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[arch][arm-m] slight code optimization in the context switch path

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This commit is contained in:
Travis Geiselbrecht
2013-01-22 00:29:30 -08:00
parent 1fe39d0976
commit 5ad38b93cc
1 changed files with 8 additions and 14 deletions
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22
arch/arm/arm-m/thread.c
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@@ -87,7 +87,7 @@ static void pendsv(struct arm_cm_exception_frame_long *frame)
arch_disable_ints();
inc_critical_section();
ASSERT(critical_section_count == 1);
DEBUG_ASSERT(critical_section_count == 1);
LTRACEF("preempting thread %p (%s)\n", current_thread, current_thread->name);
@@ -114,8 +114,7 @@ __NAKED void _pendsv(void)
"push { r4-r11, lr };"
"mov r0, sp;"
"bl %0;"
"pop { r4-r11, lr };"
"bx lr;"
"pop { r4-r11, pc };"
:: "i" (pendsv)
);
__UNREACHABLE;
@@ -130,8 +129,7 @@ __NAKED void _svc(void)
__asm__ volatile(
/* load the pointer to the original exception frame we want to restore */
"mov sp, r4;"
"pop { r4-r11, lr };"
"bx lr;"
"pop { r4-r11, pc };"
);
}
@@ -160,19 +158,18 @@ __NAKED static void _arch_non_preempt_context_switch(vaddr_t *fromsp, vaddr_t to
"str sp, [r0];"
"mov sp, r1;"
"pop { r4-r11, lr };"
"clrex;"
"bx lr;"
"pop { r4-r11, pc };"
);
}
/* second half of a regular context switch, bounced to from pendsv */
__NAKED static void _thread_mode_bounce(void)
{
__asm__ volatile(
"pop { r4-r11, lr };"
"bx lr;"
"clrex;"
"pop { r4-r11, pc };"
);
__UNREACHABLE;
}
/*
@@ -205,9 +202,7 @@ void arch_context_switch(struct thread *oldthread, struct thread *newthread)
__asm__ volatile(
"mov sp, %0;"
"cpsie i;"
"pop { r4-r11, lr };"
"clrex;"
"bx lr;"
"pop { r4-r11, pc };"
:: "r"(newthread->arch.sp)
);
__UNREACHABLE;
@@ -219,7 +214,6 @@ void arch_context_switch(struct thread *oldthread, struct thread *newthread)
frame->pc = (uint32_t)&_thread_mode_bounce;
frame->psr = (1 << 24); /* thread bit set, IPSR 0 */
frame->r0 = frame->r1 = frame->r2 = frame->r3 = frame->r12 = frame->lr = 99;
LTRACEF("iretting to user space\n");
//hexdump(frame, sizeof(*frame) + 64);