1 /*

     2  * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 

    25 package org.graalvm.compiler.lir.alloc.trace.lsra;

    26 

    27 import static jdk.vm.ci.code.ValueUtil.isRegister;

    28 import static org.graalvm.compiler.lir.LIRValueUtil.asVariable;

    29 import static org.graalvm.compiler.lir.LIRValueUtil.isStackSlotValue;

    30 import static org.graalvm.compiler.lir.LIRValueUtil.isVariable;

    31 

    32 import java.util.ArrayList;

    33 

    34 import org.graalvm.compiler.core.common.alloc.RegisterAllocationConfig;

    35 import org.graalvm.compiler.core.common.alloc.Trace;

    36 import org.graalvm.compiler.core.common.alloc.TraceBuilderResult;

    37 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;

    38 import org.graalvm.compiler.debug.Assertions;

    39 import org.graalvm.compiler.debug.DebugContext;

    40 import org.graalvm.compiler.debug.Indent;

    41 import org.graalvm.compiler.lir.LIRInsertionBuffer;

    42 import org.graalvm.compiler.lir.LIRInstruction;

    43 import org.graalvm.compiler.lir.LIRInstruction.OperandMode;

    44 import org.graalvm.compiler.lir.StandardOp.LoadConstantOp;

    45 import org.graalvm.compiler.lir.StandardOp.MoveOp;

    46 import org.graalvm.compiler.lir.StandardOp.ValueMoveOp;

    47 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceInterval.SpillState;

    48 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceLinearScanPhase.IntervalPredicate;

    49 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceLinearScanPhase.TraceLinearScan;

    50 import org.graalvm.compiler.lir.gen.LIRGenerationResult;

    51 import org.graalvm.compiler.lir.gen.LIRGeneratorTool.MoveFactory;

    52 

    53 import jdk.vm.ci.code.TargetDescription;

    54 import jdk.vm.ci.meta.AllocatableValue;

    55 

    56 final class TraceLinearScanEliminateSpillMovePhase extends TraceLinearScanAllocationPhase {

    57 

    58     private static final IntervalPredicate spilledIntervals = new TraceLinearScanPhase.IntervalPredicate() {

    59 

    60         @Override

    61         public boolean apply(TraceInterval i) {

    62             return i.isSplitParent() && SpillState.IN_MEMORY.contains(i.spillState());

    63         }

    64     };

    65 

    66     @Override

    67     protected void run(TargetDescription target, LIRGenerationResult lirGenRes, Trace trace, MoveFactory spillMoveFactory, RegisterAllocationConfig registerAllocationConfig,

    68                     TraceBuilderResult traceBuilderResult, TraceLinearScan allocator) {

    69         boolean shouldEliminateSpillMoves = shouldEliminateSpillMoves(traceBuilderResult, allocator);

    70         eliminateSpillMoves(allocator, shouldEliminateSpillMoves, traceBuilderResult, lirGenRes);

    71     }

    72 

    73     private static boolean shouldEliminateSpillMoves(TraceBuilderResult traceBuilderResult, TraceLinearScan allocator) {

    74         return !traceBuilderResult.incomingSideEdges(traceBuilderResult.getTraceForBlock(allocator.blockAt(0)));

    75     }

    76 

    77     // called once before assignment of register numbers

    78     @SuppressWarnings("try")

    79     private static void eliminateSpillMoves(TraceLinearScan allocator, boolean shouldEliminateSpillMoves, TraceBuilderResult traceBuilderResult, LIRGenerationResult res) {

    80         DebugContext debug = allocator.getDebug();

    81         try (Indent indent = debug.logAndIndent("Eliminating unnecessary spill moves: Trace%d", traceBuilderResult.getTraceForBlock(allocator.blockAt(0)).getId())) {

    82             allocator.sortIntervalsBySpillPos();

    83 

    84             /*

    85              * collect all intervals that must be stored after their definition. The list is sorted

    86              * by Interval.spillDefinitionPos.

