sse problem pcmpistri

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Roman

Joined: 21 Apr 2012
Posts: 1767

Roman 13 Aug 2023, 10:44

fasmw 1.73 amd Ryzen 3500

Code:

;32 bits program
txtFind db 'We not played We'
txtA    db 'We              '

Start:                 ;pcmpistri to ecx index mask
use32
vimm = 0
movups xmm0,dqword [txtA]
movups xmm1,dqword [txtFind]
pcmpistri xmm0,xmm1,vimm

I try any values for vimm but always get ecx=0
How i understood in ecx return bits (like as mask)

Last edited by Roman on 13 Aug 2023, 12:04; edited 1 time in total

13 Aug 2023, 10:44

Roman

Joined: 21 Apr 2012
Posts: 1767

Roman 13 Aug 2023, 12:02

This variant show 3 equal symbols in ecx

Code:

;32 bits program
txtFind db 'We not played We'
txtA    db 'We              '

Start:                 
vimm = 0x18
movups xmm0,dqword [txtA]
movups xmm1,dqword [txtFind]
pcmpistri xmm0,xmm1,vimm    ;return to ecx index mask

13 Aug 2023, 12:02

bitRAKE

Joined: 21 Jul 2003
Posts: 4020
Location: vpcmpistri

bitRAKE 13 Aug 2023, 16:23

Roman wrote:

I try any values for vimm but always get ecx=0
How i understood in ecx return bits (like as mask)

But did you try:

Code:

vimm = 1_00_11_00b
;              00  unsigned bytes
;           11     ordered mode
;        00        polarity positive
;      1           last match

... ECX returns an index because that's what the last "I" in the PCMPISTRI instruction means. The control bits ask for the last match - which starts at index 14. Ordered mode is used to find sub-string; instead of looking for single byte matches.

Feel free to say what your expectations are, and I will help you get there. If you're just exploring, try all 128 possible combinations of vimm and puzzle the stored result values.

_________________
¯\(°_o)/¯ “languages are not safe - uses can be” Bjarne Stroustrup

13 Aug 2023, 16:23

Roman

Joined: 21 Apr 2012
Posts: 1767

Roman 13 Aug 2023, 17:35

https://officedaytime.com/simd512e/simdimg/str.php?f=pcmpistri

13 Aug 2023, 17:35

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