From 14c7f71c0da641ece1b91ef0bde190f66c980a3e Mon Sep 17 00:00:00 2001 From: Bin Meng Date: Sat, 10 Jul 2021 22:00:31 +0800 Subject: [PATCH] firmware: Minor optimization in _scratch_init() Before entering _scratch_init(), register t3 already holds a copy of the firmware end address, hence there is no need to calculate it again. This reduces 3 instructions in each _scratch_init() loop. Signed-off-by: Bin Meng Reviewed-by: Xiang W Reviewed-by: Atish Patra --- firmware/fw_base.S | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/firmware/fw_base.S b/firmware/fw_base.S index a5ce946..8e40562 100644 --- a/firmware/fw_base.S +++ b/firmware/fw_base.S @@ -278,6 +278,14 @@ _bss_zero: /* hartid 0 is mandated by ISA */ li t1, 0 _scratch_init: + /* + * The following registers hold values that are computed before + * entering this block, and should remain unchanged. + * + * t3 -> the firmware end address + * s7 -> HART count + * s8 -> HART stack size + */ add tp, t3, zero mul a5, s8, t1 sub tp, tp, a5 @@ -287,10 +295,7 @@ _scratch_init: /* Initialize scratch space */ /* Store fw_start and fw_size in scratch space */ lla a4, _fw_start - lla a5, _fw_end - mul t0, s7, s8 - add a5, a5, t0 - sub a5, a5, a4 + sub a5, t3, a4 REG_S a4, SBI_SCRATCH_FW_START_OFFSET(tp) REG_S a5, SBI_SCRATCH_FW_SIZE_OFFSET(tp) /* Store next arg1 in scratch space */ -- 2.7.4