From 696a3b2a5368360c149335e2a35b8900a78f47fa Mon Sep 17 00:00:00 2001 From: Daniel Schwierzeck Date: Tue, 12 Feb 2013 22:22:13 +0100 Subject: [PATCH] MIPS: start.S: optimize BSS initialization Get the start and end address for clearing BSS from the newly introduced symbols __bss_start and __bss_end. After GOT is relocated, those symbols are already pointing to the correct addresses. Also optimize the loop by moving the address incrementation to the delay slot to avoid the initial sub instruction. Signed-off-by: Daniel Schwierzeck --- arch/mips/cpu/mips32/start.S | 20 +++++++++++--------- arch/mips/cpu/mips64/start.S | 20 +++++++++++--------- arch/mips/cpu/xburst/start.S | 23 +++++++++++++---------- 3 files changed, 35 insertions(+), 28 deletions(-) diff --git a/arch/mips/cpu/mips32/start.S b/arch/mips/cpu/mips32/start.S index 7373d4edc4..cd8b914da3 100644 --- a/arch/mips/cpu/mips32/start.S +++ b/arch/mips/cpu/mips32/start.S @@ -228,17 +228,19 @@ in_ram: blt t2, t3, 1b addi t4, 4 - /* Clear BSS */ - lw t1, -12(t0) # t1 <-- uboot_end_data - lw t2, -8(t0) # t2 <-- uboot_end - add t1, s1 # adjust pointers - add t2, s1 + /* + * Clear BSS + * + * GOT is now relocated. Thus __bss_start and __bss_end can be + * accessed directly via $gp. + */ + la t1, __bss_start # t1 <-- __bss_start + la t2, __bss_end # t2 <-- __bss_end - sub t1, 4 1: - addi t1, 4 - bltl t1, t2, 1b - sw zero, 0(t1) + sw zero, 0(t1) + blt t1, t2, 1b + addi t1, 4 move a0, s0 # a0 <-- gd la t9, board_init_r diff --git a/arch/mips/cpu/mips64/start.S b/arch/mips/cpu/mips64/start.S index c0ae41a18a..ba4ca4de38 100644 --- a/arch/mips/cpu/mips64/start.S +++ b/arch/mips/cpu/mips64/start.S @@ -220,17 +220,19 @@ in_ram: blt t2, t3, 1b daddi t8, 8 - /* Clear BSS */ - ld t1, -24(t0) # t1 <-- uboot_end_data - ld t2, -16(t0) # t2 <-- uboot_end - dadd t1, s1 # adjust pointers - dadd t2, s1 + /* + * Clear BSS + * + * GOT is now relocated. Thus __bss_start and __bss_end can be + * accessed directly via $gp. + */ + dla t1, __bss_start # t1 <-- __bss_start + dla t2, __bss_end # t2 <-- __bss_end - dsub t1, 8 1: - daddi t1, 8 - bltl t1, t2, 1b - sd zero, 0(t1) + sd zero, 0(t1) + blt t1, t2, 1b + daddi t1, 8 move a0, s0 # a0 <-- gd dla t9, board_init_r diff --git a/arch/mips/cpu/xburst/start.S b/arch/mips/cpu/xburst/start.S index 50b7fb1021..bd9390ae5e 100644 --- a/arch/mips/cpu/xburst/start.S +++ b/arch/mips/cpu/xburst/start.S @@ -143,16 +143,19 @@ in_ram: blt t2, t3, 1b addi t4, 4 - /* Clear BSS */ - lw t1, -12(t0) # t1 <-- uboot_end_data - lw t2, -8(t0) # t2 <-- uboot_end - add t1, t6 # adjust pointers - add t2, t6 - - sub t1, 4 -1: addi t1, 4 - bltl t1, t2, 1b - sw zero, 0(t1) + /* + * Clear BSS + * + * GOT is now relocated. Thus __bss_start and __bss_end can be + * accessed directly via $gp. + */ + la t1, __bss_start # t1 <-- __bss_start + la t2, __bss_end # t2 <-- __bss_end + +1: + sw zero, 0(t1) + blt t1, t2, 1b + addi t1, 4 move a0, a1 # a0 <-- gd la t9, board_init_r -- 2.39.5