Re: [PATCH 2/2] gdb: Enable finish command and inferior calls for _Float16 on amd64 and i386.

[Luis Machado via Gdb-patches <gdb-patches@sourceware.org>]

Hi,

On 7/29/21 5:38 AM, Felix Willgerodt via Gdb-patches wrote:
> Values of type _Float16 and _Float16 _Complex can now be used on CPUs with
> AVX512-FP16 support. Return values of those types are located in XMM0.
> Compiler support for gcc and clang is in progress, see e.g.:
> https://gcc.gnu.org/pipermail/gcc-patches/2021-July/574117.html

Is _Float16 equivalent to fp16? If so, the presence of yet another name 
for a fp16 type is a bit unfortunate.

> 
> gdb/ChangeLog:
> 2021-07-21  Felix Willgerodt  <Felix.Willgerodt@intel.com>
> 
> 	* amd64-tdep.c (amd64_classify): Classify _Float16 and
> 	_Float16 _Complex as AMD64_SSE.
> 	* i386-tdep.c (i386_extract_return_value): Read _Float16 and
> 	_Float16 _Complex from xmm0.
> 
> gdb/testsuite/ChangeLog:
> 2021-07-21  Felix Willgerodt  <Felix.Willgerodt@intel.com>
> 
> 	* gdb.arch/x86-avx512fp16-abi.c: New file.
> 	* gdb.arch/x86-avx512fp16-abi.exp: New file.
> ---
>   gdb/amd64-tdep.c                              | 12 ++--
>   gdb/i386-tdep.c                               |  9 ++-
>   gdb/testsuite/gdb.arch/x86-avx512fp16-abi.c   | 38 +++++++++++
>   gdb/testsuite/gdb.arch/x86-avx512fp16-abi.exp | 63 +++++++++++++++++++
>   4 files changed, 115 insertions(+), 7 deletions(-)
>   create mode 100644 gdb/testsuite/gdb.arch/x86-avx512fp16-abi.c
>   create mode 100644 gdb/testsuite/gdb.arch/x86-avx512fp16-abi.exp
> 
> diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
> index c028e1bd0f6..129f07e598d 100644
> --- a/gdb/amd64-tdep.c
> +++ b/gdb/amd64-tdep.c
> @@ -728,10 +728,10 @@ amd64_classify (struct type *type, enum amd64_reg_class theclass[2])
>         && (len == 1 || len == 2 || len == 4 || len == 8))
>       theclass[0] = AMD64_INTEGER;
>   
> -  /* Arguments of types float, double, _Decimal32, _Decimal64 and __m64
> -     are in class SSE.  */
> +  /* Arguments of types _Float16, float, double, _Decimal32, _Decimal64 and
> +     __m64 are in class SSE.  */
>     else if ((code == TYPE_CODE_FLT || code == TYPE_CODE_DECFLOAT)
> -	   && (len == 4 || len == 8))
> +	   && (len == 2 || len == 4 || len == 8))
>       /* FIXME: __m64 .  */
>       theclass[0] = AMD64_SSE;
>   
> @@ -749,8 +749,8 @@ amd64_classify (struct type *type, enum amd64_reg_class theclass[2])
>       /* Class X87 and X87UP.  */
>       theclass[0] = AMD64_X87, theclass[1] = AMD64_X87UP;
>   
> -  /* Arguments of complex T where T is one of the types float or
> -     double get treated as if they are implemented as:
> +  /* Arguments of complex T - where T is one of the types _Float16, float or
> +     double - get treated as if they are implemented as:
>   
>        struct complexT {
>          T real;
> @@ -758,7 +758,7 @@ amd64_classify (struct type *type, enum amd64_reg_class theclass[2])
>        };
>   
>     */
> -  else if (code == TYPE_CODE_COMPLEX && len == 8)
> +  else if (code == TYPE_CODE_COMPLEX && (len == 8 || len == 4))
>       theclass[0] = AMD64_SSE;
>     else if (code == TYPE_CODE_COMPLEX && len == 16)
>       theclass[0] = theclass[1] = AMD64_SSE;
> diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
> index c2835a2458d..6c7f7f7592d 100644
> --- a/gdb/i386-tdep.c
> +++ b/gdb/i386-tdep.c
> @@ -2818,7 +2818,14 @@ i386_extract_return_value (struct gdbarch *gdbarch, struct type *type,
>     int len = TYPE_LENGTH (type);
>     gdb_byte buf[I386_MAX_REGISTER_SIZE];
>   
> -  if (type->code () == TYPE_CODE_FLT)
> +  /* _FLoat16 and _Float16 _Complex values are returned via xmm0.  */

