改写以下代码为内联汇编代码：void digital_write(volatile uint32_t *gpio, int pin, int value) { // FIXME - replace this function with inline assembler // Select SET or CLR registers int reg = value ? GPIO_GPSET0 : GPIO_GPCLR0; // Pins 0-31 are in register xxx0, 32-63 are in register xxx1. if (pin > 31) { pin -= 32; reg++; } gpio[reg] = 1 << pin; }

以下是内联汇编代码：

void digital_write(volatile uint32_t *gpio, int pin, int value) {
    asm volatile(
        "cmp %[pin], #31\n\t"
        "ite gt\n\t"
        "subgt %[pin], %[pin], #32\n\t"
        "addgt %[reg], %[reg], #4\n\t"
        "ldr %[val], [%[gpio], %[reg]]\n\t"
        "mov %[mask], #1\n\t"
        "lsl %[mask], %[mask], %[pin]\n\t"
        "mov %[tmp], %[mask]\n\t"
        "ands %[tmp], %[val]\n\t"
        "beq set\n\t"
        "b clear\n"
        "set:\n\t"
        "orr %[val], %[mask]\n\t"
        "str %[val], [%[gpio], %[reg]]\n\t"
        "b end\n"
        "clear:\n\t"
        "bic %[val], %[mask]\n\t"
        "str %[val], [%[gpio], %[reg]]\n\t"
        "end:\n\t"
        :
        : [gpio] "r" (gpio),
          [pin] "r" (pin),
          [reg] "r" (value ? GPIO_GPSET0 : GPIO_GPCLR0),
          [val] "r" (0),
          [mask] "r" (0),
          [tmp] "r" (0)
        : "cc", "memory");
}