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LiteralOpUpgrader.javaAPI DocAndroid 1.5 API5522Wed May 06 22:41:02 BST 2009com.android.dx.ssa

LiteralOpUpgrader

public class LiteralOpUpgrader extends Object
Upgrades insn to their literal (constant-immediate) equivilent if possible. Also switches IF instructions that compare with a constant zero or null to be their IF_*Z equivalents.

Fields Summary
private final SsaMethod
ssaMeth
method we're processing
Constructors Summary
private LiteralOpUpgrader(SsaMethod ssaMethod)

        this.ssaMeth = ssaMethod;
Methods Summary
private static booleanisConstIntZeroOrKnownNull(com.android.dx.rop.code.RegisterSpec spec)
Returns true if the register contains an integer 0 or a known-null object reference

param
spec non-null spec
return
true for 0 or null type bearers

        TypeBearer tb = spec.getTypeBearer();
        if (tb instanceof CstLiteralBits) {
            CstLiteralBits clb = (CstLiteralBits) tb;
            return (clb.getLongBits() == 0);
        }
        return false;
public static voidprocess(SsaMethod ssaMethod)
Process a method.

param
ssaMethod non-null; method to process

        LiteralOpUpgrader dc;

        dc = new LiteralOpUpgrader(ssaMethod);
            
        dc.run();
private voidreplacePlainInsn(NormalSsaInsn insn, com.android.dx.rop.code.RegisterSpecList newSources, int newOpcode)
Replaces an SsaInsn containing a PlainInsn with a new PlainInsn. The new PlainInsn is contructed with a new RegOp and new sources. TODO move this somewhere else.

param
insn non-null; an SsaInsn containing a PlainInsn
param
newSources non-null; new sources list for new insn
param
newOpcode A RegOp from {@link RegOps}


        Insn originalRopInsn = insn.getOriginalRopInsn();
        Rop newRop = Rops.ropFor(newOpcode,
                insn.getResult(), newSources, null);
        Insn newRopInsn = new PlainInsn(newRop,
                originalRopInsn.getPosition(), insn.getResult(),
                newSources);
        NormalSsaInsn newInsn
                = new NormalSsaInsn(newRopInsn, insn.getBlock());

        List<SsaInsn> insns = insn.getBlock().getInsns();

        ssaMeth.onInsnRemoved(insn);
        insns.set(insns.lastIndexOf(insn), newInsn);
        ssaMeth.onInsnAdded(newInsn);
private voidrun()
Run the literal op upgrader

        final TranslationAdvice advice = Optimizer.getAdvice();

        ssaMeth.forEachInsn(new SsaInsn.Visitor() {
            public void visitMoveInsn(NormalSsaInsn insn) {
                // do nothing
            }

            public void visitPhiInsn(PhiInsn insn) {
                // do nothing
            }

            public void visitNonMoveInsn(NormalSsaInsn insn) {

                Insn originalRopInsn = insn.getOriginalRopInsn();
                Rop opcode = originalRopInsn.getOpcode();
                RegisterSpecList sources = insn.getSources();

                if (sources.size() != 2 ) {
                    // We're only dealing with two-source insns here.
                    return;
                }

                if (opcode.getBranchingness() == Rop.BRANCH_IF) {
                    /*
                     * An if instruction can become an if-*z instruction.
                     */
                    if (isConstIntZeroOrKnownNull(sources.get(0))) {
                        replacePlainInsn(insn, sources.withoutFirst(),
                                RegOps.flippedIfOpcode(opcode.getOpcode()));
                    } else if (isConstIntZeroOrKnownNull(sources.get(1))) {
                        replacePlainInsn(insn, sources.withoutLast(),
                                opcode.getOpcode());
                    }
                } else if (advice.hasConstantOperation(
                        opcode, sources.get(0), sources.get(1))) {
                    insn.upgradeToLiteral();
                } else  if (opcode.isCommutative()
                        && advice.hasConstantOperation(
                        opcode, sources.get(1), sources.get(0))) {
                    /*
                     * An instruction can be commuted to a literal operation
                     */

                    insn.setNewSources(
                            RegisterSpecList.make(
                                    sources.get(1), sources.get(0)));

                    insn.upgradeToLiteral();
                }
            }
        });