IntelÂ® 64 and IA-32 Architectures Optimization Reference Manual

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OPTIMIZING FOR SIMD INTEGER APPLICATIONSIntel Core microarchitecture generally executes SIMD instructions more efficientlythan previous microarchitectures in terms of latency and throughput, many of thelimitations specific to Intel Core Duo, Intel Core Solo processors do not apply. Thesame is true of Intel Core microarchitecture relative to Intel NetBurst microarchitectures.5-38
CHAPTER 6OPTIMIZING FOR SIMD FLOATING-POINTAPPLICATIONSThis chapter discusses rules for optimizing for the single-instruction, multiple-data(SIMD) floating-point instructions available in Streaming SIMD Extensions (SSE),Streaming SIMD Extensions 2 (SSE2)and Streaming SIMD Extensions 3 (SSE3). Thechapter also provides examples that illustrate the optimization techniques for singleprecisionand double-precision SIMD floating-point applications.6.1 GENERAL RULES FOR SIMD FLOATING-POINT CODEThe rules and suggestions in this section help optimize floating-point code containingSIMD floating-point instructions. Generally, it is important to understand and balanceport utilization to create efficient SIMD floating-point code. Basic rules and suggestionsinclude the following:• Follow all guidelines in Chapter 3 and Chapter 4.• Mask exceptions to achieve higher performance. When exceptions areunmasked, software performance is slower.• Utilize the flush-to-zero and denormals-are-zero modes for higher performanceto avoid the penalty of dealing with denormals and underflows.• Use the reciprocal instructions followed by iteration for increased accuracy. Theseinstructions yield reduced accuracy but execute much faster. Note the following:— If reduced accuracy is acceptable, use them with no iteration.— If near full accuracy is needed, use a Newton-Raphson iteration.— If full accuracy is needed, then use divide and square root which providemore accuracy, but slow down performance.6.2 PLANNING CONSIDERATIONSWhether adapting an existing application or creating a new one, using SIMD floatingpointinstructions to achieve optimum performance gain requires programmers toconsider several issues. In general, when choosing candidates for optimization, lookfor code segments that are computationally intensive and floating-point intensive.Also consider efficient use of the cache architecture.The sections that follow answer the questions that should be raised before implementation:• Can data layout be arranged to increase parallelism or cache utilization?6-1
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NIntel® 64 and IA-32 Architectures
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CONTENTS2.3.1 Front End. . . . . .
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CONTENTS3.7 PREFETCHING . . . . . .
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CONTENTS5.7.2.1 Increasing Memory B
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CONTENTS9.5.3 Streaming Store Instr
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CONTENTSB.7.4.3B.7.4.4B.7.4.5B.7.4.
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CONTENTSExample 4-1. Identification
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CONTENTSExample 9-8. Using HW Prefe
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CONTENTSFigure 9-7. Cache Blocking
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CHAPTER 1INTRODUCTIONThe Intel® 64
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INTRODUCTION• Chapter 10: Power O
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CHAPTER 2INTEL ® 64 AND IA-32 PROC
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INTEL® 64 AND IA-32 PROCESSOR ARCH
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CHAPTER 3GENERAL OPTIMIZATION GUIDE
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GENERAL OPTIMIZATION GUIDELINESThe
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GENERAL OPTIMIZATION GUIDELINEScomp
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GENERAL OPTIMIZATION GUIDELINES•
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GENERAL OPTIMIZATION GUIDELINESExam
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GENERAL OPTIMIZATION GUIDELINESthro
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GENERAL OPTIMIZATION GUIDELINESAsse
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GENERAL OPTIMIZATION GUIDELINESXOR
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GENERAL OPTIMIZATION GUIDELINESUse
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GENERAL OPTIMIZATION GUIDELINESMOVS
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GENERAL OPTIMIZATION GUIDELINESPack
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GENERAL OPTIMIZATION GUIDELINES3.5.
