From: miod <miod@openbsd.org>
Date: Sun, 13 Aug 2023 06:55:37 +0000 (+0000)
Subject: Make sure modf() returns correct values for infinities. While there, drop
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=f78f1c7c95a263d9fb01c2ea8977757437feec00;p=openbsd

Make sure modf() returns correct values for infinities. While there, drop
the few assembler versions as has been done on other *BSD systems; this
function (modf) turns out to be non-trivial enough, having only one
known-to-work version is preferrable.

Reported by Willemijn Coene.
---

diff --git a/lib/libc/arch/amd64/gen/Makefile.inc b/lib/libc/arch/amd64/gen/Makefile.inc
index 7dcd8bd9f79..c9f2c976e77 100644
--- a/lib/libc/arch/amd64/gen/Makefile.inc
+++ b/lib/libc/arch/amd64/gen/Makefile.inc
@@ -1,6 +1,6 @@
-#	$OpenBSD: Makefile.inc,v 1.13 2020/07/06 13:33:05 pirofti Exp $
+#	$OpenBSD: Makefile.inc,v 1.14 2023/08/13 06:55:37 miod Exp $
 
-SRCS+=	_setjmp.S fabs.S infinity.c ldexp.c modf.S nan.c setjmp.S \
+SRCS+=	_setjmp.S fabs.S infinity.c ldexp.c modf.c nan.c setjmp.S \
 	sigsetjmp.S
 SRCS+=	fpclassifyl.c isfinitel.c isinfl.c isnanl.c isnormall.c signbitl.c \
 	usertc.c
diff --git a/lib/libc/arch/amd64/gen/modf.S b/lib/libc/arch/amd64/gen/modf.S
deleted file mode 100644
index 394e682b086..00000000000
--- a/lib/libc/arch/amd64/gen/modf.S
+++ /dev/null
@@ -1,94 +0,0 @@
-/*	$OpenBSD: modf.S,v 1.6 2018/07/03 23:14:05 mortimer Exp $	*/
-/*	$NetBSD: modf.S,v 1.1 2001/06/19 00:25:03 fvdl Exp $	*/
-
-/*-
- * Copyright (c) 1990 The Regents of the University of California.
- * All rights reserved.
- *
- * This code is derived from software contributed to Berkeley by
- * Sean Eric Fagan.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- *	from: @(#)modf.s	5.5 (Berkeley) 3/18/91
- */
-
-#include <machine/asm.h>
-
-/*
- * modf(value, iptr): return fractional part of value, and stores the
- * integral part into iptr (a pointer to double).
- *
- * Written by Sean Eric Fagan (sef@kithrup.COM)
- * Sun Mar 11 20:27:30 PST 1990
- */
-
-/* With CHOP mode on, frndint behaves as TRUNC does.  Useful. */
-ENTRY(modf)
-	RETGUARD_SETUP(modf, r11)
-
-	/*
-	 * Set chop mode.
-	 */
-	fnstcw	-12(%rsp)
-	movw	-12(%rsp),%dx
-	orw	$3072,%dx
-	movw	%dx,-16(%rsp)
-	fldcw	-16(%rsp)
-
-	/*
-	 * Get integral part.
-	 */
-	movsd	%xmm0,-24(%rsp)
-	fldl	-24(%rsp)
-	frndint
-	fstpl	-8(%rsp)
-
-	/*
-	 * Restore control word.
-	 */
-	fldcw	-12(%rsp)
-
-	/*
-	 * Store integral part.
-	 */
-	movsd	-8(%rsp),%xmm0
-	movsd	%xmm0,(%rdi)
-
-	/*
-	 * Get fractional part and return it.
-	 */
-	fldl	-24(%rsp)
-	fsubl	-8(%rsp)
-	fstpl	-8(%rsp)
-	movsd   -8(%rsp),%xmm0
-
-	RETGUARD_CHECK(modf, r11)
-	ret
-END(modf)
diff --git a/lib/libc/arch/i386/gen/Makefile.inc b/lib/libc/arch/i386/gen/Makefile.inc
index 30b5f8726c5..45d0108a148 100644
--- a/lib/libc/arch/i386/gen/Makefile.inc
+++ b/lib/libc/arch/i386/gen/Makefile.inc
@@ -1,7 +1,7 @@
-#	$OpenBSD: Makefile.inc,v 1.15 2020/07/06 13:33:05 pirofti Exp $
+#	$OpenBSD: Makefile.inc,v 1.16 2023/08/13 06:55:37 miod Exp $
 
