https://openjdk.java.net/ 
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 * 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
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 */


package org.graalvm.compiler.asm;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;

import jdk.vm.ci.code.Register;
import jdk.vm.ci.code.StackSlot;
import jdk.vm.ci.code.TargetDescription;


The platform-independent base class for the assembler.

/**
 * The platform-independent base class for the assembler.
 */
public abstract class Assembler {

    public abstract static class CodeAnnotation {
        
The position (bytes from the beginning of the method) of the annotated instruction.

/**
         * The position (bytes from the beginning of the method) of the annotated instruction.
         */
        public final int instructionPosition;

        protected CodeAnnotation(int instructionStartPosition) {
            this.instructionPosition = instructionStartPosition;
        }
    }

    public final TargetDescription target;
    private List<LabelHint> jumpDisplacementHints;

    
Labels with instructions to be patched when it is bound. 
/**
     * Labels with instructions to be patched when it is {@linkplain Label#bind bound}.
     */
    Label labelsWithPatches;

    
Backing code buffer.

/**
     * Backing code buffer.
     */
    private final Buffer codeBuffer;

    protected Consumer<CodeAnnotation> codePatchingAnnotationConsumer;

    public Assembler(TargetDescription target) {
        this.target = target;
        this.codeBuffer = new Buffer(target.arch.getByteOrder());
    }

    public void setCodePatchingAnnotationConsumer(Consumer<CodeAnnotation> codeAnnotationConsumer) {
        assert this.codePatchingAnnotationConsumer == null : "overwriting existing value";
        this.codePatchingAnnotationConsumer = codeAnnotationConsumer;
    }

    
Returns the current position of the underlying code buffer.

Returns:current position in code buffer
/**
     * Returns the current position of the underlying code buffer.
     *
     * @return current position in code buffer
     */
    public int position() {
        return codeBuffer.position();
    }

    public final void emitByte(int x) {
        codeBuffer.emitByte(x);
    }

    public final void emitShort(int x) {
        codeBuffer.emitShort(x);
    }

    public final void emitInt(int x) {
        codeBuffer.emitInt(x);
    }

    public final void emitLong(long x) {
        codeBuffer.emitLong(x);
    }

    public final void emitByte(int b, int pos) {
        codeBuffer.emitByte(b, pos);
    }

    public final void emitShort(int b, int pos) {
        codeBuffer.emitShort(b, pos);
    }

    public final void emitInt(int b, int pos) {
        codeBuffer.emitInt(b, pos);
    }

    public final void emitLong(long b, int pos) {
        codeBuffer.emitLong(b, pos);
    }

    public final int getByte(int pos) {
        return codeBuffer.getByte(pos);
    }

    public final int getShort(int pos) {
        return codeBuffer.getShort(pos);
    }

    public final int getInt(int pos) {
        return codeBuffer.getInt(pos);
    }

    private static final String NEWLINE = System.lineSeparator();

    
Some GPU architectures have a text based encoding.

/**
     * Some GPU architectures have a text based encoding.
     */
    public final void emitString(String x) {
        emitString0("\t");  // XXX REMOVE ME pretty-printing
        emitString0(x);
        emitString0(NEWLINE);
    }

    // XXX for pretty-printing
    public final void emitString0(String x) {
        codeBuffer.emitBytes(x.getBytes(), 0, x.length());
    }

    public void emitString(String s, int pos) {
        codeBuffer.emitBytes(s.getBytes(), pos);
    }

    
Closes this assembler. No extra data can be written to this assembler after this call.

Params:
  • trimmedCopy – if true, then a copy of the underlying byte array up to (but not including) position() is returned
Returns:the data in this buffer or a trimmed copy if trimmedCopy is true
/**
     * Closes this assembler. No extra data can be written to this assembler after this call.
     *
     * @param trimmedCopy if {@code true}, then a copy of the underlying byte array up to (but not
     *            including) {@code position()} is returned
     * @return the data in this buffer or a trimmed copy if {@code trimmedCopy} is {@code true}
     */
    public byte[] close(boolean trimmedCopy) {
        checkAndClearLabelsWithPatches();
        return codeBuffer.close(trimmedCopy);
    }

