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MIPS: Use `.set mips2' to emulate LL/SC for the R5900 too 

GAS treats the R5900 as MIPS III, with some modifications.  The MIPS III
designation means that the GNU C Library will try to assemble the LL and
SC instructions, even though they are not implemented in the R5900.  GAS
will therefore produce the following errors:

Error: opcode not supported on this processor: r5900 (mips3) `ll $2,0($4)'
Error: opcode not supported on this processor: r5900 (mips3) `sc $6,0($4)'

The MIPS II ISA override as used here enables the kernel to trap and
emulate the LL and SC instructions, as required.

This change has been tested by compiling the GNU C Library 2.27 with a
GCC 8.2.0 cross-compiler for mipsr5900el-unknown-linux-gnu under Gentoo.

	* sysdeps/mips/sys/tas.h (_test_and_set): Handle the R5900 CPU
	with the ISA override.
This commit is contained in:
Fredrik Noring 2018-11-01 14:36:48 +00:00 committed by Maciej W. Rozycki
parent fc783076ec
commit 8e3c00db16
2 changed files with 7 additions and 1 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2018-11-01 Fredrik Noring <noring@nocrew.org>
* sysdeps/mips/sys/tas.h (_test_and_set): Handle the R5900 CPU
with the ISA override.
2018-10-31 Rafael Avila de Espindola <rafael@espindo.la>
* sysdeps/unix/sysv/linux/sysdep-vdso.h: Simplify an #if #else

3
sysdeps/mips/sys/tas.h
View File

@ -38,10 +38,11 @@ __NTH (_test_and_set (int *__p, int __v))
{
int __r, __t;
/* The R5900 reports itself as MIPS III but it does not have LL/SC. */
__asm__ __volatile__
("/* Inline test and set */\n"
".set push\n\t"
#if _MIPS_SIM == _ABIO32 && __mips < 2
#if _MIPS_SIM == _ABIO32 && (__mips < 2 || defined (_MIPS_ARCH_R5900))
".set mips2\n\t"
#endif
"sync\n\t"