--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.max.graal.compiler/src/com/sun/c1x/alloc/LinearScanWalker.java	Wed Jun 08 08:42:25 2011 +0200
@@ -0,0 +1,980 @@
+/*
+ * Copyright (c) 2009, 2011, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.c1x.alloc;
+
+import static com.sun.cri.ci.CiUtil.*;
+
+import java.util.*;
+
+import com.sun.c1x.*;
+import com.sun.c1x.alloc.Interval.*;
+import com.sun.c1x.debug.*;
+import com.sun.c1x.lir.*;
+import com.sun.c1x.util.*;
+import com.sun.cri.ci.*;
+import com.sun.cri.ci.CiRegister.*;
+
+/**
+ *
+ * @author Thomas Wuerthinger
+ */
+final class LinearScanWalker extends IntervalWalker {
+
+    private CiRegister[] availableRegs;
+
+    private final int[] usePos;
+    private final int[] blockPos;
+
+    private List<Interval>[] spillIntervals;
+
+    private MoveResolver moveResolver; // for ordering spill moves
+
+    // accessors mapped to same functions in class LinearScan
+    int blockCount() {
+        return allocator.blockCount();
+    }
+
+    LIRBlock blockAt(int idx) {
+        return allocator.blockAt(idx);
+    }
+
+    LIRBlock blockOfOpWithId(int opId) {
+        return allocator.blockForId(opId);
+    }
+
+    LinearScanWalker(LinearScan allocator, Interval unhandledFixedFirst, Interval unhandledAnyFirst) {
+        super(allocator, unhandledFixedFirst, unhandledAnyFirst);
+        moveResolver = new MoveResolver(allocator);
+        spillIntervals = Util.uncheckedCast(new List[allocator.registers.length]);
+        for (int i = 0; i < allocator.registers.length; i++) {
+            spillIntervals[i] = new ArrayList<Interval>(2);
+        }
+        usePos = new int[allocator.registers.length];
+        blockPos = new int[allocator.registers.length];
+    }
+
+    void initUseLists(boolean onlyProcessUsePos) {
+        for (CiRegister register : availableRegs) {
+            int i = register.number;
+            usePos[i] = Integer.MAX_VALUE;
+
+            if (!onlyProcessUsePos) {
+                blockPos[i] = Integer.MAX_VALUE;
+                spillIntervals[i].clear();
+            }
+        }
+    }
+
+    void excludeFromUse(Interval i) {
+        CiValue location = i.location();
+        int i1 = location.asRegister().number;
+        if (i1 >= availableRegs[0].number && i1 <= availableRegs[availableRegs.length - 1].number) {
+            usePos[i1] = 0;
+        }
+    }
+
+    void setUsePos(Interval interval, int usePos, boolean onlyProcessUsePos) {
+        if (usePos != -1) {
+            assert usePos != 0 : "must use excludeFromUse to set usePos to 0";
+            int i = interval.location().asRegister().number;
+            if (i >= availableRegs[0].number && i <= availableRegs[availableRegs.length - 1].number) {
+                if (this.usePos[i] > usePos) {
+                    this.usePos[i] = usePos;
+                }
+                if (!onlyProcessUsePos) {
+                    spillIntervals[i].add(interval);
+                }
+            }
+        }
+    }
+
+    void setBlockPos(Interval i, int blockPos) {
+        if (blockPos != -1) {
+            int reg = i.location().asRegister().number;
+            if (reg >= availableRegs[0].number && reg <= availableRegs[availableRegs.length - 1].number) {
+                if (this.blockPos[reg] > blockPos) {
+                    this.blockPos[reg] = blockPos;
+                }
+                if (usePos[reg] > blockPos) {
+                    usePos[reg] = blockPos;
+                }
+            }
+        }
+    }
+
+    void freeExcludeActiveFixed() {
+        Interval interval = activeLists.get(RegisterBinding.Fixed);
+        while (interval != Interval.EndMarker) {
+            assert interval.location().isRegister() : "active interval must have a register assigned";
+            excludeFromUse(interval);
+            interval = interval.next;
+        }
+    }
+
+    void freeExcludeActiveAny() {
+        Interval interval = activeLists.get(RegisterBinding.Any);
+        while (interval != Interval.EndMarker) {
+            assert interval.location().isRegister() : "active interval must have a register assigned";
+            excludeFromUse(interval);
+            interval = interval.next;
+        }
+    }
+
+    void freeCollectInactiveFixed(Interval current) {
+        Interval interval = inactiveLists.get(RegisterBinding.Fixed);
+        while (interval != Interval.EndMarker) {
+            if (current.to() <= interval.currentFrom()) {
+                assert interval.currentIntersectsAt(current) == -1 : "must not intersect";
+                setUsePos(interval, interval.currentFrom(), true);
+            } else {
+                setUsePos(interval, interval.currentIntersectsAt(current), true);
+            }
+            interval = interval.next;
+        }
+    }
+
+    void freeCollectInactiveAny(Interval current) {
+        Interval interval = inactiveLists.get(RegisterBinding.Any);
+        while (interval != Interval.EndMarker) {
+            setUsePos(interval, interval.currentIntersectsAt(current), true);
+            interval = interval.next;
+        }
+    }
+
+    void freeCollectUnhandled(RegisterBinding kind, Interval current) {
+        Interval interval = unhandledLists.get(kind);
+        while (interval != Interval.EndMarker) {
+            setUsePos(interval, interval.intersectsAt(current), true);
+            if (kind == RegisterBinding.Fixed && current.to() <= interval.from()) {
+                setUsePos(interval, interval.from(), true);
+            }
