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Print bfloat16 DWARF types correctly

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Even if the DWARF information contains a bfloat16 base type (__bf16), a
variable of such type will still be printed using the IEEE half float format,
which is wrong.

This patch teaches GDB how to pick the bfloat16 format for __bf16 types in
DWARF (based on the base type name) and uses IEEE half float for all the other
16-bit float formats.

Tested on aarch64-linux/x86_64-linux.

OK?

gdb/ChangeLog:

2021-04-16  Luis Machado  <luis.machado@linaro.org>

	* arch-utils.c (default_floatformat_for_type): Handle bfloat16.

gdb/testsuite:

2021-04-16  Luis Machado  <luis.machado@linaro.org>

	* gdb.dwarf2/dw2-bfloat16.exp: New file.
This commit is contained in:
Luis Machado 2021-04-14 11:20:18 -03:00
parent 6f8f6017a0
commit 1b6b755e91
4 changed files with 97 additions and 1 deletions
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4
gdb/ChangeLog
View File

@ -1,3 +1,7 @@
2021-04-16 Luis Machado <luis.machado@linaro.org>
* arch-utils.c (default_floatformat_for_type): Handle bfloat16.
2021-04-15 John Baldwin <jhb@FreeBSD.org>
* fbsd-nat.c (fbsd_lwp_debug_printf, fbsd_nat_debug_printf): New,

8
gdb/arch-utils.c
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@ -279,7 +279,13 @@ default_floatformat_for_type (struct gdbarch *gdbarch,
{
const struct floatformat **format = NULL;
if (len == gdbarch_half_bit (gdbarch))
/* Check if this is a bfloat16 type. It has the same size as the
IEEE half float type, so we use the base type name to tell them
apart. */
if (name != nullptr && strcmp (name, "__bf16") == 0
&& len == gdbarch_bfloat16_bit (gdbarch))
format = gdbarch_bfloat16_format (gdbarch);
else if (len == gdbarch_half_bit (gdbarch))
format = gdbarch_half_format (gdbarch);
else if (len == gdbarch_float_bit (gdbarch))
format = gdbarch_float_format (gdbarch);

4
gdb/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2021-04-16 Luis Machado <luis.machado@linaro.org>
* gdb.dwarf2/dw2-bfloat16.exp: New file.
2021-04-15 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.python/py-parameter.exp: Give a test a proper name to avoid

82
gdb/testsuite/gdb.dwarf2/dw2-bfloat16.exp Normal file
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@ -0,0 +1,82 @@
# 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/>.
#
# This test checks if GDB can identify bfloat16 and IEEE half float types and
# print them correctly.
#
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if {![dwarf2_support]} {
return 0
}
standard_testfile main.c -dw.S
# Make some DWARF for the test.
# 0x4049 is the equivalent of 3.141 for bfloat16.
# 0x4248 is the equivalent of 3.1406 for IEEE half float.
set asm_file [standard_output_file $srcfile2]
Dwarf::assemble $asm_file {
global srcdir subdir srcfile
cu {} {
DW_TAG_compile_unit {
{DW_AT_language @DW_LANG_C}
{DW_AT_name $srcfile}
{DW_AT_comp_dir /tmp}
} {
declare_labels bf16_type fp16_type \
bf16_var fp16_var
bf16_type: DW_TAG_base_type {
{DW_AT_name __bf16}
{encoding @DW_ATE_float}
{DW_AT_byte_size 2 DW_FORM_sdata}
}
fp16_type: DW_TAG_base_type {
{DW_AT_name __fp16}
{encoding @DW_ATE_float}
{DW_AT_byte_size 2 DW_FORM_sdata}
}
bf16_var: DW_TAG_variable {
{DW_AT_name "bf16_1"}
{DW_AT_type :${bf16_type}}
{DW_AT_const_value 0x4049 DW_FORM_sdata}
}
fp16_var: DW_TAG_variable {
{DW_AT_name "fp16_1"}
{DW_AT_type :${fp16_type}}
{DW_AT_const_value 0x4248 DW_FORM_sdata}
}
}
}
}
if { [prepare_for_testing "failed to prepare" ${testfile} \
[list $srcfile $asm_file] {nodebug}] } {
return -1
}
if ![runto_main] {
return -1
}
# Make sure we can print both types correctly.
gdb_test "print bf16_1" " = 3.141"
gdb_test "print fp16_1" " = 3.1406"