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rm48x50: optimize context_switch_interrupt_to by reuse registers 

When saving thread registers in context_switch_interrupt_to, we don't
change them, just move them. So there is no need to always r0-r3 from
stack to the real r0-r3. So just use the intermediate registers and
eliminate 2 MOV.
This commit is contained in:
Grissiom 2013-05-26 22:37:49 +08:00
parent 435f305fa2
commit 19fe6251e7
1 changed files with 5 additions and 6 deletions
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11
libcpu/arm/rm48x50/context_ccs.asm
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@ -139,12 +139,11 @@ rt_hw_context_switch_interrupt_do
STMFD sp!, {r2} ; push old task's pc
STMFD sp!, {r4-r12,lr} ; push old task's lr,r12-r4
MOV r4, r1 ; move original irq sp to r4
MOV r5, r3 ; move spsr to r5 FIXME: use `MRS r5 spsr` here?
LDMFD r4!, {r0-r3} ; restore r0-r3 of the interrupted thread
STMFD sp!, {r0-r3} ; push old task's r3-r0
; FIXME: or move the `MRS r5 spsr` here
STMFD sp!, {r5} ; push old task's cpsr
LDMFD r1!, {r4-r7} ; restore r0-r3 of the interrupted thread
STMFD sp!, {r4-r7} ; push old task's r3-r0. We don't need to push/pop them to
; r0-r3 because we just want to transfer the data and don't
; use them here.
STMFD sp!, {r3} ; push old task's cpsr
LDR r4, pfromthread
LDR r5, [r4]