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