From b1497fb64985d8b741d4e374227cd67f09863dd9 Mon Sep 17 00:00:00 2001 From: Edward Tomasz Napierala Date: Thu, 29 Oct 2020 15:36:20 +0000 Subject: [PATCH] Optimize set_syscall_retval for riscv by predicting the return value to be zero. Reviewed by: mhorne, kp MFC after: 2 weeks Sponsored by: EPSRC Differential Revision: https://reviews.freebsd.org/D26990 --- sys/riscv/riscv/vm_machdep.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/sys/riscv/riscv/vm_machdep.c b/sys/riscv/riscv/vm_machdep.c index f00928e385b..f38f1c04caa 100644 --- a/sys/riscv/riscv/vm_machdep.c +++ b/sys/riscv/riscv/vm_machdep.c @@ -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;