Re: [PATCH, MPX] MPX-specific changes in dl_runtime routines

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Sat, Jul 11, 2015 at 1:27 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Sat, Jul 11, 2015 at 12:46:54PM +0200, OndÅej BÃlka wrote:
>> On Thu, Jul 09, 2015 at 09:07:24AM -0700, H.J. Lu wrote:
>> > On Thu, Jul 9, 2015 at 7:28 AM, OndÅej BÃlka <neleai@seznam.cz> wrote:
>> > > On Thu, Jul 09, 2015 at 07:12:24AM -0700, H.J. Lu wrote:
>> > >> On Thu, Jul 9, 2015 at 6:37 AM, Zamyatin, Igor <igor.zamyatin@intel.com> wrote:
>> > >> >> On Wed, Jul 8, 2015 at 8:56 AM, Zamyatin, Igor <igor.zamyatin@intel.com>
>> > >> >> wrote:
>> > >> >> > Fixed in the attached patch
>> > >> >> >
>> > >> >>
>> > >> >> I fixed some typos and updated sysdeps/i386/configure for
>> > >> >> HAVE_MPX_SUPPORT.  Please verify both with HAVE_MPX_SUPPORT and
>> > >> >> without on i386 and x86-64.
>> > >> >
>> > >> > Done, all works fine
>> > >> >
>> > >>
>> > >> I checked it in for you.
>> > >>
>> > > These are nice but you could have same problem with lazy tls allocation.
>> > > I wrote patch to merge trampolines, which now conflicts. Could you write
>> > > similar patch to solve that? Original purpose was to always save xmm
>> > > registers so we could use sse2 routines which speeds up lookup time.
>> >
>> > So we will preserve only xmm0 to xmm7 in _dl_runtime_resolve? How
>> > much gain it will give us?
>> >
>> I couldn't measure that without patch. Gain now would be big as we now
>> use byte-by-byte loop to check symbol name which is slow, especially
>> with c++ name mangling. Would be following benchmark good to measure
>> speedup or do I need to measure startup time which is bit harder?
>>
>
> Please try this.
>
>
> H.J.
> ---
>  sysdeps/x86_64/dl-trampoline.S | 42 +++++++++++++++++++++++++++++++++++-------
>  1 file changed, 35 insertions(+), 7 deletions(-)
>
> diff --git a/sysdeps/x86_64/dl-trampoline.S b/sysdeps/x86_64/dl-trampoline.S
> index 678c57f..ea81d7d 100644
> --- a/sysdeps/x86_64/dl-trampoline.S
> +++ b/sysdeps/x86_64/dl-trampoline.S
> @@ -27,26 +27,36 @@
>  /* Area on stack to save and restore registers used for parameter
>     passing when calling _dl_fixup.  */
>  #ifdef __ILP32__
> -/* X32 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX.  */
> -# define REGISTER_SAVE_AREA    (8 * 7)
> -# define REGISTER_SAVE_RAX     0
> +/* X32 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX as well as XMM0 to
> +   XMM7.  */
> +# define REGISTER_SAVE_AREA    (8 * 7 + 16 * 8)
> +/* Align XMM register save area to 16 bytes.  */
> +# define REGISTER_SAVE_XMM0    0
>  # define PRESERVE_BND_REGS_PREFIX
>  #else
> -/* X86-64 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX as well as BND0,
> -   BND1, BND2, BND3.  */
> -# define REGISTER_SAVE_AREA    (8 * 7 + 16 * 4)
> +/* X86-64 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX as well as
> +   BND0, BND1, BND2, BND3 and XMM0 to XMM7. */