    87              */

    88             TraceInterval interval = allocator.createUnhandledListBySpillPos(spilledIntervals);

    89             if (Assertions.detailedAssertionsEnabled(allocator.getOptions())) {

    90                 checkIntervals(debug, interval);

    91             }

    92             if (debug.isLogEnabled()) {

    93                 try (Indent indent2 = debug.logAndIndent("Sorted intervals")) {

    94                     for (TraceInterval i = interval; i != null; i = i.next) {

    95                         debug.log("%5d: %s", i.spillDefinitionPos(), i);

    96                     }

    97                 }

    98             }

    99 

   100             LIRInsertionBuffer insertionBuffer = new LIRInsertionBuffer();

   101             for (AbstractBlockBase<?> block : allocator.sortedBlocks()) {

   102                 try (Indent indent1 = debug.logAndIndent("Handle %s", block)) {

   103                     ArrayList<LIRInstruction> instructions = allocator.getLIR().getLIRforBlock(block);

   104                     int numInst = instructions.size();

   105 

   106                     int lastOpId = -1;

   107                     // iterate all instructions of the block.

   108                     for (int j = 0; j < numInst; j++) {

   109                         LIRInstruction op = instructions.get(j);

   110                         int opId = op.id();

   111                         try (Indent indent2 = debug.logAndIndent("%5d %s", opId, op)) {

   112 

   113                             if (opId == -1) {

   114                                 MoveOp move = MoveOp.asMoveOp(op);

   115                                 /*

   116                                  * Remove move from register to stack if the stack slot is

   117                                  * guaranteed to be correct. Only moves that have been inserted by

   118                                  * LinearScan can be removed.

   119                                  */

   120                                 if (shouldEliminateSpillMoves && canEliminateSpillMove(allocator, block, move, lastOpId)) {

   121                                     /*

   122                                      * Move target is a stack slot that is always correct, so

   123                                      * eliminate instruction.

   124                                      */

   125                                     if (debug.isLogEnabled()) {

   126                                         if (ValueMoveOp.isValueMoveOp(op)) {

   127                                             ValueMoveOp vmove = ValueMoveOp.asValueMoveOp(op);

   128                                             debug.log("eliminating move from interval %s to %s in block %s", vmove.getInput(), vmove.getResult(), block);

   129                                         } else {

   130                                             LoadConstantOp load = LoadConstantOp.asLoadConstantOp(op);

   131                                             debug.log("eliminating constant load from %s to %s in block %s", load.getConstant(), load.getResult(),

   132                                                             block);

   133                                         }

   134                                     }

   135 

   136                                     // null-instructions are deleted by assignRegNum

   137                                     instructions.set(j, null);

   138                                 }

   139 

   140                             } else {

   141                                 lastOpId = opId;

   142                                 /*

   143                                  * Insert move from register to stack just after the beginning of

   144                                  * the interval.

   145                                  */

   146                                 // assert interval == TraceInterval.EndMarker ||

   147                                 // interval.spillDefinitionPos() >= opId : "invalid order";

   148                                 assert interval == TraceInterval.EndMarker || (interval.isSplitParent() && SpillState.IN_MEMORY.contains(interval.spillState())) : "invalid interval";

   149 

   150                                 while (interval != TraceInterval.EndMarker && interval.spillDefinitionPos() == opId) {

   151                                     debug.log("handle %s", interval);

   152                                     if (!interval.canMaterialize() && interval.spillState() != SpillState.StartInMemory) {

   153 

   154                                         AllocatableValue fromLocation = interval.getSplitChildAtOpId(opId, OperandMode.DEF).location();

   155                                         AllocatableValue toLocation = allocator.canonicalSpillOpr(interval);

   156                                         if (!fromLocation.equals(toLocation)) {

   157 

   158                                             if (!insertionBuffer.initialized()) {

   159                                                 /*

   160                                                  * prepare insertion buffer (appended when all

   161                                                  * instructions in the block are processed)

   162                                                  */

   163                                                 insertionBuffer.init(instructions);

   164                                             }

   165 

   166                                             assert isRegister(fromLocation) : "from operand must be a register but is: " + fromLocation + " toLocation=" + toLocation + " spillState=" +

   167                                                             interval.spillState();

   168                                             assert isStackSlotValue(toLocation) : "to operand must be a stack slot";

   169 

   170                                             LIRInstruction move = allocator.getSpillMoveFactory().createMove(toLocation, fromLocation);

