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

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	.assume	adl=1

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

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

	.section	.text

	.global	_ilogbf
	.type	_ilogbf, @function
	.global	_ilogb
	.type	_ilogb, @function

; int ilogbf(float)
_ilogbf:
_ilogb:
	ld	hl, 6
	add	hl, sp
	ld	a, (hl)
	dec	hl
	dec	hl
	dec	hl
	ld	hl, (hl)
	add	hl, hl
	adc	a, a
	jr	z, .L.maybe_subnormal
	inc	a
	jr	z, .L.inf_nan
	sub	a, 128	; float32_bias + 1
	sbc	hl, hl
	ld	l, a
	ret

.L.maybe_subnormal:
	add	hl, de
	or	a, a
	sbc	hl, de
	jr	z, .L.ret_zero
	call	__ictlz
	cpl
	add	a, 130
	sbc	hl, hl
	ld	l, a
	ret

.L.inf_nan:
	scf
.L.ret_zero:
	ld	hl, EDOM
	ld	(_errno), hl
	ld	hl, ___fe_cur_env
	set	FE_INVALID_BIT, (hl)
	ld	hl, $800000	; FP_ILOGB0
	ret	nc
	; FP_ILOGBNAN or INT_MAX when carry is set
	dec	hl
	ret

	.extern	_errno
	.extern	___fe_cur_env
	.extern	__ictlz