Re: port-sh3/60773: sh3 __sync_val_compare_and_swap_1 test failures

["Taylor R Campbell via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR toolchain/60773; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: Valery Ushakov <uwe%stderr.spb.ru@localhost>,
	gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost,
	Nick Hudson <skrll%NetBSD.org@localhost>
Cc: 
Subject: Re: port-sh3/60773: sh3 __sync_val_compare_and_swap_1 test failures
Date: Fri, 25 Sep 2026 19:47:19 +0000

 I did the same for Arm with -march=armv5t -mfloat-abi=soft, and here's
 how it came out -- gcc treats __sync_* as signed, not unsigned (note
 the `and r2, r2, #255' in main__ and main_u8 but not main_s8):
 
 00000000 <main__>:
    0:	e3e01077 	mvn	r1, #119	@ 0x77
    4:	e52de004 	push	{lr}		@ (str lr, [sp, #-4]!)
    8:	e24dd00c 	sub	sp, sp, #12
    c:	e3e0200f 	mvn	r2, #15
   10:	e28d0007 	add	r0, sp, #7
   14:	e5cd1007 	strb	r1, [sp, #7]
   18:	ebfffffe 	bl	0 <__sync_val_compare_and_swap_1>
 			18: R_ARM_CALL	__sync_val_compare_and_swap_1
   1c:	e1a02000 	mov	r2, r0
   20:	e3a01088 	mov	r1, #136	@ 0x88
   24:	e20220ff 	and	r2, r2, #255	@ 0xff
   28:	e59f000c 	ldr	r0, [pc, #12]	@ 3c <main__+0x3c>
   2c:	ebfffffe 	bl	0 <printf>
 ...
 00000040 <main_u8>:
   40:	e3e03077 	mvn	r3, #119	@ 0x77
   44:	e52de004 	push	{lr}		@ (str lr, [sp, #-4]!)
   48:	e24dd00c 	sub	sp, sp, #12
   4c:	e3a020f0 	mov	r2, #240	@ 0xf0
   50:	e3a01088 	mov	r1, #136	@ 0x88
   54:	e28d0007 	add	r0, sp, #7
   58:	e5cd3007 	strb	r3, [sp, #7]
   5c:	ebfffffe 	bl	0 <u8_sync_val_compare_and_swap_1>
 			5c: R_ARM_CALL	u8_sync_val_compare_and_swap_1
   60:	e3a01088 	mov	r1, #136	@ 0x88
   64:	e1a02000 	mov	r2, r0
   68:	e59f000c 	ldr	r0, [pc, #12]	@ 7c <main_u8+0x3c>
   6c:	ebfffffe 	bl	0 <printf>
 ...
 00000080 <main_s8>:
   80:	e3e01077 	mvn	r1, #119	@ 0x77
   84:	e52de004 	push	{lr}		@ (str lr, [sp, #-4]!)
   88:	e24dd00c 	sub	sp, sp, #12
   8c:	e3e0200f 	mvn	r2, #15
   90:	e28d0007 	add	r0, sp, #7
   94:	e5cd1007 	strb	r1, [sp, #7]
   98:	ebfffffe 	bl	0 <s8_sync_val_compare_and_swap_1>
 			98: R_ARM_CALL	s8_sync_val_compare_and_swap_1
   9c:	e1a02000 	mov	r2, r0
   a0:	e3a01088 	mov	r1, #136	@ 0x88
   a4:	e20220ff 	and	r2, r2, #255	@ 0xff
   a8:	e59f000c 	ldr	r0, [pc, #12]	@ bc <main_s8+0x3c>
   ac:	ebfffffe 	bl	0 <printf>
 			ac: R_ARM_CALL	printf
 ...
 
