From f5a7e78d32681503919519f13bae92bbd2db7eb2 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Thu, 6 Feb 2020 21:46:15 +0000
Subject: [PATCH] Tidy the _set_tp function for RISC-V.

- Use a constant for the offset instead of a magic number.
- Use an addi instruction that writes to tp directly instead of a mv
  that writes the result of a compiler-generated addi.

Reviewed by:	mhorne
MFC after:	1 week
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D23521
---
 lib/libc/riscv/gen/_set_tp.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/libc/riscv/gen/_set_tp.c b/lib/libc/riscv/gen/_set_tp.c
index a880465253a4..49295e26857c 100644
--- a/lib/libc/riscv/gen/_set_tp.c
+++ b/lib/libc/riscv/gen/_set_tp.c
@@ -38,13 +38,14 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <sys/types.h>
 
-#include <machine/sysarch.h>
-
 #include <stdlib.h>
 
+/* NB: size of 'struct tcb'. */
+#define	TP_OFFSET	(sizeof(void *) * 2)
+
 void
 _set_tp(void *tp)
 {
 
-	__asm __volatile("mv  tp, %0" :: "r"((char*)tp + 0x10));
+	__asm __volatile("addi  tp, %0, %1" :: "r" (tp), "I" (TP_OFFSET));
 }