toolchain/src/libc/ilogbl.src at b37490f38acd6fdcb61ddafa6193e5cc1304b571 · CE-Programming/toolchain · GitHub

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	.assume	adl=1

	.include	"errno.inc"
	.include	"fenv.inc"
	.include	"math.inc"

.if	EDOM & 0xFF != EDOM
	.print	"EDOM is assumed to be between 1 and 255"
	.err
.endif

.if	!(FP_ILOGBNAN == 0x7FFFFF)
	.print	"ilogbl assumes that FP_ILOGBNAN == 0x7FFFFF (INT_MAX)"
	.err
.endif
.if	!(FP_ILOGB0 - 1 == FP_ILOGBNAN)
	.print	"ilogbl assumes FP_ILOGB0 - 1 == FP_ILOGBNAN"
	.err
.endif

	.section	.text

	.global	_ilogbl
	.type	_ilogbl, @function

; int ilogbl(long double)
_ilogbl:
	ld	iy, 0
	lea	de, iy + 0
	add	iy, sp
	ld	hl, (iy + 9)
	add	hl, hl
	ld	a, h
	rlca
	rlca
	rlca
	add	hl, hl
	add	hl, hl
	add.s	hl, hl	; clears upper bits
	and	a, $07
	ld	l, h
	ld	h, a
	; HL = exponent
	adc	hl, de
	jr	z, .L.maybe_subnormal
	inc	hl
	bit	3, h
	jr	nz, .L.inf_nan
	; Float64_exp_bias + 1
	ld	de, -1024
	add	hl, de
	ret

.L.maybe_subnormal:
	ld	c, (iy + 9)
	ld	b, e	; DE is zero
	ld	de, (iy + 6)
	ld	hl, (iy + 3)
	call	__llctlz
	cp	a, 64
	sbc	hl, hl
	jr	z, .L.ret_zero	; A was 64
	cpl
	ld	l, a
	; -1023 + 11 + 1 + 1
	; Float64_ilogb_subnorm_max + Float64_exponent_bits + Float64_sign_bits
	ld	de, -1010
	add	hl, de
	ret

.L.ret_zero:
	ex	de, hl
	inc	de
.L.inf_nan:
	ld	hl, $7FFFFF	; FP_ILOGBNAN or INT_MAX
	add	hl, de	; FP_ILOGB0 when DE is one
	ex	de, hl
	;	DE was zero or one, so HL is now zero or one
	ld	l, EDOM
	ld	(_errno), hl
	ld	hl, ___fe_cur_env
	set	FE_INVALID_BIT, (hl)
	ex	de, hl
	ret

	.extern	__fpclassifyl
	.extern	_errno
	.extern	___fe_cur_env
	.extern	__llctlz