Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi_{u}idiv library functions | Date | Sun, 22 Nov 2015 21:37 +0100 |
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On Sunday 22 November 2015 20:03:26 Russell King - ARM Linux wrote: > On Sun, Nov 22, 2015 at 08:58:08PM +0100, Arnd Bergmann wrote: > > does it work with -mcpu=cortex-a15? I've tried crosstool as versions > > 2.23.52.20130913, 2.24.0.20141017 and 2.25.51.20150518, and they > > all seem to behave as expected, failing with -mcpu=cortex-a9 and > > marvell-pj4 but succeeding with -mcpu=cortex-a15 or marvell-pj4+idiv. > > Appears not: > > root@cubox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='cortex-a15+idiv' -marm > /tmp/ccSovg32.s: Assembler messages: > /tmp/ccSovg32.s:32: Error: selected processor does not support ARM mode `udiv ip,r5,r4' > root@cubox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='cortex-a15+idiv' -mthumb > /tmp/cchbT3EE.s: Assembler messages: > /tmp/cchbT3EE.s:36: Error: selected processor does not support Thumb mode `udiv r6,r5,r4' > > Same without the +idiv.
I've attached files with those instructions, maybe that helps.
> > I've also found some /proc/cpuinfo output to cross-reference SoCs > > to their core names. > > > > variant part revision name features > > mmp2: 0 0x581 5 PJ4 idivt > > dove: 0 0x581 5 PJ4 idivt > > Yes, that agrees with my dove.
ok.
arnd@wuerfel:/tmp$ cat idiv.c unsigned int udiv(unsigned int a, unsigned int b) { return a / b; }
int sdiv(int a, int b) { return a / b; } arnd@wuerfel:/tmp$ arm-linux-gnueabihf-gcc -Wall -O2 -mcpu=cortex-a15 idiv.c -c -o idiv-arm.o arnd@wuerfel:/tmp$ objdump -dr idiv-arm.o
idiv-arm.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <udiv>: 0: fbb0 f0f1 udiv r0, r0, r1 4: 4770 bx lr 6: bf00 nop
00000008 <sdiv>: 8: fb90 f0f1 sdiv r0, r0, r1 c: 4770 bx lr e: bf00 nop arnd@wuerfel:/tmp$ arm-linux-gnueabihf-gcc -Wall -O2 -mcpu=cortex-a15 idiv.c -c -o idiv-thumb.o -mthumb arnd@wuerfel:/tmp$ objdump -dr idiv-thumb.o
idiv-thumb.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <udiv>: 0: fbb0 f0f1 udiv r0, r0, r1 4: 4770 bx lr 6: bf00 nop
00000008 <sdiv>: 8: fb90 f0f1 sdiv r0, r0, r1 c: 4770 bx lr e: bf00 nop
Arnd[unhandled content-type:application/x-object][unhandled content-type:application/x-object]unsigned int udiv(unsigned int a, unsigned int b) { return a / b; }
int sdiv(int a, int b) { return a / b; }
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