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fp: support bfloat16 constants

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Support generating bfloat16 constants. This is a bit awkward, as "DW"
already generates IEEE half precision constants; therefore there is no
longer a single floating-point format for each size. This requires
some replumbing.

Fortunately bfloat16 fits in 64 bits, so support generating them with
a macro that uses __?bfloat16?__() to convert to integers first before
passing them to DW.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2020-07-16 23:11:03 -07:00
parent e830e92b77
commit d081f0db5d
10 changed files with 140 additions and 60 deletions
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25
asm/eval.c
View File

@ -694,21 +694,13 @@ static expr *expr5(void)
static expr *eval_floatize(enum floatize type)
{
uint8_t result[16], *p; /* Up to 128 bits */
static const struct {
int bytes, start, len;
} formats[] = {
{ 1, 0, 1 }, /* FLOAT_8 */
{ 2, 0, 2 }, /* FLOAT_16 */
{ 4, 0, 4 }, /* FLOAT_32 */
{ 8, 0, 8 }, /* FLOAT_64 */
{ 10, 0, 8 }, /* FLOAT_80M */
{ 10, 8, 2 }, /* FLOAT_80E */
{ 16, 0, 8 }, /* FLOAT_128L */
{ 16, 8, 8 }, /* FLOAT_128H */
};
int sign = 1;
int64_t val;
size_t len;
int i;
const struct ieee_format *fmt;
fmt = &fp_formats[type];
scan();
if (tt != '(') {
@ -724,7 +716,7 @@ static expr *eval_floatize(enum floatize type)
nasm_nonfatal("expecting floating-point number");
return NULL;
}
if (!float_const(tokval->t_charptr, sign, result, formats[type].bytes))
if (!float_const(tokval->t_charptr, sign, result, type))
return NULL;
scan();
if (tt != ')') {
@ -732,9 +724,12 @@ static expr *eval_floatize(enum floatize type)
return NULL;
}
p = result+formats[type].start+formats[type].len;
len = fmt->bytes - fmt->offset;
if (len > 8)
len = 8; /* Max 64 bits */
p = result + len;
val = 0;
for (i = formats[type].len; i; i--) {
for (i = len; i; i--) {
p--;
val = (val << 8) + *p;
}

