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comparison: js/src/jit/EffectiveAddressAnalysis.cpp
js/src/jit/EffectiveAddressAnalysis.cpp
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- | |
| 2 * vim: set ts=8 sts=4 et sw=4 tw=99: | |
| 3 * This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 #include "jit/EffectiveAddressAnalysis.h" | |
| 8 #include "jit/MIR.h" | |
| 9 #include "jit/MIRGraph.h" | |
| 10 | |
| 11 using namespace js; | |
| 12 using namespace jit; | |
| 13 | |
| 14 static void | |
| 15 AnalyzeLsh(TempAllocator &alloc, MLsh *lsh) | |
| 16 { | |
| 17 if (lsh->specialization() != MIRType_Int32) | |
| 18 return; | |
| 19 | |
| 20 MDefinition *index = lsh->lhs(); | |
| 21 JS_ASSERT(index->type() == MIRType_Int32); | |
| 22 | |
| 23 MDefinition *shift = lsh->rhs(); | |
| 24 if (!shift->isConstant()) | |
| 25 return; | |
| 26 | |
| 27 Value shiftValue = shift->toConstant()->value(); | |
| 28 if (!shiftValue.isInt32() || !IsShiftInScaleRange(shiftValue.toInt32())) | |
| 29 return; | |
| 30 | |
| 31 Scale scale = ShiftToScale(shiftValue.toInt32()); | |
| 32 | |
| 33 int32_t displacement = 0; | |
| 34 MInstruction *last = lsh; | |
| 35 MDefinition *base = nullptr; | |
| 36 while (true) { | |
| 37 if (!last->hasOneUse()) | |
| 38 break; | |
| 39 | |
| 40 MUseIterator use = last->usesBegin(); | |
| 41 if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isAdd()) | |
| 42 break; | |
| 43 | |
| 44 MAdd *add = use->consumer()->toDefinition()->toAdd(); | |
| 45 if (add->specialization() != MIRType_Int32 || !add->isTruncated()) | |
| 46 break; | |
| 47 | |
| 48 MDefinition *other = add->getOperand(1 - use->index()); | |
| 49 | |
| 50 if (other->isConstant()) { | |
| 51 displacement += other->toConstant()->value().toInt32(); | |
| 52 } else { | |
| 53 if (base) | |
| 54 break; | |
| 55 base = other; | |
| 56 } | |
| 57 | |
| 58 last = add; | |
| 59 } | |
| 60 | |
| 61 if (!base) { | |
| 62 uint32_t elemSize = 1 << ScaleToShift(scale); | |
| 63 if (displacement % elemSize != 0) | |
| 64 return; | |
| 65 | |
| 66 if (!last->hasOneUse()) | |
| 67 return; | |
| 68 | |
| 69 MUseIterator use = last->usesBegin(); | |
| 70 if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isBitAnd()) | |
| 71 return; | |
| 72 | |
| 73 MBitAnd *bitAnd = use->consumer()->toDefinition()->toBitAnd(); | |
| 74 MDefinition *other = bitAnd->getOperand(1 - use->index()); | |
| 75 if (!other->isConstant() || !other->toConstant()->value().isInt32()) | |
| 76 return; | |
| 77 | |
| 78 uint32_t bitsClearedByShift = elemSize - 1; | |
| 79 uint32_t bitsClearedByMask = ~uint32_t(other->toConstant()->value().toInt32()); | |
| 80 if ((bitsClearedByShift & bitsClearedByMask) != bitsClearedByMask) | |
| 81 return; | |
| 82 | |
| 83 bitAnd->replaceAllUsesWith(last); | |
| 84 return; | |
| 85 } | |
| 86 | |
| 87 MEffectiveAddress *eaddr = MEffectiveAddress::New(alloc, base, index, scale, displacement); | |
| 88 last->replaceAllUsesWith(eaddr); | |
| 89 last->block()->insertAfter(last, eaddr); | |
| 90 } | |
| 91 | |
| 92 // This analysis converts patterns of the form: | |
| 93 // truncate(x + (y << {0,1,2,3})) | |
| 94 // truncate(x + (y << {0,1,2,3}) + imm32) | |
| 95 // into a single lea instruction, and patterns of the form: | |
| 96 // asmload(x + imm32) | |
| 97 // asmload(x << {0,1,2,3}) | |
| 98 // asmload((x << {0,1,2,3}) + imm32) | |
| 99 // asmload((x << {0,1,2,3}) & mask) (where mask is redundant with shift) | |
| 100 // asmload(((x << {0,1,2,3}) + imm32) & mask) (where mask is redundant with shift + imm32) | |
| 101 // into a single asmload instruction (and for asmstore too). | |
| 102 // | |
| 103 // Additionally, we should consider the general forms: | |
| 104 // truncate(x + y + imm32) | |
| 105 // truncate((y << {0,1,2,3}) + imm32) | |
| 106 bool | |
| 107 EffectiveAddressAnalysis::analyze() | |
| 108 { | |
| 109 for (ReversePostorderIterator block(graph_.rpoBegin()); block != graph_.rpoEnd(); block++) { | |
| 110 for (MInstructionIterator i = block->begin(); i != block->end(); i++) { | |
| 111 if (i->isLsh()) | |
| 112 AnalyzeLsh(graph_.alloc(), i->toLsh()); | |
| 113 } | |
| 114 } | |
| 115 return true; | |
| 116 } |
