НОУ ИНТУИТ | Introduction to performance optimization using Intel SW tools. Лекция 5: Optimizing compiler. Vectorization

Опубликован: 12.07.2012 | Уровень: специалист | Доступ: платный

Packed data type	Vector length	Bits per element	Data type range
signed bytes	16	8	-27 to 27-1
unsigned bytes	16	8	0 до 2**8-1
signed words	8	16	-215 to 215-1
unsigned words	8	16	0 до 2**16
signed doublewords	4	32	-231 to 231-1
unsigned doublewords	4	32	0 до 2**32-1
signed quadwords	2	64	-2*63 to 263-1
unsigned quadwords	2	64	0 до 2**64-1
single-precision fps	4	32	2-126 to 2127
double-precision fps	2	64	2-1022 to 21023

Selecting the appropriate data type for calculations can significantly affect application performance.

Рис. 5.5. SIMD – SSE, SSE2, SSE3, SSE4.2 Support

Data movement instructions
Instruction	Suffix	Description
movdqa		move double quadword aligned
movdqu		move double quadword unaligned
mova	[ ps, pd ]	move floating-point aligned
movu	[ ps, pd ]	move floating-point unaligned
movhl	[ ps ]	move packed floating-point high to low
movlh	[ ps ]	move packed floating-point low to high
movh	[ ps, pd ]	move high packed floating-point
movl	[ ps, pd ]	move low packed floating-point
mov	[ d, q, ss, sd ]	move scalar data
lddqu		load double quadword unaligned
Mov <d/sh/sl>dup		move and duplicate
pextr	[ w ]	extract word
pinstr	[ w ]	insert word
pmovmsk	[ b ]	move mask
movmsk	[ ps, pd ]	move mask

An aligned data movement instruction cannot be applied to the memory location which is not aligned by 16 (bytes).

Intel arithmetic instructions
Instruction	Suffix	Description
padd	[ b, w, d, q ]	packed addition (signed and unsigned)
psub	[ b, w, d, q ]	packed subtraction (signed and unsigned)
padds	[ b, w ]	packed addition with saturation (signed)
paddus	[ b, w ]	packed addition with saturation (unsigned)
psubs	[ b, w ]	packed subtraction with saturation (signed)
psubus	[ b, w ]	packed subtraction with saturation (unsigned)
pmins	[ w ]	packed minimum (signed)
pminu	[ b ]	packed minimum (unsigned)
pmaxs	[ w ]	packed maximum (signed)
pmaxu	[ b ]	packed maximum (unsigned)

Floating-point arithmetic instructions
Instruction	Suffix	Description
add	[ ss, ps, sd, pd ]	addition
div	[ ss, ps, sd, pd ]	division
min	[ ss, ps, sd, pd ]	minimum
max	[ ss, ps, sd, pd ]	maximum
mul	[ ss, ps, sd, pd ]	multiplication
sqrt	[ ss, ps, sd, pd ]	square root
sub	[ ss, ps, sd, pd ]	subtraction
rcp	[ ss, ps]	approximated reciprocal
rsqrt	[ ss, ps]	approximated reciprocal square root

Idiomatic arithmetic instructions
Instruction	Suffix	Description
pang	[ b, w ]	packed average with rounding (unsigned)
pmulh/pmulhu/pmull	[ w ]	packed multiplication
psad	[ bw ]	packed sum of absolute differences (unsigned)
pmadd	[ wd ]	packed multiplication and addition (signed)
addsub	[ ps, pd ]	floating-point addition/subtraction
hadd	[ ps, pd ]	floating-point horizontal addition
hsub	[ ps, pd ]	floating-point horizontal subtraction

Comparison instructions :

Таблица .
Instruction	Suffix	Description
pcmp<cc>	[ b, w, d ]	packed compare
cmp<cc>	[ ss, ps, sd, pd ]	floating-point compare

<cc> defines comparison operation.

lt – less, gt – greater, eq - equal

Conversion instructions
Instruction	Suffix	Description
packss	[wb, dw]	pack with saturation (signed)
paсkus	[wb]	pack with saturation (unsigned)
cvt<s2d>		conversion
cvtt<s2d>		conversion with truncation

Shift instructions
Instruction	Suffix	Description
psll	[ w, d, q, dq ]	shift left logical (zero in)
psra	[w, d]	shift right arithmetic (sign in)
psrl	[ w, d, q, dq ]	shift right logical (zero in)

Cacheability control and prefetch instructions
Instruction	Suffix	Description
movnt	[ ps, pd, q, dq ]	move aligned non-temporal
prefetch<hint>		prefetch with hint

State management instructions

These instructions are commonly used by operating system.

Optimizing compiler. Vectorization