   171                                             insertionBuffer.append(j + 1, move);

   172                                             move.setComment(res, "TraceLSRAEliminateSpillMove: spill def pos");

   173 

   174                                             if (debug.isLogEnabled()) {

   175                                                 debug.log("inserting move after definition of interval %d to stack slot %s at opId %d", interval.operandNumber, interval.spillSlot(), opId);

   176                                             }

   177                                         }

   178                                     }

   179                                     interval = interval.next;

   180                                 }

   181                             }

   182                         }

   183                     }   // end of instruction iteration

   184 

   185                     if (insertionBuffer.initialized()) {

   186                         insertionBuffer.finish();

   187                     }

   188                 }

   189             }   // end of block iteration

   190 

   191             assert interval == TraceInterval.EndMarker : "missed an interval";

   192         }

   193     }

   194 

   195     /**

   196      * @param allocator

   197      * @param block The block {@code move} is located in.

   198      * @param move Spill move.

   199      * @param lastOpId The id of last "normal" instruction before the spill move. (Spill moves have

   200      *            no valid opId but -1.)

   201      */

   202     private static boolean canEliminateSpillMove(TraceLinearScan allocator, AbstractBlockBase<?> block, MoveOp move, int lastOpId) {

   203         assert ((LIRInstruction) move).id() == -1 : "Not a spill move: " + move;

   204         assert isVariable(move.getResult()) : "LinearScan inserts only moves to variables: " + move;

   205         assert lastOpId >= 0 : "Invalid lastOpId: " + lastOpId;

   206 

   207         TraceInterval curInterval = allocator.intervalFor(asVariable(move.getResult()));

   208 

   209         if (!isRegister(curInterval.location()) && curInterval.inMemoryAt(lastOpId) && !isPhiResolutionMove(allocator, move)) {

   210             /* Phi resolution moves cannot be removed because they define the value. */

   211             // TODO (je) check if the comment is still valid!

   212             assert isStackSlotValue(curInterval.location()) : "Not a stack slot: " + curInterval.location();

   213             return true;

   214         }

   215         return false;

   216     }

   217 

   218     /**

   219      * Checks if a (spill or split) move is a Phi resolution move.

   220      *

   221      * A spill or split move connects a split parent or a split child with another split child.

   222      * Therefore the destination of the move is always a split child. Phi resolution moves look like

   223      * spill moves (i.e. {@link LIRInstruction#id() id} is {@code 0}, but they define a new

   224      * variable. As a result the destination interval is a split parent.

   225      */

   226     private static boolean isPhiResolutionMove(TraceLinearScan allocator, MoveOp move) {

   227         assert ((LIRInstruction) move).id() == -1 : "Not a spill move: " + move;

   228         TraceInterval curInterval = allocator.intervalFor(asVariable(move.getResult()));

   229         return curInterval.isSplitParent();

   230     }

   231 

   232     private static void checkIntervals(DebugContext debug, TraceInterval interval) {

   233         TraceInterval prev = null;

   234         TraceInterval temp = interval;

   235         while (temp != TraceInterval.EndMarker) {

   236             assert temp.spillDefinitionPos() >= 0 : "invalid spill definition pos " + temp;

   237             if (prev != null) {

   238                 // assert temp.from() >= prev.from() : "intervals not sorted";

   239                 assert temp.spillDefinitionPos() >= prev.spillDefinitionPos() : "when intervals are sorted by from :  then they must also be sorted by spillDefinitionPos";

   240             }

   241 

   242             assert temp.spillSlot() != null || temp.canMaterialize() : "interval has no spill slot assigned";

   243             assert temp.spillDefinitionPos() >= temp.from() : "invalid order";

   244             // assert temp.spillDefinitionPos() <= temp.from() + 2 :

   245             // "only intervals defined once at their start-pos can be optimized";

   246 

   247             if (debug.isLogEnabled()) {

   248                 debug.log("interval %d (from %d to %d) must be stored at %d", temp.operandNumber, temp.from(), temp.to(), temp.spillDefinitionPos());

   249             }

   250 

   251             prev = temp;

   252             temp = temp.next;

   253         }

   254     }

   255 

   256 }