svn commit: r357643 - head/lib/libc/riscv/gen

[John Baldwin]

Author: jhb
Date: Thu Feb  6 21:46:15 2020
New Revision: 357643
URL: https://svnweb.freebsd.org/changeset/base/357643

Log:
  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

Modified:
  head/lib/libc/riscv/gen/_set_tp.c

Modified: head/lib/libc/riscv/gen/_set_tp.c
==============================================================================
--- head/lib/libc/riscv/gen/_set_tp.c	Thu Feb  6 21:01:19 2020	(r357642)
+++ head/lib/libc/riscv/gen/_set_tp.c	Thu Feb  6 21:46:15 2020	(r357643)
@@ -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));
 }