+            interval = interval.next;
+        }
+    }
+
+    void spillExcludeActiveFixed() {
+        Interval interval = activeLists.get(RegisterBinding.Fixed);
+        while (interval != Interval.EndMarker) {
+            excludeFromUse(interval);
+            interval = interval.next;
+        }
+    }
+
+    void spillBlockUnhandledFixed(Interval current) {
+        Interval interval = unhandledLists.get(RegisterBinding.Fixed);
+        while (interval != Interval.EndMarker) {
+            setBlockPos(interval, interval.intersectsAt(current));
+            interval = interval.next;
+        }
+    }
+
+    void spillBlockInactiveFixed(Interval current) {
+        Interval interval = inactiveLists.get(RegisterBinding.Fixed);
+        while (interval != Interval.EndMarker) {
+            if (current.to() > interval.currentFrom()) {
+                setBlockPos(interval, interval.currentIntersectsAt(current));
+            } else {
+                assert interval.currentIntersectsAt(current) == -1 : "invalid optimization: intervals intersect";
+            }
+
+            interval = interval.next;
+        }
+    }
+
+    void spillCollectActiveAny() {
+        Interval interval = activeLists.get(RegisterBinding.Any);
+        while (interval != Interval.EndMarker) {
+            setUsePos(interval, Math.min(interval.nextUsage(RegisterPriority.LiveAtLoopEnd, currentPosition), interval.to()), false);
+            interval = interval.next;
+        }
+    }
+
+    void spillCollectInactiveAny(Interval current) {
+        Interval interval = inactiveLists.get(RegisterBinding.Any);
+        while (interval != Interval.EndMarker) {
+            if (interval.currentIntersects(current)) {
+                setUsePos(interval, Math.min(interval.nextUsage(RegisterPriority.LiveAtLoopEnd, currentPosition), interval.to()), false);
+            }
+            interval = interval.next;
+        }
+    }
+
+    void insertMove(int opId, Interval srcIt, Interval dstIt) {
+        // output all moves here. When source and target are equal, the move is
+        // optimized away later in assignRegNums
+
+        opId = (opId + 1) & ~1;
+        LIRBlock opBlock = allocator.blockForId(opId);
+        assert opId > 0 && allocator.blockForId(opId - 2) == opBlock : "cannot insert move at block boundary";
+
+        // calculate index of instruction inside instruction list of current block
+        // the minimal index (for a block with no spill moves) can be calculated because the
+        // numbering of instructions is known.
+        // When the block already contains spill moves, the index must be increased until the
+        // correct index is reached.
+        List<LIRInstruction> list = opBlock.lir().instructionsList();
+        int index = (opId - list.get(0).id) >> 1;
+        assert list.get(index).id <= opId : "error in calculation";
+
+        while (list.get(index).id != opId) {
+            index++;
+            assert 0 <= index && index < list.size() : "index out of bounds";
+        }
+        assert 1 <= index && index < list.size() : "index out of bounds";
+        assert list.get(index).id == opId : "error in calculation";
+
+        // insert new instruction before instruction at position index
+        moveResolver.moveInsertPosition(opBlock.lir(), index - 1);
+        moveResolver.addMapping(srcIt, dstIt);
+    }
+
+    int findOptimalSplitPos(LIRBlock minBlock, LIRBlock maxBlock, int maxSplitPos) {
+        int fromBlockNr = minBlock.linearScanNumber();
+        int toBlockNr = maxBlock.linearScanNumber();
+
+        assert 0 <= fromBlockNr && fromBlockNr < blockCount() : "out of range";
+        assert 0 <= toBlockNr && toBlockNr < blockCount() : "out of range";
+        assert fromBlockNr < toBlockNr : "must cross block boundary";
+
+        // Try to split at end of maxBlock. If this would be after
+        // maxSplitPos, then use the begin of maxBlock
+        int optimalSplitPos = maxBlock.lastLirInstructionId() + 2;
+        if (optimalSplitPos > maxSplitPos) {
+            optimalSplitPos = maxBlock.firstLirInstructionId();
+        }
+
+        int minLoopDepth = maxBlock.loopDepth();
+        for (int i = toBlockNr - 1; i >= fromBlockNr; i--) {
+            LIRBlock cur = blockAt(i);
+
+            if (cur.loopDepth() < minLoopDepth) {
+                // block with lower loop-depth found . split at the end of this block
+                minLoopDepth = cur.loopDepth();
+                optimalSplitPos = cur.lastLirInstructionId() + 2;
+            }
+        }
+        assert optimalSplitPos > allocator.maxOpId() || allocator.isBlockBegin(optimalSplitPos) : "algorithm must move split pos to block boundary";
+
+        return optimalSplitPos;
+    }
+
+    int findOptimalSplitPos(Interval interval, int minSplitPos, int maxSplitPos, boolean doLoopOptimization) {
+        int optimalSplitPos = -1;
+        if (minSplitPos == maxSplitPos) {
+            // trivial case, no optimization of split position possible
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("      min-pos and max-pos are equal, no optimization possible");
+            }
+            optimalSplitPos = minSplitPos;
+
+        } else {
+            assert minSplitPos < maxSplitPos : "must be true then";
+            assert minSplitPos > 0 : "cannot access minSplitPos - 1 otherwise";
+
+            // reason for using minSplitPos - 1: when the minimal split pos is exactly at the
+            // beginning of a block, then minSplitPos is also a possible split position.