74
asm/floats.c
View File

@ -1,6 +1,6 @@
/* ----------------------------------------------------------------------- *
*
* Copyright 1996-2018 The NASM Authors - All Rights Reserved
* Copyright 1996-2020 The NASM Authors - All Rights Reserved
* See the file AUTHORS included with the NASM distribution for
* the specific copyright holders.
*
@ -629,13 +629,6 @@ static void ieee_shr(fp_limb *mant, int i)
- the sign bit plus exponent fit in 16 bits.
- the exponent bias is 2^(n-1)-1 for an n-bit exponent */
struct ieee_format {
int bytes;
int mantissa; /* Fractional bits in the mantissa */
int explicit; /* Explicit integer */
int exponent; /* Bits in the exponent */
};
/*
* The 16- and 128-bit formats are expected to be in IEEE 754r.
* AMD SSE5 uses the 16-bit format.
@ -646,13 +639,31 @@ struct ieee_format {
*
* The 8-bit format appears to be the consensus 8-bit floating-point
* format. It is apparently used in graphics applications.
*
* The b16 format is a 16-bit format with smaller mantissa and larger
* exponent field. It is effectively a truncated version of the standard
* IEEE 32-bit (single) format, but is explicitly supported here in
* order to support proper rounding.
*
* This array must correspond to enum floatize in include/nasm.h.
* Note that there are some formats which have more than one enum;
* both need to be listed here with the appropriate offset into the
* floating-point byte array (use for the floatize operators.)
*
* FLOAT_ERR is a value that both represents "invalid format" and the
* size of this array.
*/
static const struct ieee_format ieee_8 = { 1, 3, 0, 4 };
static const struct ieee_format ieee_16 = { 2, 10, 0, 5 };
static const struct ieee_format ieee_32 = { 4, 23, 0, 8 };
static const struct ieee_format ieee_64 = { 8, 52, 0, 11 };
static const struct ieee_format ieee_80 = { 10, 63, 1, 15 };
static const struct ieee_format ieee_128 = { 16, 112, 0, 15 };
const struct ieee_format fp_formats[FLOAT_ERR] = {
{ 1, 3, 0, 4, 0 }, /* FLOAT_8 */
{ 2, 10, 0, 5, 0 }, /* FLOAT_16 */
{ 2, 7, 0, 8, 0 }, /* FLOAT_B16 */
{ 4, 23, 0, 8, 0 }, /* FLOAT_32 */
{ 8, 52, 0, 11, 0 }, /* FLOAT_64 */
{ 10, 63, 1, 15, 0 }, /* FLOAT_80M */
{ 10, 63, 1, 15, 8 }, /* FLOAT_80E */
{ 16, 112, 0, 15, 0 }, /* FLOAT_128L */
{ 16, 112, 0, 15, 8 } /* FLOAT_128H */
};
/* Types of values we can generate */
enum floats {
@ -672,7 +683,7 @@ static int to_packed_bcd(const char *str, const char *p,
char c;
int tv = -1;
if (fmt != &ieee_80) {
if (fmt->bytes != 10) {
nasm_nonfatal("packed BCD requires an 80-bit format");
return 0;
}
@ -711,9 +722,9 @@ static int to_packed_bcd(const char *str, const char *p,
return 1; /* success */
}
static int to_float(const char *str, int s, uint8_t *result,
const struct ieee_format *fmt)
int float_const(const char *str, int s, uint8_t *result, enum floatize ffmt)
{
const struct ieee_format *fmt = &fp_formats[ffmt];
fp_limb mant[MANT_LIMBS];
int32_t exponent = 0;
const int32_t expmax = 1 << (fmt->exponent - 1);
@ -902,25 +913,20 @@ static int to_float(const char *str, int s, uint8_t *result,
return 1; /* success */
}
int float_const(const char *number, int sign, uint8_t *result, int bytes)
/*
* Get the default floating point format for this specific field size.
* Used for the Dx pseudoops.
*/
enum floatize float_deffmt(int bytes)
{
switch (bytes) {
case 1:
return to_float(number, sign, result, &ieee_8);
case 2:
return to_float(number, sign, result, &ieee_16);
case 4:
return to_float(number, sign, result, &ieee_32);
case 8:
return to_float(number, sign, result, &ieee_64);
case 10:
return to_float(number, sign, result, &ieee_80);
case 16:
return to_float(number, sign, result, &ieee_128);
default:
nasm_panic("strange value %d passed to float_const", bytes);
return 0;
enum floatize type;
for (type = 0; type < FLOAT_ERR; type++) {
if (fp_formats[type].bytes == bytes)
break;
}
return type; /* FLOAT_ERR if invalid */
}
/* Set floating-point options */

17
asm/floats.h
View File

@ -1,6 +1,6 @@
/* ----------------------------------------------------------------------- *
*
* Copyright 1996-2009 The NASM Authors - All Rights Reserved
* Copyright 1996-2020 The NASM Authors - All Rights Reserved
* See the file AUTHORS included with the NASM distribution for
* the specific copyright holders.
*
@ -48,7 +48,20 @@ enum float_round {
FLOAT_RC_UP
};
int float_const(const char *string, int sign, uint8_t *result, int bytes);
/* Note: enum floatize and FLOAT_ERR are defined in nasm.h */
/* Floating-point format description */
struct ieee_format {
int bytes; /* Total bytes */
int mantissa; /* Fractional bits in the mantissa */
int explicit; /* Explicit integer */
int exponent; /* Bits in the exponent */
int offset; /* Offset into byte array for floatize op */
};
extern const struct ieee_format fp_formats[FLOAT_ERR];
int float_const(const char *str, int s, uint8_t *result, enum floatize ffmt);
enum floatize float_deffmt(int bytes);
int float_option(const char *option);
#endif /* NASM_FLOATS_H */