 SRCS+=	_setjmp.S fabs.S infinity.c ldexp.c usertc.c \
-	modf.S nan.c setjmp.S sigsetjmp.S
+	modf.c nan.c setjmp.S sigsetjmp.S
 SRCS+=	fpclassifyl.c isfinitel.c isinfl.c isnanl.c isnormall.c signbitl.c
 SRCS+=	flt_rounds.S fpgetmask.S fpgetround.S fpgetsticky.S fpsetmask.S \
 	fpsetround.S fpsetsticky.S
diff --git a/lib/libc/arch/i386/gen/modf.S b/lib/libc/arch/i386/gen/modf.S
deleted file mode 100644
index 4b623611a60..00000000000
--- a/lib/libc/arch/i386/gen/modf.S
+++ /dev/null
@@ -1,68 +0,0 @@
-/* $OpenBSD: modf.S,v 1.7 2011/07/08 22:28:33 martynas Exp $ */
-/*-
- * Copyright (c) 1990 The Regents of the University of California.
- * All rights reserved.
- *
- * This code is derived from software contributed to Berkeley by
- * Sean Eric Fagan.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <machine/asm.h>
-
-/*
- * modf(value, iptr): return fractional part of value, and stores the
- * integral part into iptr (a pointer to double).
- *
- * Written by Sean Eric Fagan (sef@kithrup.COM)
- * Sun Mar 11 20:27:30 PST 1990
- */
-
-/* With CHOP mode on, frndint behaves as TRUNC does.  Useful. */
-ENTRY(modf)
-	pushl	%ebp
-	movl	%esp,%ebp
-	subl	$16,%esp
-	fnstcw	-12(%ebp)
-	movw	-12(%ebp),%dx
-	orw	$3072,%dx
-	movw	%dx,-16(%ebp)
-	fldcw	-16(%ebp)
-	fldl	8(%ebp)
-	frndint
-	fstpl	-8(%ebp)
-	fldcw	-12(%ebp)
-	movl	16(%ebp),%eax
-	movl	-8(%ebp),%edx
-	movl	-4(%ebp),%ecx
-	movl	%edx,(%eax)
-	movl	%ecx,4(%eax)
-	fldl	8(%ebp)
-	fsubl	-8(%ebp)
-	jmp	L1
-L1:
-	leave
-	ret
diff --git a/lib/libc/arch/mips64/gen/Makefile.inc b/lib/libc/arch/mips64/gen/Makefile.inc
index f3f88957860..ca34aefd3e4 100644
--- a/lib/libc/arch/mips64/gen/Makefile.inc
+++ b/lib/libc/arch/mips64/gen/Makefile.inc
@@ -1,6 +1,6 @@
-#	$OpenBSD: Makefile.inc,v 1.13 2020/07/06 13:33:05 pirofti Exp $
+#	$OpenBSD: Makefile.inc,v 1.14 2023/08/13 06:55:37 miod Exp $
 