+            // Use the block before as minBlock, because then minBlock.lastLirInstructionId() + 2 == minSplitPos
+            LIRBlock minBlock = allocator.blockForId(minSplitPos - 1);
+
+            // reason for using maxSplitPos - 1: otherwise there would be an assert on failure
+            // when an interval ends at the end of the last block of the method
+            // (in this case, maxSplitPos == allocator().maxLirOpId() + 2, and there is no
+            // block at this opId)
+            LIRBlock maxBlock = allocator.blockForId(maxSplitPos - 1);
+
+            assert minBlock.linearScanNumber() <= maxBlock.linearScanNumber() : "invalid order";
+            if (minBlock == maxBlock) {
+                // split position cannot be moved to block boundary : so split as late as possible
+                if (C1XOptions.TraceLinearScanLevel >= 4) {
+                    TTY.println("      cannot move split pos to block boundary because minPos and maxPos are in same block");
+                }
+                optimalSplitPos = maxSplitPos;
+
+            } else {
+                if (interval.hasHoleBetween(maxSplitPos - 1, maxSplitPos) && !allocator.isBlockBegin(maxSplitPos)) {
+                    // Do not move split position if the interval has a hole before maxSplitPos.
+                    // Intervals resulting from Phi-Functions have more than one definition (marked
+                    // as mustHaveRegister) with a hole before each definition. When the register is needed
+                    // for the second definition : an earlier reloading is unnecessary.
+                    if (C1XOptions.TraceLinearScanLevel >= 4) {
+                        TTY.println("      interval has hole just before maxSplitPos, so splitting at maxSplitPos");
+                    }
+                    optimalSplitPos = maxSplitPos;
+
+                } else {
+                    // seach optimal block boundary between minSplitPos and maxSplitPos
+                    if (C1XOptions.TraceLinearScanLevel >= 4) {
+                        TTY.println("      moving split pos to optimal block boundary between block B%d and B%d", minBlock.blockID(), maxBlock.blockID());
+                    }
+
+                    if (doLoopOptimization) {
+                        // Loop optimization: if a loop-end marker is found between min- and max-position :
+                        // then split before this loop
+                        int loopEndPos = interval.nextUsageExact(RegisterPriority.LiveAtLoopEnd, minBlock.lastLirInstructionId() + 2);
+                        if (C1XOptions.TraceLinearScanLevel >= 4) {
+                            TTY.println("      loop optimization: loop end found at pos %d", loopEndPos);
+                        }
+
+                        assert loopEndPos > minSplitPos : "invalid order";
+                        if (loopEndPos < maxSplitPos) {
+                            // loop-end marker found between min- and max-position
+                            // if it is not the end marker for the same loop as the min-position : then move
+                            // the max-position to this loop block.
