node *new_iff = split_thru_region( iff, region );
+
+ // Replace both uses of 'new_iff' with Regions merging True/False
+ // paths. This makes 'new_iff' go dead.
+ Node *old_false, *old_true;
+ Node *new_false, *new_true;
+ for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
+ Node *ifp = iff->last_out(j2);
+ assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
+ ifp->set_req(0, new_iff);
+ Node *ifpx = split_thru_region( ifp, region );
+
+ // Replace 'If' projection of a Region with a Region of
+ // 'If' projections.
+ ifpx->set_req(0, ifpx); // A TRUE RegionNode
+
+ // Setup dominator info
+ set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
+
+ // Check for splitting loop tails
+ if( get_loop(iff)->tail() == ifp )
+ get_loop(iff)->_tail = ifpx;
+
+ // Replace in the graph with lazy-update mechanism
+ new_iff->set_req(0, new_iff); // hook self so it does not go dead
+ lazy_replace_proj( ifp, ifpx );
+ new_iff->set_req(0, region);
+
+ // Record bits for later xforms
+ if( ifp->Opcode() == Op_IfFalse ) {
+ old_false = ifp;
+ new_false = ifpx;
+ } else {
+ old_true = ifp;
+ new_true = ifpx;
+ }
+ }
+ _igvn.remove_dead_node(new_iff);
+ // Lazy replace IDOM info with the region's dominator
+ lazy_replace( iff, region_dom );
+
+ // Now make the original merge point go dead, by handling all its uses.
+ small_cache region_cache;
+ // Preload some control flow in region-cache
+ region_cache.lru_insert( new_false, new_false );
+ region_cache.lru_insert( new_true , new_true );
+ // Now handle all uses of the splitting block
+ for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {
+ Node* phi = region->last_out(k);
+ if( !phi->in(0) ) { // Dead phi? Remove it
+ _igvn.remove_dead_node(phi);
+ continue;
+ }
+ assert( phi->in(0) == region, "" );
+ if( phi == region ) { // Found the self-reference
+ phi->set_req(0, NULL);
+ continue; // Break the self-cycle
+ }
+ // Expected common case: Phi hanging off of Region
+ if( phi->is_Phi() ) {
+ // Need a per-def cache. Phi represents a def, so make a cache
+ small_cache phi_cache;
+
+ // Inspect all Phi uses to make the Phi go dead
+ for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
+ Node* use = phi->last_out(l);
+ // Compute the new DEF for this USE. New DEF depends on the path
+ // taken from the original DEF to the USE. The new DEF may be some
+ // collection of PHI's merging values from different paths. The Phis
+ // inserted depend only on the location of the USE. We use a
+ // 2-element cache to handle multiple uses from the same block.
+ handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );
+ } // End of while phi has uses
+
+ // Because handle_use might relocate region->_out,
+ // we must refresh the iterator.
+ k = region->last_outs(kmin);
+
+ // Remove the dead Phi
+ _igvn.remove_dead_node( phi );
+
+ } else {
+ // Random memory op guarded by Region. Compute new DEF for USE.
+ handle_use( phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true );
+ }
+
+ } // End of while merge point has phis
+
+ // Any leftover bits in the splitting block must not have depended on local
+ // Phi inputs (these have already been split-up). Hence it's safe to hoist
+ // these guys to the dominating point.
+ lazy_replace( region, region_dom );
+#ifndef PRODUCT
+ if( VerifyLoopOptimizations ) verify();
+#endif
+}