Re: [PATCH v3 5/6] gdb/aarch64: Tests for FPMR

[Luis <luis.machado.foss@gmail.com>]

On 21/10/2025 16:02, Ezra.Sitorus@arm.com wrote:
> From: Ezra Sitorus <ezra.sitorus@arm.com>
> 
> Add tests for FPMR support in gdb/gdbserver. These tests check
> availability of FPMR, reading/writing to FPMR, core file generation and
> preservation under sighandler frame unwinding.
> 
> A run of the full gdb testsuite has been done on aarch64-none-linux-gnu
> without FPMR support. I have run the gdb.arch tests on Shrinkwrap with
> FPMR support.
> 
> ---
> Changes from v1->v2:
> * Removed fpmr modification functions to make the tests easier to
>    follow.
> * Test writing to fpmr in aarch64-fpmr.exp from outside the inferior
>    program.
> * Rewrite allow_aarch64_fpmr_tests to follow allow_aarch64_sve_tests.
> 
> Changes from v2->v3:
> * tclint: only messages now is for line length for aarch64-fpmr.exp. I
> think this is ok as it makes the test string readable.
> * Addressed comments/whitespace/formatting issues.
> * gdb.exp:allow_aarch64_fpmr_tests reads FPMR in both cases.
> 
> Ezra
> 
> gdb/testsuite/gdb.arch/aarch64-fpmr-core.c    |  40 ++++++
>   gdb/testsuite/gdb.arch/aarch64-fpmr-core.exp  |  97 ++++++++++++++
>   .../gdb.arch/aarch64-fpmr-sighandler.c        |  55 ++++++++
>   .../gdb.arch/aarch64-fpmr-sighandler.exp      |  74 +++++++++++
>   gdb/testsuite/gdb.arch/aarch64-fpmr.c         | 118 ++++++++++++++++++
>   gdb/testsuite/gdb.arch/aarch64-fpmr.exp       |  99 +++++++++++++++
>   gdb/testsuite/lib/gdb.exp                     |  66 ++++++++++
>   7 files changed, 549 insertions(+)
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr-core.c
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr-core.exp
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.c
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.exp
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr.c
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-fpmr.exp
> 
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr-core.c b/gdb/testsuite/gdb.arch/aarch64-fpmr-core.c
> new file mode 100644
> index 00000000000..785fbd42d5c
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr-core.c
> @@ -0,0 +1,40 @@
> +/* This file is part of GDB, the GNU debugger.
> +
> +   Copyright 2008-2025 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program 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 General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdint.h>
> +
> +uint64_t crash_address = 0;
> +
> +void
> +set_fpmr (uint64_t value)
> +{
> +  register uint64_t x0_val asm ("x0") = value;
> +  /* msr	fpmr, x0 */
> +  __asm__ volatile (".inst	0xd51b4440" : : );
> +}
> +
> +int
> +main (void)
> +{
> +  set_fpmr (0x3fff7fc049);
> +
> +  /* Check FPMR */
> +
> +  *((uint64_t *) crash_address) = 0xDEAD; /* crash point */
> +
> +  return 1;
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr-core.exp b/gdb/testsuite/gdb.arch/aarch64-fpmr-core.exp
> new file mode 100644
> index 00000000000..c26b0b2bba7
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr-core.exp
> @@ -0,0 +1,97 @@
> +# Copyright (C) 2018-2025 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program 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 General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# This file is part of the gdb testsuite.
> +
> +# Test generating and reading a core file with FPMR.
> +
> +proc check_fpmr_core_file {core_filename} {
> +    # Load the core file.
> +    if {
> +	[gdb_test "core $core_filename" \
> +	    [multi_line \
> +		"Core was generated by .*" \
> +		"Program terminated with signal SIGSEGV, Segmentation fault\\." \
> +		"#0  ${::hex} in main \\(.*\\) at .*" \
> +		".* \\*\\(\\(uint64_t \\*\\) crash_address\\) = 0xDEAD.*"] \
> +	    "load core file"]
> +    } {
> +	untested "failed to generate core file"
> +	return -1
> +    }
> +
> +    # Check the value of FPMR in the core file.
> +    gdb_test "print/x \$fpmr" " = 0x3fff7fc049" \
> +	"fpmr contents from core file"

Formatting: Indentation of the above line should be a couple more spaces 
ahead.

