Patchwork [U-Boot] MIPS: xburst: simplify relocation offset calculation

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Submitter Gabor Juhos
Date Jan. 30, 2013, 2:51 p.m.
Message ID <1359557466-9592-1-git-send-email-juhosg@openwrt.org>
Download mbox | patch
Permalink /patch/216934/
State Accepted
Delegated to: Daniel Schwierzeck
Headers show

Comments

Gabor Juhos - Jan. 30, 2013, 2:51 p.m.
The current code uses four instructions and a
temporary register to calculate the relocation
offset and to adjust the gp register.

The relocation offset can be calculated directly
from the CONFIG_SYS_MONITOR_BASE constant and from
the destination address. The resulting offset can
be used to adjust the gp pointer.

This approach makes the code a bit simpler because
it needs two instructions only.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Cc: Xiangfu Liu <xiangfu@openmobilefree.net>
---
 arch/mips/cpu/xburst/start.S |   12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)
Daniel Schwierzeck - Jan. 30, 2013, 11:50 p.m.
2013/1/30 Gabor Juhos <juhosg@openwrt.org>:
> The current code uses four instructions and a
> temporary register to calculate the relocation
> offset and to adjust the gp register.
>
> The relocation offset can be calculated directly
> from the CONFIG_SYS_MONITOR_BASE constant and from
> the destination address. The resulting offset can
> be used to adjust the gp pointer.
>
> This approach makes the code a bit simpler because
> it needs two instructions only.
>
> Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
> Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
> Cc: Xiangfu Liu <xiangfu@openmobilefree.net>
> ---
>  arch/mips/cpu/xburst/start.S |   12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)

applied to u-boot-mips/master, thanks

Patch

diff --git a/arch/mips/cpu/xburst/start.S b/arch/mips/cpu/xburst/start.S
index 194d745..35728eb 100644
--- a/arch/mips/cpu/xburst/start.S
+++ b/arch/mips/cpu/xburst/start.S
@@ -64,19 +64,13 @@  relocate_code:
 	move	sp, a0			# set new stack pointer
 
 	li	t0, CONFIG_SYS_MONITOR_BASE
+	sub	t6, a2, t0		# t6 <-- relocation offset
+
 	la	t3, in_ram
 	lw	t2, -12(t3)		# t2 <-- uboot_end_data
 	move	t1, a2
 
-	/*
-	 * Fix $gp:
-	 *
-	 * New $gp = (Old $gp - CONFIG_SYS_MONITOR_BASE) + Destination Address
-	 */
-	move	t6, gp
-	sub	gp, CONFIG_SYS_MONITOR_BASE
-	add	gp, a2			# gp now adjusted
-	sub	t6, gp, t6		# t6 <-- relocation offset
+	add	gp, t6			# adjust gp
 
 	/*
 	 * t0 = source address