or1k: Add hard float support

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>

1 files changed, 27 insertions, 0 deletions

diff --git a/sysdeps/or1k/math-tests-trap.h b/sysdeps/or1k/math-tests-trap.h
new file mode 100644
index 0000000..a95b42d
--- /dev/null
+++ b/sysdeps/or1k/math-tests-trap.h
@@ -0,0 +1,27 @@
+/* Configuration for math tests: support for enabling exception traps.
+   OpenRISC version.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef OR1K_MATH_TESTS_TRAP_H
+#define OR1K_MATH_TESTS_TRAP_H 1
+
+#include <fenv.h>
+
+#define EXCEPTION_ENABLE_SUPPORTED(EXCEPT)	((EXCEPT) == 0)
+
+#endif /* math-tests-trap.h */