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Optimize set_syscall_retval for riscv by predicting the return

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value to be zero.

Reviewed by:	mhorne, kp
MFC after:	2 weeks
Sponsored by:	EPSRC
Differential Revision:	https://reviews.freebsd.org/D26990
This commit is contained in:
Edward Tomasz Napierala 2020-10-29 15:36:20 +00:00
parent e3c51151a0
commit b1497fb649
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=367138
1 changed files with 5 additions and 3 deletions
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8
sys/riscv/riscv/vm_machdep.c
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@ -132,12 +132,14 @@ cpu_set_syscall_retval(struct thread *td, int error)
frame = td->td_frame;
switch (error) {
case 0:
if (__predict_true(error == 0)) {
frame->tf_a[0] = td->td_retval[0];
frame->tf_a[1] = td->td_retval[1];
frame->tf_t[0] = 0; /* syscall succeeded */
break;
return;
}
switch (error) {
case ERESTART:
frame->tf_sepc -= 4; /* prev instruction */
break;