-SRCS+=	_setjmp.S fabs.S infinity.c ldexp.S modf.S nan.c usertc.c
+SRCS+=	_setjmp.S fabs.S infinity.c ldexp.S modf.c nan.c usertc.c
 SRCS+=	flt_rounds.c fpgetmask.c fpgetround.c fpgetsticky.c fpsetmask.c \
 	fpsetround.c fpsetsticky.c
 SRCS+=	fpclassifyl.c isfinitel.c isinfl.c isnanl.c isnormall.c signbitl.c
diff --git a/lib/libc/arch/mips64/gen/modf.S b/lib/libc/arch/mips64/gen/modf.S
deleted file mode 100644
index 029e7044191..00000000000
--- a/lib/libc/arch/mips64/gen/modf.S
+++ /dev/null
@@ -1,71 +0,0 @@
-/* $OpenBSD: modf.S,v 1.5 2011/07/08 22:28:33 martynas Exp $ */
-/*-
- * Copyright (c) 1991, 1993, 1995
- *	The Regents of the University of California.  All rights reserved.
- *
- * This code is derived from software contributed to Berkeley by
- * Ralph Campbell.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <machine/asm.h>
-
-/*
- * double modf(val, iptr)
- *	double val, *iptr;
- * returns: xxx and n (in *iptr) where val == n.xxx
- */
-LEAF(modf, 0)
-	.set	reorder
-	cfc1	t0, $31			# get the control register
-	li.d	$f2, 4503599627370496e0 # f2 <- 2^52
-
-	or	t1, t0, 0x3		# set rounding mode to round to zero
-	xor	t1, t1, 0x2		#  (i.e., 01)
-	ctc1	t1, $31
-
-	mov.d	$f0, $f12		# f0 <- f12
-	abs.d	$f4, $f12		# f4 <- |f12|
-	c.olt.d $f4, $f2		# f4 ? < f2 
-	bc1f	1f			# leave f0 alone if Nan, infinity 
-					# or >=2^52
-	c.eq.d	$f12,$f4		# was f12 positive ?
-	add.d	$f4,$f2,$f4		# round off to integer
-	bc1f	2f			# No -> will have to negate result
-	sub.d	$f0,$f4,$f2		# Remove fudge factor
-	j	1f			# integer fraction got
-2:	
-	sub.d	$f0,$f2,$f4		# Remove fudge factor and negate
-1:	
-	ctc1	t0, $31			# restore old rounding mode
-#ifdef __mips64
-	s.d	$f0, 0(a1)		# save the integer part
-#else
-	s.d	$f0, 0(a2)		# save the integer part
-#endif
-	sub.d	$f0, $f12, $f0		# subtract val - integer part
-	j	ra
-END(modf)
diff --git a/lib/libc/arch/sparc64/gen/Makefile.inc b/lib/libc/arch/sparc64/gen/Makefile.inc
index 6d19faf9502..5cbb1e62227 100644
--- a/lib/libc/arch/sparc64/gen/Makefile.inc
+++ b/lib/libc/arch/sparc64/gen/Makefile.inc
@@ -1,9 +1,9 @@
-#	$OpenBSD: Makefile.inc,v 1.16 2020/07/08 09:20:28 kettenis Exp $
+#	$OpenBSD: Makefile.inc,v 1.17 2023/08/13 06:55:37 miod Exp $
 
 SRCS+=	_setjmp.S fabs.S fixunsdfsi.S flt_rounds.c fpclassifyl.c \
 	fpgetmask.c fpgetround.c fpgetsticky.c fpsetmask.c \
 	fpsetround.c fpsetsticky.c infinity.c isfinitel.c \
-	isinfl.c isnanl.c isnormall.c ldexp.c usertc.c modf.S \
+	isinfl.c isnanl.c isnormall.c ldexp.c usertc.c modf.c \
 	mul.S nan.c setjmp.S signbitl.c sigsetjmp.S umul.S
 
