Date: Thu, 16 Apr 2020 14:44:51 -0400 From: Rich Felker <dalias@...c.org> To: Adhemerval Zanella <adhemerval.zanella@...aro.org> Cc: Nicholas Piggin <npiggin@...il.com>, libc-alpha@...rceware.org, musl@...ts.openwall.com, linuxppc-dev@...ts.ozlabs.org, libc-dev@...ts.llvm.org Subject: Re: Powerpc Linux 'scv' system call ABI proposal take 2 On Thu, Apr 16, 2020 at 02:31:51PM -0400, Rich Felker wrote: > > While on musl: > > > > 0000000000000000 <kill>: > > 0: 48 83 ec 08 sub $0x8,%rsp > > 4: 48 63 ff movslq %edi,%rdi > > 7: 48 63 f6 movslq %esi,%rsi > > a: b8 3e 00 00 00 mov $0x3e,%eax > > f: 0f 05 syscall > > 11: 48 89 c7 mov %rax,%rdi > > 14: e8 00 00 00 00 callq 19 <kill+0x19> > > 19: 5a pop %rdx > > 1a: c3 retq > > Wow that's some extraordinarily bad codegen going on by gcc... The > sign-extension is semantically needed and I don't see a good way > around it (glibc's asm is kinda a hack taking advantage of kernel not > looking at high bits, I think), but the gratuitous stack adjustment > and refusal to generate a tail call isn't. I'll see if we can track > down what's going on and get it fixed. It seems to be https://gcc.gnu.org/bugzilla/show_bug.cgi?id=14441 which I've updated with a comment about the above. Rich
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