+                            // Desired result: uses tagged as shouldHaveRegister inside a loop cause a reloading
+                            // of the interval (normally, only mustHaveRegister causes a reloading)
+                            LIRBlock loopBlock = allocator.blockForId(loopEndPos);
+
+                            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                                TTY.println("      interval is used in loop that ends in block B%d, so trying to move maxBlock back from B%d to B%d", loopBlock.blockID(), maxBlock.blockID(), loopBlock.blockID());
+                            }
+                            assert loopBlock != minBlock : "loopBlock and minBlock must be different because block boundary is needed between";
+
+                            optimalSplitPos = findOptimalSplitPos(minBlock, loopBlock, loopBlock.lastLirInstructionId() + 2);
+                            if (optimalSplitPos == loopBlock.lastLirInstructionId() + 2) {
+                                optimalSplitPos = -1;
+                                if (C1XOptions.TraceLinearScanLevel >= 4) {
+                                    TTY.println("      loop optimization not necessary");
+                                }
+                            } else {
+                                if (C1XOptions.TraceLinearScanLevel >= 4) {
+                                    TTY.println("      loop optimization successful");
+                                }
+                            }
+                        }
+                    }
+
+                    if (optimalSplitPos == -1) {
+                        // not calculated by loop optimization
+                        optimalSplitPos = findOptimalSplitPos(minBlock, maxBlock, maxSplitPos);
+                    }
+                }
+            }
+        }
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("      optimal split position: %d", optimalSplitPos);
+        }
+
+        return optimalSplitPos;
+    }
+
+    // split an interval at the optimal position between minSplitPos and
+    // maxSplitPos in two parts:
+    // 1) the left part has already a location assigned
+    // 2) the right part is sorted into to the unhandled-list
+    void splitBeforeUsage(Interval interval, int minSplitPos, int maxSplitPos) {
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("----- splitting interval: ");
+        }
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println(interval.logString(allocator));
+        }
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("      between %d and %d", minSplitPos, maxSplitPos);
+        }
+
+        assert interval.from() < minSplitPos : "cannot split at start of interval";
+        assert currentPosition < minSplitPos : "cannot split before current position";
+        assert minSplitPos <= maxSplitPos : "invalid order";
+        assert maxSplitPos <= interval.to() : "cannot split after end of interval";
+
+        int optimalSplitPos = findOptimalSplitPos(interval, minSplitPos, maxSplitPos, true);
+
+        assert minSplitPos <= optimalSplitPos && optimalSplitPos <= maxSplitPos : "out of range";
+        assert optimalSplitPos <= interval.to() : "cannot split after end of interval";
+        assert optimalSplitPos > interval.from() : "cannot split at start of interval";
+
+        if (optimalSplitPos == interval.to() && interval.nextUsage(RegisterPriority.MustHaveRegister, minSplitPos) == Integer.MAX_VALUE) {
+            // the split position would be just before the end of the interval
+            // . no split at all necessary
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("      no split necessary because optimal split position is at end of interval");
+            }
+            return;
+        }
+
+        // must calculate this before the actual split is performed and before split position is moved to odd opId
+        boolean moveNecessary = !allocator.isBlockBegin(optimalSplitPos) && !interval.hasHoleBetween(optimalSplitPos - 1, optimalSplitPos);
+
+        if (!allocator.isBlockBegin(optimalSplitPos)) {
+            // move position before actual instruction (odd opId)
+            optimalSplitPos = (optimalSplitPos - 1) | 1;
+        }
+
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("      splitting at position %d", optimalSplitPos);
+        }
+        assert allocator.isBlockBegin(optimalSplitPos) || (optimalSplitPos % 2 == 1) : "split pos must be odd when not on block boundary";
+        assert !allocator.isBlockBegin(optimalSplitPos) || (optimalSplitPos % 2 == 0) : "split pos must be even on block boundary";
+
+        Interval splitPart = interval.split(optimalSplitPos, allocator);
+
+        allocator.copyRegisterFlags(interval, splitPart);
+        splitPart.setInsertMoveWhenActivated(moveNecessary);
+
+        assert splitPart.from() >= current.currentFrom() : "cannot append new interval before current walk position";
+        unhandledLists.addToListSortedByStartAndUsePositions(RegisterBinding.Any, splitPart);
+
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("      split interval in two parts (insertMoveWhenActivated: %b)", moveNecessary);
+        }
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.print("      ");
+            TTY.println(interval.logString(allocator));
+            TTY.print("      ");
+            TTY.println(splitPart.logString(allocator));
+        }
+    }
+
+// split an interval at the optimal position between minSplitPos and
+// maxSplitPos in two parts:
+// 1) the left part has already a location assigned
+// 2) the right part is always on the stack and therefore ignored in further processing
+
+    void splitForSpilling(Interval interval) {
+        // calculate allowed range of splitting position
+        int maxSplitPos = currentPosition;
+        int minSplitPos = Math.max(interval.previousUsage(RegisterPriority.ShouldHaveRegister, maxSplitPos) + 1, interval.from());
+
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.print("----- splitting and spilling interval: ");
+            TTY.println(interval.logString(allocator));