    private void checkAndClearLabelsWithPatches() throws InternalError {
        Label label = labelsWithPatches;
        while (label != null) {
            if (label.patchPositions != null) {
                throw new InternalError("Label used by instructions at following offsets has not been bound: " + label.patchPositions);
            }
            Label next = label.nextWithPatches;
            label.nextWithPatches = null;
            label = next;
        }
        labelsWithPatches = null;
    }

    public void bind(Label l) {
        assert !l.isBound() : "can bind label only once";
        l.bind(position(), this);
    }

    public abstract void align(int modulus);

    public abstract void jmp(Label l);

    protected abstract void patchJumpTarget(int branch, int jumpTarget);

    private Map<Label, String> nameMap;

    
Creates a name for a label.

Params:
  • l – the label for which a name is being created
  • id – a label identifier that is unique with the scope of this assembler
Returns:a label name in the form of "L123"
/**
     * Creates a name for a label.
     *
     * @param l the label for which a name is being created
     * @param id a label identifier that is unique with the scope of this assembler
     * @return a label name in the form of "L123"
     */
    protected String createLabelName(Label l, int id) {
        return "L" + id;
    }

    
Gets a name for a label, creating it if it does not yet exist. By default, the returned name
is only unique with the scope of this assembler.

/**
     * Gets a name for a label, creating it if it does not yet exist. By default, the returned name
     * is only unique with the scope of this assembler.
     */
    public String nameOf(Label l) {
        if (nameMap == null) {
            nameMap = new HashMap<>();
        }
        String name = nameMap.get(l);
        if (name == null) {
            name = createLabelName(l, nameMap.size());
            nameMap.put(l, name);
        }
        return name;
    }

    
This is used by the CompilationResultBuilder to convert a StackSlot to an AbstractAddress. 
/**
     * This is used by the CompilationResultBuilder to convert a {@link StackSlot} to an
     * {@link AbstractAddress}.
     */
    public abstract AbstractAddress makeAddress(Register base, int displacement);

    
Returns a target specific placeholder address that can be used for code patching.

Params:
  • instructionStartPosition – The start of the instruction, i.e., the value that is used as
           the key for looking up placeholder patching information.
/**
     * Returns a target specific placeholder address that can be used for code patching.
     *
     * @param instructionStartPosition The start of the instruction, i.e., the value that is used as
     *            the key for looking up placeholder patching information.
     */
    public abstract AbstractAddress getPlaceholder(int instructionStartPosition);

    
Emits a NOP instruction to advance the current PC.

/**
     * Emits a NOP instruction to advance the current PC.
     */
    public abstract void ensureUniquePC();

    public void reset() {
        codeBuffer.reset();
        captureLabelPositions();
    }

    private void captureLabelPositions() {
        if (jumpDisplacementHints == null) {
            return;
        }
        for (LabelHint request : this.jumpDisplacementHints) {
            request.capture();
        }
    }

    public LabelHint requestLabelHint(Label label) {
        if (jumpDisplacementHints == null) {
            jumpDisplacementHints = new ArrayList<>();
        }
        LabelHint hint = new LabelHint(label, position());
        this.jumpDisplacementHints.add(hint);
        return hint;
    }

    public InstructionCounter getInstructionCounter() {
        throw new UnsupportedOperationException("Instruction counter is not implemented for " + this);
    }

    public static class LabelHint {
        private Label label;
        private int forPosition;
        private int capturedTarget = -1;

        protected LabelHint(Label label, int lastPosition) {
            super();
            this.label = label;
            this.forPosition = lastPosition;
        }

        protected void capture() {
            this.capturedTarget = label.position();
        }

        public int getTarget() {
            assert isValid();
            return capturedTarget;
        }

        public int getPosition() {
            assert isValid();
            return forPosition;
        }

        public boolean isValid() {
            return capturedTarget >= 0;
        }
    }

    
Instruction counter class which gives the user of the assembler to count different kinds of
instructions in the generated assembler code.

/**
     * Instruction counter class which gives the user of the assembler to count different kinds of
     * instructions in the generated assembler code.
     */
    public interface InstructionCounter {
        String[] getSupportedInstructionTypes();

        int[] countInstructions(String[] instructionTypes, int beginPc, int endPc);
    }
}