7
asm/parser.c
View File

@ -531,10 +531,12 @@ static int parse_eops(extop **result, bool critical, int elem)
goto is_float;
}
} else if (i == TOKEN_FLOAT) {
enum floatize fmt;
is_float:
eop->type = EOT_DB_FLOAT;
if (eop->elem > 16) {
fmt = float_deffmt(eop->elem);
if (fmt == FLOAT_ERR) {
nasm_nonfatal("no %d-bit floating-point format supported",
eop->elem << 3);
eop->val.string.len = 0;
@ -552,8 +554,7 @@ static int parse_eops(extop **result, bool critical, int elem)
eop = nasm_realloc(eop, sizeof(extop) + eop->val.string.len);
eop->val.string.data = (char *)eop + sizeof(extop);
if (!float_const(tokval.t_charptr, sign,
(uint8_t *)eop->val.string.data,
eop->val.string.len))
(uint8_t *)eop->val.string.data, fmt))
eop->val.string.len = 0;
}
if (!eop->val.string.len)

3
asm/tokens.dat
View File

@ -113,6 +113,9 @@ __?float80e?__
__?float128l?__
__?float128h?__
% TOKEN_FLOATIZE, 0, 0, FLOAT_B{__?bfloat*?__}
__?bfloat16?__
% TOKEN_STRFUNC, 0, 0, STRFUNC_{__?*?__}
__?utf16?__
__?utf16le?__

3
doc/changes.src
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@ -12,6 +12,9 @@ since 2007.
\b Add instructions from the Intel Instruction Set Extensions and
Future Features Programming Reference, June 2020.
\b Support for \c{bfloat16} floating-point constants. See \k{fltconst}
and \k{pkg_fp}.
\b Properly display warnings in preprocess-only mode.
\b Fix copy-and-paste of examples from the PDF documentation.

20
doc/nasmdoc.src
View File

@ -1692,9 +1692,9 @@ context.
\i{Floating-point} constants are acceptable only as arguments to
\i\c{DB}, \i\c{DW}, \i\c{DD}, \i\c{DQ}, \i\c{DT}, and \i\c{DO}, or as
arguments to the special operators \i\c{__?float8?__},
\i\c{__?float16?__}, \i\c{__?float32?__}, \i\c{__?float64?__},
\i\c{__?float80m?__}, \i\c{__?float80e?__}, \i\c{__?float128l?__}, and
\i\c{__?float128h?__}.
\i\c{__?float16?__}, \i\c{__?bfloat16?__}, \i\c{__?float32?__},
\i\c{__?float64?__}, \i\c{__?float80m?__}, \i\c{__?float80e?__},
\i\c{__?float128l?__}, and \i\c{__?float128h?__}. See also \k{pkg_fp}.
Floating-point constants are expressed in the traditional form:
digits, then a period, then optionally more digits, then optionally an
@ -1733,6 +1733,13 @@ appears to be the most frequently used 8-bit floating-point format,
although it is not covered by any formal standard. This is sometimes
called a "\i{minifloat}."
The \i\c{bfloat16} format is effectively a compressed version of the
32-bit single precision format, with a reduced mantissa. It is
effectively the same as truncating the 32-bit format to the upper 16
bits, except for rounding. There is no \c{D}\e{x} directive that
corresponds to \c{bfloat16} as it obviously has the same size as the
IEEE standard 16-bit half precision format, see however \k{pkg_fp}.
The special operators are used to produce floating-point numbers in
other contexts. They produce the binary representation of a specific
floating-point number as an integer, and can use anywhere integer
@ -4633,6 +4640,7 @@ This packages contains the following floating-point convenience macros:
\c
\c %define float8(x) __?float8?__(x)
\c %define float16(x) __?float16?__(x)
\c %define bfloat16(x) __?bfloat16?__(x)
\c %define float32(x) __?float32?__(x)
\c %define float64(x) __?float64?__(x)
\c %define float80m(x) __?float80m?__(x)
@ -4640,6 +4648,12 @@ This packages contains the following floating-point convenience macros:
\c %define float128l(x) __?float128l?__(x)
\c %define float128h(x) __?float128h?__(x)
It also defines the a multi-line macro \i\c{bf16} that can be used
in a similar way to the \c{D}\e{x} directives for the other
floating-point numbers:
\c bf16 -3.1415, NaN, 2000.0, +Inf
\H{pkg_ifunc} \i\c{ifunc}: \i{Integer functions}