 CFLAGS += -Wa,-Av9b
diff --git a/lib/libc/arch/sparc64/gen/modf.S b/lib/libc/arch/sparc64/gen/modf.S
deleted file mode 100644
index 4fa2ea515f2..00000000000
--- a/lib/libc/arch/sparc64/gen/modf.S
+++ /dev/null
@@ -1,188 +0,0 @@
-/*	$OpenBSD: modf.S,v 1.7 2023/01/13 17:52:08 miod Exp $	*/
-/*	$NetBSD: modf.S,v 1.3 2000/11/01 23:32:41 eeh Exp $	*/
-
-/*
- * Copyright (c) 1992, 1993
- *	The Regents of the University of California.  All rights reserved.
- *
- * This software was developed by the Computer Systems Engineering group
- * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
- * contributed to Berkeley.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <machine/asm.h>
-
-#include <machine/fsr.h>
-
-/*
- * double modf(double val, double *iptr)
- *
- * Returns the fractional part of `val', storing the integer part of
- * `val' in *iptr.  Both *iptr and the return value have the same sign
- * as `val'.
- *
- * Method:
- *
- * We use the fpu's normalization hardware to compute the integer portion
- * of the double precision argument.  Sun IEEE double precision numbers
- * have 52 bits of mantissa, 11 bits of exponent, and one bit of sign,
- * with the sign occupying bit 31 of word 0, and the exponent bits 30:20
- * of word 0.  Thus, values >= 2^52 are by definition integers.
- *
- * If we take a value that is in the range [+0..2^52) and add 2^52, all
- * of the fractional bits fall out and all of the integer bits are summed
- * with 2^52.  If we then subtract 2^52, we get those integer bits back.
- * This must be done with rounding set to `towards 0' or `towards -inf'.
- * `Toward -inf' fails when the value is 0 (we get -0 back)....
- *
- * Note that this method will work anywhere, but is machine dependent in
- * various aspects.
- *
- * Stack usage:
- *	4@[%fp + BIAS - 4]	saved %fsr
- *	4@[%fp + BIAS - 8]	new %fsr with rounding set to `towards 0'
- *	8@[%fp + BIAS - 16]	space for moving between %i and %f registers
- * Register usage:
- *	%f0:f1		double val;
- *	%l0		scratch
- *	%l1		sign bit (0x80000000)
- *	%i1		double *iptr;
- *	%f2:f3		`magic number' 2^52, in fpu registers
- *	%f4:f5		double v, in fpu registers
- *	%f6:f7		double temp.
- */
-
-	.section .rodata
-	.align	8
-Lmagic:
-	.word	0x43300000	! sign = 0, exponent = 52 + 1023, mantissa = 0
-	.word	0		! (i.e., .double 0r4503599627370496e+00)
-
-L0:
-	.word	0		! 0.0
-	.word	0
-
-	.text
-ENTRY(modf)
-	save	%sp, -CC64FSZ-16, %sp
-#ifdef __PIC__
-	PIC_PROLOGUE(%o5, %o4)
-#endif
-
-	/*
-	 * First, compute v = abs(val)
-	 */
-	fabsd	%f0, %f4		! %f4:f5 = v
-	fcmped	%fcc1, %f0, %f4		! %fcc1 = (val == abs(val))
-#ifdef __PIC__
-	set	Lmagic, %o4
-	ldx	[%o5 + %o4], %l0
-	ldd	[%l0], %f2
-#else
-	sethi	%hi(Lmagic), %l0
-	ldd	[%l0 + %lo(Lmagic)], %f2
-#endif
-
-	/*
-	 * Is %f4:f5 >= %f2:f3 ?  If so, it is all integer bits.
-	 * It is probably less, though.
