irqlock.h

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#ifndef ALCHEMY_IRQLOCK_H
#define ALCHEMY_IRQLOCK_H
 
/// @file
/// Saving, disabling and restoring the interrupt master enable.
 
#include "io_reg.h"
#include "types.h"
 
// The three steps take ime, a pointer to REG_IME. Disabling writes the
// pointer's low halfword (0x0208, bit 0 clear) back through it. Each step is a
// do { } while (0) statement macro, the shape the lock sites match through;
// the two restores' wrappers are devices, since a plain restore matches at
// some sites. SerialRuntime_Initialize writes IRQ_LOCK out (see its tag).
 
/// Saves the original IME value in saved.
#define IME_SAVE(ime, saved)                                                   \
  do {                                                                         \
    (saved) = *(ime);                                                          \
  } while (0)
 
/// Disables interrupts.
#define IME_DISABLE(ime)                                                       \
  do {                                                                         \
    *(ime) = (u16)(u32)(ime);                                                  \
  } while (0)
 
/// Restores IME from saved.
/* FAKEMATCH(one-pass): the wrapper; as *(ime) = (saved), 2 and 6 instructions
 * differ in BattleFx_PlayUnitElementEffect and BattleFx_RunJudgment, all six ☀️
 * editions. */
#define IME_RESTORE(ime, saved)                                                \
  do {                                                                         \
    *(ime) = (saved);                                                          \
  } while (0)
 
/// Disables interrupts and saves IME in saved; IRQ_UNLOCK restores it.
#define IRQ_LOCK(saved)                                                        \
  do {                                                                         \
    volatile u16 *ime_ = &REG_IME;                                             \
                                                                               \
    IME_SAVE(ime_, saved);                                                     \
    IME_DISABLE(ime_);                                                         \
  } while (0)
 
/// Restores the IME value saved by IRQ_LOCK.
/* FAKEMATCH(one-pass): the wrapper keeps the restore apart from the code
 * before it; as REG_IME = saved, 2 instructions differ in 7 of the 8 locking
 * Scheduler_ functions in tbs-en. */
#define IRQ_UNLOCK(saved)                                                      \
  do {                                                                         \
    REG_IME = saved;                                                           \
  } while (0)
 
#endif