[Bug target/86040] [avr]: RAMPZ is not always cleared after loading __flashN data

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86040

--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
...and here is code that triggers the wrong path of the 2-byte case:

typedef struct S
{
    const __flash2 struct S *p;
    struct S *q;
} S;

const __flash2 S* func2 (const S *s)
{
    return s->p->q->p;
}

$ avr-gcc -std=gnu99 -mmcu=atxmega128a1 -S foo.c -Os -dp

func2:
        movw r26,r24     ;  20  [c=4 l=1]  *movhi/0
        ld r30,X+        ;  6   [c=8 l=2]  *movhi/2
        ld r31,X
        adiw r30,2       ;  8   [c=4 l=1]  addhi3_clobber/0
        ldi r18,2        ;  9   [c=8 l=5]  *movhi/2
        out __RAMPZ__,r18
        elpm r0,Z+
        elpm r31,Z
        mov r30,r0
        ld r24,Z         ;  15  [c=8 l=2]  *movhi/2
        ldd r25,Z+1
/* epilogue start */
        ret              ;  23  [c=0 l=1]  return

Insn 9 is missing the reset of RAMPZ so that insn 15 loads with a high-byte of
2.