C++ MInstruction::clearResumePoint方法代码示例

//.........这里部分代码省略.........
            // of the uses and the original instruction. This prevent moving the
            // computation of the arguments into an inline function if there is
            // no major win.
            MBasicBlock* lastJoin = usesDominator;
            while (*block != lastJoin && lastJoin->numPredecessors() == 1) {
                MOZ_ASSERT(lastJoin != lastJoin->immediateDominator());
                MBasicBlock* next = lastJoin->immediateDominator();
                if (next->numSuccessors() > 1)
                    break;
                lastJoin = next;
            }
            if (*block == lastJoin)
                continue;

            // Skip to the next instruction if we cannot find a common dominator
            // for all the uses of this instruction, or if the common dominator
            // correspond to the block of the current instruction.
            if (!usesDominator || usesDominator == *block)
                continue;

            // Only instruction which can be recovered on bailout and which are
            // sinkable can be moved into blocks which are below while filling
            // the resume points with a clone which is recovered on bailout.

            // If the instruction has live uses and if it is clonable, then we
            // can clone the instruction for all non-dominated uses and move the
            // instruction into the block which is dominating all live uses.
            if (!ins->canClone())
                continue;

            // If the block is a split-edge block, which is created for folding
            // test conditions, then the block has no resume point and has
            // multiple predecessors.  In such case, we cannot safely move
            // bailing instruction to these blocks as we have no way to bailout.
            if (!usesDominator->entryResumePoint() && usesDominator->numPredecessors() != 1)
                continue;

            JitSpewDef(JitSpew_Sink, "  Can Clone & Recover, sink instruction\n", ins);
            JitSpew(JitSpew_Sink, "  into Block %u", usesDominator->id());

            // Copy the arguments and clone the instruction.
            MDefinitionVector operands(alloc);
            for (size_t i = 0, end = ins->numOperands(); i < end; i++) {
                if (!operands.append(ins->getOperand(i)))
                    return false;
            }

            MInstruction* clone = ins->clone(alloc, operands);
            ins->block()->insertBefore(ins, clone);
            clone->setRecoveredOnBailout();

            // We should not update the producer of the entry resume point, as
            // it cannot refer to any instruction within the basic block excepts
            // for Phi nodes.
            MResumePoint* entry = usesDominator->entryResumePoint();

            // Replace the instruction by its clone in all the resume points /
            // recovered-on-bailout instructions which are not in blocks which
            // are dominated by the usesDominator block.
            for (MUseIterator i(ins->usesBegin()), e(ins->usesEnd()); i != e; ) {
                MUse* use = *i++;
                MNode* consumer = use->consumer();

                // If the consumer is a Phi, then we look for the index of the
                // use to find the corresponding predecessor block, which is
                // then used as the consumer block.
                MBasicBlock* consumerBlock = consumer->block();
                if (consumer->isDefinition() && consumer->toDefinition()->isPhi()) {
                    consumerBlock = consumerBlock->getPredecessor(
                        consumer->toDefinition()->toPhi()->indexOf(use));
                }

                // Keep the current instruction for all dominated uses, except
                // for the entry resume point of the block in which the
                // instruction would be moved into.
                if (usesDominator->dominates(consumerBlock) &&
                    (!consumer->isResumePoint() || consumer->toResumePoint() != entry))
                {
                    continue;
                }

                use->replaceProducer(clone);
            }

            // As we move this instruction in a different block, we should
            // verify that we do not carry over a resume point which would refer
            // to an outdated state of the control flow.
            if (ins->resumePoint())
                ins->clearResumePoint();

            // Now, that all uses which are not dominated by usesDominator are
            // using the cloned instruction, we can safely move the instruction
            // into the usesDominator block.
            MInstruction* at = usesDominator->safeInsertTop(nullptr, MBasicBlock::IgnoreRecover);
            block->moveBefore(at, ins);
        }
    }

    return true;
}