This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] powerpc: Fix POWER7/PPC64 performance regression on LE
- From: Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>
- To: Richard Henderson <rth at twiddle dot net>, libc-alpha at sourceware dot org
- Date: Tue, 13 Jan 2015 23:18:49 -0200
- Subject: Re: [PATCH] powerpc: Fix POWER7/PPC64 performance regression on LE
- Authentication-results: sourceware.org; auth=none
- References: <54B3BD8A dot 1010608 at linux dot vnet dot ibm dot com> <54B57559 dot 2080108 at linux dot vnet dot ibm dot com> <54B57C0E dot 9090703 at twiddle dot net>
On 13-01-2015 18:11, Richard Henderson wrote:
> On 01/13/2015 11:43 AM, Adhemerval Zanella wrote:
>> + std rWORD8, rWORD8SAVE(r1)
>> + cfi_offset(rWORD8, rWORD8SAVE)
>> + std rWORD7, rWORD7SAVE(r1)
>> + cfi_offset(rWORD7, rWORD7SAVE)
>> + std rOFF8, rOFF8SAVE(r1)
>> + cfi_offset(rWORD7, rOFF8SAVE)
>> + std rOFF16, rOFF16SAVE(r1)
>> + cfi_offset(rWORD7, rOFF16SAVE)
>> + std rOFF24, rOFF24SAVE(r1)
>> + cfi_offset(rWORD7, rOFF24SAVE)
>> + std rOFF32, rOFF32SAVE(r1)
>> + cfi_offset(rWORD7, rOFF32SAVE)
> Given a sequence of stores like this, it's better to
> put all of the cfi_offset annotations after the last store.
>
> By interspersing them like this, you're just adding unnecessary
> DW_CFA_advance opcodes to the unwind info.
>
>
> r~
>
I was not aware of this, but I think the performance implications for such
organization is just to unwind and debuggers, right?