> +}
> +
> +require is_aarch64_target
> +require allow_aarch64_fpmr_tests
> +
> +standard_testfile
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> +    return -1
> +}
> +
> +set binfile [standard_output_file ${testfile}]
> +
> +if {![runto_main]} {
> +    return -1
> +}
> +
> +set crash_breakpoint "crash point"
> +gdb_breakpoint [gdb_get_line_number $crash_breakpoint]
> +gdb_continue_to_breakpoint $crash_breakpoint
> +
> +gdb_test "print/x \$fpmr" " = 0x3fff7fc049" "fpmr contents from core file"
> +
> +gdb_test "continue" \
> +    [multi_line \
> +	"Program received signal SIGSEGV, Segmentation fault\\." \
> +	"${::hex} in main \\(\\).* at .*" \
> +	".* \\*\\(\\(uint64_t \\*\\) crash_address\\) = 0xDEAD.*"] \
> +    "run to crash"

Formatting: Indentation looks off above. Could you please check?

> +
> +# Generate the gcore core file.
> +set gcore_filename [standard_output_file "${testfile}.gcore"]
> +set gcore_generated [gdb_gcore_cmd "$gcore_filename" "generate gcore file"]
> +
> +# Generate a native core file.
> +set core_filename [core_find ${binfile}]
> +set core_generated [expr {$core_filename != ""}]
> +
> +# At this point we have a couple core files, the gcore one generated by GDB
> +# and the native one generated by the Linux Kernel.  Make sure GDB can read
> +# both correctly.
> +
> +if {$gcore_generated} {
> +    clean_restart
> +    gdb_load ${binfile}
> +    with_test_prefix "gcore corefile" {
> +	check_fpmr_core_file $gcore_filename
> +    }
> +} else {
> +    fail "gcore corefile not generated"
> +}
> +
> +if {$core_generated} {
> +    clean_restart
> +    gdb_load ${binfile}
> +    with_test_prefix "native corefile" {
> +	check_fpmr_core_file $core_filename
> +    }
> +} else {
> +    untested "native corefile not generated"
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.c b/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.c
> new file mode 100644
> index 00000000000..e8056d40b4c
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.c
> @@ -0,0 +1,55 @@
> +/* This file is part of GDB, the GNU debugger.
> +
> +   Copyright 2008-2025 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program 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 General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdint.h>
> +#include <signal.h>
> +#include <unistd.h>
> +#include <stdlib.h>
> +
> +void
> +set_fpmr (uint64_t value)
> +{
> +  register uint64_t x0_val asm ("x0") = value;
> +  /* msr	fpmr, x0 */
> +  __asm__ volatile (".inst	0xd51b4440" : : );
> +}
> +
> +void
> +handler (int sig)
> +{
> +  set_fpmr (0xff008041);
> +  exit(0);
> +}
> +
> +int
> +main ()
> +{
> +  /* Ensure no signals are blocked.  */
> +  sigset_t newset;
> +  sigemptyset (&newset);
> +  sigprocmask (SIG_SETMASK, &newset, NULL);
> +
> +  signal (SIGILL, handler);
> +
> +  set_fpmr (0x3fff7fc049);
> +
> +  /* 0x06000000 : Causes an illegal instruction.  Value undefined as per ARM
> +     Architecture Reference Manual ARMv8, Section C4.1.  */
> +  __asm __volatile (".inst 0x06000000");
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.exp b/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.exp
> new file mode 100644
> index 00000000000..89b5a5cc010
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr-sighandler.exp
> @@ -0,0 +1,74 @@
> +# Copyright 2018-2025 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program 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 General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +#
> +# This file is part of the gdb testsuite.
> +#
> +# Test FPMR register set is properly preserved when unwiding sighandler frames.

Typo: unwiding -> unwinding.

