Bug 962

Summary:	design integer-versions of fft/dct "butterfly" instructions
Product:	Libre-SOC's first SoC	Reporter:	Luke Kenneth Casson Leighton <lkcl>
Component:	Specification	Assignee:	Luke Kenneth Casson Leighton <lkcl>
Status:	RESOLVED DUPLICATE
Severity:	enhancement	CC:	konstantinos, libre-soc-isa
Priority:	---
Version:	unspecified
Hardware:	PC
OS:	Linux
See Also:	https://bugs.libre-soc.org/show_bug.cgi?id=1028 https://bugs.libre-soc.org/show_bug.cgi?id=1042
NLnet milestone:	---	total budget (EUR) for completion of task and all subtasks:	0
budget (EUR) for this task, excluding subtasks' budget:	0	parent task for budget allocation:
child tasks for budget allocation:		The table of payments (in EUR) for this task; TOML format:
Bug Depends on:
Bug Blocks:	952, 1028

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 ***