On Wed, Oct 8, 2008 at 12:10 PM, Dean McNamee <[EMAIL PROTECTED]> wrote:
>
> Won't memcpy always be an inlined intrinsic?
Not with variable size:
$ cat copy.cc
#include <string.h>
extern void foo(char* a, char* b, int size) {
memcpy(a, b, size);
}
$ g++ -S -O3 copy.cc
$ cat copy.s
.file "copy.cc"
.text
.align 2
.globl _Z3fooPcS_i
.type _Z3fooPcS_i, @function
_Z3fooPcS_i:
.LFB2:
pushl %ebp
.LCFI0:
movl %esp, %ebp
.LCFI1:
popl %ebp
jmp memcpy
.LFE2:
.size _Z3fooPcS_i, .-_Z3fooPcS_i
.ident "GCC: (GNU) 4.0.3 (Ubuntu 4.0.3-1ubuntu5)"
.section .note.GNU-stack,"",@progbits
>
> On Wed, Oct 8, 2008 at 10:38 AM, Kevin Millikin <[EMAIL PROTECTED]>
wrote:
>> LGTM.
>>
>> On Wed, Oct 8, 2008 at 10:31 AM, <[EMAIL PROTECTED]> wrote:
>>>
>>> Reviewers: Kevin Millikin,
>>>
>>> Description:
>>> Minor adjustments to the object migration code: When copying
>>> large objects we use memcpy. If this turns out to be a wash
>>> on the benchmarks, I'd be happy to rip it out again.
>>>
>>> Please review this at http://codereview.chromium.org/6576
>>>
>>> Affected files:
>>> M src/heap.cc
>>>
>>>
>>> Index: src/heap.cc
>>> ===================================================================
>>> --- src/heap.cc (revision 465)
>>> +++ src/heap.cc (working copy)
>>> @@ -733,11 +733,21 @@
>>> int size) {
>>> void** src = reinterpret_cast<void**>((*source_p)->address());
>>> void** dst = reinterpret_cast<void**>(target->address());
>>> - int counter = size/kPointerSize - 1;
>>> - do {
>>> - *dst++ = *src++;
>>> - } while (counter-- > 0);
>>>
>>> + // Use block copying memcpy if the object we're migrating is big
>>> + // enough to justify the extra call/setup overhead.
>>> + static const int kBlockCopyLimit = 16 * kPointerSize;
>>> +
>>> + if (size >= kBlockCopyLimit) {
>>> + memcpy(dst, src, size);
>>> + } else {
>>> + int remaining = size / kPointerSize;
>>> + do {
>>> + remaining--;
>>> + *dst++ = *src++;
>>> + } while (remaining > 0);
>>> + }
>>> +
>>> // Set the forwarding address.
>>> (*source_p)->set_map_word(MapWord::FromForwardingAddress(target));
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> Google Denmark ApS
>> CVR nr. 28 86 69 84
>> c/o Philip & Partners, 7 Vognmagergade, P.O. Box 2227, DK-1018 Copenhagen
K,
>> Denmark
>>
>> >
>>
>
> >
>
--
Erik Corry, Software Engineer
Google Denmark ApS. CVR nr. 28 86 69 84
c/o Philip & Partners, 7 Vognmagergade, P.O. Box 2227, DK-1018 Copenhagen K,
Denmark.
--~--~---------~--~----~------------~-------~--~----~
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
-~----------~----~----~----~------~----~------~--~---