+            TTY.println("      between %d and %d", minSplitPos, maxSplitPos);
+        }
+
+        assert interval.state == State.Active : "why spill interval that is not active?";
+        assert interval.from() <= minSplitPos : "cannot split before start of interval";
+        assert minSplitPos <= maxSplitPos : "invalid order";
+        assert maxSplitPos < interval.to() : "cannot split at end end of interval";
+        assert currentPosition < interval.to() : "interval must not end before current position";
+
+        if (minSplitPos == interval.from()) {
+            // the whole interval is never used, so spill it entirely to memory
+            if (C1XOptions.TraceLinearScanLevel >= 2) {
+                TTY.println("      spilling entire interval because split pos is at beginning of interval");
+                TTY.println("      use positions: " + interval.usePosList().size());
+            }
+            assert interval.firstUsage(RegisterPriority.ShouldHaveRegister) > currentPosition : "interval must not have use position before currentPosition";
+
+            allocator.assignSpillSlot(interval);
+            allocator.changeSpillState(interval, minSplitPos);
+
+            // Also kick parent intervals out of register to memory when they have no use
+            // position. This avoids short interval in register surrounded by intervals in
+            // memory . avoid useless moves from memory to register and back
+            Interval parent = interval;
+            while (parent != null && parent.isSplitChild()) {
+                parent = parent.getSplitChildBeforeOpId(parent.from());
+
+                if (parent.location().isRegister()) {
+                    if (parent.firstUsage(RegisterPriority.ShouldHaveRegister) == Integer.MAX_VALUE) {
+                        // parent is never used, so kick it out of its assigned register
+                        if (C1XOptions.TraceLinearScanLevel >= 4) {
+                            TTY.println("      kicking out interval %d out of its register because it is never used", parent.operandNumber);
+                        }
+                        allocator.assignSpillSlot(parent);
+                    } else {
+                        // do not go further back because the register is actually used by the interval
+                        parent = null;
+                    }
+                }
+            }
+
+        } else {
+            // search optimal split pos, split interval and spill only the right hand part
+            int optimalSplitPos = findOptimalSplitPos(interval, minSplitPos, maxSplitPos, false);
+
+            assert minSplitPos <= optimalSplitPos && optimalSplitPos <= maxSplitPos : "out of range";
+            assert optimalSplitPos < interval.to() : "cannot split at end of interval";
+            assert optimalSplitPos >= interval.from() : "cannot split before start of interval";
+
+            if (!allocator.isBlockBegin(optimalSplitPos)) {
+                // move position before actual instruction (odd opId)
+                optimalSplitPos = (optimalSplitPos - 1) | 1;
+            }
+
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("      splitting at position %d", optimalSplitPos);
+            }
+            assert allocator.isBlockBegin(optimalSplitPos) || (optimalSplitPos % 2 == 1) : "split pos must be odd when not on block boundary";
+            assert !allocator.isBlockBegin(optimalSplitPos) || (optimalSplitPos % 2 == 0) : "split pos must be even on block boundary";
+
+            Interval spilledPart = interval.split(optimalSplitPos, allocator);
+            allocator.assignSpillSlot(spilledPart);
+            allocator.changeSpillState(spilledPart, optimalSplitPos);
+
+            if (!allocator.isBlockBegin(optimalSplitPos)) {
+                if (C1XOptions.TraceLinearScanLevel >= 4) {
+                    TTY.println("      inserting move from interval %d to %d", interval.operandNumber, spilledPart.operandNumber);
+                }
+                insertMove(optimalSplitPos, interval, spilledPart);
+            }
+
+            // the currentSplitChild is needed later when moves are inserted for reloading
+            assert spilledPart.currentSplitChild() == interval : "overwriting wrong currentSplitChild";
+            spilledPart.makeCurrentSplitChild();
+
+            if (C1XOptions.TraceLinearScanLevel >= 2) {
+                TTY.println("      split interval in two parts");
+                TTY.print("      ");
+                TTY.println(interval.logString(allocator));
+                TTY.print("      ");
+                TTY.println(spilledPart.logString(allocator));
+            }
+        }
+    }
+
+    void splitStackInterval(Interval interval) {
+        int minSplitPos = currentPosition + 1;
+        int maxSplitPos = Math.min(interval.firstUsage(RegisterPriority.ShouldHaveRegister), interval.to());
+
+        splitBeforeUsage(interval, minSplitPos, maxSplitPos);
+    }
+
+    void splitWhenPartialRegisterAvailable(Interval interval, int registerAvailableUntil) {
+        int minSplitPos = Math.max(interval.previousUsage(RegisterPriority.ShouldHaveRegister, registerAvailableUntil), interval.from() + 1);
+        splitBeforeUsage(interval, minSplitPos, registerAvailableUntil);
+    }
+
+    void splitAndSpillInterval(Interval interval) {
+        assert interval.state == State.Active || interval.state == State.Inactive : "other states not allowed";
+
+        int currentPos = currentPosition;
+        if (interval.state == State.Inactive) {
+            // the interval is currently inactive, so no spill slot is needed for now.
+            // when the split part is activated, the interval has a new chance to get a register,
+            // so in the best case no stack slot is necessary
+            assert interval.hasHoleBetween(currentPos - 1, currentPos + 1) : "interval can not be inactive otherwise";
+            splitBeforeUsage(interval, currentPos + 1, currentPos + 1);
+
+        } else {
+            // search the position where the interval must have a register and split
+            // at the optimal position before.