> +
> +require is_aarch64_target
> +require allow_aarch64_fpmr_tests
> +
> +standard_testfile
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> +    return -1
> +}
> +
> +if {![runto_main]} {
> +    return -1
> +}
> +
> +set reg_main_value "0x3fff7fc049"
> +set reg_handler_value "0xff008041"
> +
> +proc check_fpmr {value} {
> +    gdb_test "print /x \$fpmr" ".* = {?$value}?" \
> +	"check register \$fpmr has value $value"
> +}
> +
> +# Run until end of signal handler
> +
> +gdb_test "continue" "Continuing.*Program received signal SIGILL.*" \
> +    "continue until signal"
> +
> +gdb_breakpoint [gdb_get_line_number "exit(0)"]
> +gdb_continue_to_breakpoint "exit" ".*exit.*"
> +
> +set handlerframe [get_current_frame_number]
> +set mainframe [expr {$handlerframe + 2}]
> +
> +# Check register values
> +
> +with_test_prefix "handler frame 1st" {
> +  check_fpmr $reg_handler_value
> +}
> +
> +# Switch to the frame for main(), and check register values

Formatting: Space before parens.

Also, it would be worth checking this for consistency. Some comments end 
in period but others don´t, like this one. As you fix some of these 
nits, it is worth checking those as well.

