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glibc/sysdeps/i386/fpu/e_expl.S
Siddhesh Poyarekar 30891f35fa Remove "Contributed by" lines
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date.  Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.

Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions.  These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.

The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively.  These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:

https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc
https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-09-03 22:06:44 +05:30

227 lines
5.7 KiB
ArmAsm

/*
* Public domain.
*
*/
/*
* The 8087 method for the exponential function is to calculate
* exp(x) = 2^(x log2(e))
* after separating integer and fractional parts
* x log2(e) = i + f, |f| <= .5
* 2^i is immediate but f needs to be precise for long double accuracy.
* Suppress range reduction error in computing f by the following.
* Separate x into integer and fractional parts
* x = xi + xf, |xf| <= .5
* Separate log2(e) into the sum of an exact number c0 and small part c1.
* c0 + c1 = log2(e) to extra precision
* Then
* f = (c0 xi - i) + c0 xf + c1 x
* where c0 xi is exact and so also is (c0 xi - i).
* -- moshier@na-net.ornl.gov
*/
#include <libm-alias-ldouble.h>
#include <machine/asm.h>
#include <i386-math-asm.h>
#include <libm-alias-finite.h>
#ifdef USE_AS_EXP10L
# define IEEE754_EXPL __ieee754_exp10l
# define FLDLOG fldl2t
#elif defined USE_AS_EXPM1L
# define IEEE754_EXPL __expm1l
# define FLDLOG fldl2e
#else
# define IEEE754_EXPL __ieee754_expl
# define FLDLOG fldl2e
#endif
.section .rodata.cst16,"aM",@progbits,16
.p2align 4
#ifdef USE_AS_EXP10L
.type c0,@object
c0: .byte 0, 0, 0, 0, 0, 0, 0x9a, 0xd4, 0x00, 0x40
.byte 0, 0, 0, 0, 0, 0
ASM_SIZE_DIRECTIVE(c0)
.type c1,@object
c1: .byte 0x58, 0x92, 0xfc, 0x15, 0x37, 0x9a, 0x97, 0xf0, 0xef, 0x3f
.byte 0, 0, 0, 0, 0, 0
ASM_SIZE_DIRECTIVE(c1)
#else
.type c0,@object
c0: .byte 0, 0, 0, 0, 0, 0, 0xaa, 0xb8, 0xff, 0x3f
.byte 0, 0, 0, 0, 0, 0
ASM_SIZE_DIRECTIVE(c0)
.type c1,@object
c1: .byte 0x20, 0xfa, 0xee, 0xc2, 0x5f, 0x70, 0xa5, 0xec, 0xed, 0x3f
.byte 0, 0, 0, 0, 0, 0
ASM_SIZE_DIRECTIVE(c1)
#endif
#ifndef USE_AS_EXPM1L
.type csat,@object
csat: .byte 0, 0, 0, 0, 0, 0, 0, 0x80, 0x0e, 0x40
.byte 0, 0, 0, 0, 0, 0
ASM_SIZE_DIRECTIVE(csat)
DEFINE_LDBL_MIN
#endif
#ifdef PIC
# define MO(op) op##@GOTOFF(%ecx)
#else
# define MO(op) op
#endif
.text
ENTRY(IEEE754_EXPL)
#ifdef USE_AS_EXPM1L
movzwl 4+8(%esp), %eax
xorb $0x80, %ah // invert sign bit (now 1 is "positive")
cmpl $0xc006, %eax // is num positive and exp >= 6 (number is >= 128.0)?
jae HIDDEN_JUMPTARGET (__expl) // (if num is denormal, it is at least >= 64.0)
#endif
fldt 4(%esp)
/* I added the following ugly construct because expl(+-Inf) resulted
in NaN. The ugliness results from the bright minds at Intel.
For the i686 the code can be written better.
-- drepper@cygnus.com. */