 
 On sparc, though, as on sh3, __sync_* is treated as unsigned (note the
 `and %o0, 0xff, %o2' in main_s8 but not in main__ or main_u8):
 
 00000000 <main__>:
 main__():
    0:	9d e3 bf 98 	save  %sp, -104, %sp
    4:	82 10 3f 88 	mov  -120, %g1
    8:	94 10 20 f0 	mov  0xf0, %o2
    c:	c2 2f bf ff 	stb  %g1, [ %fp + -1 ]
   10:	92 10 20 88 	mov  0x88, %o1
   14:	40 00 00 00 	call  14 <main__+0x14>
 			14: R_SPARC_WDISP30	__sync_val_compare_and_swap_1
   18:	90 07 bf ff 	add  %fp, -1, %o0
   1c:	92 10 20 88 	mov  0x88, %o1
   20:	94 10 00 08 	mov  %o0, %o2
   24:	b0 10 20 00 	clr  %i0
   28:	11 00 00 00 	sethi  %hi(0), %o0
 			28: R_SPARC_HI22	.rodata.str1.8
   2c:	40 00 00 00 	call  2c <main__+0x2c>
 			2c: R_SPARC_WDISP30	printf
   30:	90 12 20 00 	mov  %o0, %o0	! 0 <main__>
 			30: R_SPARC_LO10	.rodata.str1.8
   34:	81 c7 e0 08 	ret 
   38:	81 e8 00 00 	restore 
 
 0000003c <main_u8>:
 main_u8():
   3c:	9d e3 bf 98 	save  %sp, -104, %sp
   40:	82 10 3f 88 	mov  -120, %g1
   44:	94 10 20 f0 	mov  0xf0, %o2
   48:	c2 2f bf ff 	stb  %g1, [ %fp + -1 ]
   4c:	92 10 20 88 	mov  0x88, %o1
   50:	40 00 00 00 	call  50 <main_u8+0x14>
 			50: R_SPARC_WDISP30	u8_sync_val_compare_and_swap_1
   54:	90 07 bf ff 	add  %fp, -1, %o0
   58:	92 10 20 88 	mov  0x88, %o1
   5c:	94 10 00 08 	mov  %o0, %o2
   60:	b0 10 20 00 	clr  %i0
   64:	11 00 00 00 	sethi  %hi(0), %o0
 			64: R_SPARC_HI22	.rodata.str1.8
   68:	40 00 00 00 	call  68 <main_u8+0x2c>
 			68: R_SPARC_WDISP30	printf
   6c:	90 12 20 00 	mov  %o0, %o0	! 0 <main__>
 			6c: R_SPARC_LO10	.rodata.str1.8
   70:	81 c7 e0 08 	ret 
   74:	81 e8 00 00 	restore 
 
 00000078 <main_s8>:
 main_s8():
   78:	9d e3 bf 98 	save  %sp, -104, %sp
   7c:	82 10 3f 88 	mov  -120, %g1
   80:	94 10 3f f0 	mov  -16, %o2
   84:	c2 2f bf ff 	stb  %g1, [ %fp + -1 ]
   88:	92 10 3f 88 	mov  -120, %o1
   8c:	40 00 00 00 	call  8c <main_s8+0x14>
 			8c: R_SPARC_WDISP30	s8_sync_val_compare_and_swap_1
   90:	90 07 bf ff 	add  %fp, -1, %o0
   94:	92 10 20 88 	mov  0x88, %o1
   98:	94 0a 20 ff 	and  %o0, 0xff, %o2
   9c:	b0 10 20 00 	clr  %i0
   a0:	11 00 00 00 	sethi  %hi(0), %o0
 			a0: R_SPARC_HI22	.rodata.str1.8
   a4:	40 00 00 00 	call  a4 <main_s8+0x2c>
 			a4: R_SPARC_WDISP30	printf
   a8:	90 12 20 00 	mov  %o0, %o0	! 0 <main__>
 			a8: R_SPARC_LO10	.rodata.str1.8
   ac:	81 c7 e0 08 	ret 
   b0:	81 e8 00 00 	restore 
 
 
 So something screwy is going on with gcc's internal concept of what
 signedness to use for __sync_*.