>> So even though my implementation is slightly faster we're still >> getting a 70% perf hit. > interesting. > > can you show the assembly (objdump -d) for __asan_load8 in both variants?
My disas: 00000000004cf6a0 <__asan_load8>: 4cf6a0: 48 89 f8 mov %rdi,%rax 4cf6a3: 48 c1 e8 03 shr $0x3,%rax 4cf6a7: 80 b8 00 80 ff 7f 00 cmpb $0x0,0x7fff8000(%rax) 4cf6ae: 75 08 jne 4cf6b8 <__asan_load8+0x18> 4cf6b0: f3 c3 repz retq 4cf6b2: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) 4cf6b8: e9 f3 55 fc ff jmpq 494cb0 <__asan_report_load8> 4cf6bd: 0f 1f 00 nopl (%rax) And here's the trunk version: 0000000000493b00 <__asan_load8>: 493b00: 48 89 f8 mov %rdi,%rax 493b03: 48 c1 e8 03 shr $0x3,%rax 493b07: 80 b8 00 80 ff 7f 00 cmpb $0x0,0x7fff8000(%rax) 493b0e: 74 40 je 493b50 <__asan_load8+0x50> 493b10: 48 8b 05 51 83 26 00 mov 0x268351(%rip),%rax # 6fbe68 <_DYNAMIC+0x13a0> 493b17: 48 8b 00 mov (%rax),%rax 493b1a: 48 85 c0 test %rax,%rax 493b1d: 74 09 je 493b28 <__asan_load8+0x28> 493b1f: 48 89 38 mov %rdi,(%rax) 493b22: c3 retq 493b23: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 493b28: 55 push %rbp 493b29: 48 89 f9 mov %rdi,%rcx 493b2c: 41 b9 08 00 00 00 mov $0x8,%r9d 493b32: 45 31 c0 xor %r8d,%r8d 493b35: 48 89 e5 mov %rsp,%rbp 493b38: 48 83 ec 10 sub $0x10,%rsp 493b3c: 48 8b 7d 08 mov 0x8(%rbp),%rdi 493b40: 48 8d 55 f8 lea -0x8(%rbp),%rdx 493b44: 48 89 ee mov %rbp,%rsi 493b47: e8 64 e3 ff ff callq 491eb0 <__asan_report_error> 493b4c: c9 leaveq 493b4d: 0f 1f 00 nopl (%rax) 493b50: f3 c3 repz retq 493b52: 66 66 66 66 66 2e 0f data32 data32 data32 data32 nopw %cs:0x0(%rax,%rax,1) 493b59: 1f 84 00 00 00 00 00 > If you want to rely on a custom ABI, you should implement in on both > callee and caller sides. Sure. > That might indeed improve the speed, but imho is not worth it here. I still think that most of the overhead comes from ABI overheads (IMHO x86/amd64 are particularly bad at this). E.g. removing _all_ code from callbacks results in 16 sec runtime (so callback code overhead is only (17.3 - 16)/(17.3 - 11) = 20%) so improving it further is practically worthless. -Y -- You received this message because you are subscribed to the Google Groups "address-sanitizer" group. To unsubscribe from this group and stop receiving emails from it, send an email to address-sanitizer+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