_Float16

> +  if (((type->code () == TYPE_CODE_FLT) && len == 2)
> +      || ((type->code () == TYPE_CODE_COMPLEX) && len == 4))
> +    {
> +	regcache->raw_read (I387_XMM0_REGNUM (tdep), valbuf);
> +	return;
> +    }
> +  else if (type->code () == TYPE_CODE_FLT)
>       {
>         if (tdep->st0_regnum < 0)
>   	{
> diff --git a/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.c b/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.c
> new file mode 100644
> index 00000000000..c5b188ea546
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.c
> @@ -0,0 +1,38 @@
> +/* Test program for bfloat16 of AVX 512 registers.

float16 and not bfloat16, right?

> +
> +   Copyright 2021 Free Software Foundation, Inc.
> +
> +   This file is part of GDB.
> +
> +   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 <complex.h>
> +
> +_Float16
> +square (_Float16 num) {
> +  return num * num; /* BP1.  */
> +}
> +
> +_Float16 _Complex
> +plus (_Float16 _Complex num) {
> +  return num + (2.5 + 0.5I); /* BP2.  */
> +}
> +
> +int
> +main ()
> +{
> +  _Float16 a = square (1.25);
> +  _Float16 _Complex b = 6.25 + I;
> +  _Float16 _Complex ret = plus (b); /* BP3.  */
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.exp b/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.exp
> new file mode 100644
> index 00000000000..61cd189a3dd
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/x86-avx512fp16-abi.exp
> @@ -0,0 +1,63 @@
> +# Copyright 2021 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/>.
> +
> +# Test support for _Float16 parameters and return values.
> +
> +if { [skip_avx512fp16_tests] } {
> +    unsupported "target does not support AVX512fp16"
> +    return -1
> +}
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
> +     {debug additional_flags="-mavx512fp16"}] } {
> +    return -1
> +}
> +
> +if { ![runto_main] } {
> +    unsupported "could not run to main"
> +    return -1
> +}
> +
> +gdb_test "p square(2.2)" "= 4\\.8359"
> +
> +set line1 [gdb_get_line_number "BP1"]
> +set line2 [gdb_get_line_number "BP2"]
> +set line3 [gdb_get_line_number "BP3"]
> +gdb_breakpoint $line1
> +gdb_breakpoint $line3
> +
> +gdb_continue_to_breakpoint "line1" ".*$srcfile:$line1.*"
> +
> +with_test_prefix "real" {
> +    gdb_test "p num" "= 1\\.25"
> +    gdb_test "ptype num" "type = _Float16"
> +    gdb_test "finish" "Value returned is.*= 1\\.5625"
> +}
> +
> +gdb_continue_to_breakpoint "line3" ".*$srcfile:$line3.*"
> +gdb_test "p plus(b)" "= 8\\.75 \\+ 1\\.5i"
> +
> +gdb_breakpoint $line2
> +gdb_continue_to_breakpoint "line2" ".*$srcfile:$line2.*"
> +
> +with_test_prefix "complex" {
> +    gdb_test "p num" "= 6\\.25 \\+ 1i"
> +    gdb_test "ptype num" "type = complex _Float16"
> +    gdb_test "finish" "Value returned is.*= 8\\.75 \\+ 1\\.5i"
> +}
> +
> +gdb_continue_to_end
>