-	 */
-	fcmped	%f4, %f2
-	fbuge	Lbig			! if >= (or unordered), go out
-	nop
-
-	/*
-	 * v < 2^52, so add 2^52, then subtract 2^52, but do it all
-	 * with rounding set towards zero.  We leave any enabled
-	 * traps enabled, but change the rounding mode.  This might
-	 * not be so good.  Oh well....
-	 */
-	st	%fsr, [%fp + BIAS - 4]	! %l5 = current FSR mode
-	set	FSR_RD, %l3		! %l3 = rounding direction mask
-	ld	[%fp + BIAS - 4], %l5
-	set	FSR_RD_RZ << FSR_RD_SHIFT, %l4
-	andn	%l5, %l3, %l6
-	or	%l6, %l4, %l6		! round towards zero, please
-	and	%l5, %l3, %l5		! save original rounding mode
-	st	%l6, [%fp + BIAS - 8]
-	ld	[%fp + BIAS - 8], %fsr
-
-	faddd	%f4, %f2, %f4		! %f4:f5 += 2^52
-	fsubd	%f4, %f2, %f4		! %f4:f5 -= 2^52
-
-	/*
-	 * Restore %fsr, but leave exceptions accrued.
-	 */
-	st	%fsr, [%fp + BIAS - 4]
-	ld	[%fp + BIAS - 4], %l6
-	andn	%l6, %l3, %l6		! %l6 = %fsr & ~FSR_RD;
-	or	%l5, %l6, %l5		! %l5 |= %l6;
-	st	%l5, [%fp + BIAS - 4]
-	ld	[%fp + BIAS - 4], %fsr	! restore %fsr, leaving accrued stuff
-
-	/*
-	 * Now insert the original sign in %f4:f5.
-	 * %fcc1 should still have the reults of (val == abs(val))
-	 * from above, so we use a conditional move on %fcc1 to: 
-	 *
-	 *	%f4 = (val == abs(val)) ? %f4 : -%f4
-	 *
-	 */
-	fnegd	%f4, %f6
-	fmovdnz	%fcc1, %f6, %f4
-1:
-
-	/*
-	 * The value in %f4:f5 is now the integer portion of the original
-	 * argument.  We need to store this in *ival (%i1), subtract it
-	 * from the original value argument (%d0), and return the result.
-	 */
-	std	%f4, [%i1]		! *ival = %f4:f5;
-	fsubd	%f0, %f4, %f0		! %f0:f1 -= %f4:f5;
-	ret
-	restore
-
-Lbig:
-	/*
-	 * We get here if the original comparison of %f4:f5 (v) to
-	 * %f2:f3 (2^52) came out `greater or unordered'.  In this
-	 * case the integer part is the original value, and the
-	 * fractional part is 0.
-	 */
-#ifdef __PIC__
-	set	L0, %o4
-	ldx	[%o5 + %o4], %l0
-	std	%f0, [%i1]		! *ival = val;
-	ldd	[%l0], %f0		! return 0.0;
-#else
-	sethi	%hi(L0), %l0
-	std	%f0, [%i1]		! *ival = val;
-	ldd	[%l0 + %lo(L0)], %f0	! return 0.0;
-#endif
-	ret
-	 restore
-
diff --git a/lib/libc/gen/modf.c b/lib/libc/gen/modf.c
index 5c523519ba6..e02e8c106bf 100644
--- a/lib/libc/gen/modf.c
+++ b/lib/libc/gen/modf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: modf.c,v 1.6 2013/07/03 04:46:36 espie Exp $	*/
+/*	$OpenBSD: modf.c,v 1.7 2023/08/13 06:55:37 miod Exp $	*/
 /*	$NetBSD: modf.c,v 1.1 1995/02/10 17:50:25 cgd Exp $	*/
 
 /*
@@ -51,11 +51,13 @@ modf(double val, double *iptr)
 	u_int64_t frac;
 
 	/*
-	 * If input is Inf or NaN, return it and leave i alone.
+	 * If input is +/-Inf or NaN, return +/-0 or NaN.
 	 */
 	u.v = val;
-	if (u.s.dbl_exp == DBL_EXP_INFNAN)
-		return (u.v);
+	if (u.s.dbl_exp == DBL_EXP_INFNAN) {
+		*iptr = u.v;
+		return (0.0 / u.v);
+	}
 
 	/*
 	 * If input can't have a fractional part, return