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x86 tsc: mark %eax as earlyclobber in tscp_get_timecount_low().

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i386 codegen insists on preloading tc_priv into register on i386, and
this register cannot be %eax because RDTSCP instruction clobbers it
before it is used.

Reported and tested by:	dim
MFC after:	6 days
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2021-01-11 00:05:49 +02:00
parent 148a227bf8
commit a013e285df
1 changed files with 1 additions and 1 deletions
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2
sys/x86/x86/tsc.c
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@ -826,7 +826,7 @@ tscp_get_timecount_low(struct timecounter *tc)
uint32_t rv;
__asm __volatile("rdtscp; movl %1, %%ecx; shrd %%cl, %%edx, %0"
: "=a" (rv) : "m" (tc->tc_priv) : "ecx", "edx");
: "=&a" (rv) : "m" (tc->tc_priv) : "ecx", "edx");
return (rv);
}