Untitled

What is the specific GCC flag that turns on immediate value propagation for inline assembly parameters?
#include <stdlib.h>

static int i;

static inline __attribute__((always_inline)) test(int x)
{
    asm volatile("mov %1, %0" : "=r"(i): "i"(x));
}

int main(void)
{
    test(5);

    return i;
}

gcc -O test.c

gcc test.c

void foo (void)
{
  int i = 6;

  asm volatile ("" : : "i" (i));
}

gcc -ftree-ter test.c   # no errors

alw.c: In function ‘main’:
alw.c:7:5: warning: asm operand 1 probably doesn’t match constraints [enabled by default]
alw.c:7:5: error: impossible constraint in ‘asm’