> +
> +gdb_test "frame $mainframe" "#$mainframe.*main ().*" \
> +    "set to main frame"
> +
> +with_test_prefix "main frame" {
> +  check_fpmr $reg_main_value
> +}
> +
> +# Switch back to the signal handler frame, and check register values
> +
> +gdb_test "frame $handlerframe" \
> +    "#$handlerframe.*handler \\\(sig=4\\\).*" \
> +    "set to signal handler frame"
> +
> +with_test_prefix "handler frame 2nd" {
> +  check_fpmr $reg_handler_value
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr.c b/gdb/testsuite/gdb.arch/aarch64-fpmr.c
> new file mode 100644
> index 00000000000..d29205fb63d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr.c
> @@ -0,0 +1,118 @@
> +/* This file is part of GDB, the GNU debugger.
> +
> +   Copyright 2008-2025 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program 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 General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdint.h>
> +
> +enum FPM_FORMAT
> +{
> +  E5M2,
> +  E4M3,
> +};
> +
> +enum FPM_OVERFLOW
> +{
> +  INFNAN,
> +  SATURATE,
> +};
> +
> +void
> +set_fpmr (uint64_t value)
> +{
> +  register uint64_t x0_val asm ("x0") = value;
> +  __asm__ volatile (".inst	0xd51b4440" : : );
> +  /* msr	fpmr, x0 */
> +}
> +
> +uint64_t
> +modify_src1_fmt (uint64_t fpmr, uint64_t fmt)
> +{
> +  return (fpmr & ~(0x7)) | (fmt & 0x7);
> +}
> +
> +uint64_t
> +modify_src2_fmt (uint64_t fpmr, uint64_t fmt)
> +{
> +  return (fpmr & ~((0x7) << 3)) | ((fmt & 0x7) << 3);
> +}
> +
> +uint64_t
> +modify_dst_fmt (uint64_t fpmr, uint64_t fmt)
> +{
> +  return (fpmr & ~((0x7) << 6)) | ((fmt & 0x7) << 6);
> +}
> +
> +uint64_t
> +modify_osm (uint64_t fpmr, uint64_t overflow)
> +{
> +  return (fpmr & ~((0x1) << 14)) | ((overflow & 0x1) << 14);
> +}
> +
> +uint64_t
> +modify_osc (uint64_t fpmr, uint64_t overflow)
> +{
> +  return (fpmr & ~((0x1) << 15)) | ((overflow & 0x1) << 15);
> +}
> +
> +uint64_t
> +modify_lscale (uint64_t fpmr, uint64_t scale)
> +{
> +  return (fpmr & ~((0x7f) << 16)) | ((scale & 0x7f) << 16);
> +}
> +
> +uint64_t
> +modify_nscale (uint64_t fpmr, uint64_t scale)
> +{
> +  return (fpmr & ~((0xff) << 24)) | ((scale & 0xff) << 24);
> +}
> +
> +uint64_t
> +modify_lscale2 (uint64_t fpmr, uint64_t scale)
> +{
> +  return (fpmr & ~((uint64_t)(0x3f) << 32)) | ((uint64_t)(scale & 0x3f) << 32);
> +}
> +
> +int
> +main (void)
> +{
> +  uint64_t fpmr = 0;
> +
> +  fpmr = modify_src1_fmt (fpmr, E4M3);
> +  set_fpmr (fpmr); /* MODIFY SRC1 */
> +
> +  fpmr = modify_src2_fmt (fpmr, E4M3);
> +  set_fpmr (fpmr); /* MODIFY SRC2 */
> +
> +  fpmr = modify_dst_fmt (fpmr, E4M3);
> +  set_fpmr (fpmr); /* MODIFY DST */
> +
> +  fpmr = modify_osm (fpmr, SATURATE);
> +  set_fpmr (fpmr); /* MODIFY OSM */
> +
> +  fpmr = modify_osc (fpmr, SATURATE);
> +  set_fpmr (fpmr); /* MODIFY OSC */
> +
> +  fpmr = modify_lscale (fpmr, -1);
> +  set_fpmr (fpmr); /* MODIFY LSCALE */
> +
> +  fpmr = modify_nscale (fpmr, -1);
> +  set_fpmr (fpmr); /* MODIFY NSCALE */
> +
> +  fpmr = modify_lscale2 (fpmr, -1);
> +  set_fpmr (fpmr); /* MODIFY LSCALE2 */
> +
> +  return 1;
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-fpmr.exp b/gdb/testsuite/gdb.arch/aarch64-fpmr.exp
> new file mode 100644
> index 00000000000..142d8172332
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-fpmr.exp
> @@ -0,0 +1,99 @@
> +# Copyright 2023-2025 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program 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 General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +# Exercise reading/writing FPMR when it is present.
> +
> +require is_aarch64_target
> +require allow_aarch64_fpmr_tests
> +
> +standard_testfile
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> +    return -1
> +}
> +
> +if {![runto_main]} {
> +    return -1
> +}
> +
> +gdb_test_multiple "info register \$fpmr" "Test FPMR SRC1 E5M2" {
> +    -re ".*\r\n.*\[ \
> +	F8S1=E5M2 \
> +	F8S2=E5M2 \
> +	F8D=E5M2 \
> +	OSM=Inf \
> +	OSC=Inf/NaN \
> +	LSCALE=0 \
> +	NSCALE=0 \
> +	LSCALE2=0 \]" {
> +	pass "FPMR SRC1 matches E5M2"
> +    }
> +}
> +
> +set breakpoints \
> +    [list \
