qadd7()

LIB8STATIC_ALWAYS_INLINE int8_t qadd7	(	int8_t	i,
		int8_t	j )

Add one byte to another, saturating at 0x7F and -0x80.

Parameters

i	first byte to add
j	second byte to add

Returns

the sum of i + j, capped at 0x7F and -0x80

Definition at line 73 of file math8.h.

                                                          {
#if QADD7_C == 1
    int16_t t = i + j;
    if (t > 127)
        t = 127;
    else if (t < -128)
        t = -128;
    return static_cast<int8_t>(t);
#elif QADD7_AVRASM == 1
    asm volatile(
        /* First, add j to i, conditioning the V and C flags */
        "add %0, %1    \n\t"
 
        /* Now test the V flag.
        If V is clear, we branch to end.
        If V is set, we go ahead and load 0x7F into i.
        */
        "brvc L_%=     \n\t"
        "ldi %0, 0x7F  \n\t"
 
        /* When both numbers are negative, C is set.
        Adding it to make result negative. */
        "adc %0, __zero_reg__\n\t"
        "L_%=: "
        : "+d"(i) // r16-r31, restricted by ldi
        : "r"(j));
    return i;
#elif QADD7_ARM_DSP_ASM == 1
    asm volatile("qadd8 %0, %0, %1" : "+r"(i) : "r"(j));
    return i;
#else
#error "No implementation for qadd7 available."
#endif
}

References LIB8STATIC_ALWAYS_INLINE, and t.