provide a NEON version of arm/sgemm#5800
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martin-frbg merged 4 commits intoOpenMathLib:developfrom May 6, 2026
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Non-local labels interfere with profiling. Same thing was done for arm64 in commit a0128aa.
According to ARM AAPCS (Procedure Call Standard) 5.1.2.1, only registers s16-s31 must be preserved across subroutine calls; registers s0-s15 do not need to be preserved.
benchmark/sgemm.goto before: M= 200, N= 200, K= 200 : 9262.97 MFlops 0.001727 sec after: M= 200, N= 200, K= 200 : 30223.64 MFlops 0.000529 sec Conveniently the registers are already allocated suitably for vector operation, so the conversion from vfpv3 was rather straightforward. Prefetching was left out because it doesn't help Cortex-A76, only hurts it slightly.
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Thanks - ARMV7 hasn't received much work in recent years, and I believe in the early days of CORTEXA53/A57 it was assumed/claimed that NEON wasn't significantly faster in V7 code. (Telling the compiler it's allowed to use NEON was required for some code contribution that used universal intrinsics, I think, and it was obviously trivial to do...) |
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Surprisingly OpenBLAS lacks NEON optimized kernels for armv7, even though it auto-enables NEON during build by default (passes
-mfpu=neonto the compiler, meaning the compiler will use NEON instructions wherever it can).The speedup on Cortex-A76 is significant, before:
after: