The Tor Browser / file diff

     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/js/src/jit/EffectiveAddressAnalysis.cpp	Wed Dec 31 06:09:35 2014 +0100
     1.3 @@ -0,0 +1,116 @@
     1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
     1.5 + * vim: set ts=8 sts=4 et sw=4 tw=99:
     1.6 + * This Source Code Form is subject to the terms of the Mozilla Public
     1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
     1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
     1.9 +
    1.10 +#include "jit/EffectiveAddressAnalysis.h"
    1.11 +#include "jit/MIR.h"
    1.12 +#include "jit/MIRGraph.h"
    1.13 +
    1.14 +using namespace js;
    1.15 +using namespace jit;
    1.16 +
    1.17 +static void
    1.18 +AnalyzeLsh(TempAllocator &alloc, MLsh *lsh)
    1.19 +{
    1.20 +    if (lsh->specialization() != MIRType_Int32)
    1.21 +        return;
    1.22 +
    1.23 +    MDefinition *index = lsh->lhs();
    1.24 +    JS_ASSERT(index->type() == MIRType_Int32);
    1.25 +
    1.26 +    MDefinition *shift = lsh->rhs();
    1.27 +    if (!shift->isConstant())
    1.28 +        return;
    1.29 +
    1.30 +    Value shiftValue = shift->toConstant()->value();
    1.31 +    if (!shiftValue.isInt32() || !IsShiftInScaleRange(shiftValue.toInt32()))
    1.32 +        return;
    1.33 +
    1.34 +    Scale scale = ShiftToScale(shiftValue.toInt32());
    1.35 +
    1.36 +    int32_t displacement = 0;
    1.37 +    MInstruction *last = lsh;
    1.38 +    MDefinition *base = nullptr;
    1.39 +    while (true) {
    1.40 +        if (!last->hasOneUse())
    1.41 +            break;
    1.42 +
    1.43 +        MUseIterator use = last->usesBegin();
    1.44 +        if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isAdd())
    1.45 +            break;
    1.46 +
    1.47 +        MAdd *add = use->consumer()->toDefinition()->toAdd();
    1.48 +        if (add->specialization() != MIRType_Int32 || !add->isTruncated())
    1.49 +            break;
    1.50 +
    1.51 +        MDefinition *other = add->getOperand(1 - use->index());
    1.52 +
    1.53 +        if (other->isConstant()) {
    1.54 +            displacement += other->toConstant()->value().toInt32();
    1.55 +        } else {
    1.56 +            if (base)
    1.57 +                break;
    1.58 +            base = other;
    1.59 +        }
    1.60 +
    1.61 +        last = add;
    1.62 +    }
    1.63 +
    1.64 +    if (!base) {
    1.65 +        uint32_t elemSize = 1 << ScaleToShift(scale);
    1.66 +        if (displacement % elemSize != 0)
    1.67 +            return;
    1.68 +
    1.69 +        if (!last->hasOneUse())
    1.70 +            return;
    1.71 +
    1.72 +        MUseIterator use = last->usesBegin();
    1.73 +        if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isBitAnd())
    1.74 +            return;
    1.75 +
    1.76 +        MBitAnd *bitAnd = use->consumer()->toDefinition()->toBitAnd();
    1.77 +        MDefinition *other = bitAnd->getOperand(1 - use->index());
    1.78 +        if (!other->isConstant() || !other->toConstant()->value().isInt32())
    1.79 +            return;
    1.80 +
    1.81 +        uint32_t bitsClearedByShift = elemSize - 1;
    1.82 +        uint32_t bitsClearedByMask = ~uint32_t(other->toConstant()->value().toInt32());
    1.83 +        if ((bitsClearedByShift & bitsClearedByMask) != bitsClearedByMask)
    1.84 +            return;
    1.85 +
    1.86 +        bitAnd->replaceAllUsesWith(last);
    1.87 +        return;
    1.88 +    }
    1.89 +
    1.90 +    MEffectiveAddress *eaddr = MEffectiveAddress::New(alloc, base, index, scale, displacement);
    1.91 +    last->replaceAllUsesWith(eaddr);
    1.92 +    last->block()->insertAfter(last, eaddr);
    1.93 +}
    1.94 +
    1.95 +// This analysis converts patterns of the form:
    1.96 +//   truncate(x + (y << {0,1,2,3}))
    1.97 +//   truncate(x + (y << {0,1,2,3}) + imm32)
    1.98 +// into a single lea instruction, and patterns of the form:
    1.99 +//   asmload(x + imm32)
   1.100 +//   asmload(x << {0,1,2,3})
   1.101 +//   asmload((x << {0,1,2,3}) + imm32)
   1.102 +//   asmload((x << {0,1,2,3}) & mask)            (where mask is redundant with shift)
   1.103 +//   asmload(((x << {0,1,2,3}) + imm32) & mask)  (where mask is redundant with shift + imm32)
   1.104 +// into a single asmload instruction (and for asmstore too).
   1.105 +//
   1.106 +// Additionally, we should consider the general forms:
   1.107 +//   truncate(x + y + imm32)
   1.108 +//   truncate((y << {0,1,2,3}) + imm32)
   1.109 +bool
   1.110 +EffectiveAddressAnalysis::analyze()
   1.111 +{
   1.112 +    for (ReversePostorderIterator block(graph_.rpoBegin()); block != graph_.rpoEnd(); block++) {
   1.113 +        for (MInstructionIterator i = block->begin(); i != block->end(); i++) {
   1.114 +            if (i->isLsh())
   1.115 +                AnalyzeLsh(graph_.alloc(), i->toLsh());
   1.116 +        }
   1.117 +    }
   1.118 +    return true;
   1.119 +}