> +# define REGISTER_SAVE_AREA    (8 * 7 + 16 * 4 + 16 * 8)
>  /* Align bound register save area to 16 bytes.  */
>  # define REGISTER_SAVE_BND0    0
>  # define REGISTER_SAVE_BND1    (REGISTER_SAVE_BND0 + 16)
>  # define REGISTER_SAVE_BND2    (REGISTER_SAVE_BND1 + 16)
>  # define REGISTER_SAVE_BND3    (REGISTER_SAVE_BND2 + 16)
> -# define REGISTER_SAVE_RAX     (REGISTER_SAVE_BND3 + 16)
> +# define REGISTER_SAVE_XMM0    (REGISTER_SAVE_BND3 + 16)
>  # ifdef HAVE_MPX_SUPPORT
>  #  define PRESERVE_BND_REGS_PREFIX bnd
>  # else
>  #  define PRESERVE_BND_REGS_PREFIX .byte 0xf2
>  # endif
>  #endif
> +#define REGISTER_SAVE_XMM1     (REGISTER_SAVE_XMM0 + 16)
> +#define REGISTER_SAVE_XMM2     (REGISTER_SAVE_XMM1 + 16)
> +#define REGISTER_SAVE_XMM3     (REGISTER_SAVE_XMM2 + 16)
> +#define REGISTER_SAVE_XMM4     (REGISTER_SAVE_XMM3 + 16)
> +#define REGISTER_SAVE_XMM5     (REGISTER_SAVE_XMM4 + 16)
> +#define REGISTER_SAVE_XMM6     (REGISTER_SAVE_XMM5 + 16)
> +#define REGISTER_SAVE_XMM7     (REGISTER_SAVE_XMM6 + 16)
> +#define REGISTER_SAVE_RAX      (REGISTER_SAVE_XMM7 + 16)
>  #define REGISTER_SAVE_RCX      (REGISTER_SAVE_RAX + 8)
>  #define REGISTER_SAVE_RDX      (REGISTER_SAVE_RCX + 8)
>  #define REGISTER_SAVE_RSI      (REGISTER_SAVE_RDX + 8)
> @@ -71,6 +81,15 @@ _dl_runtime_resolve:
>         movq %rdi, REGISTER_SAVE_RDI(%rsp)
>         movq %r8, REGISTER_SAVE_R8(%rsp)
>         movq %r9, REGISTER_SAVE_R9(%rsp)
> +       # movaps is 1-byte shorter.
> +       movaps %xmm0, REGISTER_SAVE_XMM0(%rsp)
> +       movaps %xmm1, REGISTER_SAVE_XMM1(%rsp)
> +       movaps %xmm2, REGISTER_SAVE_XMM2(%rsp)
> +       movaps %xmm3, REGISTER_SAVE_XMM3(%rsp)
> +       movaps %xmm4, REGISTER_SAVE_XMM4(%rsp)
> +       movaps %xmm5, REGISTER_SAVE_XMM5(%rsp)
> +       movaps %xmm6, REGISTER_SAVE_XMM6(%rsp)
> +       movaps %xmm7, REGISTER_SAVE_XMM7(%rsp)
>  #ifndef __ILP32__
>         # We also have to preserve bound registers.  These are nops if
>         # Intel MPX isn't available or disabled.
> @@ -123,6 +142,15 @@ _dl_runtime_resolve:
>         movq REGISTER_SAVE_RDX(%rsp), %rdx
>         movq REGISTER_SAVE_RCX(%rsp), %rcx
>         movq REGISTER_SAVE_RAX(%rsp), %rax
> +       # movaps is 1-byte shorter.
> +       movaps REGISTER_SAVE_XMM0(%rsp), %xmm0
> +       movaps REGISTER_SAVE_XMM1(%rsp), %xmm1
> +       movaps REGISTER_SAVE_XMM2(%rsp), %xmm2
> +       movaps REGISTER_SAVE_XMM3(%rsp), %xmm3
> +       movaps REGISTER_SAVE_XMM4(%rsp), %xmm4
> +       movaps REGISTER_SAVE_XMM5(%rsp), %xmm5
> +       movaps REGISTER_SAVE_XMM6(%rsp), %xmm6
> +       movaps REGISTER_SAVE_XMM7(%rsp), %xmm7
>         # Adjust stack(PLT did 2 pushes)
>         addq $(REGISTER_SAVE_AREA + 16), %rsp
>         cfi_adjust_cfa_offset(-(REGISTER_SAVE_AREA + 16))
> --
> 2.4.3
>

movaps doesn't work since the stack is misaligned when
__tls_get_addr is called due to:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066

-- 
H.J.