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js/src/jit/EffectiveAddressAnalysis.cpp@129ffea94266 (annotated)

js/src/jit/EffectiveAddressAnalysis.cpp

Sat, 03 Jan 2015 20:18:00 +0100

author

Michael Schloh von Bennewitz <michael@schloh.com>

date

Sat, 03 Jan 2015 20:18:00 +0100

branch

TOR_BUG_3246

changeset 7

129ffea94266

permissions

-rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

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