fxam /* Is NaN or +-Inf? */
#ifdef PIC
LOAD_PIC_REG (cx)
#endif
#ifdef USE_AS_EXPM1L
xorb $0x80, %ah
cmpl $0xc006, %eax
fstsw %ax
movb $0x45, %dh
jb 4f
/* Below -64.0 (may be -NaN or -Inf). */
andb %ah, %dh
cmpb $0x01, %dh
je 6f /* Is +-NaN, jump. */
jmp 1f /* -large, possibly -Inf. */
4: /* In range -64.0 to 64.0 (may be +-0 but not NaN or +-Inf). */
/* Test for +-0 as argument. */
andb %ah, %dh
cmpb $0x40, %dh
je 2f
/* Test for arguments that are small but not subnormal. */
movzwl 4+8(%esp), %eax
andl $0x7fff, %eax
cmpl $0x3fbf, %eax
jge 3f
/* Argument's exponent below -64; avoid spurious underflow if
normal. */
cmpl $0x0001, %eax
jge 2f
/* Force underflow and return the argument, to avoid wrong signs
of zero results from the code below in some rounding modes. */
fld %st
fmul %st
fstp %st
jmp 2f
#else
movzwl 4+8(%esp), %eax
andl $0x7fff, %eax
cmpl $0x400d, %eax
jg 5f
cmpl $0x3fbc, %eax
jge 3f
/* Argument's exponent below -67, result rounds to 1. */
fld1
faddp
jmp 2f
5: /* Overflow, underflow or infinity or NaN as argument. */
fstsw %ax
movb $0x45, %dh
andb %ah, %dh
cmpb $0x05, %dh
je 1f /* Is +-Inf, jump. */
cmpb $0x01, %dh
je 6f /* Is +-NaN, jump. */
/* Overflow or underflow; saturate. */
fstp %st
fldt MO(csat)
andb $2, %ah
jz 3f
fchs
#endif
3: FLDLOG /* 1 log2(base) */
fmul %st(1), %st /* 1 x log2(base) */
/* Set round-to-nearest temporarily. */
subl $8, %esp
cfi_adjust_cfa_offset (8)
fstcw 4(%esp)
movl $0xf3ff, %edx
andl 4(%esp), %edx
movl %edx, (%esp)
fldcw (%esp)
frndint /* 1 i */
fld %st(1) /* 2 x */
frndint /* 2 xi */
fldcw 4(%esp)
addl $8, %esp
cfi_adjust_cfa_offset (-8)
fld %st(1) /* 3 i */
fldt MO(c0) /* 4 c0 */
fld %st(2) /* 5 xi */
fmul %st(1), %st /* 5 c0 xi */
fsubp %st, %st(2) /* 4 f = c0 xi - i */
fld %st(4) /* 5 x */
fsub %st(3), %st /* 5 xf = x - xi */
fmulp %st, %st(1) /* 4 c0 xf */
faddp %st, %st(1) /* 3 f = f + c0 xf */
fldt MO(c1) /* 4 */
fmul %st(4), %st /* 4 c1 * x */
faddp %st, %st(1) /* 3 f = f + c1 * x */
f2xm1 /* 3 2^(fract(x * log2(base))) - 1 */
#ifdef USE_AS_EXPM1L
fstp %st(1) /* 2 */
fscale /* 2 scale factor is st(1); base^x - 2^i */
fxch /* 2 i */
fld1 /* 3 1.0 */
fscale /* 3 2^i */
fld1 /* 4 1.0 */
fsubrp %st, %st(1) /* 3 2^i - 1.0 */
fstp %st(1) /* 2 */
faddp %st, %st(1) /* 1 base^x - 1.0 */
#else
fld1 /* 4 1.0 */
faddp /* 3 2^(fract(x * log2(base))) */
fstp %st(1) /* 2 */
fscale /* 2 scale factor is st(1); base^x */
fstp %st(1) /* 1 */
LDBL_CHECK_FORCE_UFLOW_NONNEG
#endif
fstp %st(1) /* 0 */
jmp 2f
1:
#ifdef USE_AS_EXPM1L
/* For expm1l, only negative sign gets here. */
fstp %st
fld1
fchs
#else
testl $0x200, %eax /* Test sign. */
jz 2f /* If positive, jump. */
fstp %st
fldz /* Set result to 0. */
#endif
2: ret
6: /* NaN argument. */
fadd %st
ret
END(IEEE754_EXPL)
#ifdef USE_AS_EXPM1L
libm_hidden_def (__expm1l)
libm_alias_ldouble (__expm1, expm1)
#elif defined USE_AS_EXP10L
libm_alias_finite (__ieee754_exp10l, __exp10l)
#else
libm_alias_finite (__ieee754_expl, __expl)
#endif