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GENERAL OPTIMIZATION GUIDELINESFor
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GENERAL OPTIMIZATION GUIDELINESAs a
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GENERAL OPTIMIZATION GUIDELINESTher
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GENERAL OPTIMIZATION GUIDELINES—
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GENERAL OPTIMIZATION GUIDELINESmore
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GENERAL OPTIMIZATION GUIDELINESrequ
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GENERAL OPTIMIZATION GUIDELINESpref
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GENERAL OPTIMIZATION GUIDELINESpref
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GENERAL OPTIMIZATION GUIDELINES—
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GENERAL OPTIMIZATION GUIDELINESTher
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GENERAL OPTIMIZATION GUIDELINESstat
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GENERAL OPTIMIZATION GUIDELINESexte
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GENERAL OPTIMIZATION GUIDELINESFor
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CODING FOR SIMD ARCHITECTURES4.1.1
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CODING FOR SIMD ARCHITECTURESSoftwa
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CODING FOR SIMD ARCHITECTURESTo use
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CODING FOR SIMD ARCHITECTURES4.3.1
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CODING FOR SIMD ARCHITECTURESExampl
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CODING FOR SIMD ARCHITECTURESmance
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CODING FOR SIMD ARCHITECTURESpurpos
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MULTICORE AND HYPER-THREADING TECHN
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OPTIMIZING CACHE USAGE• Take adva
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OPTIMIZING CACHE USAGEHardware pref
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OPTIMIZING CACHE USAGEThe non-tempo
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OPTIMIZING CACHE USAGE9.5.1.3 Memor
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OPTIMIZING CACHE USAGENOTEFailure t
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OPTIMIZING CACHE USAGE9.5.5 CLFLUSH
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OPTIMIZING CACHE USAGE• The hardw
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OPTIMIZING CACHE USAGETimeExecution
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OPTIMIZING CACHE USAGEschedule pref
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OPTIMIZING CACHE USAGEtime is large
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OPTIMIZING CACHE USAGEresource stal
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OPTIMIZING CACHE USAGEPrefetchntaDa
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OPTIMIZING CACHE USAGEExample 9-7.
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OPTIMIZING CACHE USAGEA characteris
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OPTIMIZING CACHE USAGE9.7 MEMORY OP
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OPTIMIZING CACHE USAGE9.7.2.3 Concl
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OPTIMIZING CACHE USAGEis not reside
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OPTIMIZING CACHE USAGEExample 9-11.
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OPTIMIZING CACHE USAGETable 9-3. De
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OPTIMIZING CACHE USAGE• If a proc
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64-BIT MODE CODING GUIDELINESAssemb
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64-BIT MODE CODING GUIDELINESinstru
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64-BIT MODE CODING GUIDELINES9-6
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POWER OPTIMIZATION FOR MOBILE USAGE
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APPLICATION PERFORMANCE TOOLSThe /f
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APPLICATION PERFORMANCE TOOLSTable
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APPLICATION PERFORMANCE TOOLSA.1.6.
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APPLICATION PERFORMANCE TOOLSExampl
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APPLICATION PERFORMANCE TOOLSExampl
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APPLICATION PERFORMANCE TOOLSprogra
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APPLICATION PERFORMANCE TOOLSThe Li
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APPLICATION PERFORMANCE TOOLSA.5 IN
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USING PERFORMANCE MONITORING EVENTS
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INSTRUCTION LATENCY AND THROUGHPUTW
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INSTRUCTION LATENCY AND THROUGHPUT
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INSTRUCTION LATENCY AND THROUGHPUTC
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STACK ALIGNMENTThe solution to this
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STACK ALIGNMENTExample D-1. Aligned
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STACK ALIGNMENTExample D-2. Aligned
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STACK ALIGNMENTD-8
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SUMMARY OF RULES AND SUGGESTIONSret
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SUMMARY OF RULES AND SUGGESTIONSvar
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SUMMARY OF RULES AND SUGGESTIONSCor
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SUMMARY OF RULES AND SUGGESTIONSE-1
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INDEXsummary of rules, E-1tuning hi
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INDEXevent ratios, B-50execution co
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INDEXprefetching, 8-5SFENCE instruc
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INDEXPMAXSW, 5-28PMAXUB, 5-28PMINSW
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INDEXIndex-10
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IntelÂ® 64 and IA-32 Architectures Optimization Reference Manual

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