From eeae3d95827ec33e74d853596b89ee49d83ff751 Mon Sep 17 00:00:00 2001 From: Anup Patel <anup.patel@wdc.com> Date: Wed, 11 Mar 2020 19:25:24 +0530 Subject: firmware: fw_base: Optimize _hartid_to_scratch() implementation This patch optimizes _hartid_to_scratch() in following ways: 1. Use caller saved registers instead of callee saved registers so that we don't need to save/restore registers on stack 2. Remove second redundant mul instruction by re-arranging instructions Overall, we reduce 9 instructions in _hartid_to_scratch() implementation. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Atish Patra <atish.patra@wdc.com> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> --- firmware/fw_base.S | 37 ++++++++++++++----------------------- 1 file changed, 14 insertions(+), 23 deletions(-) (limited to 'firmware') diff --git a/firmware/fw_base.S b/firmware/fw_base.S index 119622c..dbe5b10 100644 --- a/firmware/fw_base.S +++ b/firmware/fw_base.S @@ -409,35 +409,26 @@ _link_end: .align 3 .globl _hartid_to_scratch _hartid_to_scratch: - add sp, sp, -(3 * __SIZEOF_POINTER__) - REG_S s0, (sp) - REG_S s1, (__SIZEOF_POINTER__)(sp) - REG_S s2, (__SIZEOF_POINTER__ * 2)(sp) /* * a0 -> HART ID (passed by caller) - * s0 -> HART Stack Size - * s1 -> HART Stack End - * s2 -> Temporary + * t0 -> HART Stack Size + * t1 -> HART Stack End + * t2 -> Temporary */ - la s2, platform + la t2, platform #if __riscv_xlen == 64 - lwu s0, SBI_PLATFORM_HART_STACK_SIZE_OFFSET(s2) - lwu s2, SBI_PLATFORM_HART_COUNT_OFFSET(s2) + lwu t0, SBI_PLATFORM_HART_STACK_SIZE_OFFSET(t2) + lwu t2, SBI_PLATFORM_HART_COUNT_OFFSET(t2) #else - lw s0, SBI_PLATFORM_HART_STACK_SIZE_OFFSET(s2) - lw s2, SBI_PLATFORM_HART_COUNT_OFFSET(s2) + lw t0, SBI_PLATFORM_HART_STACK_SIZE_OFFSET(t2) + lw t2, SBI_PLATFORM_HART_COUNT_OFFSET(t2) #endif - mul s2, s2, s0 - la s1, _fw_end - add s1, s1, s2 - mul s2, s0, a0 - sub s1, s1, s2 - li s2, SBI_SCRATCH_SIZE - sub a0, s1, s2 - REG_L s0, (sp) - REG_L s1, (__SIZEOF_POINTER__)(sp) - REG_L s2, (__SIZEOF_POINTER__ * 2)(sp) - add sp, sp, (3 * __SIZEOF_POINTER__) + sub t2, t2, a0 + mul t2, t2, t0 + la t1, _fw_end + add t1, t1, t2 + li t2, SBI_SCRATCH_SIZE + sub a0, t1, t2 ret .section .entry, "ax", %progbits -- cgit v1.2.3