Comment by rep_lodsb

With an older version, it works (as long as there is no optimization at least, with -O2 all the register init code disappears):

$ gcc -v

... gcc version 10.2.1 20210110 (Debian 10.2.1-6)

    0000000000001125 <main>:
        1125: 55                    push   %rbp
        1126: 48 89 e5              mov    %rsp,%rbp
        1129: b8 01 00 00 00        mov    $0x1,%eax
        112e: bf 01 00 00 00        mov    $0x1,%edi
        1133: 48 8d 35 ca 0e 00 00  lea    0xeca(%rip),%rsi        # 2004 <_IO_stdin_used+0x4>
        113a: ba 0e 00 00 00        mov    $0xe,%edx
        113f: 0f 05                 syscall 

No idea why a newer version produces worse code in this case (though of course, this way of doing inline assembly isn't "correct" anyway, so nasal demons may result)