The SiFive U74 (RV64GC; e.g. StarFive JH7110 / VisionFive 2) is a scalar,
in-order core with no RVV, so today it falls back to RISCV64_GENERIC whose
S/D GEMM uses the generic 2x2 C micro-kernel.
Per the U74 Core Complex Manual (Table 169) fmadd.d has a 7-cycle latency
at repeat rate 1 (fully pipelined). A 2x2 tile exposes only 4 independent
accumulator chains -- fewer than the FMA latency -- so the FP pipe stalls
on the accumulator dependency, and the 1:1 load:FMA ratio saturates the
single load/store pipe ("only one outstanding line fill", manual 8.2).
This adds a portable 4x4 GEMM micro-kernel and a dedicated U74 target:
- kernel/generic/gemmkernel_4x4.c: 16-accumulator 4x4 register tile. 16
independent chains exceed the 7-cycle latency, and the load:FMA ratio
drops to 1:2. 16 acc + 4 A + 4 B fit RV64G's 32 FP registers without
spilling. Full 4/2/1 edge handling in both M and N.
- U74 target wiring: getarch.c (FORCE_U74, 32 KiB/64 B L1D, 2 MiB L2),
param.h (S/D UNROLL 4/4; complex stays 2/2), kernel/riscv64/KERNEL.U74
(S/D GEMM -> gemmkernel_4x4 + gemm_[nt]copy_4; S/D TRMM -> existing
trmmkernel_4x4), Makefile.prebuild + Makefile.riscv64 (-mtune=sifive-u74),
TargetList.txt, cpuid_riscv64.c.
The 4x4 kernel was verified numerically against a naive reference GEMM,
driven through the real gemm_tcopy_4 / gemm_ncopy_4 packing routines,
across 27,436 M/N/K x alpha combinations covering every 4/2/1 tail case:
worst absolute error 0.
Build with: make TARGET=U74
When building on a non-x86 host the Makefile definitions for HAVE_* are
never printed which leads to build failures and/or silently targeting the
wrong microarchitecture. The issue is that INTEL_AMD is defined if the
host architecture is x86, but for cross builds we need to test whether
the target is x86. Test for that using the macro FORCE_INTEL.
Use microarchitecture name instead of meaningless strings to name the core,
the legacy core is still retained.
1. Rename LOONGSONGENERIC to LA64_GENERIC
2. Rename LOONGSON3R5 to LA464
3. Rename LOONGSON2K1000 to LA264
* Fixed bugs in dgemm, [a]min\max, asum kernels
* Added zero checks for BLAS kernels
* Added dsdot implementation for RVV 0.7.1
* Fixed bugs in _vector files for C910V and RISCV64_ZVL256B targets
* Added additional definitions for RISCV64_ZVL256B target
Current RVV x280 target depends on vlen=512-bits for Level 3 operations.
Commit adds generic target that supports vlen=128-bits.
New target uses the same scalable kernels as x280 for Level 1&2 operations, and autogenerated kernels for Level 3 operations.
Functional correctness of Level 3 operations tested on vlen=128-bits using QEMU v8.1.1 for ctests and BLAS-Tester.
This adds an SVE implementation to sdot/ddot when available, falling back to the previous Advanced SIMD kernel where there's no SVE implementation for the kernel.
All the targets were essentially treating `dot_thunderx2t99.c` as the Advanced SIMD implementation so I've renamed it to better fit with the feature detection.
hmeiland
Xianyi Zhang