[RFC PATCH 0/2] Add RISC-V vector math library support

[Pincheng Wang]

Hi all,

This RFC patch series propose adding RISC-V Vector Extension (RVV)
optimized math functions to newlib, starting with a vectorized
implementation of sin().

The motivation is to enable automatic vectorization of math functions on
RISC-V platforms with vector extensions, which can provide significant
performance improvements for numerical applications.

After applying the gcc vecmath patch[1], compiler supports automatic
vectorzation using the vector ABI[2](also in RFC). When compiling with
auto-vectorization enabled (-O3 -ffast-math), the compiler can replace
scalar math function calls with vector variants if they are available in
the math library.

This patch series adds infrastructure support for building vector math
functions conditionally via a newly added "--enable-vecmath" configure
option (disabled by default), and a vectorized sin() implementation for
RISC-V using intrinsics from the RISC-V Vector Extension.

While adding the above option, I encountered an automake compatibility
issue during math object copying. Therefore, commit 1 is dedicated to
fixing that issue and does not involve any vector math changes.

The vector sin implementation is derived from the SLEEF library (Boost
licensed) and adapted for newlib's RISC-V target. It uses RVV 1.0
intrinsics and provides performance-optimized computation with proper
handling of edge cases.

To configure and build, use below command.
	configure --target=riscv64-unknown-elf \
		--prefix=/opt/vecmath-newlib \
		CFLAGS_FOR_TARGET="-O2 -march=rv64gcv -mabi=lp64d" \
		--enable-vecmath

To compile a program that can take
benefit of this patch, use the patched[1] gcc and run command like
below.
	/opt/vecmath-gcc/bin/riscv64-unknown-elf-gcc \
		-O3 -ffast-math -march=rv64gcv \
		--sysroot=/opt/vecmath-newlib \
		-L/opt/vecmath-newlib/riscv64-unknown-elf/lib \
		-I/opt/vecmath-newlib/riscv64-unknown-elf/include \
		test_sin.c -o test_sin -lm

Comments and suggestions are welcome!

[1] https://gcc.gnu.org/pipermail/gcc-patches/2024-November/667352.html
[2] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/455

Thanks,
Pincheng Wang

Pincheng Wang (2):
  newlib: Fix automake 1.16 compatibility for math object copying
  newlib: Add RISC-V vector math library support

 newlib/Makefile.am                         |   26 +-
 newlib/configure.ac                        |   10 +
 newlib/libc/include/math.h                 |    1 +
 newlib/libm/machine/riscv/Makefile.inc     |    5 +
 newlib/libm/machine/riscv/riscv-vec-math.h | 1461 ++++++++++++++++++++
 newlib/libm/machine/riscv/vec_sin.c        |   79 ++
 6 files changed, 1569 insertions(+), 13 deletions(-)
 create mode 100644 newlib/libm/machine/riscv/riscv-vec-math.h
 create mode 100644 newlib/libm/machine/riscv/vec_sin.c

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2.39.5