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[Patch][binutils][aarch64] .bfloat16 directive for AArch64 [7/10] 

Hi,

This patch is part of a series that adds support for Armv8.6-A
(Matrix Multiply and BFloat16 extensions) to binutils.

This patch implements the '.bfloat' directive for the AArch64 backend.

The syntax for the directive is:
  .bfloat16 <0-n numbers>
e.g.
  .bfloat16 12.0
  .bfloat16 0.123, 1.0, NaN, 5

This is implemented by utilizing the ieee_atof_detail function in order
to encode the slightly
different bfloat16 format.

Added testcases to verify the correct encoding for various bfloat16
values (NaN, Infinity (+ & -), normals, subnormals etc...).

Cross compiled and tested on aarch64-none-elf and aarch64-none-linux-gnu
with no issues.

Committed on behalf of Mihail Ionescu.

gas/ChangeLog:

2019-10-29  Mihail Ionescu  <mihail.ionescu@arm.com>
2019-10-29  Barnaby Wilks  <barnaby.wilks@arm.com>

	* config/tc-aarch64.c (md_atof): Add encoding for the bfloat16 format.
	* testsuite/gas/aarch64/bfloat16-directive-le.d: New test.
	* testsuite/gas/aarch64/bfloat16-directive-be.d: New test.
	* testsuite/gas/aarch64/bfloat16-directive.s: New test.

Is it ok for trunk?

Regards,
Mihail
This commit is contained in:
Matthew Malcomson 2019-11-07 17:07:32 +00:00
parent 27cce8667f
commit eb5bbc4821
5 changed files with 98 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
gas/ChangeLog
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@ -1,3 +1,11 @@
2019-11-07 Mihail Ionescu <mihail.ionescu@arm.com>
2019-11-07 Barnaby Wilks <barnaby.wilks@arm.com>
* config/tc-aarch64.c (md_atof): Add encoding for the bfloat16 format.
* testsuite/gas/aarch64/bfloat16-directive-le.d: New test.
* testsuite/gas/aarch64/bfloat16-directive-be.d: New test.
* testsuite/gas/aarch64/bfloat16-directive.s: New test.
2019-11-07 Mihail Ionescu <mihail.ionescu@arm.com>
2019-11-07 Barnaby Wilks <barnaby.wilks@arm.com>

49
gas/config/tc-aarch64.c
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@ -635,6 +635,54 @@ my_get_expression (expressionS * ep, char **str, int prefix_mode,
const char *
md_atof (int type, char *litP, int *sizeP)
{
/* If this is a bfloat16 type, then parse it slightly differently -
as it does not follow the IEEE standard exactly. */
if (type == 'b')
{
char * t;
LITTLENUM_TYPE words[MAX_LITTLENUMS];
FLONUM_TYPE generic_float;
t = atof_ieee_detail (input_line_pointer, 1, 8, words, &generic_float);
if (t)
input_line_pointer = t;
else
return _("invalid floating point number");
switch (generic_float.sign)
{
/* Is +Inf. */
case 'P':
words[0] = 0x7f80;
break;
/* Is -Inf. */
case 'N':
words[0] = 0xff80;
break;
/* Is NaN. */
/* bfloat16 has two types of NaN - quiet and signalling.
Quiet NaN has bit[6] == 1 && faction != 0, whereas
signalling Nan's have bit[0] == 0 && fraction != 0.
Chose this specific encoding as it is the same form
as used by other IEEE 754 encodings in GAS. */
case 0:
words[0] = 0x7fff;
break;
default:
break;
}
*sizeP = 2;
md_number_to_chars (litP, (valueT) words[0], sizeof (LITTLENUM_TYPE));
return NULL;
}
return ieee_md_atof (type, litP, sizeP, target_big_endian);
}
@ -2107,6 +2155,7 @@ const pseudo_typeS md_pseudo_table[] = {
{"variant_pcs", s_variant_pcs, 0},
#endif
{"float16", float_cons, 'h'},
{"bfloat16", float_cons, 'b'},
{0, 0, 0}
};

11
gas/testsuite/gas/aarch64/bfloat16-directive-be.d Normal file
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@ -0,0 +1,11 @@
# name: Big endian bfloat16 literal directives
# source: bfloat16-directive.s
# as: -mbig-endian
# objdump: -s --section=.data
.*: +file format .*
Contents of section \.data:
0000 41403dfc 000042f7 8000c2f7 7fff7f80 .*
0010 ff807f7f ff7f0080 80800001 8001007f .*
0020 807f3f80 bf804000 c000 .*

11
gas/testsuite/gas/aarch64/bfloat16-directive-le.d Normal file
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@ -0,0 +1,11 @@
# name: Little endian bfloat16 literal directives
# source: bfloat16-directive.s
# as: -mlittle-endian
# objdump: -s --section=.data
.*: +file format .*
Contents of section \.data:
0000 4041fc3d 0000f742 0080f7c2 ff7f807f .*
0010 80ff7f7f 7fff8000 80800100 01807f00 .*
0020 7f80803f 80bf0040 00c0 .*

19
gas/testsuite/gas/aarch64/bfloat16-directive.s Normal file
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@ -0,0 +1,19 @@
.data
.bfloat16 12.0
.bfloat16 0.123
.bfloat16 +0.0
.bfloat16 123.4
.bfloat16 -0.0
.bfloat16 -123.4
.bfloat16 NaN
.bfloat16 Inf
.bfloat16 -Inf
.bfloat16 3.390e+38
.bfloat16 -3.390e+38
.bfloat16 1.175e-38
.bfloat16 -1.175e-38
.bfloat16 9.194e-41
.bfloat16 -9.194e-41
.bfloat16 1.167e-38
.bfloat16 -1.167e-38
.bfloat16 1.0, -1, 2.0, -2