[Bug inline-asm/87733] New: local register variable not honored with earlyclobber

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87733

            Bug ID: 87733
           Summary: local register variable not honored with earlyclobber
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Keywords: ra
          Severity: normal
          Priority: P3
         Component: inline-asm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
                CC: ilya.lesokhin at gmail dot com
  Target Milestone: ---

GCC fails to allocate %rsi for the first operand of the asm at -O2:

int test()
{
    register int r0 asm("rsi");
    asm("# %0 %1" : "=&r"(r0) : "r"(0));
    return r0;
}

test:
        .cfi_startproc
        xorl    %esi, %esi
#APP
        # %eax %esi
#NO_APP
        ret