1/*
2 * Copyright (c) 2014 The University of Wisconsin
3 *
4 * Copyright (c) 2006 INRIA (Institut National de Recherche en
5 * Informatique et en Automatique / French National Research Institute
6 * for Computer Science and Applied Mathematics)
7 *
8 * All rights reserved.

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50LTAGE::LTAGE(const LTAGEParams *params)
51 : BPredUnit(params),
52 logSizeBiMP(params->logSizeBiMP),
53 logRatioBiModalHystEntries(params->logRatioBiModalHystEntries),
54 logSizeTagTables(params->logSizeTagTables),
55 logSizeLoopPred(params->logSizeLoopPred),
56 nHistoryTables(params->nHistoryTables),
57 tagTableCounterBits(params->tagTableCounterBits),
58 tagTableUBits(params->tagTableUBits),
59 histBufferSize(params->histBufferSize),
60 minHist(params->minHist),
61 maxHist(params->maxHist),
62 minTagWidth(params->minTagWidth),
63 loopTableAgeBits(params->loopTableAgeBits),
64 loopTableConfidenceBits(params->loopTableConfidenceBits),
65 loopTableTagBits(params->loopTableTagBits),
66 loopTableIterBits(params->loopTableIterBits),
67 confidenceThreshold((1 << loopTableConfidenceBits) - 1),
68 loopTagMask((1 << loopTableTagBits) - 1),
69 loopNumIterMask((1 << loopTableIterBits) - 1),
70 threadHistory(params->numThreads)
71{
72 // Current method for periodically resetting the u counter bits only
73 // works for 1 or 2 bits
74 // Also make sure that it is not 0
75 assert(tagTableUBits <= 2 && (tagTableUBits > 0));
76
77 // we use uint16_t type for these vales, so they cannot be more than
78 // 16 bits
79 assert(loopTableTagBits <= 16);
80 assert(loopTableIterBits <= 16);
81
82 assert(params->histBufferSize > params->maxHist * 2);
83 useAltPredForNewlyAllocated = 0;
84 logTick = 19;

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577 ctrUpdate(useAltPredForNewlyAllocated,
578 bi->altTaken == taken, 4);
579 }
580 }
581 }
582
583 if (alloc) {
584 // is there some "unuseful" entry to allocate
585 uint8_t min = 1;
586 for (int i = nHistoryTables; i > bi->hitBank; i--) {
587 if (gtable[i][bi->tableIndices[i]].u < min) {
588 min = gtable[i][bi->tableIndices[i]].u;
589 }
590 }
591
592 // we allocate an entry with a longer history
593 // to avoid ping-pong, we do not choose systematically the next

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606 }
607
608
609 //Allocate only one entry
610 for (int i = X; i <= nHistoryTables; i++) {
611 if ((gtable[i][bi->tableIndices[i]].u == 0)) {
612 gtable[i][bi->tableIndices[i]].tag = bi->tableTags[i];
613 gtable[i][bi->tableIndices[i]].ctr = (taken) ? 0 : -1;
614 break;
615 }
616 }
617 }
618 //periodic reset of u: reset is not complete but bit by bit
619 tCounter++;
620 if ((tCounter & ((ULL(1) << logTick) - 1)) == 0) {
621 // reset least significant bit

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643 branch_pc);
644 }
645 if (bi->altBank == 0) {
646 baseUpdate(pc, taken, bi);
647 }
648 }
649
650 // update the u counter
651 if (bi->tagePred != bi->altTaken) {
652 unsignedCtrUpdate(gtable[bi->hitBank][bi->hitBankIndex].u,
653 bi->tagePred == taken, tagTableUBits);
654 }
655 } else {
656 baseUpdate(pc, taken, bi);
657 }
658
659 //END PREDICTOR UPDATE
660 }
661 if (!squashed) {

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