Messages in this thread | | | Date | Mon, 6 Feb 2023 11:07:14 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v1.1 3/3] x86/static_call: Add support for Jcc tail-calls |
| |
On Thu, 26 Jan 2023 10:14:49 -0800 Nick Desaulniers <ndesaulniers@google.com> wrote:
> On Thu, Jan 26, 2023 at 7:34 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Tue, Jan 24, 2023 at 10:07:53AM -0500, Steven Rostedt wrote: > > > On Tue, 24 Jan 2023 14:06:49 +0100 > > > Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > > > Just to confirm, as it's not clear if this is the static call site or one > > > > > of the functions that is being called. > > > > > > > > Ah, you've not looked at enough asm then? ;-) Yes this is the static > > > > call site, see the __SCT_ target (instruction at 0x35d). > > > > > > Yeah, could you specify it a bit more in the change log such that those > > > looking back at this don't have to have that requirement of staring at > > > enough asm ;-) > > > > How's this then?
Better :-)
Anyway... Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> > > > --- > > Subject: x86/static_call: Add support for Jcc tail-calls > > From: Peter Zijlstra <peterz@infradead.org> > > Date: Fri Jan 20 16:40:33 CET 2023 > > > > Clang likes to create conditional tail calls like: > > > > 0000000000000350 <amd_pmu_add_event>: > > 350: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 351: R_X86_64_NONE __fentry__-0x4 > > 355: 48 83 bf 20 01 00 00 00 cmpq $0x0,0x120(%rdi) > > 35d: 0f 85 00 00 00 00 jne 363 <amd_pmu_add_event+0x13> 35f: R_X86_64_PLT32 __SCT__amd_pmu_branch_add-0x4 > > 363: e9 00 00 00 00 jmp 368 <amd_pmu_add_event+0x18> 364: R_X86_64_PLT32 __x86_return_thunk-0x4 > > If it helps reduce the line width in the commit message to focus on > just the instructions, lately I've been using > `--no-addresses --no-show-raw-insn` flags to llvm-objdump.
Actually, I like the full output. Even if we do reduce it, it will still be over 80.
-- Steve
| |