This patch adds hardware floating point support to OpenRISC. Hardware
floating point toolchain builds are enabled by passing the machine
specific argument -mhard-float to gcc via CFLAGS. With this enabled GCC
generates floating point instructions for single-precision operations
and exports __or1k_hard_float__.
There are 2 main parts to this patch.
- Implement fenv functions to update the FPCSR flags keeping it in sync
with sfp (software floating point).
- Update machine context functions to store and restore the FPCSR
state.
*On mcontext_t ABI*
This patch adds __fpcsr to mcontext_t. This is an ABI change, but also
an ABI fix. The Linux kernel has always defined padding in mcontext_t
that space was missing from the glibc ABI. In Linux this unused space
has now been re-purposed for storing the FPCSR. This patch brings
OpenRISC glibc in line with the Linux kernel and other libc
implementation (musl).
Compatibility getcontext, setcontext, etc symbols have been added to
allow for binaries expecting the old ABI to continue to work.
*Hard float ABI*
The calling conventions and types do not change with OpenRISC hard-float
so glibc hard-float builds continue to use dynamic linker
/lib/ld-linux-or1k.so.1.
*Testing*
I have tested this patch both with hard-float and soft-float builds and
the test results look fine to me. Results are as follows:
Hard Float
# failures
FAIL: elf/tst-sprof-basic (Haven't figured out yet, not related to hard-float)
FAIL: gmon/tst-gmon-pie (PIE bug in or1k toolchain)
FAIL: gmon/tst-gmon-pie-gprof (PIE bug in or1k toolchain)
FAIL: iconvdata/iconv-test (timeout, passed when run manually)
FAIL: nptl/tst-cond24 (Timeout)
FAIL: nptl/tst-mutex10 (Timeout)
# summary
6 FAIL
4289 PASS
86 UNSUPPORTED
16 XFAIL
2 XPASS
# versions
Toolchain: or1k-smhfpu-linux-gnu
Compiler: gcc version 14.0.1 20240324 (experimental) [master r14-9649-gbb04a11418f] (GCC)
Binutils: GNU assembler version 2.42.0 (or1k-smhfpu-linux-gnu) using BFD version (GNU Binutils) 2.42.0.20240324
Linux: Linux buildroot 6.9.0-rc1-00008-g4dc70e1aadfa #112 SMP Sat Apr 27 06:43:11 BST 2024 openrisc GNU/Linux
Tester: shorne
Glibc: 2024-04-25 b62928f907 Florian Weimer x86: In ld.so, diagnose missing APX support in APX-only builds (origin/master, origin/HEAD)
Soft Float
# failures
FAIL: elf/tst-sprof-basic
FAIL: gmon/tst-gmon-pie
FAIL: gmon/tst-gmon-pie-gprof
FAIL: nptl/tst-cond24
FAIL: nptl/tst-mutex10
# summary
5 FAIL
4295 PASS
81 UNSUPPORTED
16 XFAIL
2 XPASS
# versions
Toolchain: or1k-smh-linux-gnu
Compiler: gcc version 14.0.1 20240324 (experimental) [master r14-9649-gbb04a11418f] (GCC)
Binutils: GNU assembler version 2.42.0 (or1k-smh-linux-gnu) using BFD version (GNU Binutils) 2.42.0.20240324
Linux: Linux buildroot 6.9.0-rc1-00008-g4dc70e1aadfa #112 SMP Sat Apr 27 06:43:11 BST 2024 openrisc GNU/Linux
Tester: shorne
Glibc: 2024-04-25 b62928f907 Florian Weimer x86: In ld.so, diagnose missing APX support in APX-only builds (origin/master, origin/HEAD)
Documentation: https://raw.githubusercontent.com/openrisc/doc/master/openrisc-arch-1.4-rev0.pdf
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
OpenRISC support hard float but I will like to submit that after glibc
soft float goes upstream. The hard float support depends on adding user
access to the FPCSR, which is not supported by the kernel yet.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
