Skip to content

riscv: allow single-precision float ABI (lp64f / ilp32f) #349

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ViralBShah merged 2 commits into from
Jun 23, 2026
Merged

riscv: allow single-precision float ABI (lp64f / ilp32f) #349

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
78bd52b
riscv: allow single-precision float ABI (lp64f / ilp32f)
ViralBShah Jun 22, 2026
ef48409
add CI coverage for the RISC-V single-float ABI (#262)
ViralBShah Jun 22, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
32 changes: 32 additions & 0 deletions .github/workflows/cross.yml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -66,3 +66,35 @@ jobs:
QEMU_LD_PREFIX: /usr/${{ matrix.config.triple }}
LD_LIBRARY_PATH: .
run: make test ARCH=$ARCH TOOLPREFIX=$TRIPLE- ${CC:+CC=$CC} ${AR:+AR=$AR}

# Regression test for #262 / #349: the RISC-V single-float ABI (lp64f /
# ilp32f) used to be rejected by include/openlibm_fenv_riscv.h with an
# `#error`. This job rebuilds the whole library with `-mabi=lp64f` to make
# sure the header (and the rest of openlibm) accepts that ABI.
#
# This is a COMPILE-ONLY check (build the static libopenlibm.a, no qemu run).
# Ubuntu's gcc-riscv64-linux-gnu ships only the default lp64d sysroot, so a
# full shared-library link or a qemu execution under lp64f is impossible
# without a custom single-float sysroot the distro does not provide. Building
# the static archive needs no libc/CRT link, so it compiles every source file
# (including riscv64/fenv.c, which pulls in the fixed header) under the
# single-float ABI and directly regresses the removed `#error`. Adding a
# bespoke lp64f sysroot would be exactly the kind of fragile, unmaintainable
# toolchain dependency that got mips64 disabled in #347, so we deliberately
# avoid it.
build-cross-riscv64-lp64f:
runs-on: ubuntu-24.04
timeout-minutes: 10
name: build-cross-riscv64-lp64f
steps:
- uses: actions/checkout@v7
- name: Install RISC-V toolchain
run: |
sudo apt update
sudo apt install -y gcc-riscv64-linux-gnu
- name: Build libopenlibm.a for the single-float ABI (lp64f)
run: |
make -j$(nproc) ARCH=riscv64 TOOLPREFIX=riscv64-linux-gnu- \
CFLAGS_arch='-march=rv64imafc -mabi=lp64f' \
SFLAGS_arch='-march=rv64imafc -mabi=lp64f' \
libopenlibm.a
7 changes: 2 additions & 5 deletions include/openlibm_fenv_riscv.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -74,13 +74,10 @@ __BEGIN_DECLS
extern const fenv_t __fe_dfl_env;
#define FE_DFL_ENV (&__fe_dfl_env)

#if !defined(__riscv_float_abi_soft) && !defined(__riscv_float_abi_double)
#if defined(__riscv_float_abi_single)
#error single precision floating point ABI not supported
#else
#if !defined(__riscv_float_abi_soft) && !defined(__riscv_float_abi_double) && \
!defined(__riscv_float_abi_single)
#error compiler did not set soft/hard float macros
#endif
#endif

#ifndef __riscv_float_abi_soft
#define __rfs(__fcsr) __asm __volatile("csrr %0, fcsr" : "=r" (__fcsr))
Expand Down