5
include/nasm.h
View File

@ -196,15 +196,18 @@ enum token_type { /* token types, other than chars */
TOKEN_OPMASK /* translated token for opmask registers */
};
/* Must match the fp_formats[] array in asm/floats.c */
enum floatize {
FLOAT_8,
FLOAT_16,
FLOAT_B16,
FLOAT_32,
FLOAT_64,
FLOAT_80M,
FLOAT_80E,
FLOAT_128L,
FLOAT_128H
FLOAT_128H,
FLOAT_ERR /* Invalid format, MUST BE LAST */
};
/* Must match the list in string_transform(), in strfunc.c */

10
macros/fp.mac
View File

@ -1,6 +1,6 @@
;; --------------------------------------------------------------------------
;;
;; Copyright 2010 The NASM Authors - All Rights Reserved
;; Copyright 2010-2020 The NASM Authors - All Rights Reserved
;; See the file AUTHORS included with the NASM distribution for
;; the specific copyright holders.
;;
@ -46,9 +46,17 @@ USE: fp
%define float8(x) __?float8?__(x)
%define float16(x) __?float16?__(x)
%define bfloat16(x) __?bfloat16?__(x)
%define float32(x) __?float32?__(x)
%define float64(x) __?float64?__(x)
%define float80m(x) __?float80m?__(x)
%define float80e(x) __?float80e?__(x)
%define float128l(x) __?float128l?__(x)
%define float128h(x) __?float128h?__(x)
%imacro bf16 1-*.nolist
%rep %0
dw __?bfloat16?__(%1)
%rotate 1
%endrep
%endmacro

36
test/float.asm
View File

@ -5,6 +5,8 @@
; Test of floating-point formats
;
%use fp
; 8-bit
db 1.0
db +1.0
@ -65,6 +67,37 @@
dw __SNaN__
dw 3.1415926535_8979323846_2643383279_5028841971_6939937510_5
; 16-bit bfloat
bf16 1.0
bf16 +1.0
bf16 -1.0
bf16 1.5
bf16 +1.5
bf16 -1.5
bf16 0.0
bf16 +0.0
bf16 -0.0
bf16 1.83203125
bf16 +1.83203125
bf16 -1.83203125
bf16 1.83203125e15
bf16 +1.83203125e15
bf16 -1.83203125e15
bf16 1.83203125e-15
bf16 +1.83203125e-15
bf16 -1.83203125e-15
bf16 1.83203125e-40 ; Denormal!
bf16 +1.83203125e-40 ; Denormal!
bf16 -1.83203125e-40 ; Denormal!
bf16 __Infinity__
bf16 +__Infinity__
bf16 -__Infinity__
bf16 __NaN__
bf16 __QNaN__
bf16 __SNaN__
bf16 3.1415926535_8979323846_2643383279_5028841971_6939937510_5
bf16 -3.1415, NaN, 2000.0, +Inf
; 32-bit
dd 1.0
dd +1.0
@ -94,6 +127,7 @@
dd __QNaN__
dd __SNaN__
dd 3.1415926535_8979323846_2643383279_5028841971_6939937510_5
dd -3.1415, NaN, 2000.0, +Inf
; 64-bit
dq 1.0
@ -124,7 +158,7 @@
dq __QNaN__
dq __SNaN__
dq 3.1415926535_8979323846_2643383279_5028841971_6939937510_5
; 80-bit
dt 1.0
dt +1.0