+            // The new created part is added to the unhandled list and will get a register
+            // when it is activated
+            int minSplitPos = currentPos + 1;
+            int maxSplitPos = Math.min(interval.nextUsage(RegisterPriority.MustHaveRegister, minSplitPos), interval.to());
+
+            splitBeforeUsage(interval, minSplitPos, maxSplitPos);
+
+            assert interval.nextUsage(RegisterPriority.MustHaveRegister, currentPos) == Integer.MAX_VALUE : "the remaining part is spilled to stack and therefore has no register";
+            splitForSpilling(interval);
+        }
+    }
+
+    boolean allocFreeRegister(Interval interval) {
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("trying to find free register for " + interval.logString(allocator));
+        }
+
+        initUseLists(true);
+        freeExcludeActiveFixed();
+        freeExcludeActiveAny();
+        freeCollectInactiveFixed(interval);
+        freeCollectInactiveAny(interval);
+        // freeCollectUnhandled(fixedKind, cur);
+        assert unhandledLists.get(RegisterBinding.Fixed) == Interval.EndMarker : "must not have unhandled fixed intervals because all fixed intervals have a use at position 0";
+
+        // usePos contains the start of the next interval that has this register assigned
+        // (either as a fixed register or a normal allocated register in the past)
+        // only intervals overlapping with cur are processed, non-overlapping invervals can be ignored safely
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("      state of registers:");
+            for (CiRegister register : availableRegs) {
+                int i = register.number;
+                TTY.println("      reg %d: usePos: %d", register.number, usePos[i]);
+            }
+        }
+
+        CiRegister hint = null;
+        Interval locationHint = interval.locationHint(true, allocator);
+        if (locationHint != null && locationHint.location() != null && locationHint.location().isRegister()) {
+            hint = locationHint.location().asRegister();
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("      hint register %d from interval %s", hint.number, locationHint.logString(allocator));
+            }
+        }
+        assert interval.location() == null : "register already assigned to interval";
+
+        // the register must be free at least until this position
+        int regNeededUntil = interval.from() + 1;
+        int intervalTo = interval.to();
+
+        boolean needSplit = false;
+        int splitPos = -1;
+
+        CiRegister reg = null;
+        CiRegister minFullReg = null;
+        CiRegister maxPartialReg = null;
+
+        for (int i = 0; i < availableRegs.length; ++i) {
+            CiRegister availableReg = availableRegs[i];
+            int number = availableReg.number;
+            if (usePos[number] >= intervalTo) {
+                // this register is free for the full interval
+                if (minFullReg == null || availableReg == hint || (usePos[number] < usePos[minFullReg.number] && minFullReg != hint)) {
+                    minFullReg = availableReg;
+                }
+            } else if (usePos[number] > regNeededUntil) {
+                // this register is at least free until regNeededUntil
+                if (maxPartialReg == null || availableReg == hint || (usePos[number] > usePos[maxPartialReg.number] && maxPartialReg != hint)) {
+                    maxPartialReg = availableReg;
+                }
+            }
+        }
+
+        if (minFullReg != null) {
+            reg = minFullReg;
+        } else if (maxPartialReg != null) {
+            needSplit = true;
+            reg = maxPartialReg;
+        } else {
+            return false;
+        }
+
+        splitPos = usePos[reg.number];
+        interval.assignLocation(reg.asValue(interval.kind()));
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("selected register %d", reg.number);
+        }
+
+        assert splitPos > 0 : "invalid splitPos";
+        if (needSplit) {
+            // register not available for full interval, so split it
+            splitWhenPartialRegisterAvailable(interval, splitPos);
+        }
+
+        // only return true if interval is completely assigned
+        return true;
+    }
+
+    CiRegister findLockedRegister(int regNeededUntil, int intervalTo, CiValue ignoreReg, boolean[] needSplit) {
+        int maxReg = -1;
+        CiRegister ignore = ignoreReg.isRegister() ? ignoreReg.asRegister() : null;
+
+        for (CiRegister reg : availableRegs) {
+            int i = reg.number;
+            if (reg == ignore) {
+                // this register must be ignored
+
+            } else if (usePos[i] > regNeededUntil) {
+                if (maxReg == -1 || (usePos[i] > usePos[maxReg])) {
+                    maxReg = i;
+                }
+            }
+        }
+
+        if (maxReg != -1) {
+            if (blockPos[maxReg] <= intervalTo) {
+                needSplit[0] = true;
+            }
+            return availableRegs[maxReg];
+        }
+
+        return null;
+    }
+
+    void splitAndSpillIntersectingIntervals(CiRegister reg) {
+        assert reg != null : "no register assigned";
+
+        for (int i = 0; i < spillIntervals[reg.number].size(); i++) {
+            Interval interval = spillIntervals[reg.number].get(i);
+            removeFromList(interval);
+            splitAndSpillInterval(interval);
+        }
+    }
+
+    // Split an Interval and spill it to memory so that cur can be placed in a register
+    void allocLockedRegister(Interval interval) {
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("need to split and spill to get register for " + interval.logString(allocator));
+        }
+
+        // collect current usage of registers
+        initUseLists(false);
+        spillExcludeActiveFixed();
+        //  spillBlockUnhandledFixed(cur);
+        assert unhandledLists.get(RegisterBinding.Fixed) == Interval.EndMarker : "must not have unhandled fixed intervals because all fixed intervals have a use at position 0";
+        spillBlockInactiveFixed(interval);
+        spillCollectActiveAny();
+        spillCollectInactiveAny(interval);
