Bug 962 - design integer-versions of fft/dct "butterfly" instructions
Summary: design integer-versions of fft/dct "butterfly" instructions
Status: RESOLVED DUPLICATE of bug 1074
Alias: None
Product: Libre-SOC's first SoC
Classification: Unclassified
Component: Specification (show other bugs)
Version: unspecified
Hardware: PC Linux
: --- enhancement
Assignee: Luke Kenneth Casson Leighton
URL:
Depends on:
Blocks: 952 1028
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Reported: 2022-10-22 10:24 BST by Luke Kenneth Casson Leighton
Modified: 2023-04-28 18:31 BST (History)
2 users (show)

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Description Luke Kenneth Casson Leighton 2022-10-22 10:24:48 BST 
from the bug #137 video codecs it was clear that many implementations
of DCT/FFT are integer-based.  therefore integer butterfly instructions.
ARM already has them: vqrdmulhq_s16/vqrdmulhq_s32

<markos> https://developer.arm.com/architectures/instruction-sets/intrinsics/#f:@navigationhierarchiessimdisa=[Neon]&q=vqrdmulhq_s16
<markos> https://developer.arm.com/documentation/ddi0596/2021-03/SIMD-FP-Instructions/SQRDMULH--vector---Signed-saturating-Rounding-Doubling-Multiply-returning-High-half-?lang=en for the asm instruction
Comment 1 Konstantinos Margaritis (markos) 2023-04-28 18:10:35 BST 
First working prototype/design here:

https://libre-soc.org/openpower/sv/twin_butterfly/
Comment 2 Luke Kenneth Casson Leighton 2023-04-28 18:22:59 BST 
(In reply to Konstantinos Margaritis (markos) from comment #1)
> First working prototype/design here:
> 
> https://libre-soc.org/openpower/sv/twin_butterfly/

awesome.  comments:

    * maddsubrs RT,RA,SH,RB

normally (by convention) RB is in the 3rd operand position.
Comment 3 Luke Kenneth Casson Leighton 2023-04-28 18:31:32 BST 

*** This bug has been marked as a duplicate of bug 1074 ***