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rewrite inline asm blocks with single instructions
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Apparently Clang actually parses them, so perhaps let's make its job a
little bit easier.
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@dmitmel
dmitmel committed Nov 7, 2023
1 parent 23ce415 commit 9a0f999
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Showing 3 changed files with 29 additions and 80 deletions.
24 changes: 16 additions & 8 deletions src/stmes/kernel/task.c
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Original file line number Diff line number Diff line change
Expand Up @@ -385,12 +385,16 @@ static void syscall_handler_entry(usize arg1, usize arg2, usize arg3, enum Sysca
// largely to be a barrier for debugger's stack trace unwinder (by being
// implemented in assembly and having no hint directives whatsoever).
static __NO_RETURN __NAKED void task_launchpad(__UNUSED void* user_data, __UNUSED TaskFn* func) {
// Call the function passed in the second parameter with the user data as its
// first parameter which is already in r0.
__ASM volatile("blx r1");
__ASM volatile("bl %0" ::"i"(&task_exit));
// The task has been terminated, a return here must cause a fault.
__ASM volatile("udf #0");
__ASM volatile( //
// Call the function passed in the second parameter with the user data as
// its first parameter which is already in r0.
"blx r1\n\t"
// Call task_exit() if the task function has returned.
"bl %0\n\t"
// The task has been terminated, a return here must cause a fault.
"udf #0" :: //
"i"(&task_exit)
);
}

void task_spawn(struct Task* task, const struct TaskParams* params) {
Expand Down Expand Up @@ -637,8 +641,12 @@ static __NAKED void context_switch(__UNUSED enum Syscall syscall_nr) {

__NAKED void PendSV_Handler(void) {
// The PendSV handler effectively emulates the DEFERRED_YIELD syscall.
__ASM volatile("movs r0, %0" ::"n"(SYSCALL_DEFERRED_YIELD));
__ASM volatile("b %0" ::"i"(&context_switch));
__ASM volatile( //
"movs r0, %0\n\t"
"b %1" :: //
"n"(SYSCALL_DEFERRED_YIELD),
"i"(&context_switch)
);
}

__NAKED void SVC_Handler(void) {
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23 changes: 13 additions & 10 deletions src/stmes/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -43,13 +43,16 @@ int main(void) {
// functions can be executed on boot right away, however, some setup needs to
// be done first before we can reach main().
__NAKED void Reset_Handler(void) {
// Pass the initial stack pointer as the first argument (the need to be able
// to read it is the reason for writing the reset handler in assembly).
__ASM volatile("mov r0, sp");
// Call the prestart() function.
__ASM volatile("bl %0" ::"i"(&prestart));
// Execution should never return here, trigger an exception if it did.
__ASM volatile("udf #0");
__ASM volatile( //
// Pass the initial stack pointer as the first argument (the need to be
// able to read it is the reason for writing the reset handler in assembly)
"mov r0, sp\n\t"
// Call the prestart() function.
"bl %0\n\t"
// Execution should never return here, trigger an exception if it did.
"udf #0" :: //
"i"(&prestart)
);
}

// Performs the early boot sequence and eventually calls main().
Expand Down Expand Up @@ -129,10 +132,10 @@ static __NAKED void main_task_launcher(__UNUSED void* initial_stack_ptr) {
"msr msp, r0\n\t" // MSP = initial_stack_ptr;
"isb\n\t" // apply the changes
"cpsie i\n\t" // __enable_irq();
// And now, tail-call main() (this is the reason for writing this wrapper
// in assembly: to not waste any stack space before even entering main()).
"b %0" ::"i"(&main)
);
// And now the main() can be tail-called (this is the reason for writing this
// wrapper in assembly: to not waste any stack space before entering main()).
__ASM volatile("b %0" ::"i"(&main));
}

void HAL_MspInit(void) {
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62 changes: 0 additions & 62 deletions src/stmes/utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -82,68 +82,6 @@ void fast_memcpy_u32(u32* dst, const u32* src, usize n);
#define WAIT_FOR_EVENT() __WFE()
#define WAIT_FOR_INTERRUPT() __WFI()

#define __ldmia2(ptr, r1, r2, a, b) \
do { \
register u32 __a __ASM(r1); \
register u32 __b __ASM(r2); \
register u32* __ptr = *(ptr); \
__ASM("ldmia %0!, {%1, %2}" : "+r"(__ptr), "=r"(__a), "=r"(__b) : "m"(*(u32(*)[2])__ptr)); \
*(ptr) = __ptr, *(a) = __a, *(b) = __b; \
} while (0)

#define __ldmia4(ptr, r1, r2, r3, r4, a, b, c, d) \
do { \
register u32 __a __ASM(r1); \
register u32 __b __ASM(r2); \
register u32 __c __ASM(r3); \
register u32 __d __ASM(r4); \
register u32* __ptr = *(ptr); \
__ASM("ldmia %0!, {%1, %2, %3, %4}" \
: "+r"(__ptr), "=r"(__a), "=r"(__b), "=r"(__c), "=r"(__d) \
: "m"(*(u32(*)[4])__ptr)); \
*(ptr) = __ptr, *(a) = __a, *(b) = __b, *(c) = __c, *(d) = __d; \
} while (0)

#define __ldmia8(ptr, r1, r2, r3, r4, r5, r6, r7, r8, a, b, c, d, e, f, g, h) \
do { \
register u32 __a __ASM(r1); \
register u32 __b __ASM(r2); \
register u32 __c __ASM(r3); \
register u32 __d __ASM(r4); \
register u32 __e __ASM(r5); \
register u32 __f __ASM(r6); \
register u32 __g __ASM(r7); \
register u32 __h __ASM(r8); \
register u32* __ptr = *(ptr); \
__ASM("ldmia %0!, {%1, %2, %3, %4, %5, %6, %7, %8}" \
: "+r"(__ptr), \
"=r"(__a), \
"=r"(__b), \
"=r"(__c), \
"=r"(__d), \
"=r"(__e), \
"=r"(__f), \
"=r"(__g), \
"=r"(__h) \
: "m"(*(u32(*)[8])__ptr)); \
*(ptr) = __ptr; \
*(a) = __a, *(b) = __b, *(c) = __c, *(d) = __d; \
*(e) = __e, *(f) = __f, *(g) = __g, *(h) = __h; \
} while (0)

#define __stmia4(ptr, r1, r2, r3, r4, a, b, c, d) \
do { \
register u32 __a __ASM(r1) = (a); \
register u32 __b __ASM(r2) = (b); \
register u32 __c __ASM(r3) = (c); \
register u32 __d __ASM(r4) = (d); \
register u32* __ptr = *(ptr); \
__ASM("stmia %1!, {%2, %3, %4, %5}" \
: "=m"(*(u32(*)[4])__ptr), "+r"(__ptr) \
: "r"(__a), "r"(__b), "r"(__c), "r"(__d)); \
*(ptr) = __ptr; \
} while (0)

#define BITBAND_ADDR(base, bb_base, addr, bit) \
((volatile u32*)(bb_base + 32ul * ((usize)(addr) - (base)) + 4ul * (bit)))
#define SRAM1_BITBAND_ADDR(addr, bit) BITBAND_ADDR(SRAM1_BASE, SRAM1_BB_BASE, addr, bit)
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