+
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("      state of registers:");
+            for (CiRegister reg : availableRegs) {
+                int i = reg.number;
+                TTY.print("      reg %d: usePos: %d, blockPos: %d, intervals: ", i, usePos[i], blockPos[i]);
+                for (int j = 0; j < spillIntervals[i].size(); j++) {
+                    TTY.print("%d ", spillIntervals[i].get(j).operandNumber);
+                }
+                TTY.println();
+            }
+        }
+
+        // the register must be free at least until this position
+        int firstUsage = interval.firstUsage(RegisterPriority.MustHaveRegister);
+        int regNeededUntil = Math.min(firstUsage, interval.from() + 1);
+        int intervalTo = interval.to();
+        assert regNeededUntil > 0 && regNeededUntil < Integer.MAX_VALUE : "interval has no use";
+
+        CiRegister reg = null;
+        CiRegister ignore = interval.location() != null && interval.location().isRegister() ? interval.location().asRegister() : null;
+        for (CiRegister availableReg : availableRegs) {
+            int number = availableReg.number;
+            if (availableReg == ignore) {
+                // this register must be ignored
+            } else if (usePos[number] > regNeededUntil) {
+                if (reg == null || (usePos[number] > usePos[reg.number])) {
+                    reg = availableReg;
+                }
+            }
+        }
+
+        if (reg == null || usePos[reg.number] <= firstUsage) {
+            // the first use of cur is later than the spilling position -> spill cur
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("able to spill current interval. firstUsage(register): %d, usePos: %d", firstUsage, reg == null ? 0 : usePos[reg.number]);
+            }
+
+            if (firstUsage <= interval.from() + 1) {
+                assert false : "cannot spill interval that is used in first instruction (possible reason: no register found) firstUsage=" + firstUsage + ", interval.from()=" + interval.from();
+                // assign a reasonable register and do a bailout in product mode to avoid errors
+                allocator.assignSpillSlot(interval);
+                throw new CiBailout("LinearScan: no register found");
+            }
+
+            splitAndSpillInterval(interval);
+            return;
+        }
+
+        boolean needSplit = blockPos[reg.number] <= intervalTo;
+
+        int splitPos = blockPos[reg.number];
+
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("decided to use register %d", reg.number);
+        }
+        assert splitPos > 0 : "invalid splitPos";
+        assert needSplit || splitPos > interval.from() : "splitting interval at from";
+
+        interval.assignLocation(reg.asValue(interval.kind()));
+        if (needSplit) {
+            // register not available for full interval :  so split it
+            splitWhenPartialRegisterAvailable(interval, splitPos);
+        }
+
+        // perform splitting and spilling for all affected intervals
+        splitAndSpillIntersectingIntervals(reg);
+    }
+
+    boolean noAllocationPossible(Interval interval) {
+
+        if (compilation.target.arch.isX86()) {
+            // fast calculation of intervals that can never get a register because the
+            // the next instruction is a call that blocks all registers
+            // Note: this does not work if callee-saved registers are available (e.g. on Sparc)
+
+            // check if this interval is the result of a split operation
+            // (an interval got a register until this position)
+            int pos = interval.from();
+            if (isOdd(pos)) {
+                // the current instruction is a call that blocks all registers
+                if (pos < allocator.maxOpId() && allocator.hasCall(pos + 1) && interval.to() > pos + 1) {
+                    if (C1XOptions.TraceLinearScanLevel >= 4) {
+                        TTY.println("      free register cannot be available because all registers blocked by following call");
+                    }
+
+                    // safety check that there is really no register available
+                    assert !allocFreeRegister(interval) : "found a register for this interval";
+                    return true;
+                }
+
+            }
+        }
+        return false;
+    }
+
+    void initVarsForAlloc(Interval interval) {
+        EnumMap<RegisterFlag, CiRegister[]> categorizedRegs = allocator.compilation.registerConfig.getCategorizedAllocatableRegisters();
+        if (allocator.operands.mustBeByteRegister(interval.operand)) {
+            assert interval.kind() != CiKind.Float && interval.kind() != CiKind.Double : "cpu regs only";
+            availableRegs = categorizedRegs.get(RegisterFlag.Byte);
+        } else if (interval.kind() == CiKind.Float || interval.kind() == CiKind.Double) {
+            availableRegs = categorizedRegs.get(RegisterFlag.FPU);
+        } else {
+            availableRegs = categorizedRegs.get(RegisterFlag.CPU);
+        }
+    }
+
+    boolean isMove(LIRInstruction op, Interval from, Interval to) {
+        if (op.code != LIROpcode.Move) {
+            return false;
+        }
+        assert op instanceof LIROp1 : "move must be LIROp1";
+
+        CiValue input = ((LIROp1) op).operand();
+        CiValue result = ((LIROp1) op).result();
+        return input.isVariable() && result.isVariable() && input == from.operand && result == to.operand;
+    }
+
+    // optimization (especially for phi functions of nested loops):
+    // assign same spill slot to non-intersecting intervals
+    void combineSpilledIntervals(Interval interval) {
+        if (interval.isSplitChild()) {
+            // optimization is only suitable for split parents
+            return;
+        }
+
+        Interval registerHint = interval.locationHint(false, allocator);
+        if (registerHint == null) {
+            // cur is not the target of a move : otherwise registerHint would be set
+            return;
+        }
+        assert registerHint.isSplitParent() : "register hint must be split parent";
+
+        if (interval.spillState() != SpillState.NoOptimization || registerHint.spillState() != SpillState.NoOptimization) {
