Intel ARCHITECTURE IA-32 User Manual download pdf (Page 7)

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Considerations for Code Conversion to SIMD Programming.................................................. 3-8

Identifying Hot Spots ...................................................................................................... 3-10

Determine If Code Benefits by Conversion to SIMD Execution...................................... 3-11

Coding Techniques ............................................................................................................... 3-12

Coding Methodologies.................................................................................................... 3-13

Assembly.................................................................................................................. 3-15

Intrinsics.................................................................................................................... 3-15

Classes..................................................................................................................... 3-17

Automatic Vectorization ............................................................................................ 3-18

Stack and Data Alignment..................................................................................................... 3-20

Alignment and Contiguity of Data Access Patterns........................................................ 3-20

Using Padding to Align Data..................................................................................... 3-20

Using Arrays to Make Data Contiguous.................................................................... 3-21

Stack Alignment For 128-bit SIMD Technologies ........................................................... 3-22

Data Alignment for MMX Technology ............................................................................. 3-23

Data Alignment for 128-bit data...................................................................................... 3-24

Compiler-Supported Alignment................................................................................. 3-24

Improving Memory Utilization................................................................................................ 3-27

Data Structure Layout..................................................................................................... 3-27

Strip Mining..................................................................................................................... 3-32

Loop Blocking................................................................................................................. 3-34

Instruction Selection.............................................................................................................. 3-37

SIMD Optimizations and Microarchitectures .................................................................. 3-38

Tuning the Final Application.................................................................................................. 3-39

Chapter 4 Optimizing for SIMD Integer Applications

General Rules on SIMD Integer Code .................................................................................... 4-2

Using SIMD Integer with x87 Floating-point............................................................................ 4-3

Using the EMMS Instruction............................................................................................. 4-3

Guidelines for Using EMMS Instruction............................................................................ 4-4

Data Alignment........................................................................................................................ 4-6

Data Movement Coding Techniques ....................................................................................... 4-6

Unsigned Unpack ............................................................................................................. 4-6

Signed Unpack................................................................................................................. 4-7

Interleaved Pack with Saturation...................................................................................... 4-8

Interleaved Pack without Saturation............................................................................... 4-10

Non-Interleaved Unpack................................................................................................. 4-11

Extract Word................................................................................................................... 4-13

Insert Word..................................................................................................................... 4-14

Move Byte Mask to Integer............................................................................................. 4-16

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Intel ARCHITECTURE IA-32 User Manual Page 7