> +	"SRC1" \
> +	"SRC2" \
> +	"DST" \
> +	"OSM" \
> +	"OSC" \
> +	"LSCALE" \
> +	"NSCALE" \
> +	"LSCALE2"]
> +
> +set reg_values \
> +    [list \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E5M2 F8D=E5M2 OSM=Inf OSC=Inf/NaN LSCALE=0 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E5M2 OSM=Inf OSC=Inf/NaN LSCALE=0 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=Inf OSC=Inf/NaN LSCALE=0 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=MaxNormal OSC=Inf/NaN LSCALE=0 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=MaxNormal OSC=MaxNormal LSCALE=0 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=MaxNormal OSC=MaxNormal LSCALE=127 NSCALE=0 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=MaxNormal OSC=MaxNormal LSCALE=127 NSCALE=255 LSCALE2=0 \]" \
> +	".*\r\n.*\[ F8S1=E4M3 F8S2=E4M3 F8D=E4M3 OSM=MaxNormal OSC=MaxNormal LSCALE=127 NSCALE=255 LSCALE2=63 \]"]
> +
> +set pass_messages \
> +    [list \
> +	"FPMR SRC1 matches E4M3" \
> +	"FPMR SRC2 matches E4M3" \
> +	"FPMR DST matches E4M3" \
> +	"FPMR OSM matches MaxNormal" \
> +	"FPMR OSC matches MaxNormal" \
> +	"FPMR LSCALE matches" \
> +	"FPMR NSCALE matches" \
> +	"FPMR LSCALE2 matches"]
> +
> +for {set i 0} {$i < 8} {incr i} {
> +    set bp [lindex $breakpoints $i]
> +    gdb_breakpoint [gdb_get_line_number $bp]
> +    gdb_continue_to_breakpoint $bp
> +
> +    gdb_test_multiple "info register \$fpmr" "" {
> +	-re [lindex $reg_values $i] {
> +	    pass [lindex $pass_messages $i]
> +	}
> +    }
> +}
> +
> +gdb_test_multiple "set \$fpmr=0x0" "" {
> +    -re ".*\r\n.*\[ F8S1=E5M2 F8S2=E5M2 F8D=E5M2 OSM=Inf OSC=Inf/NaN LSCALE=0 NSCALE=0 LSCALE2=0 \]" {
> +	pass "Reset FPMR to 0 from GDB"
> +    }
> +}
> +
> +gdb_test_multiple "set \$fpmr=0x3f007f4008" "" {
> +    -re ".*\r\n.*\[ F8S1=E5M2 F8S2=E4M3 F8D=E5M2 OSM=MaxNormal OSC=Inf/NaN LSCALE=127 NSCALE=0 LSCALE2=63 \]" {
> +	pass "Write to FPMR from GDB"
> +    }
> +}
> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index 930462f63fa..cdb6ccdfa35 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -5201,6 +5201,72 @@ proc aarch64_supports_sme_svl { length } {
>       return 1
>   }
>   
> +# Run a test on the target to see if it supports the AArch64 FPMR feature.
> +# Return 1 if so, 0 if it does not.  Note this causes a restart of GDB.
> +
> +gdb_caching_proc allow_aarch64_fpmr_tests {} {
> +    global srcdir subdir gdb_prompt inferior_exited_re
> +
> +    set me "allow_aarch64_fpmr_tests"
> +
> +    if { ![is_aarch64_target]} {
> +	return 0
> +    }
> +
> +    set compile_flags "{additional_flags=-march=armv8-a}"
> +
> +    # Compile a test program reading FPMR.
> +    set src {
> +	int main() {
> +	    asm volatile ("mrs x0, fpmr");
> +	    return 0;
> +	}
> +    }
> +    if {![gdb_simple_compile $me $src executable $compile_flags]} {
> +	# Try again, but with a raw hex instruction so we don't rely on
> +	# assembler support for FPMR.
> +
> +	set compile_flags "{additional_flags=-march=armv8-a}"
> +
> +	# Compile a test program reading FPMR.
> +	set src {
> +	    int main() {
> +		asm volatile (".word 0xD53B4440");
> +		return 0;
> +	    }
> +	}
> +
> +	if {![gdb_simple_compile $me $src executable $compile_flags]} {
> +	    return 0
> +	}
> +    }
> +
> +    # Compilation succeeded so now run it via gdb.
> +    clean_restart
> +    gdb_load $obj
> +    gdb_run_cmd
> +
> +    gdb_expect {
> +	-re ".*Illegal instruction.*${gdb_prompt} $" {
> +	    verbose -log "\n$me fpmr support not detected"
> +	    set allow_fpmr_tests 0
> +	}
> +	-re ".*$inferior_exited_re normally.*${gdb_prompt} $" {
> +	    verbose -log "\n$me: fpmr support detected"
> +	    set allow_fpmr_tests 1
> +	}
> +	default {
> +	  warning "\n$me: default case taken"
> +	    set allow_fpmr_tests 0
> +	}
> +    }
> +    gdb_exit
> +    remote_file build delete $obj
> +
> +    verbose "$me:  returning $allow_fpmr_tests" 2
> +    return $allow_fpmr_tests
> +}
> +
>   # Run a test on the target to see if it supports AArch64 MOPS (Memory
>   # Operations) extensions.  Return 1 if so, 0 if it does not.  Note this
>   # causes a restart of GDB.