[PATCH 06/11] x86: introduce .bfloat16 directive
Jan Beulich
jbeulich@suse.com
Fri Jul 23 06:55:30 GMT 2021
This is to be able to generate data acted upon by AVX512-BF16 and
AMX-BF16 insns. While not part of the IEEE standard, the format is
sufficiently standardized to warrant handling in config/atof-ieee.c.
Arm, where custom handling was implemented, may want to leverage this as
well. To be able to also use the hex forms supported for other floating
point formats, a small addition to the generic hex_float() is needed.
Extend existing x86 testcases.
--- a/gas/config/atof-ieee.c
+++ b/gas/config/atof-ieee.c
@@ -27,6 +27,7 @@ extern FLONUM_TYPE generic_floating_poin
/* Don't count the gap in the m68k extended precision format. */
#define MAX_PRECISION 5
#define H_PRECISION 1
+#define B_PRECISION 1 /* Not strictly IEEE, but handled here anyway. */
#define F_PRECISION 2
#define D_PRECISION 4
#define X_PRECISION 5
@@ -243,6 +244,12 @@ atof_ieee (char *str, /* Text to conve
exponent_bits = 5;
break;
+ case 'b':
+ case 'B':
+ precision = B_PRECISION;
+ exponent_bits = 8;
+ break;
+
case 'f':
case 'F':
case 's':
@@ -368,9 +375,9 @@ gen_to_words (LITTLENUM_TYPE *words, int
as_warn (_("Infinities are not supported by this target"));
/* +INF: Do the right thing. */
- if (precision == H_PRECISION)
+ if (precision == H_PRECISION /* also B_PRECISION */)
{
- words[0] = 0x7c00;
+ words[0] = exponent_bits == 5 ? 0x7c00 : 0x7f80;
}
else if (precision == F_PRECISION)
{
@@ -413,9 +420,9 @@ gen_to_words (LITTLENUM_TYPE *words, int
as_warn (_("Infinities are not supported by this target"));
/* Negative INF. */
- if (precision == H_PRECISION)
+ if (precision == H_PRECISION /* also B_PRECISION */)
{
- words[0] = 0xfc00;
+ words[0] = exponent_bits == 5 ? 0xfc00 : 0xff80;
}
else if (precision == F_PRECISION)
{
@@ -777,6 +784,11 @@ ieee_md_atof (int type,
prec = H_PRECISION;
break;
+ case 'B':
+ case 'b':
+ prec = B_PRECISION;
+ break;
+
case 'f':
case 'F':
case 's':
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -511,7 +511,7 @@ const char EXP_CHARS[] = "eE";
/* Chars that mean this number is a floating point constant
As in 0f12.456
or 0d1.2345e12. */
-const char FLT_CHARS[] = "fFdDxXhH";
+const char FLT_CHARS[] = "fFdDxXhHbB";
/* Tables for lexical analysis. */
static char mnemonic_chars[256];
@@ -1353,6 +1353,7 @@ const pseudo_typeS md_pseudo_table[] =
{"dfloat", float_cons, 'd'},
{"tfloat", float_cons, 'x'},
{"hfloat", float_cons, 'h'},
+ {"bfloat16", float_cons, 'b'},
{"value", cons, 2},
{"slong", signed_cons, 4},
{"noopt", s_ignore, 0},
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -1312,20 +1312,22 @@ data type. Constructors build these dat
@cindex @code{double} directive, i386
@cindex @code{tfloat} directive, i386
@cindex @code{hfloat} directive, i386
+@cindex @code{bfloat16} directive, i386
@cindex @code{float} directive, x86-64
@cindex @code{single} directive, x86-64
@cindex @code{double} directive, x86-64
@cindex @code{tfloat} directive, x86-64
@cindex @code{hfloat} directive, x86-64
+@cindex @code{bfloat16} directive, x86-64
@itemize @bullet
@item
Floating point constructors are @samp{.float} or @samp{.single},
-@samp{.double}, @samp{.tfloat}, and @samp{.hfloat} for 32-, 64-, 80-, and
-16-bit formats respectively. The former three correspond to instruction
-mnemonic suffixes @samp{s}, @samp{l}, and @samp{t}. @samp{t} stands for
-80-bit (ten byte) real. The 80387 only supports this format via the
-@samp{fldt} (load 80-bit real to stack top) and @samp{fstpt} (store 80-bit
-real and pop stack) instructions.
+@samp{.double}, @samp{.tfloat}, @samp{.hfloat}, and @samp{.bfloat16} for 32-,
+64-, 80-, and 16-bit (two flavors) formats respectively. The former three
+correspond to instruction mnemonic suffixes @samp{s}, @samp{l}, and @samp{t}.
+@samp{t} stands for 80-bit (ten byte) real. The 80387 only supports this
+format via the @samp{fldt} (load 80-bit real to stack top) and @samp{fstpt}
+(store 80-bit real and pop stack) instructions.
@cindex @code{word} directive, i386
@cindex @code{long} directive, i386
--- a/gas/read.c
+++ b/gas/read.c
@@ -4852,6 +4852,8 @@ hex_float (int float_type, char *bytes)
switch (float_type)
{
+ case 'b':
+ case 'B':
case 'h':
case 'H':
length = 2;
--- a/gas/testsuite/gas/i386/fp-elf32.d
+++ b/gas/testsuite/gas/i386/fp-elf32.d
@@ -14,4 +14,4 @@ Contents of section .data:
0060 00000000 00000080 fe3f0000 00000000 .*
0070 00000080 fdbf0000 00000000 00000080 .*
0080 ff030000 aaaaaaaa aaaaaaaa aaaaaaaa .*
- 0090 003c00c0 003c5555 55555555 55555555 .*
+ 0090 003c00c0 003c803f 00c0803f 55555555 .*
--- a/gas/testsuite/gas/i386/fp-elf64.d
+++ b/gas/testsuite/gas/i386/fp-elf64.d
@@ -14,4 +14,4 @@ Contents of section .data:
0060 00000000 00000080 fe3f0000 00000000 .*
0070 00000000 00000080 fdbf0000 00000000 .*
0080 00000000 00000080 ff030000 00000000 .*
- 0090 003c00c0 003c5555 55555555 55555555 .*
+ 0090 003c00c0 003c803f 00c0803f 55555555 .*
--- a/gas/testsuite/gas/i386/fp.d
+++ b/gas/testsuite/gas/i386/fp.d
@@ -12,4 +12,4 @@ Contents of section .data:
0050 ffffffff ffffffff ffffcccc cccccccc .*
0060 00000000 00000080 fe3f0000 00000000 .*
0070 0080fdbf 00000000 00000080 ff03aaaa .*
- 0080 003c00c0 003c5555 55555555 55555555 .*
+ 0080 003c00c0 003c803f 00c0803f 55555555 .*
--- a/gas/testsuite/gas/i386/fp.s
+++ b/gas/testsuite/gas/i386/fp.s
@@ -31,4 +31,5 @@
.p2align 4,0xaa
.hfloat 1, -2, 0x:3c00
+ .bfloat16 1, -2, 0x:3f80
.p2align 4,0x55
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