ARM thumb-interwork libgcc asm functions have no bx

[Giuliano Procida <Giuliano dot Procida at red-m dot com>]

With:

../egcs-20000619/configure
--with-gcc-version-trigger=/u/gprocida/lad-tools/egcs-20000619/gcc/version.c
--host=i686-pc-linux --srcdir=../egcs-20000619 --target=arm-elf
--with-headers=../newlib-1.8.2/newlib/libc/include --enable-multilib
--without-fp --with-cpu=arm7tdmi --norecursion 

and the config/arm/t-arm-elf file edited to produce normal and interworking
libgcc variants (only).

Some of the gcc/libgcc/interwork/*.o use BX, some don't (rm-elf-objdump -d
$i | grep -q bx && echo $i). The ones that do not use BX seem to all come
from:

../egcs-20000619/gcc/config/arm/lib1funcs.asm

In any case, returning from __udivsi3 to thumb code is broken. Example:

bar.c, compiled with -mthumb -mthumb-interwork

int main () {
  volatile unsigned x = 20;
  volatile unsigned y = 35;
  unsigned z = y / x;
}

Relevant bits of objdump -d output:

bar:     file format elf32-littlearm

Disassembly of section .text:

000080e0 <main>:
    80e0:	b590      	push	{r4, r7, lr}
    80e2:	466f      	mov	r7, sp
    80e4:	b083      	sub	sp, #12
    80e6:	ff95f002 	bl	b014 <____gccmain_from_thumb>
    80ea:	46bc      	mov	ip, r7
    80ec:	1f3a      	sub	r2, r7, #4
    80ee:	2314      	mov	r3, #20
    80f0:	6013      	str	r3, [r2, #0]
    80f2:	46bc      	mov	ip, r7
    80f4:	1c3a      	mov	r2, r7		(add r2, r7, #0)
    80f6:	3a08      	sub	r2, #8
    80f8:	2323      	mov	r3, #35
    80fa:	6013      	str	r3, [r2, #0]
    80fc:	46bc      	mov	ip, r7
    80fe:	1c3c      	mov	r4, r7		(add r4, r7, #0)
    8100:	3c0c      	sub	r4, #12
    8102:	46bc      	mov	ip, r7
    8104:	1c3a      	mov	r2, r7		(add r2, r7, #0)
    8106:	3a08      	sub	r2, #8
    8108:	46bc      	mov	ip, r7
    810a:	1f3b      	sub	r3, r7, #4
    810c:	6810      	ldr	r0, [r2, #0]
    810e:	6819      	ldr	r1, [r3, #0]
    8110:	ff84f002 	bl	b01c <____udivsi3_from_thumb>
    8114:	1c03      	mov	r3, r0		(add r3, r0, #0)
    8116:	1c03      	mov	r3, r0		(add r3, r0, #0)
    8118:	6023      	str	r3, [r4, #0]
    811a:	2000      	mov	r0, #0
    811c:	46bd      	mov	sp, r7
    811e:	bc90      	pop	{r4, r7}
    8120:	bc02      	pop	{r1}
    8122:	4708      	bx	r1

00008124 <__udivsi3>:
    8124:	e3510000 	cmp	r1, #0	; 0x0
    8128:	0a00001f 	beq	81ac <Ldiv0>
    812c:	e3a03001 	mov	r3, #1	; 0x1
    8130:	e3a02000 	mov	r2, #0	; 0x0
    8134:	e1500001 	cmp	r0, r1
    8138:	3a000019 	bcc	81a4 <Lgot_result>

000081a4 <Lgot_result>:
    81a4:	e1a00002 	mov	r0, r2
    81a8:	e1a0f00e 	mov	pc, lr

000081ac <Ldiv0>:
    81ac:	e52de004 	str	lr, [sp, -#4]!
    81b0:	eb000001 	bl	81bc <__div0>
    81b4:	e3a00000 	mov	r0, #0	; 0x0
    81b8:	e8bd8000 	ldmia	sp!, {pc}

000081bc <__div0>:
    81bc:	e1a0f00e 	mov	pc, lr

0000b01c <____udivsi3_from_thumb>:
    b01c:	4778      	bx	pc
    b01e:	46c0      	nop			(mov r8,r8)

0000b020 <____udivsi3_change_to_arm>:
    b020:	eafff43f 	b	8124 <__udivsi3>

I hope this is pretty clear.

Giuliano.