+            // combining the stack slots for intervals where spill move optimization is applied
+            // is not benefitial and would cause problems
+            return;
+        }
+
+        int beginPos = interval.from();
+        int endPos = interval.to();
+        if (endPos > allocator.maxOpId() || isOdd(beginPos) || isOdd(endPos)) {
+            // safety check that lirOpWithId is allowed
+            return;
+        }
+
+        if (!isMove(allocator.instructionForId(beginPos), registerHint, interval) || !isMove(allocator.instructionForId(endPos), interval, registerHint)) {
+            // cur and registerHint are not connected with two moves
+            return;
+        }
+
+        Interval beginHint = registerHint.getSplitChildAtOpId(beginPos, LIRInstruction.OperandMode.Input, allocator);
+        Interval endHint = registerHint.getSplitChildAtOpId(endPos, LIRInstruction.OperandMode.Output, allocator);
+        if (beginHint == endHint || beginHint.to() != beginPos || endHint.from() != endPos) {
+            // registerHint must be split : otherwise the re-writing of use positions does not work
+            return;
+        }
+
+        assert beginHint.location() != null : "must have register assigned";
+        assert endHint.location() == null : "must not have register assigned";
+        assert interval.firstUsage(RegisterPriority.MustHaveRegister) == beginPos : "must have use position at begin of interval because of move";
+        assert endHint.firstUsage(RegisterPriority.MustHaveRegister) == endPos : "must have use position at begin of interval because of move";
+
+        if (beginHint.location().isRegister()) {
+            // registerHint is not spilled at beginPos : so it would not be benefitial to immediately spill cur
+            return;
+        }
+        assert registerHint.spillSlot() != null : "must be set when part of interval was spilled";
+
+        // modify intervals such that cur gets the same stack slot as registerHint
+        // delete use positions to prevent the intervals to get a register at beginning
+        interval.setSpillSlot(registerHint.spillSlot());
+        interval.removeFirstUsePos();
+        endHint.removeFirstUsePos();
+    }
+
+    // allocate a physical register or memory location to an interval
+    @Override
+    boolean activateCurrent() {
+        Interval interval = current;
+        boolean result = true;
+
+        if (C1XOptions.TraceLinearScanLevel >= 2) {
+            TTY.println("+++++ activating interval " + interval.logString(allocator));
+        }
+
+        if (C1XOptions.TraceLinearScanLevel >= 4) {
+            TTY.println("      splitParent: %s, insertMoveWhenActivated: %b", interval.splitParent().operandNumber, interval.insertMoveWhenActivated());
+        }
+
+        final CiValue operand = interval.operand;
+        if (interval.location() != null && interval.location().isStackSlot()) {
+            // activating an interval that has a stack slot assigned . split it at first use position
+            // used for method parameters
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("      interval has spill slot assigned (method parameter) . split it before first use");
+            }
+            splitStackInterval(interval);
+            result = false;
+
+        } else {
+            if (operand.isVariable() && allocator.operands.mustStartInMemory((CiVariable) operand)) {
+                assert interval.location() == null : "register already assigned";
+                allocator.assignSpillSlot(interval);
+
+                if (!allocator.operands.mustStayInMemory((CiVariable) operand)) {
+                    // activating an interval that must start in a stack slot but may get a register later
+                    // used for lirRoundfp: rounding is done by store to stack and reload later
+                    if (C1XOptions.TraceLinearScanLevel >= 4) {
+                        TTY.println("      interval must start in stack slot . split it before first use");
+                    }
+                    splitStackInterval(interval);
+                }
+
+                result = false;
+            } else if (interval.location() == null) {
+                // interval has not assigned register . normal allocation
+                // (this is the normal case for most intervals)
+                if (C1XOptions.TraceLinearScanLevel >= 4) {
+                    TTY.println("      normal allocation of register");
+                }
+
+                // assign same spill slot to non-intersecting intervals
+                combineSpilledIntervals(interval);
+
+                initVarsForAlloc(interval);
+                if (noAllocationPossible(interval) || !allocFreeRegister(interval)) {
+                    // no empty register available.
+                    // split and spill another interval so that this interval gets a register
+                    allocLockedRegister(interval);
+                }
+
+                // spilled intervals need not be move to active-list
+                if (!interval.location().isRegister()) {
+                    result = false;
+                }
+            }
+        }
+
+        // load spilled values that become active from stack slot to register
+        if (interval.insertMoveWhenActivated()) {
+            assert interval.isSplitChild();
+            assert interval.currentSplitChild() != null;
+            assert interval.currentSplitChild().operand != operand : "cannot insert move between same interval";
+            if (C1XOptions.TraceLinearScanLevel >= 4) {
+                TTY.println("Inserting move from interval %d to %d because insertMoveWhenActivated is set", interval.currentSplitChild().operandNumber, interval.operandNumber);
+            }
+
+            insertMove(interval.from(), interval.currentSplitChild(), interval);
+        }
+        interval.makeCurrentSplitChild();
+
+        return result; // true = interval is moved to active list
+    }
+
+    public void finishAllocation() {
+        // must be called when all intervals are allocated
+        moveResolver.resolveAndAppendMoves();
+    }
+}